ci/tasks/readme: register hitbox-tool

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmdG9GqfSWCzts7AkDwRDh

.gitea/workflows/release.yml

@@ -0,0 +1,111 @@
+name: release-tools
+
+# På varje push till master/main: bygg de tools som fått ändringar
+# (linux x64 + arm64) och lägg binärerna på en rullande
+# "<tool>-latest"-release på släppsidan i Gitea.
+on:
+  push:
+    branches: [master, main]
+  workflow_dispatch: {} # manuell körning bygger ALLA tools
+
+jobs:
+  build-release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # hela historiken behövs för diffen mot 'before'
+
+      - name: Detektera ändrade tools
+        id: changed
+        run: |
+          TOOLS="pixel-sprite-maker mesh-tool bitmap-font-maker sfx-maker hitbox-tool"
+          BEFORE="${{ github.event.before }}"
+          CHANGED=""
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ] \
+             || [ -z "$BEFORE" ] \
+             || echo "$BEFORE" | grep -Eq '^0+$' \
+             || ! git cat-file -e "$BEFORE" 2>/dev/null; then
+            echo "första push / manuell körning -> bygger alla tools"
+            CHANGED="$TOOLS"
+          else
+            for t in $TOOLS; do
+              if ! git diff --quiet "$BEFORE" "${{ github.sha }}" -- "$t/"; then
+                CHANGED="$CHANGED $t"
+              fi
+            done
+          fi
+          CHANGED="$(echo $CHANGED)"   # trimma whitespace
+          echo "tools=$CHANGED" >> "$GITHUB_OUTPUT"
+          echo "bygger: ${CHANGED:-inget}"
+
+      - name: Installera Go
+        if: steps.changed.outputs.tools != ''
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+          cache: false
+
+      - name: Testa + bygg (x64 + arm64)
+        if: steps.changed.outputs.tools != ''
+        run: |
+          set -e
+          VERSION="latest-$(git rev-parse --short HEAD)"
+          for t in ${{ steps.changed.outputs.tools }}; do
+            case "$t" in
+              pixel-sprite-maker) BIN=spritec ;;
+              mesh-tool)          BIN=mesht ;;
+              bitmap-font-maker)  BIN=fontc ;;
+              sfx-maker)          BIN=sfxc ;;
+              hitbox-tool)        BIN=hitbox ;;
+              *) echo "okänt tool $t"; exit 1 ;;
+            esac
+            echo "=== $t ($BIN) ==="
+            cd "$t"
+            go test ./...
+            mkdir -p build
+            GOOS=linux GOARCH=amd64 go build -trimpath \
+              -ldflags "-s -w -X main.version=$VERSION" -o "build/$BIN-linux-x64" .
+            GOOS=linux GOARCH=arm64 go build -trimpath \
+              -ldflags "-s -w -X main.version=$VERSION" -o "build/$BIN-linux-arm64" .
+            (cd build && sha256sum "$BIN"-linux-* > checksums.txt && ls -la)
+            cd ..
+          done
+
+      - name: Skapa/uppdatera releaser + ladda upp binärer
+        if: steps.changed.outputs.tools != ''
+        env:
+          API: http://gitea-d:3000/api/v1
+          REPO: ${{ github.repository }}
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set -e
+          for t in ${{ steps.changed.outputs.tools }}; do
+            case "$t" in
+              pixel-sprite-maker) BIN=spritec ;;
+              mesh-tool)          BIN=mesht ;;
+              bitmap-font-maker)  BIN=fontc ;;
+              sfx-maker)          BIN=sfxc ;;
+              hitbox-tool)        BIN=hitbox ;;
+            esac
+            TAG="$t-latest"
+            BODY="$t (binär: $BIN) - rullande bygge från senaste master. Commit: ${{ github.sha }}. Arkitekturer: linux x64 + arm64 (Pi5)."
+            rid=$(curl -s -X POST "$API/repos/$REPO/releases" \
+              -H "Authorization: token $TOKEN" -H 'Content-Type: application/json' \
+              -d "{\"tag_name\":\"$TAG\",\"name\":\"$TAG\",\"body\":\"$BODY\"}" | jq -r '.id // empty')
+            [ -z "$rid" ] && rid=$(curl -s "$API/repos/$REPO/releases/tags/$TAG" \
+              -H "Authorization: token $TOKEN" | jq -r '.id')
+            echo "$t -> release id $rid"
+            for f in "$BIN-linux-x64" "$BIN-linux-arm64" checksums.txt; do
+              aid=$(curl -s "$API/repos/$REPO/releases/$rid/assets" \
+                -H "Authorization: token $TOKEN" | jq -r ".[] | select(.name==\"$f\") | .id")
+              if [ -n "$aid" ] && [ "$aid" != "null" ]; then
+                curl -s -X DELETE "$API/repos/$REPO/releases/$rid/assets/$aid" \
+                  -H "Authorization: token $TOKEN" -o /dev/null
+              fi
+              curl -s -X POST "$API/repos/$REPO/releases/$rid/assets?name=$f" \
+                -H "Authorization: token $TOKEN" \
+                -F "attachment=@$t/build/$f" -o /dev/null -w "  $f -> HTTP %{http_code}\n"
+            done
+          done

.gitignore

@@ -0,0 +1,3 @@
+build/
+*.exe
+mesh-tool/examples/downloads/

.vscode/tasks.json

@@ -0,0 +1,92 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "build pixel-sprite-maker",
+      "type": "shell",
+      "command": "go build -trimpath -ldflags '-s -w' -o build/spritec .",
+      "options": { "cwd": "${workspaceFolder}/pixel-sprite-maker" },
+      "group": "build",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "build mesh-tool",
+      "type": "shell",
+      "command": "go build -trimpath -ldflags '-s -w' -o build/mesht .",
+      "options": { "cwd": "${workspaceFolder}/mesh-tool" },
+      "group": "build",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "build bitmap-font-maker",
+      "type": "shell",
+      "command": "go build -trimpath -ldflags '-s -w' -o build/fontc .",
+      "options": { "cwd": "${workspaceFolder}/bitmap-font-maker" },
+      "group": "build",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "test bitmap-font-maker",
+      "type": "shell",
+      "command": "go test ./...",
+      "options": { "cwd": "${workspaceFolder}/bitmap-font-maker" },
+      "group": "test",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "build sfx-maker",
+      "type": "shell",
+      "command": "go build -trimpath -ldflags '-s -w' -o build/sfxc .",
+      "options": { "cwd": "${workspaceFolder}/sfx-maker" },
+      "group": "build",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "test sfx-maker",
+      "type": "shell",
+      "command": "go test ./...",
+      "options": { "cwd": "${workspaceFolder}/sfx-maker" },
+      "group": "test",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "build hitbox-tool",
+      "type": "shell",
+      "command": "go build -trimpath -ldflags '-s -w' -o build/hitbox .",
+      "options": { "cwd": "${workspaceFolder}/hitbox-tool" },
+      "group": "build",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "test hitbox-tool",
+      "type": "shell",
+      "command": "go test ./...",
+      "options": { "cwd": "${workspaceFolder}/hitbox-tool" },
+      "group": "test",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "test pixel-sprite-maker",
+      "type": "shell",
+      "command": "go test ./...",
+      "options": { "cwd": "${workspaceFolder}/pixel-sprite-maker" },
+      "group": "test",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "test mesh-tool",
+      "type": "shell",
+      "command": "go test ./...",
+      "options": { "cwd": "${workspaceFolder}/mesh-tool" },
+      "group": "test",
+      "problemMatcher": ["$go"]
+    },
+    {
+      "label": "build",
+      "dependsOn": ["build pixel-sprite-maker", "build mesh-tool", "build bitmap-font-maker", "build sfx-maker", "build hitbox-tool"],
+      "dependsOrder": "parallel",
+      "group": { "kind": "build", "isDefault": true },
+      "problemMatcher": []
+    }
+  ]
+}

README.md

@@ -1,3 +1,49 @@
 # agent-tools
 
-smal tools for ai agents
+Small, self-contained CLI tools built for **AI agents** to use during
+development work. Every tool is a single static Go binary with a
+text-first interface: input formats an agent can read and write
+directly, and output (names, errors, previews) explicit enough that the
+agent understands the result without opening an image viewer.
+
+| Tool | Binary | What it does |
+|------|--------|--------------|
+| [`pixel-sprite-maker/`](pixel-sprite-maker/) | `spritec` | Turns `.sprite` text files (palette + character grid) into PNG/JPG/SVG pixel art, up to 256x256 px per sprite. Combines several sprites into sprite sheets / animation strips whose **file names document the layout** (`walk_8x8_4x1.png` = 8x8 px frames, 4 columns, 1 row). |
+| [`mesh-tool/`](mesh-tool/) | `mesht` | Creates, inspects and edits 3D models (OBJ + STL). ASCII multi-view rendering + measurements (bbox, volume, watertightness) let an agent *see* a model, edit it (scale/rotate/mirror/merge/primitives) and verify the result. |
+| [`bitmap-font-maker/`](bitmap-font-maker/) | `fontc` | Turns `.font` text files (pixel glyph grids, proportional widths) into font atlases (PNG + JSON metrics) and renders text strings to PNG or the terminal. |
+| [`sfx-maker/`](sfx-maker/) | `sfxc` | Synthesizes retro game sound effects (sfxr-style) from `.sfx` text presets to 16-bit WAV: waves, envelope, pitch slides, vibrato, arpeggio, filters. Deterministic, with built-in presets (jump, coin, laser…). |
+| [`hitbox-tool/`](hitbox-tool/) | `hitbox` | Scans sprite sheet PNGs and writes per-frame collision boxes as JSON from the alpha channel. Understands the spritec sheet naming convention including upscaled sheets. |
+
+Each tool has its own folder, its own README with the full format/CLI
+reference, its own tests and its own dev branch (`dev/<tool>`).
+
+## Building
+
+```bash
+# Arch/Garuda prerequisite:
+sudo pacman -S go
+
+cd <tool>/ && go build -o build/<binary> .    # per tool
+go test ./...                                 # per tool
+```
+
+VS Code: **Terminal → Run Build Task** — `build` builds every tool into
+its own `<tool>/build/` folder; per-tool `build <tool>` and
+`test <tool>` tasks also exist.
+
+## CI / releases
+
+`.gitea/workflows/release.yml` runs on every push to `master`/`main` on
+the self-hosted runner: tools whose folders changed are tested, built
+for **linux x64 + arm64** (the Pi5), and published to a rolling
+release per tool on the repo's release page:
+
+- tag `pixel-sprite-maker-latest` → assets `spritec-linux-x64`, `spritec-linux-arm64`, `checksums.txt`
+- tag `mesh-tool-latest` → assets `mesht-linux-x64`, `mesht-linux-arm64`, `checksums.txt`
+
+A manual `workflow_dispatch` run builds all tools regardless of diffs.
+
+## Branch layout
+
+- `main` — stable, releases are built from here
+- `dev/pixel-sprite-maker`, `dev/mesh-tool` — per-tool development branches

bitmap-font-maker/README.md

@@ -0,0 +1,75 @@
+# bitmap-font-maker (`fontc`)
+
+Turns `.font` text files — pixel glyph grids an agent can read and edit
+directly — into **font atlases (PNG + JSON metrics)** and renders text
+strings to PNG. Proportional widths, unicode glyph names (ÅÄÖ works).
+Go, zero dependencies, single static binary.
+
+## Build
+
+```bash
+# Arch/Garuda: sudo pacman -S go
+cd bitmap-font-maker
+go build -o build/fontc .        # or the VS Code task "build bitmap-font-maker"
+go test ./...
+```
+
+## The `.font` format
+
+```
+# comment
+font: tiny5          optional name
+spacing: 1           px between glyphs (default 1)
+space-width: 3       advance of ' ' (default: width of '0')
+line-height: 7       default: glyph height + 1
+baseline: 5          default: glyph height
+
+glyph A:
+  .#.
+  #.#
+  ###
+  #.#
+  #.#
+
+glyph ::             the char between "glyph " and ":" is literal
+  .
+  #
+  .
+  #
+  .
+```
+
+- `#` = pixel on, `.` = off.
+- **All glyphs share one height; widths may differ** (proportional fonts —
+  `M` can be 5 px wide while `.` is 1 px).
+- Max glyph size 64x64.
+
+## Commands
+
+```bash
+fontc build tiny5.font -o out/tiny5        # -> tiny5.png (atlas) + tiny5.json (metrics)
+fontc render tiny5.font 'HEJ!\nRAD 2' --scale 4 --color '#FFD700' -o title.png
+fontc info tiny5.font                      # validate + list glyphs
+fontc preview tiny5.font 'HELLO'           # draw in the terminal
+```
+
+## Atlas + metrics
+
+The atlas draws glyphs **white on transparent** so game engines can tint
+them. The JSON carries everything a loader needs:
+
+```json
+{
+  "name": "tiny5", "atlas": "tiny5.png",
+  "height": 5, "lineHeight": 6, "baseline": 5,
+  "spacing": 1, "spaceWidth": 3,
+  "glyphs": { "A": {"x": 0, "y": 0, "w": 3, "h": 5, "advance": 4}, ... }
+}
+```
+
+Drawing text in a game: blit `glyphs[c]` from the atlas, advance the
+cursor by `advance`; spaces advance `spaceWidth + spacing`; new lines
+step `lineHeight`.
+
+[`examples/tiny5.font`](examples/tiny5.font) is a complete 3x5 font:
+A-Z, ÅÄÖ, 0-9 and punctuation.

bitmap-font-maker/examples/out/tiny5.json

@@ -0,0 +1,340 @@
+{
+  "name": "tiny5",
+  "atlas": "tiny5.png",
+  "height": 5,
+  "lineHeight": 6,
+  "baseline": 5,
+  "spacing": 1,
+  "spaceWidth": 3,
+  "glyphs": {
+    "!": {
+      "x": 36,
+      "y": 30,
+      "w": 1,
+      "h": 5,
+      "advance": 2
+    },
+    "'": {
+      "x": 24,
+      "y": 36,
+      "w": 1,
+      "h": 5,
+      "advance": 2
+    },
+    "+": {
+      "x": 18,
+      "y": 36,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    ",": {
+      "x": 30,
+      "y": 30,
+      "w": 2,
+      "h": 5,
+      "advance": 3
+    },
+    "-": {
+      "x": 12,
+      "y": 36,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    ".": {
+      "x": 24,
+      "y": 30,
+      "w": 1,
+      "h": 5,
+      "advance": 2
+    },
+    "0": {
+      "x": 6,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "1": {
+      "x": 12,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "2": {
+      "x": 18,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "3": {
+      "x": 24,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "4": {
+      "x": 30,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "5": {
+      "x": 36,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "6": {
+      "x": 0,
+      "y": 30,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "7": {
+      "x": 6,
+      "y": 30,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "8": {
+      "x": 12,
+      "y": 30,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "9": {
+      "x": 18,
+      "y": 30,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    ":": {
+      "x": 6,
+      "y": 36,
+      "w": 1,
+      "h": 5,
+      "advance": 2
+    },
+    "?": {
+      "x": 0,
+      "y": 36,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "A": {
+      "x": 0,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "B": {
+      "x": 6,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "C": {
+      "x": 12,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "D": {
+      "x": 18,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "E": {
+      "x": 24,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "F": {
+      "x": 30,
+      "y": 0,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "G": {
+      "x": 36,
+      "y": 0,
+      "w": 4,
+      "h": 5,
+      "advance": 5
+    },
+    "H": {
+      "x": 0,
+      "y": 6,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "I": {
+      "x": 6,
+      "y": 6,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "J": {
+      "x": 12,
+      "y": 6,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "K": {
+      "x": 18,
+      "y": 6,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "L": {
+      "x": 24,
+      "y": 6,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "M": {
+      "x": 30,
+      "y": 6,
+      "w": 5,
+      "h": 5,
+      "advance": 6
+    },
+    "N": {
+      "x": 36,
+      "y": 6,
+      "w": 4,
+      "h": 5,
+      "advance": 5
+    },
+    "O": {
+      "x": 0,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "P": {
+      "x": 6,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Q": {
+      "x": 12,
+      "y": 12,
+      "w": 4,
+      "h": 5,
+      "advance": 5
+    },
+    "R": {
+      "x": 18,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "S": {
+      "x": 24,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "T": {
+      "x": 30,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "U": {
+      "x": 36,
+      "y": 12,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "V": {
+      "x": 0,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "W": {
+      "x": 6,
+      "y": 18,
+      "w": 5,
+      "h": 5,
+      "advance": 6
+    },
+    "X": {
+      "x": 12,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Y": {
+      "x": 18,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Z": {
+      "x": 24,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Ä": {
+      "x": 36,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Å": {
+      "x": 30,
+      "y": 18,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    },
+    "Ö": {
+      "x": 0,
+      "y": 24,
+      "w": 3,
+      "h": 5,
+      "advance": 4
+    }
+  }
+}

bitmap-font-maker/examples/tiny5.font

@@ -0,0 +1,334 @@
+# tiny5 - a 3x5 pixel font (uppercase + digits + Swedish ÅÄÖ).
+# Widths vary: M/W are 5 px, punctuation as narrow as 1 px.
+font: tiny5
+spacing: 1
+space-width: 3
+
+glyph A:
+.#.
+#.#
+###
+#.#
+#.#
+
+glyph B:
+##.
+#.#
+##.
+#.#
+##.
+
+glyph C:
+.##
+#..
+#..
+#..
+.##
+
+glyph D:
+##.
+#.#
+#.#
+#.#
+##.
+
+glyph E:
+###
+#..
+##.
+#..
+###
+
+glyph F:
+###
+#..
+##.
+#..
+#..
+
+glyph G:
+.###
+#...
+#.##
+#..#
+.##.
+
+glyph H:
+#.#
+#.#
+###
+#.#
+#.#
+
+glyph I:
+###
+.#.
+.#.
+.#.
+###
+
+glyph J:
+..#
+..#
+..#
+#.#
+.#.
+
+glyph K:
+#.#
+#.#
+##.
+#.#
+#.#
+
+glyph L:
+#..
+#..
+#..
+#..
+###
+
+glyph M:
+#...#
+##.##
+#.#.#
+#...#
+#...#
+
+glyph N:
+#..#
+##.#
+#.##
+#..#
+#..#
+
+glyph O:
+.#.
+#.#
+#.#
+#.#
+.#.
+
+glyph P:
+##.
+#.#
+##.
+#..
+#..
+
+glyph Q:
+.##.
+#..#
+#..#
+#.#.
+.#.#
+
+glyph R:
+##.
+#.#
+##.
+#.#
+#.#
+
+glyph S:
+.##
+#..
+.#.
+..#
+##.
+
+glyph T:
+###
+.#.
+.#.
+.#.
+.#.
+
+glyph U:
+#.#
+#.#
+#.#
+#.#
+###
+
+glyph V:
+#.#
+#.#
+#.#
+#.#
+.#.
+
+glyph W:
+#...#
+#...#
+#.#.#
+##.##
+#...#
+
+glyph X:
+#.#
+#.#
+.#.
+#.#
+#.#
+
+glyph Y:
+#.#
+#.#
+.#.
+.#.
+.#.
+
+glyph Z:
+###
+..#
+.#.
+#..
+###
+
+glyph Å:
+.#.
+.#.
+#.#
+###
+#.#
+
+glyph Ä:
+#.#
+.#.
+#.#
+###
+#.#
+
+glyph Ö:
+#.#
+.#.
+#.#
+#.#
+.#.
+
+glyph 0:
+###
+#.#
+#.#
+#.#
+###
+
+glyph 1:
+.#.
+##.
+.#.
+.#.
+###
+
+glyph 2:
+##.
+..#
+.#.
+#..
+###
+
+glyph 3:
+###
+..#
+.##
+..#
+###
+
+glyph 4:
+#.#
+#.#
+###
+..#
+..#
+
+glyph 5:
+###
+#..
+##.
+..#
+##.
+
+glyph 6:
+.##
+#..
+###
+#.#
+###
+
+glyph 7:
+###
+..#
+.#.
+.#.
+.#.
+
+glyph 8:
+###
+#.#
+###
+#.#
+###
+
+glyph 9:
+###
+#.#
+###
+..#
+##.
+
+glyph .:
+.
+.
+.
+.
+#
+
+glyph ,:
+..
+..
+..
+.#
+#.
+
+glyph !:
+#
+#
+#
+.
+#
+
+glyph ?:
+###
+..#
+.#.
+...
+.#.
+
+glyph ::
+.
+#
+.
+#
+.
+
+glyph -:
+...
+...
+###
+...
+...
+
+glyph +:
+...
+.#.
+###
+.#.
+...
+
+glyph ':
+#
+#
+.
+.
+.

bitmap-font-maker/font/font.go

@@ -0,0 +1,238 @@
+// Package font parses .font text files and renders bitmap fonts to
+// atlases (PNG + JSON metrics) and text images.
+package font
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// MaxGlyphSize bounds glyph width/height in pixels.
+const MaxGlyphSize = 64
+
+// Glyph is one character's bitmap: rows of booleans (true = pixel on).
+// All glyphs in a font share the same height; widths vary
+// (proportional fonts).
+type Glyph struct {
+	Char rune
+	W, H int
+	Rows [][]bool
+}
+
+// Font is a parsed .font file.
+type Font struct {
+	Name       string
+	Height     int // glyph height, uniform across the font
+	LineHeight int // suggested distance between text baselines
+	Baseline   int // rows from glyph top to the baseline
+	Spacing    int // horizontal px between glyphs
+	SpaceWidth int // advance of ' '
+	Glyphs     map[rune]*Glyph
+	Order      []rune // file order, for stable atlas layout
+}
+
+// ParseFile reads a .font file; the font name defaults to the file name.
+func ParseFile(path string) (*Font, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	ft, err := Parse(f)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", path, err)
+	}
+	if ft.Name == "" {
+		ft.Name = strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
+	}
+	return ft, nil
+}
+
+// Parse reads the .font text format:
+//
+//	# comment
+//	font: tiny5            optional name
+//	spacing: 1             px between glyphs (default 1)
+//	space-width: 3         advance of ' ' (default: width of '0' or 3)
+//	line-height: 7         default: glyph height + 1
+//	baseline: 5            default: glyph height
+//
+//	glyph A:
+//	  .#.
+//	  #.#
+//	  ###
+//	  #.#
+//	  #.#
+//
+// Glyph grids use '#' for on and '.' for off. Every glyph must have the
+// same height; widths may differ. The char between "glyph " and the
+// trailing ':' is taken literally (one character, e.g. "glyph ::").
+func Parse(r io.Reader) (*Font, error) {
+	ft := &Font{
+		Spacing:    1,
+		SpaceWidth: -1, // resolved in validate
+		LineHeight: -1,
+		Baseline:   -1,
+		Glyphs:     map[rune]*Glyph{},
+	}
+	var cur *Glyph
+	sc := bufio.NewScanner(r)
+	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	lineNo := 0
+	flush := func() error {
+		if cur == nil {
+			return nil
+		}
+		if len(cur.Rows) == 0 {
+			return fmt.Errorf("glyph %q has no grid rows", string(cur.Char))
+		}
+		cur.H = len(cur.Rows)
+		cur.W = len(cur.Rows[0])
+		for i, row := range cur.Rows {
+			if len(row) != cur.W {
+				return fmt.Errorf("glyph %q row %d is %d px wide, expected %d", string(cur.Char), i+1, len(row), cur.W)
+			}
+		}
+		if cur.W > MaxGlyphSize || cur.H > MaxGlyphSize {
+			return fmt.Errorf("glyph %q is %dx%d; the maximum is %dx%d", string(cur.Char), cur.W, cur.H, MaxGlyphSize, MaxGlyphSize)
+		}
+		if _, dup := ft.Glyphs[cur.Char]; dup {
+			return fmt.Errorf("glyph %q defined twice", string(cur.Char))
+		}
+		ft.Glyphs[cur.Char] = cur
+		ft.Order = append(ft.Order, cur.Char)
+		cur = nil
+		return nil
+	}
+	for sc.Scan() {
+		lineNo++
+		line := strings.TrimSpace(sc.Text())
+		if line == "" {
+			continue
+		}
+		// '#' starts a comment — except inside a glyph where a line of
+		// only '#'/'.' is a grid row.
+		if strings.HasPrefix(line, "#") && !(cur != nil && isGridLine(line)) {
+			continue
+		}
+		if strings.HasPrefix(strings.ToLower(line), "glyph ") && strings.HasSuffix(line, ":") {
+			if err := flush(); err != nil {
+				return nil, fmt.Errorf("line %d: %w", lineNo, err)
+			}
+			name := strings.TrimSuffix(line[len("glyph "):], ":")
+			runes := []rune(name)
+			if len(runes) != 1 {
+				return nil, fmt.Errorf("line %d: glyph name %q must be exactly one character", lineNo, name)
+			}
+			cur = &Glyph{Char: runes[0]}
+			continue
+		}
+		if cur != nil && isGridLine(line) {
+			row := make([]bool, 0, len(line))
+			for _, r := range line {
+				row = append(row, r == '#')
+			}
+			cur.Rows = append(cur.Rows, row)
+			continue
+		}
+		// header key: value
+		if i := strings.Index(line, ":"); i > 0 && cur == nil {
+			key := strings.ToLower(strings.TrimSpace(line[:i]))
+			val := strings.TrimSpace(line[i+1:])
+			var err error
+			switch key {
+			case "font":
+				ft.Name = val
+			case "spacing":
+				ft.Spacing, err = strconv.Atoi(val)
+			case "space-width":
+				ft.SpaceWidth, err = strconv.Atoi(val)
+			case "line-height":
+				ft.LineHeight, err = strconv.Atoi(val)
+			case "baseline":
+				ft.Baseline, err = strconv.Atoi(val)
+			default:
+				return nil, fmt.Errorf("line %d: unknown setting %q", lineNo, key)
+			}
+			if err != nil {
+				return nil, fmt.Errorf("line %d: %s: %v", lineNo, key, err)
+			}
+			continue
+		}
+		return nil, fmt.Errorf("line %d: unexpected %q (want 'key: value', 'glyph X:' or a #/. grid row)", lineNo, line)
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+	if err := flush(); err != nil {
+		return nil, err
+	}
+	return ft, ft.validate()
+}
+
+// isGridLine reports whether the line consists solely of '#' and '.'.
+func isGridLine(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, r := range s {
+		if r != '#' && r != '.' {
+			return false
+		}
+	}
+	return true
+}
+
+func (ft *Font) validate() error {
+	if len(ft.Order) == 0 {
+		return fmt.Errorf("font has no glyphs")
+	}
+	ft.Height = ft.Glyphs[ft.Order[0]].H
+	for _, r := range ft.Order {
+		if g := ft.Glyphs[r]; g.H != ft.Height {
+			return fmt.Errorf("glyph %q is %d px tall but %q is %d — all glyphs must share one height",
+				string(r), g.H, string(ft.Order[0]), ft.Height)
+		}
+	}
+	if ft.LineHeight < 0 {
+		ft.LineHeight = ft.Height + 1
+	}
+	if ft.Baseline < 0 {
+		ft.Baseline = ft.Height
+	}
+	if ft.SpaceWidth < 0 {
+		if g, ok := ft.Glyphs['0']; ok {
+			ft.SpaceWidth = g.W
+		} else {
+			ft.SpaceWidth = 3
+		}
+	}
+	if ft.Spacing < 0 {
+		return fmt.Errorf("spacing must be >= 0")
+	}
+	return nil
+}
+
+// MaxGlyphWidth returns the widest glyph's width.
+func (ft *Font) MaxGlyphWidth() int {
+	w := 0
+	for _, r := range ft.Order {
+		if g := ft.Glyphs[r]; g.W > w {
+			w = g.W
+		}
+	}
+	return w
+}
+
+// SortedChars returns the glyph chars sorted by codepoint (JSON stability).
+func (ft *Font) SortedChars() []rune {
+	out := append([]rune(nil), ft.Order...)
+	sort.Slice(out, func(i, j int) bool { return out[i] < out[j] })
+	return out
+}

bitmap-font-maker/font/font_test.go

@@ -0,0 +1,144 @@
+package font
+
+import (
+	"bytes"
+	"encoding/json"
+	"image/color"
+	"strings"
+	"testing"
+)
+
+const tiny = `
+font: t
+spacing: 1
+space-width: 2
+
+glyph A:
+.#.
+#.#
+###
+
+glyph I:
+#
+#
+#
+`
+
+func parseOK(t *testing.T, src string) *Font {
+	t.Helper()
+	ft, err := Parse(strings.NewReader(src))
+	if err != nil {
+		t.Fatalf("parse: %v", err)
+	}
+	return ft
+}
+
+func TestParseBasics(t *testing.T) {
+	ft := parseOK(t, tiny)
+	if ft.Name != "t" || ft.Height != 3 || len(ft.Order) != 2 {
+		t.Errorf("name=%q height=%d glyphs=%d", ft.Name, ft.Height, len(ft.Order))
+	}
+	a := ft.Glyphs['A']
+	if a.W != 3 || a.H != 3 {
+		t.Errorf("A is %dx%d, want 3x3", a.W, a.H)
+	}
+	if !a.Rows[1][0] || a.Rows[0][0] {
+		t.Error("A pixel pattern wrong")
+	}
+	i := ft.Glyphs['I']
+	if i.W != 1 {
+		t.Errorf("I width = %d, want 1 (proportional)", i.W)
+	}
+	if ft.LineHeight != 4 || ft.Baseline != 3 {
+		t.Errorf("defaults: lineHeight=%d baseline=%d", ft.LineHeight, ft.Baseline)
+	}
+}
+
+func TestParseErrors(t *testing.T) {
+	cases := map[string]string{
+		"no glyphs":      "font: x\n",
+		"ragged glyph":   "glyph A:\n##\n#\n",
+		"height differs": "glyph A:\n#\n#\n\nglyph B:\n#\n",
+		"dup glyph":      "glyph A:\n#\n\nglyph A:\n#\n",
+		"bad name":       "glyph AB:\n#\n",
+		"unknown key":    "wat: 3\nglyph A:\n#\n",
+	}
+	for name, src := range cases {
+		if _, err := Parse(strings.NewReader(src)); err == nil {
+			t.Errorf("%s: expected error", name)
+		}
+	}
+}
+
+func TestGlyphNameColon(t *testing.T) {
+	ft := parseOK(t, "glyph ::\n#\n#\n")
+	if _, ok := ft.Glyphs[':']; !ok {
+		t.Error("glyph ':' not parsed")
+	}
+}
+
+func TestAtlasAndMetrics(t *testing.T) {
+	ft := parseOK(t, tiny)
+	img, m := ft.BuildAtlas("t.png")
+	if m.Glyphs["A"].Advance != 4 {
+		t.Errorf("A advance = %d, want 4 (w3 + spacing1)", m.Glyphs["A"].Advance)
+	}
+	g := m.Glyphs["A"]
+	// center-top pixel of A within its atlas cell: (x+1, y+0)
+	if img.NRGBAAt(g.X+1, g.Y).A == 0 {
+		t.Error("A apex pixel missing in atlas")
+	}
+	if img.NRGBAAt(g.X, g.Y).A != 0 {
+		t.Error("A corner should be empty")
+	}
+	var buf bytes.Buffer
+	if err := WriteMetrics(&buf, m); err != nil {
+		t.Fatal(err)
+	}
+	var back Metrics
+	if err := json.Unmarshal(buf.Bytes(), &back); err != nil {
+		t.Fatalf("metrics json invalid: %v", err)
+	}
+	if back.Glyphs["I"].W != 1 {
+		t.Errorf("metrics roundtrip: I.w = %d", back.Glyphs["I"].W)
+	}
+}
+
+func TestRenderText(t *testing.T) {
+	ft := parseOK(t, tiny)
+	white := color.NRGBA{255, 255, 255, 255}
+	img, warns := ft.RenderText("AI", 1, white)
+	if len(warns) != 0 {
+		t.Errorf("warnings: %v", warns)
+	}
+	// width: A(3) + spacing(1) + I(1) = 5
+	if b := img.Bounds(); b.Dx() != 5 || b.Dy() != 3 {
+		t.Errorf("size = %dx%d, want 5x3", b.Dx(), b.Dy())
+	}
+	// I column at x=4
+	if img.NRGBAAt(4, 0).A == 0 {
+		t.Error("I pixel missing")
+	}
+
+	_, warns = ft.RenderText("AXA", 1, white)
+	if len(warns) != 1 {
+		t.Errorf("missing-glyph warning expected, got %v", warns)
+	}
+
+	img, _ = ft.RenderText(`A\nA`, 1, white)
+	if b := img.Bounds(); b.Dy() != ft.LineHeight+ft.Height {
+		t.Errorf("two-line height = %d, want %d", b.Dy(), ft.LineHeight+ft.Height)
+	}
+
+	img2, _ := ft.RenderText("A", 3, white)
+	if b := img2.Bounds(); b.Dx() != 9 || b.Dy() != 9 {
+		t.Errorf("scaled size = %dx%d, want 9x9", b.Dx(), b.Dy())
+	}
+}
+
+func TestSpaceWidthDefaultFromZero(t *testing.T) {
+	ft := parseOK(t, "glyph 0:\n####\n####\n")
+	if ft.SpaceWidth != 4 {
+		t.Errorf("space-width = %d, want 4 (width of '0')", ft.SpaceWidth)
+	}
+}

bitmap-font-maker/font/render.go

@@ -0,0 +1,165 @@
+package font
+
+import (
+	"encoding/json"
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+	"io"
+	"strings"
+)
+
+// AtlasGlyph is one glyph's placement in the atlas.
+type AtlasGlyph struct {
+	X       int `json:"x"`
+	Y       int `json:"y"`
+	W       int `json:"w"`
+	H       int `json:"h"`
+	Advance int `json:"advance"` // cursor movement after drawing: W + spacing
+}
+
+// Metrics is the JSON sidecar written next to the atlas PNG.
+type Metrics struct {
+	Name       string                `json:"name"`
+	Atlas      string                `json:"atlas"`
+	Height     int                   `json:"height"`
+	LineHeight int                   `json:"lineHeight"`
+	Baseline   int                   `json:"baseline"`
+	Spacing    int                   `json:"spacing"`
+	SpaceWidth int                   `json:"spaceWidth"`
+	Glyphs     map[string]AtlasGlyph `json:"glyphs"`
+}
+
+// BuildAtlas packs all glyphs into a grid atlas image (white pixels on
+// transparency, so game engines can tint) and returns the metrics.
+// atlasName is stored in the metrics so loaders can find the image.
+func (ft *Font) BuildAtlas(atlasName string) (*image.NRGBA, *Metrics) {
+	n := len(ft.Order)
+	cols := 1
+	for cols*cols < n {
+		cols++
+	}
+	rows := (n + cols - 1) / cols
+	cellW := ft.MaxGlyphWidth() + 1 // 1 px padding against bleed
+	cellH := ft.Height + 1
+	img := image.NewNRGBA(image.Rect(0, 0, cols*cellW, rows*cellH))
+	white := color.NRGBA{255, 255, 255, 255}
+
+	m := &Metrics{
+		Name:       ft.Name,
+		Atlas:      atlasName,
+		Height:     ft.Height,
+		LineHeight: ft.LineHeight,
+		Baseline:   ft.Baseline,
+		Spacing:    ft.Spacing,
+		SpaceWidth: ft.SpaceWidth,
+		Glyphs:     map[string]AtlasGlyph{},
+	}
+	for i, r := range ft.Order {
+		g := ft.Glyphs[r]
+		x0 := (i % cols) * cellW
+		y0 := (i / cols) * cellH
+		drawGlyph(img, g, x0, y0, white)
+		m.Glyphs[string(r)] = AtlasGlyph{X: x0, Y: y0, W: g.W, H: g.H, Advance: g.W + ft.Spacing}
+	}
+	return img, m
+}
+
+func drawGlyph(img *image.NRGBA, g *Glyph, x0, y0 int, c color.NRGBA) {
+	for y, row := range g.Rows {
+		for x, on := range row {
+			if on {
+				img.SetNRGBA(x0+x, y0+y, c)
+			}
+		}
+	}
+}
+
+// RenderText draws text into a new image using the font. scale is an
+// integer upscale factor; unknown characters are skipped with a warning
+// returned. "\n" (literal backslash-n) and real newlines both break lines.
+func (ft *Font) RenderText(text string, scale int, fg color.NRGBA) (*image.NRGBA, []string) {
+	if scale < 1 {
+		scale = 1
+	}
+	text = strings.ReplaceAll(text, `\n`, "\n")
+	lines := strings.Split(text, "\n")
+
+	var warnings []string
+	width := 0
+	for _, line := range lines {
+		if w := ft.lineWidth(line); w > width {
+			width = w
+		}
+	}
+	if width == 0 {
+		width = 1
+	}
+	height := ft.LineHeight*(len(lines)-1) + ft.Height
+
+	small := image.NewNRGBA(image.Rect(0, 0, width, height))
+	for li, line := range lines {
+		x := 0
+		y := li * ft.LineHeight
+		for _, r := range line {
+			if r == ' ' {
+				x += ft.SpaceWidth + ft.Spacing
+				continue
+			}
+			g, ok := ft.Glyphs[r]
+			if !ok {
+				warnings = append(warnings, fmt.Sprintf("no glyph for %q — skipped", string(r)))
+				x += ft.SpaceWidth + ft.Spacing
+				continue
+			}
+			drawGlyph(small, g, x, y, fg)
+			x += g.W + ft.Spacing
+		}
+	}
+	if scale == 1 {
+		return small, warnings
+	}
+	b := small.Bounds()
+	big := image.NewNRGBA(image.Rect(0, 0, b.Dx()*scale, b.Dy()*scale))
+	for y := 0; y < b.Dy(); y++ {
+		for x := 0; x < b.Dx(); x++ {
+			c := small.NRGBAAt(x, y)
+			for dy := 0; dy < scale; dy++ {
+				for dx := 0; dx < scale; dx++ {
+					big.SetNRGBA(x*scale+dx, y*scale+dy, c)
+				}
+			}
+		}
+	}
+	return big, warnings
+}
+
+func (ft *Font) lineWidth(line string) int {
+	x := 0
+	for _, r := range line {
+		if r == ' ' {
+			x += ft.SpaceWidth + ft.Spacing
+			continue
+		}
+		if g, ok := ft.Glyphs[r]; ok {
+			x += g.W + ft.Spacing
+		} else {
+			x += ft.SpaceWidth + ft.Spacing
+		}
+	}
+	if x > 0 {
+		x -= ft.Spacing // no trailing spacing
+	}
+	return x
+}
+
+// WritePNG encodes an image as PNG.
+func WritePNG(w io.Writer, img image.Image) error { return png.Encode(w, img) }
+
+// WriteMetrics encodes metrics as indented JSON.
+func WriteMetrics(w io.Writer, m *Metrics) error {
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	return enc.Encode(m)
+}

bitmap-font-maker/go.mod

@@ -0,0 +1,3 @@
+module gitea.brasse-pc.eu/brasse/agent-tools/bitmap-font-maker
+
+go 1.24

bitmap-font-maker/main.go

@@ -0,0 +1,258 @@
+// fontc turns .font text files (pixel glyph grids) into font atlases
+// (PNG + JSON metrics) and renders text strings to images.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"image/color"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gitea.brasse-pc.eu/brasse/agent-tools/bitmap-font-maker/font"
+)
+
+var version = "dev"
+
+const usage = `fontc - bitmap font maker for agents
+
+Usage:
+  fontc build <file.font> [flags]     build atlas PNG + metrics JSON
+  fontc render <file.font> <text> [flags]
+                                      render a text string to PNG
+  fontc info <file.font>              validate + list glyphs
+  fontc preview <file.font> <text>    draw text in the terminal
+  fontc version
+
+Build flags:
+  -o <base>        output base name -> <base>.png + <base>.json
+                   (default: font file name without extension)
+
+Render flags:
+  -o <path>        output PNG (default text.png)
+  --scale <n>      integer upscale, default 1
+  --color <c>      text color (#RRGGBB, CSS names not supported here), default #FFFFFF
+  Use \n in <text> for line breaks.
+
+The .font format:
+  font: tiny5          optional name
+  spacing: 1           px between glyphs (default 1)
+  space-width: 3       advance of ' ' (default: width of '0')
+  line-height: 7       default: glyph height + 1
+  baseline: 5          default: glyph height
+
+  glyph A:
+    .#.
+    #.#
+    ###
+    #.#
+    #.#
+
+'#' = pixel on, '.' = off. All glyphs share one height; widths may
+differ (proportional). The atlas draws glyphs in white so engines can
+tint them; metrics JSON carries x/y/w/h/advance per glyph.
+`
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Print(usage)
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "build":
+		cmdBuild(os.Args[2:])
+	case "render":
+		cmdRender(os.Args[2:])
+	case "info":
+		cmdInfo(os.Args[2:])
+	case "preview":
+		cmdPreview(os.Args[2:])
+	case "version", "--version", "-v":
+		fmt.Println("fontc", version)
+	case "help", "--help", "-h":
+		fmt.Print(usage)
+	default:
+		die("unknown command %q — run 'fontc help'", os.Args[1])
+	}
+}
+
+// parseInterspersed lets flags appear before or after positional args.
+func parseInterspersed(fs *flag.FlagSet, args []string) {
+	var flags, pos []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if len(a) > 1 && a[0] == '-' {
+			flags = append(flags, a)
+			name := strings.TrimLeft(a, "-")
+			if !strings.Contains(name, "=") {
+				f := fs.Lookup(name)
+				isBool := false
+				if f != nil {
+					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
+						isBool = true
+					}
+				}
+				if !isBool && i+1 < len(args) {
+					i++
+					flags = append(flags, args[i])
+				}
+			}
+		} else {
+			pos = append(pos, a)
+		}
+	}
+	fs.Parse(append(flags, pos...))
+}
+
+func cmdBuild(args []string) {
+	fs := flag.NewFlagSet("build", flag.ExitOnError)
+	out := fs.String("o", "", "output base name")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("build takes exactly one .font file")
+	}
+	ft, err := font.ParseFile(fs.Arg(0))
+	if err != nil {
+		die("%v", err)
+	}
+	base := *out
+	if base == "" {
+		base = strings.TrimSuffix(fs.Arg(0), filepath.Ext(fs.Arg(0)))
+	}
+	base = strings.TrimSuffix(base, ".png")
+	img, metrics := ft.BuildAtlas(filepath.Base(base) + ".png")
+
+	pngF, err := os.Create(base + ".png")
+	if err != nil {
+		die("%v", err)
+	}
+	defer pngF.Close()
+	if err := font.WritePNG(pngF, img); err != nil {
+		die("%v", err)
+	}
+	jsonF, err := os.Create(base + ".json")
+	if err != nil {
+		die("%v", err)
+	}
+	defer jsonF.Close()
+	if err := font.WriteMetrics(jsonF, metrics); err != nil {
+		die("%v", err)
+	}
+	b := img.Bounds()
+	fmt.Printf("%s.png  (%dx%d atlas, %d glyphs)\n%s.json\n", base, b.Dx(), b.Dy(), len(ft.Order), base)
+}
+
+func parseHexColor(s string) (r, g, b uint8, err error) {
+	s = strings.TrimPrefix(strings.TrimSpace(s), "#")
+	if len(s) != 6 {
+		return 0, 0, 0, fmt.Errorf("color must be #RRGGBB, got %q", s)
+	}
+	var v [3]uint8
+	for i := 0; i < 3; i++ {
+		var n int
+		if _, err := fmt.Sscanf(s[i*2:i*2+2], "%02x", &n); err != nil {
+			return 0, 0, 0, fmt.Errorf("bad hex color %q", s)
+		}
+		v[i] = uint8(n)
+	}
+	return v[0], v[1], v[2], nil
+}
+
+func cmdRender(args []string) {
+	fs := flag.NewFlagSet("render", flag.ExitOnError)
+	out := fs.String("o", "text.png", "output PNG")
+	scale := fs.Int("scale", 1, "integer upscale")
+	col := fs.String("color", "#FFFFFF", "text color #RRGGBB")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 2 {
+		die("render takes a .font file and a text string")
+	}
+	ft, err := font.ParseFile(fs.Arg(0))
+	if err != nil {
+		die("%v", err)
+	}
+	r, g, b, err := parseHexColor(*col)
+	if err != nil {
+		die("%v", err)
+	}
+	img, warnings := ft.RenderText(fs.Arg(1), *scale, rgba(r, g, b))
+	for _, w := range warnings {
+		fmt.Fprintln(os.Stderr, "fontc:", w)
+	}
+	f, err := os.Create(*out)
+	if err != nil {
+		die("%v", err)
+	}
+	defer f.Close()
+	if err := font.WritePNG(f, img); err != nil {
+		die("%v", err)
+	}
+	bd := img.Bounds()
+	fmt.Printf("%s  (%dx%d px)\n", *out, bd.Dx(), bd.Dy())
+}
+
+func cmdInfo(args []string) {
+	if len(args) != 1 {
+		die("info takes exactly one .font file")
+	}
+	ft, err := font.ParseFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("font:        %s\n", ft.Name)
+	fmt.Printf("height:      %d px\n", ft.Height)
+	fmt.Printf("line-height: %d px\n", ft.LineHeight)
+	fmt.Printf("baseline:    %d\n", ft.Baseline)
+	fmt.Printf("spacing:     %d px\n", ft.Spacing)
+	fmt.Printf("space-width: %d px\n", ft.SpaceWidth)
+	fmt.Printf("glyphs:      %d\n", len(ft.Order))
+	var chars []string
+	for _, r := range ft.SortedChars() {
+		chars = append(chars, string(r))
+	}
+	fmt.Printf("  %s\n", strings.Join(chars, " "))
+	fmt.Println("valid:       yes")
+}
+
+func cmdPreview(args []string) {
+	if len(args) != 2 {
+		die("preview takes a .font file and a text string")
+	}
+	ft, err := font.ParseFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	img, warnings := ft.RenderText(args[1], 1, rgba(255, 255, 255))
+	for _, w := range warnings {
+		fmt.Fprintln(os.Stderr, "fontc:", w)
+	}
+	b := img.Bounds()
+	for y := 0; y < b.Dy(); y += 2 {
+		var sb strings.Builder
+		for x := 0; x < b.Dx(); x++ {
+			top := img.NRGBAAt(x, y).A >= 128
+			bot := y+1 < b.Dy() && img.NRGBAAt(x, y+1).A >= 128
+			switch {
+			case top && bot:
+				sb.WriteRune('█')
+			case top:
+				sb.WriteRune('▀')
+			case bot:
+				sb.WriteRune('▄')
+			default:
+				sb.WriteByte(' ')
+			}
+		}
+		fmt.Println(sb.String())
+	}
+}
+
+func rgba(r, g, b uint8) color.NRGBA {
+	return color.NRGBA{R: r, G: g, B: b, A: 255}
+}
+
+func die(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, "fontc: "+format+"\n", a...)
+	os.Exit(1)
+}

doc/plan.md

@@ -0,0 +1,43 @@
+# agent-tools — plan
+
+## Goal
+
+A collection of small, agent-friendly CLI tools. The common thread:
+**text in, verifiable artifacts out**. An agent should be able to author
+the input format directly, predict what the output will look like, and
+verify results without a GUI.
+
+## Stack
+
+- Go (single static binaries, zero deps, trivial cross-compile to the
+  Pi5's arm64 runner), one Go module per tool.
+- Targets: linux x64 + linux arm64.
+
+## Deploy target
+
+Pattern A (distributable binaries): rolling `<tool>-latest` release per
+tool on Gitea, built by `.gitea/workflows/release.yml` on push to
+master/main. Only tools whose folders changed get rebuilt.
+
+## Milestones
+
+1. ✅ `pixel-sprite-maker` (`spritec`): .sprite text format → PNG/JPG/SVG,
+   sprite sheets with self-documenting file names, terminal preview.
+2. ✅ `mesh-tool` (`mesht`): OBJ/STL create/inspect/edit with ASCII
+   multi-view rendering, measurements and watertightness checks.
+3. ✅ Per-tool VS Code build tasks → `<tool>/build/`.
+4. ✅ CI: changed-tool detection + per-tool rolling releases.
+
+## Roadmap / expansion ideas (not agreed yet)
+
+- spritec: palette import from image files, GIF export for animations,
+  tile-map composer (map file referencing sprite tiles).
+- mesht: OBJ vertex-color support, simple boolean ops (union via
+  voxelization), PNG snapshot rendering, glTF export.
+- New tools: bitmap-font maker, sound-effect generator (sfxr-style text
+  presets), tiled-map (.tmx) writer.
+
+## Open questions
+
+- Versioned releases (`vX.Y.Z` tags per tool) on top of the rolling
+  `latest` — add when something depends on a pinned version.

hitbox-tool/README.md

@@ -0,0 +1,66 @@
+# hitbox-tool (`hitbox`)
+
+Scans **sprite sheet PNGs** and writes per-frame **collision boxes as
+JSON**, computed from the alpha channel. Closes the loop with
+[`pixel-sprite-maker`](../pixel-sprite-maker/): render a sheet with
+`spritec`, scan it with `hitbox`, and your game gets both graphics and
+hitboxes without a human drawing rectangles. Go, zero dependencies,
+single static binary.
+
+## Build
+
+```bash
+# Arch/Garuda: sudo pacman -S go
+cd hitbox-tool
+go build -o build/hitbox .        # or the VS Code task "build hitbox-tool"
+go test ./...
+```
+
+## Usage
+
+```bash
+# spritec-named sheets need no flags — layout is parsed from the name,
+# and integer upscales are auto-detected (a _8x8_4x1 sheet that is
+# 256x64 px was rendered at --scale 8, so cells are 64x64):
+hitbox scan walk_8x8_4x1.png -o walk.hitbox.json
+
+hitbox scan boss.png --cell 32x32 -o boss.json   # explicit frame size
+hitbox scan portrait.png                          # whole image = one frame, JSON to stdout
+
+hitbox show walk_8x8_4x1.png --frame 2            # verify visually in the terminal
+
+# tuning:
+--threshold 128     # ignore faint pixels (alpha < 128)
+--shrink 1          # tighter, more forgiving hitboxes (n px per side)
+--pad 2             # generous hitboxes (e.g. pickups)
+```
+
+## Output
+
+```json
+{
+  "image": "walk_8x8_4x1.png",
+  "cellW": 8, "cellH": 8, "cols": 4, "rows": 1,
+  "alphaThreshold": 1,
+  "frames": [
+    { "index": 0, "col": 0, "row": 0, "empty": false,
+      "box": { "x": 1, "y": 0, "w": 5, "h": 8 } },
+    { "index": 1, "col": 1, "row": 0, "empty": true, "box": null }
+  ]
+}
+```
+
+- Boxes are **relative to each frame's top-left corner**.
+- Frame order is row-major (`index = row * cols + col`), matching
+  spritec sheets.
+- Cells with no solid pixels get `"empty": true`.
+
+In game code:
+
+```
+hit = px >= frameX + box.x && px < frameX + box.x + box.w
+   && py >= frameY + box.y && py < frameY + box.y + box.h
+```
+
+`hitbox show` draws each frame with `#` for solid pixels and `+` for the
+box outline, so an agent can verify the result without an image viewer.

hitbox-tool/examples/walk_8x8_4x1.hitbox.json

@@ -0,0 +1,58 @@
+{
+  "image": "examples/walk_8x8_4x1.png",
+  "cellW": 64,
+  "cellH": 64,
+  "cols": 4,
+  "rows": 1,
+  "alphaThreshold": 1,
+  "frames": [
+    {
+      "index": 0,
+      "col": 0,
+      "row": 0,
+      "empty": false,
+      "box": {
+        "x": 8,
+        "y": 0,
+        "w": 40,
+        "h": 64
+      }
+    },
+    {
+      "index": 1,
+      "col": 1,
+      "row": 0,
+      "empty": false,
+      "box": {
+        "x": 8,
+        "y": 0,
+        "w": 40,
+        "h": 64
+      }
+    },
+    {
+      "index": 2,
+      "col": 2,
+      "row": 0,
+      "empty": false,
+      "box": {
+        "x": 8,
+        "y": 0,
+        "w": 40,
+        "h": 64
+      }
+    },
+    {
+      "index": 3,
+      "col": 3,
+      "row": 0,
+      "empty": false,
+      "box": {
+        "x": 8,
+        "y": 0,
+        "w": 40,
+        "h": 64
+      }
+    }
+  ]
+}

hitbox-tool/go.mod

@@ -0,0 +1,3 @@
+module gitea.brasse-pc.eu/brasse/agent-tools/hitbox-tool
+
+go 1.24

hitbox-tool/hitbox/hitbox.go

@@ -0,0 +1,230 @@
+// Package hitbox computes per-frame collision boxes from sprite sheet
+// images by scanning the alpha channel.
+package hitbox
+
+import (
+	"encoding/json"
+	"fmt"
+	"image"
+	"image/png"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+)
+
+// Box is a rectangle relative to its frame's top-left corner.
+type Box struct {
+	X int `json:"x"`
+	Y int `json:"y"`
+	W int `json:"w"`
+	H int `json:"h"`
+}
+
+// Frame is the scan result for one sheet cell.
+type Frame struct {
+	Index int  `json:"index"`
+	Col   int  `json:"col"`
+	Row   int  `json:"row"`
+	Empty bool `json:"empty"`
+	Box   *Box `json:"box"` // nil when Empty
+}
+
+// Sheet is the full scan result; the JSON deliverable.
+type Sheet struct {
+	Image     string  `json:"image"`
+	CellW     int     `json:"cellW"`
+	CellH     int     `json:"cellH"`
+	Cols      int     `json:"cols"`
+	Rows      int     `json:"rows"`
+	Threshold int     `json:"alphaThreshold"`
+	Frames    []Frame `json:"frames"`
+}
+
+// layoutRe matches the spritec sheet naming convention:
+// <base>_<cellW>x<cellH>_<cols>x<rows>.<ext>
+var layoutRe = regexp.MustCompile(`_(\d+)x(\d+)_(\d+)x(\d+)\.[A-Za-z]+$`)
+
+// LayoutFromName extracts cell size and grid from a spritec-style file
+// name. ok is false when the name doesn't follow the convention.
+func LayoutFromName(path string) (cellW, cellH, cols, rows int, ok bool) {
+	m := layoutRe.FindStringSubmatch(filepath.Base(path))
+	if m == nil {
+		return 0, 0, 0, 0, false
+	}
+	cellW, _ = strconv.Atoi(m[1])
+	cellH, _ = strconv.Atoi(m[2])
+	cols, _ = strconv.Atoi(m[3])
+	rows, _ = strconv.Atoi(m[4])
+	return cellW, cellH, cols, rows, true
+}
+
+// InferScale detects integer-upscaled sheets: when the image is exactly
+// s times bigger than the name-declared layout (both axes, s >= 1), the
+// real cell size is cell*s. Returns 0 when the layout doesn't fit.
+func InferScale(imgW, imgH, cellW, cellH, cols, rows int) int {
+	baseW, baseH := cellW*cols, cellH*rows
+	if baseW <= 0 || baseH <= 0 || imgW%baseW != 0 || imgH%baseH != 0 {
+		return 0
+	}
+	s := imgW / baseW
+	if s < 1 || imgH/baseH != s {
+		return 0
+	}
+	return s
+}
+
+// LoadPNG reads a PNG image from disk.
+func LoadPNG(path string) (image.Image, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	img, err := png.Decode(f)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w (only PNG is supported — sheets need an alpha channel)", path, err)
+	}
+	return img, nil
+}
+
+// Scan computes a tight box per frame: the smallest rectangle covering
+// every pixel with alpha >= threshold. shrink/pad (in pixels) contract or
+// expand each box afterwards, clamped to the cell.
+func Scan(img image.Image, name string, cellW, cellH, threshold, shrink, pad int) (*Sheet, error) {
+	b := img.Bounds()
+	if cellW <= 0 || cellH <= 0 {
+		cellW, cellH = b.Dx(), b.Dy() // whole image = one frame
+	}
+	if b.Dx()%cellW != 0 || b.Dy()%cellH != 0 {
+		return nil, fmt.Errorf("image is %dx%d which is not divisible by cell %dx%d",
+			b.Dx(), b.Dy(), cellW, cellH)
+	}
+	if threshold < 1 || threshold > 255 {
+		return nil, fmt.Errorf("alpha threshold %d out of range 1-255", threshold)
+	}
+	cols, rows := b.Dx()/cellW, b.Dy()/cellH
+	sheet := &Sheet{
+		Image: name, CellW: cellW, CellH: cellH,
+		Cols: cols, Rows: rows, Threshold: threshold,
+	}
+	for row := 0; row < rows; row++ {
+		for col := 0; col < cols; col++ {
+			fr := Frame{Index: row*cols + col, Col: col, Row: row}
+			minX, minY := cellW, cellH
+			maxX, maxY := -1, -1
+			for y := 0; y < cellH; y++ {
+				for x := 0; x < cellW; x++ {
+					_, _, _, a := img.At(b.Min.X+col*cellW+x, b.Min.Y+row*cellH+y).RGBA()
+					if int(a>>8) >= threshold {
+						if x < minX {
+							minX = x
+						}
+						if y < minY {
+							minY = y
+						}
+						if x > maxX {
+							maxX = x
+						}
+						if y > maxY {
+							maxY = y
+						}
+					}
+				}
+			}
+			if maxX < 0 {
+				fr.Empty = true
+			} else {
+				box := Box{X: minX, Y: minY, W: maxX - minX + 1, H: maxY - minY + 1}
+				box = adjust(box, shrink-pad, cellW, cellH)
+				fr.Box = &box
+			}
+			sheet.Frames = append(sheet.Frames, fr)
+		}
+	}
+	return sheet, nil
+}
+
+// adjust contracts the box by delta px on every side (negative delta
+// expands), clamped to the cell and to a minimum size of 1x1.
+func adjust(b Box, delta, cellW, cellH int) Box {
+	b.X += delta
+	b.Y += delta
+	b.W -= 2 * delta
+	b.H -= 2 * delta
+	if b.X < 0 {
+		b.W += b.X
+		b.X = 0
+	}
+	if b.Y < 0 {
+		b.H += b.Y
+		b.Y = 0
+	}
+	if b.X+b.W > cellW {
+		b.W = cellW - b.X
+	}
+	if b.Y+b.H > cellH {
+		b.H = cellH - b.Y
+	}
+	if b.W < 1 {
+		b.W = 1
+		if b.X > cellW-1 {
+			b.X = cellW - 1
+		}
+	}
+	if b.H < 1 {
+		b.H = 1
+		if b.Y > cellH-1 {
+			b.Y = cellH - 1
+		}
+	}
+	return b
+}
+
+// WriteJSON encodes the sheet as indented JSON.
+func (s *Sheet) WriteJSON(w io.Writer) error {
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	return enc.Encode(s)
+}
+
+// Ascii draws one frame with '#' for solid pixels and '+' for the box
+// outline, so results can be verified in a terminal.
+func Ascii(img image.Image, s *Sheet, index, threshold int) string {
+	if index < 0 || index >= len(s.Frames) {
+		return "(no such frame)\n"
+	}
+	fr := s.Frames[index]
+	b := img.Bounds()
+	out := make([]rune, 0, (s.CellW+1)*s.CellH)
+	onBoxEdge := func(x, y int) bool {
+		if fr.Box == nil {
+			return false
+		}
+		bx := fr.Box
+		inX := x >= bx.X && x < bx.X+bx.W
+		inY := y >= bx.Y && y < bx.Y+bx.H
+		edgeX := x == bx.X || x == bx.X+bx.W-1
+		edgeY := y == bx.Y || y == bx.Y+bx.H-1
+		return (inX && inY) && (edgeX || edgeY)
+	}
+	for y := 0; y < s.CellH; y++ {
+		for x := 0; x < s.CellW; x++ {
+			_, _, _, a := img.At(b.Min.X+fr.Col*s.CellW+x, b.Min.Y+fr.Row*s.CellH+y).RGBA()
+			solid := int(a>>8) >= threshold
+			switch {
+			case solid && onBoxEdge(x, y):
+				out = append(out, '#')
+			case solid:
+				out = append(out, '#')
+			case onBoxEdge(x, y):
+				out = append(out, '+')
+			default:
+				out = append(out, '.')
+			}
+		}
+		out = append(out, '\n')
+	}
+	return string(out)
+}

hitbox-tool/hitbox/hitbox_test.go

@@ -0,0 +1,137 @@
+package hitbox
+
+import (
+	"bytes"
+	"encoding/json"
+	"image"
+	"image/color"
+	"testing"
+)
+
+// sheet4 builds a 2x1 sheet of 4x4 cells: frame 0 has a 2x2 blob at
+// (1,1); frame 1 is empty.
+func sheet4() image.Image {
+	img := image.NewNRGBA(image.Rect(0, 0, 8, 4))
+	for y := 1; y <= 2; y++ {
+		for x := 1; x <= 2; x++ {
+			img.SetNRGBA(x, y, color.NRGBA{255, 0, 0, 255})
+		}
+	}
+	return img
+}
+
+func TestScanTightBox(t *testing.T) {
+	s, err := Scan(sheet4(), "test.png", 4, 4, 1, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Cols != 2 || s.Rows != 1 || len(s.Frames) != 2 {
+		t.Fatalf("layout %dx%d frames=%d", s.Cols, s.Rows, len(s.Frames))
+	}
+	f0 := s.Frames[0]
+	if f0.Empty || f0.Box == nil {
+		t.Fatal("frame 0 should have a box")
+	}
+	if *f0.Box != (Box{X: 1, Y: 1, W: 2, H: 2}) {
+		t.Errorf("frame 0 box = %+v", *f0.Box)
+	}
+	f1 := s.Frames[1]
+	if !f1.Empty || f1.Box != nil {
+		t.Errorf("frame 1 should be empty, got %+v", f1)
+	}
+}
+
+func TestScanWholeImageDefault(t *testing.T) {
+	s, err := Scan(sheet4(), "x.png", 0, 0, 1, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(s.Frames) != 1 || s.CellW != 8 || s.CellH != 4 {
+		t.Errorf("whole-image scan: %+v", s)
+	}
+}
+
+func TestScanErrors(t *testing.T) {
+	if _, err := Scan(sheet4(), "x.png", 3, 4, 1, 0, 0); err == nil {
+		t.Error("non-divisible cell size should error")
+	}
+	if _, err := Scan(sheet4(), "x.png", 4, 4, 0, 0, 0); err == nil {
+		t.Error("threshold 0 should error")
+	}
+}
+
+func TestShrinkAndPad(t *testing.T) {
+	img := image.NewNRGBA(image.Rect(0, 0, 4, 4))
+	for y := 0; y < 4; y++ {
+		for x := 0; x < 4; x++ {
+			img.SetNRGBA(x, y, color.NRGBA{0, 0, 0, 255})
+		}
+	}
+	s, _ := Scan(img, "x.png", 4, 4, 1, 1, 0) // shrink 1
+	if *s.Frames[0].Box != (Box{X: 1, Y: 1, W: 2, H: 2}) {
+		t.Errorf("shrunk box = %+v", *s.Frames[0].Box)
+	}
+	s, _ = Scan(img, "x.png", 4, 4, 1, 0, 3) // pad clamps to cell
+	if *s.Frames[0].Box != (Box{X: 0, Y: 0, W: 4, H: 4}) {
+		t.Errorf("padded box = %+v", *s.Frames[0].Box)
+	}
+	s, _ = Scan(img, "x.png", 4, 4, 1, 10, 0) // over-shrink -> min 1x1
+	if s.Frames[0].Box.W < 1 || s.Frames[0].Box.H < 1 {
+		t.Errorf("over-shrunk box = %+v", *s.Frames[0].Box)
+	}
+}
+
+func TestThreshold(t *testing.T) {
+	img := image.NewNRGBA(image.Rect(0, 0, 2, 1))
+	img.SetNRGBA(0, 0, color.NRGBA{0, 0, 0, 100})
+	img.SetNRGBA(1, 0, color.NRGBA{0, 0, 0, 200})
+	s, _ := Scan(img, "x.png", 2, 1, 150, 0, 0)
+	if *s.Frames[0].Box != (Box{X: 1, Y: 0, W: 1, H: 1}) {
+		t.Errorf("threshold box = %+v", *s.Frames[0].Box)
+	}
+	s, _ = Scan(img, "x.png", 2, 1, 50, 0, 0)
+	if *s.Frames[0].Box != (Box{X: 0, Y: 0, W: 2, H: 1}) {
+		t.Errorf("low-threshold box = %+v", *s.Frames[0].Box)
+	}
+}
+
+func TestLayoutFromName(t *testing.T) {
+	w, h, c, r, ok := LayoutFromName("/tmp/walk_8x8_4x1.png")
+	if !ok || w != 8 || h != 8 || c != 4 || r != 1 {
+		t.Errorf("parsed %d %d %d %d ok=%v", w, h, c, r, ok)
+	}
+	if _, _, _, _, ok := LayoutFromName("plain.png"); ok {
+		t.Error("plain.png should not match")
+	}
+}
+
+func TestInferScale(t *testing.T) {
+	// walk_8x8_4x1.png rendered at scale 8 -> 256x64
+	if s := InferScale(256, 64, 8, 8, 4, 1); s != 8 {
+		t.Errorf("scale = %d, want 8", s)
+	}
+	if s := InferScale(32, 8, 8, 8, 4, 1); s != 1 {
+		t.Errorf("unscaled = %d, want 1", s)
+	}
+	if s := InferScale(250, 64, 8, 8, 4, 1); s != 0 {
+		t.Errorf("non-divisible = %d, want 0", s)
+	}
+	if s := InferScale(256, 32, 8, 8, 4, 1); s != 0 {
+		t.Errorf("axis mismatch = %d, want 0", s)
+	}
+}
+
+func TestJSONShape(t *testing.T) {
+	s, _ := Scan(sheet4(), "test.png", 4, 4, 1, 0, 0)
+	var buf bytes.Buffer
+	if err := s.WriteJSON(&buf); err != nil {
+		t.Fatal(err)
+	}
+	var back Sheet
+	if err := json.Unmarshal(buf.Bytes(), &back); err != nil {
+		t.Fatalf("invalid json: %v", err)
+	}
+	if back.Frames[0].Box.W != 2 {
+		t.Errorf("json roundtrip box = %+v", back.Frames[0].Box)
+	}
+}

hitbox-tool/main.go

@@ -0,0 +1,204 @@
+// hitbox scans sprite sheet PNGs and writes per-frame collision boxes
+// as JSON, using the alpha channel to find each frame's solid pixels.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+
+	"gitea.brasse-pc.eu/brasse/agent-tools/hitbox-tool/hitbox"
+)
+
+var version = "dev"
+
+const usage = `hitbox - collision box annotator for sprite sheets
+
+Usage:
+  hitbox scan <sheet.png> [flags]     compute per-frame boxes -> JSON
+  hitbox show <sheet.png> [flags]     draw frames + boxes in the terminal
+  hitbox version
+
+Scan flags:
+  --cell <WxH>       frame size, e.g. 8x8. Default: parsed from the
+                     spritec naming convention <name>_<W>x<H>_<C>x<R>.png;
+                     if neither is given the whole image is one frame.
+  --threshold <n>    alpha 1-255 that counts as solid (default 1)
+  --shrink <n>       contract every box by n px per side (forgiving hits)
+  --pad <n>          expand every box by n px per side
+  -o <path>          write JSON here (default: stdout)
+
+Show flags: --cell, --threshold, plus
+  --frame <n>        only this frame index (default: all)
+
+Boxes are relative to each frame's top-left corner. Frame indices are
+row-major (index = row * cols + col), matching spritec sheets.
+In game code: hit if (px,py) inside (frameX + box.x, frameY + box.y,
+box.w, box.h).
+`
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Print(usage)
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "scan":
+		cmdScan(os.Args[2:])
+	case "show":
+		cmdShow(os.Args[2:])
+	case "version", "--version", "-v":
+		fmt.Println("hitbox", version)
+	case "help", "--help", "-h":
+		fmt.Print(usage)
+	default:
+		die("unknown command %q — run 'hitbox help'", os.Args[1])
+	}
+}
+
+// parseInterspersed lets flags appear before or after positional args.
+func parseInterspersed(fs *flag.FlagSet, args []string) {
+	var flags, pos []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if len(a) > 1 && a[0] == '-' {
+			flags = append(flags, a)
+			name := strings.TrimLeft(a, "-")
+			if !strings.Contains(name, "=") {
+				f := fs.Lookup(name)
+				isBool := false
+				if f != nil {
+					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
+						isBool = true
+					}
+				}
+				if !isBool && i+1 < len(args) {
+					i++
+					flags = append(flags, args[i])
+				}
+			}
+		} else {
+			pos = append(pos, a)
+		}
+	}
+	fs.Parse(append(flags, pos...))
+}
+
+// parseCell resolves the frame size from --cell, or from the spritec
+// naming convention (auto-detecting integer upscales: a sheet named
+// _8x8_4x1 that is 256x64 px was rendered at scale 8, so cells are 64x64).
+func parseCell(spec, path string, imgW, imgH int) (int, int, error) {
+	if spec != "" {
+		parts := strings.SplitN(strings.ToLower(spec), "x", 2)
+		if len(parts) == 2 {
+			w, err1 := strconv.Atoi(parts[0])
+			h, err2 := strconv.Atoi(parts[1])
+			if err1 == nil && err2 == nil && w > 0 && h > 0 {
+				return w, h, nil
+			}
+		}
+		return 0, 0, fmt.Errorf("--cell %q must look like 8x8", spec)
+	}
+	if w, h, cols, rows, ok := hitbox.LayoutFromName(path); ok {
+		if s := hitbox.InferScale(imgW, imgH, w, h, cols, rows); s > 1 {
+			fmt.Fprintf(os.Stderr, "hitbox: image is %dx the named layout — using %dx%d cells\n", s, w*s, h*s)
+			return w * s, h * s, nil
+		}
+		return w, h, nil
+	}
+	return 0, 0, nil // whole image = one frame
+}
+
+func cmdScan(args []string) {
+	fs := flag.NewFlagSet("scan", flag.ExitOnError)
+	cell := fs.String("cell", "", "frame size WxH")
+	threshold := fs.Int("threshold", 1, "solid alpha 1-255")
+	shrink := fs.Int("shrink", 0, "contract boxes n px per side")
+	pad := fs.Int("pad", 0, "expand boxes n px per side")
+	out := fs.String("o", "", "output JSON path (default stdout)")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("scan takes exactly one PNG file")
+	}
+	path := fs.Arg(0)
+	img, err := hitbox.LoadPNG(path)
+	if err != nil {
+		die("%v", err)
+	}
+	b := img.Bounds()
+	cw, ch, err := parseCell(*cell, path, b.Dx(), b.Dy())
+	if err != nil {
+		die("%v", err)
+	}
+	sheet, err := hitbox.Scan(img, path, cw, ch, *threshold, *shrink, *pad)
+	if err != nil {
+		die("%v", err)
+	}
+	if *out == "" {
+		if err := sheet.WriteJSON(os.Stdout); err != nil {
+			die("%v", err)
+		}
+		return
+	}
+	f, err := os.Create(*out)
+	if err != nil {
+		die("%v", err)
+	}
+	defer f.Close()
+	if err := sheet.WriteJSON(f); err != nil {
+		die("%v", err)
+	}
+	solid := 0
+	for _, fr := range sheet.Frames {
+		if !fr.Empty {
+			solid++
+		}
+	}
+	fmt.Printf("%s  (%d frames of %dx%d, %d with pixels)\n",
+		*out, len(sheet.Frames), sheet.CellW, sheet.CellH, solid)
+}
+
+func cmdShow(args []string) {
+	fs := flag.NewFlagSet("show", flag.ExitOnError)
+	cell := fs.String("cell", "", "frame size WxH")
+	threshold := fs.Int("threshold", 1, "solid alpha 1-255")
+	frame := fs.Int("frame", -1, "frame index (default: all)")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("show takes exactly one PNG file")
+	}
+	path := fs.Arg(0)
+	img, err := hitbox.LoadPNG(path)
+	if err != nil {
+		die("%v", err)
+	}
+	b := img.Bounds()
+	cw, ch, err := parseCell(*cell, path, b.Dx(), b.Dy())
+	if err != nil {
+		die("%v", err)
+	}
+	sheet, err := hitbox.Scan(img, path, cw, ch, *threshold, 0, 0)
+	if err != nil {
+		die("%v", err)
+	}
+	for _, fr := range sheet.Frames {
+		if *frame >= 0 && fr.Index != *frame {
+			continue
+		}
+		if fr.Empty {
+			fmt.Printf("frame %d (col %d, row %d): empty\n\n", fr.Index, fr.Col, fr.Row)
+			continue
+		}
+		fmt.Printf("frame %d (col %d, row %d): box x=%d y=%d w=%d h=%d\n",
+			fr.Index, fr.Col, fr.Row, fr.Box.X, fr.Box.Y, fr.Box.W, fr.Box.H)
+		fmt.Print(hitbox.Ascii(img, sheet, fr.Index, *threshold))
+		fmt.Println()
+	}
+}
+
+func die(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, "hitbox: "+format+"\n", a...)
+	os.Exit(1)
+}

mesh-tool/.gitignore

@@ -0,0 +1,2 @@
+build/
+examples/downloads/

mesh-tool/README.md

@@ -0,0 +1,101 @@
+# mesh-tool (`mesht`)
+
+Create, inspect and edit **3D models** from the command line — built so an
+agent can *see* a model (ASCII multi-view rendering + measurements),
+reason about it, and edit it step by step. Written in Go, zero
+dependencies, single static binary.
+
+## Formats
+
+| Format | Read | Write | Notes |
+|--------|------|-------|-------|
+| OBJ    | ✔    | ✔     | multiple named objects, quads/ngons triangulated |
+| STL    | ✔    | ✔     | binary + ASCII, auto-detected; vertices re-welded on load |
+
+OBJ and STL cover the vast majority of simple editing/printing/game
+pipelines and are plain enough to survive round-trips. glTF/GLB is out of
+scope for now (a full JSON+buffer+material model; use Blender for that).
+
+Normals, UVs and materials are ignored on read — this tool edits
+*geometry*. Viewers recompute normals; STL export writes correct face
+normals from the winding.
+
+## Build
+
+```bash
+# Arch/Garuda: sudo pacman -S go
+cd mesh-tool
+go build -o build/mesht .        # or the VS Code task "build mesh-tool"
+go test ./...
+```
+
+## Commands
+
+```bash
+mesht info model.obj           # verts/tris, bbox, size, area, volume, watertight?
+mesht view model.obj           # ASCII render: front, side, top (default)
+mesht view model.obj --views iso --width 100 --object wheel
+
+# creation — box|sphere|cylinder|cone|plane|torus
+mesht create box --size 2,1,1 --name crate -o crate.obj
+mesht create sphere --radius 1 --segments 32 --rings 16 -o ball.stl
+
+# editing (applied in the listed order)
+mesht transform m.obj --center                    # bbox center -> origin
+mesht transform m.obj --mirror x                  # winding auto-corrected
+mesht transform m.obj --scale 2                   # or --scale 1,2,1
+mesht transform m.obj --rotate 0,45,0             # degrees, X then Y then Z
+mesht transform m.obj --translate 0,2,0
+mesht transform m.obj --fit 10                    # largest dimension -> 10 units
+mesht transform m.obj --object wheel --scale 1.2 -o out.obj   # edit one part
+
+mesht merge body.obj wheels.obj -o car.obj        # keeps objects, renames dups
+mesht merge a.stl b.stl --flatten -o one.obj      # single combined object
+mesht convert model.obj -o model.stl              # --ascii for text STL
+```
+
+`-o` picks the output format from the extension. `transform` overwrites
+the input when `-o` is omitted.
+
+## Conventions
+
+- **Axes:** right-handed, **+Y up**, +X right, +Z toward the "front" viewer.
+- Primitives are centered on the origin.
+- Mirroring / negative scaling automatically flips triangle winding so
+  surfaces keep facing outward.
+- `info` reports **volume only for watertight meshes** — otherwise it
+  tells you how many boundary/non-manifold edges the mesh has.
+
+## How an agent should edit a model
+
+1. `mesht info m.obj` — learn size, orientation and object names.
+2. `mesht view m.obj` — see the shape (front/side/top; add `iso` for depth).
+3. Apply **one small transform**, write to a new file.
+4. `mesht view` again and compare — verify before continuing.
+
+The ASCII views are z-buffered orthographic renders; brightness = how
+much the surface faces the light over the viewer's shoulder, so shape
+and curvature read directly from the text. Each view header repeats the
+axis legend and model dimensions.
+
+Example (a 32-segment sphere, front view, width 48):
+
+```
+front view — X→right Y↑up (seen from +Z)
+model 2 x 2 x 2 (XYZ)
+           ==++**####%%%%%%%%%%%%###*
+        -==++**######%%%%%%%%%%%%%%####*
+      :-=+++**#######%%%%%%%%%%%%%%%%%%#**
+     -==++***#######%%%%%%%%%%%%%%%%%%%%##*
+  .:--+++***########%%%%%%%%%%%%%%%%%%%%%%##*+
+```
+
+## Viewing the results as a human
+
+Any of these (Arch/Garuda):
+
+```bash
+sudo pacman -S f3d        # fast minimal viewer:  f3d model.obj
+sudo pacman -S blender    # full editor
+flatpak install org.prusa3d.PrusaSlicer   # if you also want to print
+```

mesh-tool/go.mod

@@ -0,0 +1,3 @@
+module gitea.brasse-pc.eu/brasse/agent-tools/mesh-tool
+
+go 1.24

mesh-tool/main.go

@@ -0,0 +1,406 @@
+// mesht creates, inspects and edits 3D models (OBJ and STL) from the
+// command line, with ASCII multi-view rendering so agents can "see"
+// a model before and after editing it.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+
+	"gitea.brasse-pc.eu/brasse/agent-tools/mesh-tool/mesh"
+)
+
+var version = "dev"
+
+const usage = `mesht - 3D model tool for agents (OBJ + STL)
+
+Usage:
+  mesht info <file>                     stats: size, volume, watertightness
+  mesht view <file> [flags]             ASCII render from several angles
+  mesht create <primitive> [flags]      box|sphere|cylinder|cone|plane|torus
+  mesht transform <file> [flags]        scale/rotate/translate/mirror/center/fit
+  mesht merge <a> <b> ... -o <out>      combine several files into one
+  mesht convert <in> -o <out>           obj <-> stl
+  mesht version
+
+View flags:
+  --views front,side,top,iso,back       which views to draw (default front,side,top)
+  --width <n>                           characters per view (default 64)
+  --object <name>                       only draw one object from the file
+
+Create flags (always with -o <out.obj|out.stl>):
+  box:      --size x,y,z          (default 1,1,1)
+  sphere:   --radius r --segments n --rings n     (default 1, 24, 12)
+  cylinder: --radius r --height h --segments n    (default 0.5, 1, 24)
+  cone:     --radius r --height h --segments n    (default 0.5, 1, 24)
+  plane:    --size w,d            (default 1,1)
+  torus:    --radius R --tube r --segments n --rings n (default 1, 0.25, 24, 12)
+  --name <s>                      object name in the output
+
+Transform flags (applied in this order):
+  --center                 move bounding-box center to the origin
+  --mirror x|y|z           mirror across that axis' plane
+  --scale s | x,y,z        uniform or per-axis scale
+  --rotate x,y,z           degrees around X, then Y, then Z
+  --translate x,y,z        move
+  --fit n                  uniformly scale so the largest dimension = n
+  --object <name>          only transform the named object (obj files)
+  -o <out>                 output file (default: overwrite input)
+
+Common:
+  --ascii                  write text STL instead of binary
+  Formats are picked from file extensions (.obj, .stl).
+
+Axes: +Y is up, +X right, +Z toward the front viewer (right-handed).
+`
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Print(usage)
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "info":
+		cmdInfo(os.Args[2:])
+	case "view":
+		cmdView(os.Args[2:])
+	case "create":
+		cmdCreate(os.Args[2:])
+	case "transform":
+		cmdTransform(os.Args[2:])
+	case "merge":
+		cmdMerge(os.Args[2:])
+	case "convert":
+		cmdConvert(os.Args[2:])
+	case "version", "--version", "-v":
+		fmt.Println("mesht", version)
+	case "help", "--help", "-h":
+		fmt.Print(usage)
+	default:
+		die("unknown command %q — run 'mesht help'", os.Args[1])
+	}
+}
+
+// parseInterspersed lets flags appear before or after positional args.
+func parseInterspersed(fs *flag.FlagSet, args []string) {
+	var flags, pos []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if len(a) > 1 && a[0] == '-' {
+			flags = append(flags, a)
+			name := strings.TrimLeft(a, "-")
+			if !strings.Contains(name, "=") {
+				f := fs.Lookup(name)
+				isBool := false
+				if f != nil {
+					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
+						isBool = true
+					}
+				}
+				if !isBool && i+1 < len(args) {
+					i++
+					flags = append(flags, args[i])
+				}
+			}
+		} else {
+			pos = append(pos, a)
+		}
+	}
+	fs.Parse(append(flags, pos...))
+}
+
+func parseVec(s string, uniformOK bool) (mesh.Vec3, error) {
+	parts := strings.Split(s, ",")
+	switch len(parts) {
+	case 1:
+		if !uniformOK {
+			return mesh.Vec3{}, fmt.Errorf("%q: want x,y,z", s)
+		}
+		v, err := strconv.ParseFloat(strings.TrimSpace(parts[0]), 64)
+		return mesh.Vec3{X: v, Y: v, Z: v}, err
+	case 3:
+		var v [3]float64
+		for i, p := range parts {
+			f, err := strconv.ParseFloat(strings.TrimSpace(p), 64)
+			if err != nil {
+				return mesh.Vec3{}, fmt.Errorf("%q: bad number %q", s, p)
+			}
+			v[i] = f
+		}
+		return mesh.Vec3{X: v[0], Y: v[1], Z: v[2]}, nil
+	}
+	return mesh.Vec3{}, fmt.Errorf("%q: want one value or x,y,z", s)
+}
+
+func cmdInfo(args []string) {
+	if len(args) != 1 {
+		die("info takes exactly one file")
+	}
+	scene, err := mesh.ReadFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	merged := scene.Merged()
+	mn, mx := merged.BBox()
+	size := mx.Sub(mn)
+	center := mn.Add(size.Mul(0.5))
+	fmt.Printf("file:     %s\n", args[0])
+	fmt.Printf("objects:  %d\n", len(scene.Meshes))
+	fmt.Printf("verts:    %d\n", scene.TotalVerts())
+	fmt.Printf("tris:     %d\n", scene.TotalTris())
+	fmt.Printf("bbox min: (%.4g, %.4g, %.4g)\n", mn.X, mn.Y, mn.Z)
+	fmt.Printf("bbox max: (%.4g, %.4g, %.4g)\n", mx.X, mx.Y, mx.Z)
+	fmt.Printf("size:     %.4g x %.4g x %.4g (X Y Z)\n", size.X, size.Y, size.Z)
+	fmt.Printf("center:   (%.4g, %.4g, %.4g)\n", center.X, center.Y, center.Z)
+	fmt.Printf("area:     %.6g\n", merged.SurfaceArea())
+	if b, nm := merged.EdgeStats(); b == 0 && nm == 0 {
+		fmt.Printf("volume:   %.6g (closed mesh)\n", merged.Volume())
+	} else {
+		fmt.Printf("volume:   n/a (open mesh: %d boundary edges, %d non-manifold edges)\n", b, nm)
+	}
+	if len(scene.Meshes) > 1 {
+		fmt.Println("per object:")
+		for _, m := range scene.Meshes {
+			closed := "open"
+			if m.Closed() {
+				closed = "closed"
+			}
+			fmt.Printf("  %-24s %7d verts %7d tris  %s\n", m.Name, len(m.Verts), len(m.Tris), closed)
+		}
+	}
+}
+
+func cmdView(args []string) {
+	fs := flag.NewFlagSet("view", flag.ExitOnError)
+	views := fs.String("views", "front,side,top", "comma-separated view list")
+	width := fs.Int("width", 64, "characters per view")
+	object := fs.String("object", "", "only draw this object")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("view takes exactly one file")
+	}
+	scene, err := mesh.ReadFile(fs.Arg(0))
+	if err != nil {
+		die("%v", err)
+	}
+	m := scene.Merged()
+	if *object != "" {
+		if m = scene.Mesh(*object); m == nil {
+			die("no object named %q in %s (use 'mesht info' to list)", *object, fs.Arg(0))
+		}
+	}
+	for _, name := range strings.Split(*views, ",") {
+		name = strings.TrimSpace(strings.ToLower(name))
+		v, ok := mesh.Views[name]
+		if !ok {
+			die("unknown view %q (available: %s)", name, strings.Join(mesh.ViewOrder, ", "))
+		}
+		fmt.Println(mesh.RenderASCII(m, v, *width))
+	}
+}
+
+func cmdCreate(args []string) {
+	if len(args) < 1 {
+		die("create needs a primitive: box, sphere, cylinder, cone, plane, torus")
+	}
+	prim := args[0]
+	fs := flag.NewFlagSet("create", flag.ExitOnError)
+	size := fs.String("size", "1,1,1", "box/plane size")
+	radius := fs.Float64("radius", 0, "radius")
+	tube := fs.Float64("tube", 0.25, "torus tube radius")
+	height := fs.Float64("height", 1, "height")
+	segments := fs.Int("segments", 24, "segments around")
+	rings := fs.Int("rings", 12, "rings (sphere/torus)")
+	name := fs.String("name", "", "object name")
+	out := fs.String("o", "", "output file (.obj or .stl)")
+	ascii := fs.Bool("ascii", false, "write text STL")
+	parseInterspersed(fs, args[1:])
+	if *out == "" {
+		die("create needs -o <out.obj|out.stl>")
+	}
+	var m *mesh.Mesh
+	switch prim {
+	case "box":
+		sz, err := parseVec(*size, true)
+		if err != nil {
+			die("--size: %v", err)
+		}
+		m = mesh.Box(sz)
+	case "sphere":
+		m = mesh.Sphere(defRadius(*radius, 1), *segments, *rings)
+	case "cylinder":
+		m = mesh.Cylinder(defRadius(*radius, 0.5), *height, *segments)
+	case "cone":
+		m = mesh.Cone(defRadius(*radius, 0.5), *height, *segments)
+	case "plane":
+		sz, err := parseVec(*size, true)
+		if err != nil {
+			die("--size: %v", err)
+		}
+		m = mesh.Plane(sz.X, sz.Z)
+	case "torus":
+		m = mesh.Torus(defRadius(*radius, 1), *tube, *segments, *rings)
+	default:
+		die("unknown primitive %q", prim)
+	}
+	if *name != "" {
+		m.Name = *name
+	}
+	scene := &mesh.Scene{Meshes: []*mesh.Mesh{m}}
+	if err := mesh.WriteFile(*out, scene, *ascii); err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("%s  (%s: %d verts, %d tris)\n", *out, m.Name, len(m.Verts), len(m.Tris))
+}
+
+func defRadius(r, def float64) float64 {
+	if r <= 0 {
+		return def
+	}
+	return r
+}
+
+func cmdTransform(args []string) {
+	fs := flag.NewFlagSet("transform", flag.ExitOnError)
+	center := fs.Bool("center", false, "move bbox center to origin")
+	mirror := fs.String("mirror", "", "x|y|z")
+	scale := fs.String("scale", "", "s or x,y,z")
+	rotate := fs.String("rotate", "", "degrees x,y,z")
+	translate := fs.String("translate", "", "x,y,z")
+	fit := fs.Float64("fit", 0, "scale so the largest dimension equals this")
+	object := fs.String("object", "", "only transform this object")
+	out := fs.String("o", "", "output file (default: overwrite input)")
+	ascii := fs.Bool("ascii", false, "write text STL")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("transform takes exactly one file")
+	}
+	in := fs.Arg(0)
+	scene, err := mesh.ReadFile(in)
+	if err != nil {
+		die("%v", err)
+	}
+	targets := scene.Meshes
+	if *object != "" {
+		m := scene.Mesh(*object)
+		if m == nil {
+			die("no object named %q in %s (use 'mesht info' to list)", *object, in)
+		}
+		targets = []*mesh.Mesh{m}
+	}
+
+	if *center {
+		mn, mx := mesh.SceneBBox(targets)
+		c := mn.Add(mx.Sub(mn).Mul(0.5))
+		mesh.ApplyAll(targets, mesh.Translate(c.Mul(-1)))
+	}
+	if *mirror != "" {
+		s := mesh.Vec3{X: 1, Y: 1, Z: 1}
+		switch strings.ToLower(*mirror) {
+		case "x":
+			s.X = -1
+		case "y":
+			s.Y = -1
+		case "z":
+			s.Z = -1
+		default:
+			die("--mirror must be x, y or z")
+		}
+		mesh.ApplyAll(targets, mesh.ScaleXYZ(s))
+	}
+	if *scale != "" {
+		v, err := parseVec(*scale, true)
+		if err != nil {
+			die("--scale: %v", err)
+		}
+		mesh.ApplyAll(targets, mesh.ScaleXYZ(v))
+	}
+	if *rotate != "" {
+		v, err := parseVec(*rotate, false)
+		if err != nil {
+			die("--rotate: %v", err)
+		}
+		rot := mesh.RotateZ(v.Z).Mul(mesh.RotateY(v.Y)).Mul(mesh.RotateX(v.X))
+		mesh.ApplyAll(targets, rot)
+	}
+	if *translate != "" {
+		v, err := parseVec(*translate, false)
+		if err != nil {
+			die("--translate: %v", err)
+		}
+		mesh.ApplyAll(targets, mesh.Translate(v))
+	}
+	if *fit > 0 {
+		mn, mx := mesh.SceneBBox(targets)
+		size := mx.Sub(mn)
+		longest := math.Max(size.X, math.Max(size.Y, size.Z))
+		if longest > 0 {
+			f := *fit / longest
+			mesh.ApplyAll(targets, mesh.ScaleXYZ(mesh.Vec3{X: f, Y: f, Z: f}))
+		}
+	}
+
+	if *out == "" {
+		*out = in
+	}
+	if err := mesh.WriteFile(*out, scene, *ascii); err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("%s  (%d objects, %d verts, %d tris)\n", *out, len(scene.Meshes), scene.TotalVerts(), scene.TotalTris())
+}
+
+func cmdMerge(args []string) {
+	fs := flag.NewFlagSet("merge", flag.ExitOnError)
+	out := fs.String("o", "", "output file")
+	flatten := fs.Bool("flatten", false, "merge everything into a single object")
+	ascii := fs.Bool("ascii", false, "write text STL")
+	parseInterspersed(fs, args)
+	if fs.NArg() < 2 {
+		die("merge needs at least two input files")
+	}
+	if *out == "" {
+		die("merge needs -o <out>")
+	}
+	scene := &mesh.Scene{}
+	for _, path := range fs.Args() {
+		s, err := mesh.ReadFile(path)
+		if err != nil {
+			die("%v", err)
+		}
+		scene.Append(s)
+	}
+	if *flatten {
+		scene = &mesh.Scene{Meshes: []*mesh.Mesh{scene.Merged()}}
+	}
+	if err := mesh.WriteFile(*out, scene, *ascii); err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("%s  (%d objects, %d verts, %d tris)\n", *out, len(scene.Meshes), scene.TotalVerts(), scene.TotalTris())
+}
+
+func cmdConvert(args []string) {
+	fs := flag.NewFlagSet("convert", flag.ExitOnError)
+	out := fs.String("o", "", "output file")
+	ascii := fs.Bool("ascii", false, "write text STL")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 || *out == "" {
+		die("convert takes one input file and -o <out>")
+	}
+	scene, err := mesh.ReadFile(fs.Arg(0))
+	if err != nil {
+		die("%v", err)
+	}
+	if err := mesh.WriteFile(*out, scene, *ascii); err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("%s  (%d objects, %d verts, %d tris)\n", *out, len(scene.Meshes), scene.TotalVerts(), scene.TotalTris())
+}
+
+func die(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, "mesht: "+format+"\n", a...)
+	os.Exit(1)
+}

mesh-tool/mesh/ascii.go

@@ -0,0 +1,169 @@
+package mesh
+
+import (
+	"fmt"
+	"math"
+	"strings"
+)
+
+// View is an orthographic camera basis: Right/Up span the screen plane,
+// Toward points from the scene toward the viewer (bigger depth = closer).
+type View struct {
+	Name              string
+	Axes              string // human-readable axis legend
+	Right, Up, Toward Vec3
+}
+
+var Views = map[string]View{
+	"front": {"front", "X→right Y↑up (seen from +Z)", Vec3{1, 0, 0}, Vec3{0, 1, 0}, Vec3{0, 0, 1}},
+	"back":  {"back", "-X→right Y↑up (seen from -Z)", Vec3{-1, 0, 0}, Vec3{0, 1, 0}, Vec3{0, 0, -1}},
+	"side":  {"side", "-Z→right Y↑up (seen from +X)", Vec3{0, 0, -1}, Vec3{0, 1, 0}, Vec3{1, 0, 0}},
+	"top":   {"top", "X→right Z↓down-screen (seen from above, +Y)", Vec3{1, 0, 0}, Vec3{0, 0, -1}, Vec3{0, 1, 0}},
+	"iso": {"iso", "isometric from (+X +Y +Z)",
+		Vec3{1, 0, -1}.Norm(), Vec3{-1, 2, -1}.Norm(), Vec3{1, 1, 1}.Norm()},
+}
+
+// ViewOrder is the canonical ordering for multi-view output.
+var ViewOrder = []string{"front", "side", "top", "iso", "back"}
+
+const shadeRamp = " .:-=+*#%@"
+
+// charAspect compensates terminal cells being ~2x taller than wide.
+const charAspect = 0.5
+
+// RenderASCII draws the mesh from the given view into a text block of
+// the given character width. Triangles are z-buffer rasterized and
+// shaded by how much each face points toward the light (over the
+// viewer's shoulder), so curvature and depth read as brightness.
+func RenderASCII(m *Mesh, v View, width int) string {
+	if width < 8 {
+		width = 8
+	}
+	if len(m.Tris) == 0 {
+		return "(empty mesh)\n"
+	}
+
+	// project all vertices into view space
+	type pv struct{ x, y, z float64 }
+	pts := make([]pv, len(m.Verts))
+	minX, minY := math.Inf(1), math.Inf(1)
+	maxX, maxY := math.Inf(-1), math.Inf(-1)
+	for i, w := range m.Verts {
+		p := pv{w.Dot(v.Right), w.Dot(v.Up), w.Dot(v.Toward)}
+		pts[i] = p
+		minX, maxX = math.Min(minX, p.x), math.Max(maxX, p.x)
+		minY, maxY = math.Min(minY, p.y), math.Max(maxY, p.y)
+	}
+	spanX, spanY := maxX-minX, maxY-minY
+	if spanX == 0 {
+		spanX = 1e-9
+	}
+	if spanY == 0 {
+		spanY = 1e-9
+	}
+	height := int(float64(width) * (spanY / spanX) * charAspect)
+	if height < 1 {
+		height = 1
+	}
+	if height > 4*width {
+		height = 4 * width
+	}
+	sx := float64(width-1) / spanX
+	sy := float64(height-1) / spanY
+
+	depth := make([]float64, width*height)
+	for i := range depth {
+		depth[i] = math.Inf(-1)
+	}
+	shade := make([]float64, width*height)
+	for i := range shade {
+		shade[i] = -1
+	}
+
+	light := v.Toward.Mul(0.8).Add(v.Up.Mul(0.5)).Add(v.Right.Mul(0.3)).Norm()
+
+	for ti, t := range m.Tris {
+		n := m.FaceNormal(ti)
+		// abs: downloaded models often have mixed winding; treat both
+		// sides as lit so the silhouette never goes black
+		lum := 0.15 + 0.85*math.Abs(n.Dot(light))
+
+		a, b, c := pts[t[0]], pts[t[1]], pts[t[2]]
+		ax, ay := (a.x-minX)*sx, (maxY-a.y)*sy
+		bx, by := (b.x-minX)*sx, (maxY-b.y)*sy
+		cx, cy := (c.x-minX)*sx, (maxY-c.y)*sy
+
+		x0 := int(math.Floor(math.Min(ax, math.Min(bx, cx))))
+		x1 := int(math.Ceil(math.Max(ax, math.Max(bx, cx))))
+		y0 := int(math.Floor(math.Min(ay, math.Min(by, cy))))
+		y1 := int(math.Ceil(math.Max(ay, math.Max(by, cy))))
+		if x0 < 0 {
+			x0 = 0
+		}
+		if y0 < 0 {
+			y0 = 0
+		}
+		if x1 >= width {
+			x1 = width - 1
+		}
+		if y1 >= height {
+			y1 = height - 1
+		}
+
+		area := (bx-ax)*(cy-ay) - (by-ay)*(cx-ax)
+		if area == 0 {
+			continue
+		}
+		for py := y0; py <= y1; py++ {
+			for px := x0; px <= x1; px++ {
+				fx, fy := float64(px), float64(py)
+				w0 := (bx-ax)*(fy-ay) - (by-ay)*(fx-ax)
+				w1 := (cx-bx)*(fy-by) - (cy-by)*(fx-bx)
+				w2 := (ax-cx)*(fy-cy) - (ay-cy)*(fx-cx)
+				if !sameSide(w0, w1, w2, area) {
+					continue
+				}
+				// barycentric depth: w2 tracks b, w0 tracks c
+				l1 := w2 / area
+				l2 := w0 / area
+				l0 := 1 - l1 - l2
+				z := l0*a.z + l1*b.z + l2*c.z
+				idx := py*width + px
+				if z > depth[idx] {
+					depth[idx] = z
+					shade[idx] = lum
+				}
+			}
+		}
+	}
+
+	var sb strings.Builder
+	mn, mx := m.BBox()
+	size := mx.Sub(mn)
+	fmt.Fprintf(&sb, "%s view — %s\nmodel %.3g x %.3g x %.3g (XYZ)\n",
+		v.Name, v.Axes, size.X, size.Y, size.Z)
+	ramp := []rune(shadeRamp)
+	for py := 0; py < height; py++ {
+		for px := 0; px < width; px++ {
+			s := shade[py*width+px]
+			if s < 0 {
+				sb.WriteByte(' ')
+				continue
+			}
+			i := int(s * float64(len(ramp)-1))
+			if i >= len(ramp) {
+				i = len(ramp) - 1
+			}
+			sb.WriteRune(ramp[i])
+		}
+		sb.WriteByte('\n')
+	}
+	return sb.String()
+}
+
+func sameSide(w0, w1, w2, area float64) bool {
+	if area > 0 {
+		return w0 >= 0 && w1 >= 0 && w2 >= 0
+	}
+	return w0 <= 0 && w1 <= 0 && w2 <= 0
+}

mesh-tool/mesh/measure.go

@@ -0,0 +1,59 @@
+package mesh
+
+import "math"
+
+// BBox returns the axis-aligned bounding box of the mesh.
+func (m *Mesh) BBox() (min, max Vec3) {
+	if len(m.Verts) == 0 {
+		return Vec3{}, Vec3{}
+	}
+	min, max = m.Verts[0], m.Verts[0]
+	for _, v := range m.Verts[1:] {
+		min = min.Min(v)
+		max = max.Max(v)
+	}
+	return
+}
+
+// SurfaceArea sums the area of all triangles.
+func (m *Mesh) SurfaceArea() float64 {
+	sum := 0.0
+	for _, t := range m.Tris {
+		a, b, c := m.Verts[t[0]], m.Verts[t[1]], m.Verts[t[2]]
+		sum += b.Sub(a).Cross(c.Sub(a)).Len() / 2
+	}
+	return sum
+}
+
+// SignedVolume computes the enclosed volume via the divergence theorem.
+// Only meaningful for closed meshes; positive when windings face outward.
+func (m *Mesh) SignedVolume() float64 {
+	sum := 0.0
+	for _, t := range m.Tris {
+		a, b, c := m.Verts[t[0]], m.Verts[t[1]], m.Verts[t[2]]
+		sum += a.Dot(b.Cross(c))
+	}
+	return sum / 6
+}
+
+// Volume is the absolute enclosed volume.
+func (m *Mesh) Volume() float64 { return math.Abs(m.SignedVolume()) }
+
+// SceneBBox returns the bounding box over the given meshes.
+func SceneBBox(meshes []*Mesh) (min, max Vec3) {
+	first := true
+	for _, m := range meshes {
+		if len(m.Verts) == 0 {
+			continue
+		}
+		mn, mx := m.BBox()
+		if first {
+			min, max = mn, mx
+			first = false
+		} else {
+			min = min.Min(mn)
+			max = max.Max(mx)
+		}
+	}
+	return
+}

mesh-tool/mesh/mesh.go

@@ -0,0 +1,129 @@
+package mesh
+
+import "fmt"
+
+// Triangle indexes three vertices, counter-clockwise seen from outside.
+type Triangle [3]int
+
+// Mesh is one named object: a triangle soup over a shared vertex list.
+type Mesh struct {
+	Name  string
+	Verts []Vec3
+	Tris  []Triangle
+}
+
+// Scene is an ordered list of meshes, matching OBJ objects. STL files
+// load as a single-mesh scene.
+type Scene struct {
+	Meshes []*Mesh
+}
+
+func (s *Scene) TotalVerts() int {
+	n := 0
+	for _, m := range s.Meshes {
+		n += len(m.Verts)
+	}
+	return n
+}
+
+func (s *Scene) TotalTris() int {
+	n := 0
+	for _, m := range s.Meshes {
+		n += len(m.Tris)
+	}
+	return n
+}
+
+// Mesh returns the named mesh, or nil.
+func (s *Scene) Mesh(name string) *Mesh {
+	for _, m := range s.Meshes {
+		if m.Name == name {
+			return m
+		}
+	}
+	return nil
+}
+
+// Merged flattens the scene into a single mesh (copies data).
+func (s *Scene) Merged() *Mesh {
+	out := &Mesh{Name: "merged"}
+	for _, m := range s.Meshes {
+		off := len(out.Verts)
+		out.Verts = append(out.Verts, m.Verts...)
+		for _, t := range m.Tris {
+			out.Tris = append(out.Tris, Triangle{t[0] + off, t[1] + off, t[2] + off})
+		}
+	}
+	if len(s.Meshes) == 1 {
+		out.Name = s.Meshes[0].Name
+	}
+	return out
+}
+
+// Append adds meshes from another scene, de-duplicating names by
+// appending _2, _3, ...
+func (s *Scene) Append(other *Scene) {
+	taken := map[string]bool{}
+	for _, m := range s.Meshes {
+		taken[m.Name] = true
+	}
+	for _, m := range other.Meshes {
+		name := m.Name
+		for i := 2; taken[name]; i++ {
+			name = fmt.Sprintf("%s_%d", m.Name, i)
+		}
+		m.Name = name
+		taken[name] = true
+		s.Meshes = append(s.Meshes, m)
+	}
+}
+
+// FaceNormal returns the (unit) normal of triangle i.
+func (m *Mesh) FaceNormal(i int) Vec3 {
+	t := m.Tris[i]
+	a, b, c := m.Verts[t[0]], m.Verts[t[1]], m.Verts[t[2]]
+	return b.Sub(a).Cross(c.Sub(a)).Norm()
+}
+
+// FlipWinding reverses the orientation of every triangle.
+func (m *Mesh) FlipWinding() {
+	for i, t := range m.Tris {
+		m.Tris[i] = Triangle{t[0], t[2], t[1]}
+	}
+}
+
+type edge struct{ a, b int }
+
+func normEdge(a, b int) edge {
+	if a > b {
+		a, b = b, a
+	}
+	return edge{a, b}
+}
+
+// EdgeStats classifies the mesh topology: boundary edges belong to one
+// triangle, manifold edges to two, anything more is non-manifold. A
+// closed (watertight) mesh has zero boundary and zero non-manifold edges.
+func (m *Mesh) EdgeStats() (boundary, nonManifold int) {
+	count := map[edge]int{}
+	for _, t := range m.Tris {
+		count[normEdge(t[0], t[1])]++
+		count[normEdge(t[1], t[2])]++
+		count[normEdge(t[2], t[0])]++
+	}
+	for _, n := range count {
+		switch {
+		case n == 1:
+			boundary++
+		case n > 2:
+			nonManifold++
+		}
+	}
+	return
+}
+
+// Closed reports whether the mesh is watertight.
+func (m *Mesh) Closed() bool {
+	b, nm := m.EdgeStats()
+	return b == 0 && nm == 0
+}

mesh-tool/mesh/mesh_test.go

@@ -0,0 +1,184 @@
+package mesh
+
+import (
+	"bytes"
+	"math"
+	"strings"
+	"testing"
+)
+
+func almost(t *testing.T, name string, got, want, tol float64) {
+	t.Helper()
+	if math.Abs(got-want) > tol {
+		t.Errorf("%s = %g, want %g (±%g)", name, got, want, tol)
+	}
+}
+
+func TestPrimitiveVolumes(t *testing.T) {
+	box := Box(Vec3{1, 2, 3})
+	almost(t, "box volume", box.SignedVolume(), 6, 1e-9)
+	almost(t, "box area", box.SurfaceArea(), 22, 1e-9)
+	if !box.Closed() {
+		t.Error("box should be watertight")
+	}
+
+	sph := Sphere(1, 64, 32)
+	almost(t, "sphere volume", sph.SignedVolume(), 4*math.Pi/3, 0.07)
+	almost(t, "sphere area", sph.SurfaceArea(), 4*math.Pi, 0.15)
+	if !sph.Closed() {
+		t.Error("sphere should be watertight")
+	}
+
+	cyl := Cylinder(0.5, 2, 64)
+	almost(t, "cylinder volume", cyl.SignedVolume(), math.Pi*0.25*2, 0.01)
+	if !cyl.Closed() {
+		t.Error("cylinder should be watertight")
+	}
+
+	cone := Cone(1, 3, 64)
+	almost(t, "cone volume", cone.SignedVolume(), math.Pi/3*3, 0.02)
+	if !cone.Closed() {
+		t.Error("cone should be watertight")
+	}
+
+	tor := Torus(2, 0.5, 64, 32)
+	almost(t, "torus volume", tor.SignedVolume(), 2*math.Pi*math.Pi*2*0.25, 0.25)
+	if !tor.Closed() {
+		t.Error("torus should be watertight")
+	}
+}
+
+func TestBBoxAndMeasure(t *testing.T) {
+	box := Box(Vec3{2, 4, 6})
+	mn, mx := box.BBox()
+	if mn != (Vec3{-1, -2, -3}) || mx != (Vec3{1, 2, 3}) {
+		t.Errorf("bbox = %v..%v", mn, mx)
+	}
+}
+
+func TestTransformMirrorKeepsVolumePositive(t *testing.T) {
+	box := Box(Vec3{1, 1, 1})
+	box.Apply(ScaleXYZ(Vec3{-1, 1, 1}))
+	almost(t, "mirrored box volume", box.SignedVolume(), 1, 1e-9)
+	box.Apply(RotateY(45).Mul(RotateX(30)))
+	almost(t, "rotated box volume", box.SignedVolume(), 1, 1e-9)
+	box.Apply(Translate(Vec3{10, -5, 3}))
+	almost(t, "translated box volume", box.SignedVolume(), 1, 1e-6)
+}
+
+func TestOBJRoundTrip(t *testing.T) {
+	scene := &Scene{Meshes: []*Mesh{Box(Vec3{1, 2, 3}), Sphere(1, 8, 4)}}
+	scene.Meshes[0].Name = "crate"
+	scene.Meshes[1].Name = "ball"
+	var buf bytes.Buffer
+	if err := WriteOBJ(&buf, scene); err != nil {
+		t.Fatal(err)
+	}
+	back, err := ReadOBJ(&buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(back.Meshes) != 2 {
+		t.Fatalf("got %d meshes, want 2", len(back.Meshes))
+	}
+	if back.Meshes[0].Name != "crate" || back.Meshes[1].Name != "ball" {
+		t.Errorf("names = %q, %q", back.Meshes[0].Name, back.Meshes[1].Name)
+	}
+	almost(t, "roundtrip crate volume", back.Meshes[0].SignedVolume(), 6, 1e-9)
+	if !back.Meshes[1].Closed() {
+		t.Error("roundtripped sphere should stay watertight")
+	}
+}
+
+func TestOBJQuadsAndNegativeIndices(t *testing.T) {
+	src := `
+v 0 0 0
+v 1 0 0
+v 1 1 0
+v 0 1 0
+f 1 2 3 4
+f -4 -3 -2
+`
+	s, err := ReadOBJ(strings.NewReader(src))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := s.TotalTris(); got != 3 {
+		t.Errorf("tris = %d, want 3 (quad fan + one negative-index tri)", got)
+	}
+}
+
+func TestSTLRoundTrips(t *testing.T) {
+	box := Box(Vec3{1, 2, 3})
+	scene := &Scene{Meshes: []*Mesh{box}}
+
+	var bin bytes.Buffer
+	if err := WriteSTLBinary(&bin, scene); err != nil {
+		t.Fatal(err)
+	}
+	back, err := ReadSTL(bytes.NewReader(bin.Bytes()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	m := back.Meshes[0]
+	if len(m.Verts) != 8 {
+		t.Errorf("binary stl weld: %d verts, want 8", len(m.Verts))
+	}
+	almost(t, "binary stl volume", m.SignedVolume(), 6, 1e-6)
+
+	var asc bytes.Buffer
+	if err := WriteSTLAscii(&asc, scene); err != nil {
+		t.Fatal(err)
+	}
+	back2, err := ReadSTL(bytes.NewReader(asc.Bytes()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	almost(t, "ascii stl volume", back2.Meshes[0].SignedVolume(), 6, 1e-6)
+	if !back2.Meshes[0].Closed() {
+		t.Error("ascii stl roundtrip should stay watertight")
+	}
+}
+
+func TestSceneAppendRenames(t *testing.T) {
+	a := &Scene{Meshes: []*Mesh{Box(Vec3{1, 1, 1})}}
+	b := &Scene{Meshes: []*Mesh{Box(Vec3{2, 2, 2})}}
+	a.Append(b)
+	if a.Meshes[0].Name == a.Meshes[1].Name {
+		t.Errorf("duplicate names after append: %q", a.Meshes[0].Name)
+	}
+}
+
+func TestRenderASCII(t *testing.T) {
+	sph := Sphere(1, 32, 16)
+	out := RenderASCII(sph, Views["front"], 40)
+	if !strings.Contains(out, "front view") {
+		t.Errorf("missing header:\n%s", out)
+	}
+	ink := 0
+	for _, r := range out {
+		if strings.ContainsRune(shadeRamp[1:], r) {
+			ink++
+		}
+	}
+	if ink < 100 {
+		t.Errorf("sphere render suspiciously empty (%d shaded cells):\n%s", ink, out)
+	}
+	// a sphere should be roughly as tall as wide after aspect correction
+	lines := strings.Split(strings.TrimRight(out, "\n"), "\n")
+	rows := len(lines) - 2 // minus the two header lines
+	if rows < 15 || rows > 25 {
+		t.Errorf("40-wide sphere should be ~20 rows, got %d", rows)
+	}
+}
+
+func TestEdgeStatsOpenMesh(t *testing.T) {
+	p := Plane(1, 1)
+	if p.Closed() {
+		t.Error("plane must not be watertight")
+	}
+	b, nm := p.EdgeStats()
+	if b != 4 || nm != 0 {
+		t.Errorf("plane edge stats = %d boundary, %d non-manifold; want 4, 0", b, nm)
+	}
+}

mesh-tool/mesh/obj.go

@@ -0,0 +1,203 @@
+package mesh
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// ReadOBJ parses a Wavefront OBJ file. Vertices (v), objects/groups
+// (o/g) and faces (f) are honored; polygons are fan-triangulated;
+// normals, texture coords and materials are ignored (they are
+// recomputed or irrelevant for geometry editing).
+func ReadOBJ(r io.Reader) (*Scene, error) {
+	var verts []Vec3
+	type objFaces struct {
+		name string
+		tris []Triangle // indices into the global vert list
+	}
+	objs := []*objFaces{}
+	current := func() *objFaces {
+		if len(objs) == 0 {
+			objs = append(objs, &objFaces{name: "default"})
+		}
+		return objs[len(objs)-1]
+	}
+
+	sc := bufio.NewScanner(r)
+	sc.Buffer(make([]byte, 0, 64*1024), 16*1024*1024)
+	lineNo := 0
+	for sc.Scan() {
+		lineNo++
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		fields := strings.Fields(line)
+		switch fields[0] {
+		case "v":
+			if len(fields) < 4 {
+				return nil, fmt.Errorf("obj line %d: vertex needs x y z", lineNo)
+			}
+			var v Vec3
+			var err error
+			if v.X, err = strconv.ParseFloat(fields[1], 64); err == nil {
+				if v.Y, err = strconv.ParseFloat(fields[2], 64); err == nil {
+					v.Z, err = strconv.ParseFloat(fields[3], 64)
+				}
+			}
+			if err != nil {
+				return nil, fmt.Errorf("obj line %d: bad vertex: %v", lineNo, err)
+			}
+			verts = append(verts, v)
+		case "o", "g":
+			name := "unnamed"
+			if len(fields) > 1 {
+				name = strings.Join(fields[1:], " ")
+			}
+			// only open a new object if the current one has faces
+			if len(objs) > 0 && len(objs[len(objs)-1].tris) == 0 {
+				objs[len(objs)-1].name = name
+			} else {
+				objs = append(objs, &objFaces{name: name})
+			}
+		case "f":
+			if len(fields) < 4 {
+				return nil, fmt.Errorf("obj line %d: face needs at least 3 vertices", lineNo)
+			}
+			idx := make([]int, 0, len(fields)-1)
+			for _, f := range fields[1:] {
+				// "v", "v/vt", "v//vn", "v/vt/vn" — we only need v
+				vs := strings.SplitN(f, "/", 2)[0]
+				i, err := strconv.Atoi(vs)
+				if err != nil {
+					return nil, fmt.Errorf("obj line %d: bad face index %q", lineNo, f)
+				}
+				if i < 0 {
+					i = len(verts) + i // negative = relative to current count
+				} else {
+					i-- // obj is 1-based
+				}
+				if i < 0 || i >= len(verts) {
+					return nil, fmt.Errorf("obj line %d: face index %q out of range (have %d vertices)", lineNo, f, len(verts))
+				}
+				idx = append(idx, i)
+			}
+			o := current()
+			for k := 1; k+1 < len(idx); k++ { // fan triangulation
+				o.tris = append(o.tris, Triangle{idx[0], idx[k], idx[k+1]})
+			}
+		}
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+
+	// Compact the global vertex list into per-mesh local lists.
+	scene := &Scene{}
+	for _, o := range objs {
+		if len(o.tris) == 0 {
+			continue
+		}
+		m := &Mesh{Name: o.name}
+		remap := map[int]int{}
+		for _, t := range o.tris {
+			var lt Triangle
+			for k, gi := range t {
+				li, ok := remap[gi]
+				if !ok {
+					li = len(m.Verts)
+					m.Verts = append(m.Verts, verts[gi])
+					remap[gi] = li
+				}
+				lt[k] = li
+			}
+			m.Tris = append(m.Tris, lt)
+		}
+		scene.Meshes = append(scene.Meshes, m)
+	}
+	if len(scene.Meshes) == 0 {
+		return nil, fmt.Errorf("obj contains no faces")
+	}
+	return scene, nil
+}
+
+// WriteOBJ writes the scene as OBJ, one "o" object per mesh.
+func WriteOBJ(w io.Writer, s *Scene) error {
+	bw := bufio.NewWriter(w)
+	fmt.Fprintln(bw, "# exported by mesht (agent-tools)")
+	offset := 1 // obj indices are global and 1-based
+	for _, m := range s.Meshes {
+		fmt.Fprintf(bw, "o %s\n", m.Name)
+		for _, v := range m.Verts {
+			fmt.Fprintf(bw, "v %g %g %g\n", v.X, v.Y, v.Z)
+		}
+		for _, t := range m.Tris {
+			fmt.Fprintf(bw, "f %d %d %d\n", t[0]+offset, t[1]+offset, t[2]+offset)
+		}
+		offset += len(m.Verts)
+	}
+	return bw.Flush()
+}
+
+// ReadFile loads a scene, picking the format from the file extension
+// (.obj, .stl).
+func ReadFile(path string) (*Scene, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	switch ext(path) {
+	case "obj":
+		s, err := ReadOBJ(f)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", path, err)
+		}
+		return s, nil
+	case "stl":
+		s, err := ReadSTL(f)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", path, err)
+		}
+		return s, nil
+	}
+	return nil, fmt.Errorf("%s: unsupported format (use .obj or .stl)", path)
+}
+
+// WriteFile saves a scene, picking the format from the file extension.
+// asciiSTL selects text STL instead of the default binary.
+func WriteFile(path string, s *Scene, asciiSTL bool) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	switch ext(path) {
+	case "obj":
+		err = WriteOBJ(f, s)
+	case "stl":
+		if asciiSTL {
+			err = WriteSTLAscii(f, s)
+		} else {
+			err = WriteSTLBinary(f, s)
+		}
+	default:
+		err = fmt.Errorf("unsupported output format (use .obj or .stl)")
+	}
+	if err != nil {
+		return fmt.Errorf("%s: %w", path, err)
+	}
+	return f.Close()
+}
+
+func ext(path string) string {
+	i := strings.LastIndex(path, ".")
+	if i < 0 {
+		return ""
+	}
+	return strings.ToLower(path[i+1:])
+}

mesh-tool/mesh/primitives.go

@@ -0,0 +1,179 @@
+package mesh
+
+import "math"
+
+// All primitives are centered at the origin with +Y up and get outward
+// (counter-clockwise) winding; ensureOutward fixes the global
+// orientation via the signed volume as a safety net.
+
+func ensureOutward(m *Mesh) *Mesh {
+	if m.SignedVolume() < 0 {
+		m.FlipWinding()
+	}
+	return m
+}
+
+// Box builds an axis-aligned box of the given size.
+func Box(size Vec3) *Mesh {
+	x, y, z := size.X/2, size.Y/2, size.Z/2
+	m := &Mesh{
+		Name: "box",
+		Verts: []Vec3{
+			{-x, -y, -z}, {x, -y, -z}, {x, y, -z}, {-x, y, -z}, // back  (z-)
+			{-x, -y, z}, {x, -y, z}, {x, y, z}, {-x, y, z}, // front (z+)
+		},
+	}
+	quads := [][4]int{
+		{0, 3, 2, 1}, // back
+		{4, 5, 6, 7}, // front
+		{0, 1, 5, 4}, // bottom
+		{2, 3, 7, 6}, // top
+		{1, 2, 6, 5}, // right
+		{0, 4, 7, 3}, // left
+	}
+	for _, q := range quads {
+		m.Tris = append(m.Tris, Triangle{q[0], q[1], q[2]}, Triangle{q[0], q[2], q[3]})
+	}
+	return ensureOutward(m)
+}
+
+// Plane builds a flat rectangle in the XZ plane (an open mesh).
+func Plane(w, d float64) *Mesh {
+	x, z := w/2, d/2
+	return &Mesh{
+		Name:  "plane",
+		Verts: []Vec3{{-x, 0, -z}, {x, 0, -z}, {x, 0, z}, {-x, 0, z}},
+		Tris:  []Triangle{{0, 2, 1}, {0, 3, 2}}, // +Y facing
+	}
+}
+
+// Sphere builds a UV sphere. segments = around the equator (>= 3),
+// rings = from pole to pole (>= 2).
+func Sphere(r float64, segments, rings int) *Mesh {
+	if segments < 3 {
+		segments = 3
+	}
+	if rings < 2 {
+		rings = 2
+	}
+	m := &Mesh{Name: "sphere"}
+	top := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, r, 0})
+	// interior rings, top to bottom
+	ringStart := make([]int, rings)
+	for i := 1; i < rings; i++ {
+		theta := math.Pi * float64(i) / float64(rings)
+		y := r * math.Cos(theta)
+		rad := r * math.Sin(theta)
+		ringStart[i] = len(m.Verts)
+		for j := 0; j < segments; j++ {
+			phi := 2 * math.Pi * float64(j) / float64(segments)
+			m.Verts = append(m.Verts, Vec3{rad * math.Cos(phi), y, rad * math.Sin(phi)})
+		}
+	}
+	bottom := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, -r, 0})
+
+	at := func(ring, seg int) int { return ringStart[ring] + seg%segments }
+	for j := 0; j < segments; j++ {
+		m.Tris = append(m.Tris, Triangle{top, at(1, j), at(1, j+1)}) // top cap
+		m.Tris = append(m.Tris, Triangle{bottom, at(rings-1, j+1), at(rings-1, j)})
+	}
+	for i := 1; i < rings-1; i++ {
+		for j := 0; j < segments; j++ {
+			a, b := at(i, j), at(i, j+1)
+			c, d := at(i+1, j+1), at(i+1, j)
+			m.Tris = append(m.Tris, Triangle{a, b, c}, Triangle{a, c, d})
+		}
+	}
+	return ensureOutward(m)
+}
+
+// Cylinder builds a closed cylinder of height h around the Y axis.
+func Cylinder(r, h float64, segments int) *Mesh {
+	if segments < 3 {
+		segments = 3
+	}
+	m := &Mesh{Name: "cylinder"}
+	y := h / 2
+	topC := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, y, 0})
+	botC := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, -y, 0})
+	topStart := len(m.Verts)
+	for j := 0; j < segments; j++ {
+		phi := 2 * math.Pi * float64(j) / float64(segments)
+		m.Verts = append(m.Verts, Vec3{r * math.Cos(phi), y, r * math.Sin(phi)})
+	}
+	botStart := len(m.Verts)
+	for j := 0; j < segments; j++ {
+		phi := 2 * math.Pi * float64(j) / float64(segments)
+		m.Verts = append(m.Verts, Vec3{r * math.Cos(phi), -y, r * math.Sin(phi)})
+	}
+	t := func(j int) int { return topStart + j%segments }
+	b := func(j int) int { return botStart + j%segments }
+	for j := 0; j < segments; j++ {
+		m.Tris = append(m.Tris,
+			Triangle{topC, t(j + 1), t(j)},     // top cap
+			Triangle{botC, b(j), b(j + 1)},     // bottom cap
+			Triangle{t(j), t(j + 1), b(j + 1)}, // side
+			Triangle{t(j), b(j + 1), b(j)},     // side
+		)
+	}
+	return ensureOutward(m)
+}
+
+// Cone builds a closed cone with its base at -h/2 and apex at +h/2.
+func Cone(r, h float64, segments int) *Mesh {
+	if segments < 3 {
+		segments = 3
+	}
+	m := &Mesh{Name: "cone"}
+	apex := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, h / 2, 0})
+	baseC := len(m.Verts)
+	m.Verts = append(m.Verts, Vec3{0, -h / 2, 0})
+	start := len(m.Verts)
+	for j := 0; j < segments; j++ {
+		phi := 2 * math.Pi * float64(j) / float64(segments)
+		m.Verts = append(m.Verts, Vec3{r * math.Cos(phi), -h / 2, r * math.Sin(phi)})
+	}
+	at := func(j int) int { return start + j%segments }
+	for j := 0; j < segments; j++ {
+		m.Tris = append(m.Tris,
+			Triangle{apex, at(j + 1), at(j)},
+			Triangle{baseC, at(j), at(j + 1)},
+		)
+	}
+	return ensureOutward(m)
+}
+
+// Torus builds a torus around the Y axis: ring radius R (center of tube
+// to center of torus) and tube radius r.
+func Torus(R, r float64, segments, rings int) *Mesh {
+	if segments < 3 {
+		segments = 3
+	}
+	if rings < 3 {
+		rings = 3
+	}
+	m := &Mesh{Name: "torus"}
+	for i := 0; i < segments; i++ { // around the main ring
+		phi := 2 * math.Pi * float64(i) / float64(segments)
+		cx, cz := math.Cos(phi), math.Sin(phi)
+		for j := 0; j < rings; j++ { // around the tube
+			theta := 2 * math.Pi * float64(j) / float64(rings)
+			rad := R + r*math.Cos(theta)
+			m.Verts = append(m.Verts, Vec3{rad * cx, r * math.Sin(theta), rad * cz})
+		}
+	}
+	at := func(i, j int) int { return (i%segments)*rings + j%rings }
+	for i := 0; i < segments; i++ {
+		for j := 0; j < rings; j++ {
+			a, b := at(i, j), at(i+1, j)
+			c, d := at(i+1, j+1), at(i, j+1)
+			m.Tris = append(m.Tris, Triangle{a, b, c}, Triangle{a, c, d})
+		}
+	}
+	return ensureOutward(m)
+}

mesh-tool/mesh/stl.go

@@ -0,0 +1,182 @@
+package mesh
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"math"
+	"strconv"
+	"strings"
+)
+
+// ReadSTL reads binary or ASCII STL (auto-detected). STL stores loose
+// triangles, so identical vertices are welded back together to recover
+// connectivity (needed for watertight checks and sane OBJ export).
+func ReadSTL(r io.Reader) (*Scene, error) {
+	data, err := io.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	if len(data) >= 84 {
+		n := binary.LittleEndian.Uint32(data[80:84])
+		if int(84+50*n) == len(data) {
+			return readSTLBinary(data)
+		}
+	}
+	if bytes.HasPrefix(bytes.TrimLeft(data, " \t\r\n"), []byte("solid")) {
+		return readSTLAscii(data)
+	}
+	return nil, fmt.Errorf("not a valid STL file (neither binary layout nor 'solid ...' text)")
+}
+
+type welder struct {
+	mesh  *Mesh
+	index map[Vec3]int
+}
+
+func newWelder(name string) *welder {
+	return &welder{mesh: &Mesh{Name: name}, index: map[Vec3]int{}}
+}
+
+func (w *welder) add(a, b, c Vec3) {
+	var t Triangle
+	for i, v := range [3]Vec3{a, b, c} {
+		idx, ok := w.index[v]
+		if !ok {
+			idx = len(w.mesh.Verts)
+			w.mesh.Verts = append(w.mesh.Verts, v)
+			w.index[v] = idx
+		}
+		t[i] = idx
+	}
+	if t[0] == t[1] || t[1] == t[2] || t[2] == t[0] {
+		return // degenerate
+	}
+	w.mesh.Tris = append(w.mesh.Tris, t)
+}
+
+func readSTLBinary(data []byte) (*Scene, error) {
+	n := int(binary.LittleEndian.Uint32(data[80:84]))
+	w := newWelder("stl")
+	off := 84
+	f32 := func(o int) float64 {
+		return float64(math.Float32frombits(binary.LittleEndian.Uint32(data[o : o+4])))
+	}
+	for i := 0; i < n; i++ {
+		// 12 bytes normal (ignored), 3 * 12 bytes vertices, 2 bytes attrs
+		var v [3]Vec3
+		for k := 0; k < 3; k++ {
+			base := off + 12 + k*12
+			v[k] = Vec3{f32(base), f32(base + 4), f32(base + 8)}
+		}
+		w.add(v[0], v[1], v[2])
+		off += 50
+	}
+	return &Scene{Meshes: []*Mesh{w.mesh}}, nil
+}
+
+func readSTLAscii(data []byte) (*Scene, error) {
+	name := "stl"
+	w := newWelder(name)
+	var cur []Vec3
+	sc := bufio.NewScanner(bytes.NewReader(data))
+	sc.Buffer(make([]byte, 0, 64*1024), 16*1024*1024)
+	lineNo := 0
+	for sc.Scan() {
+		lineNo++
+		fields := strings.Fields(sc.Text())
+		if len(fields) == 0 {
+			continue
+		}
+		switch fields[0] {
+		case "solid":
+			if len(fields) > 1 {
+				w.mesh.Name = fields[1]
+			}
+		case "vertex":
+			if len(fields) < 4 {
+				return nil, fmt.Errorf("stl line %d: vertex needs x y z", lineNo)
+			}
+			var v Vec3
+			var err error
+			if v.X, err = strconv.ParseFloat(fields[1], 64); err == nil {
+				if v.Y, err = strconv.ParseFloat(fields[2], 64); err == nil {
+					v.Z, err = strconv.ParseFloat(fields[3], 64)
+				}
+			}
+			if err != nil {
+				return nil, fmt.Errorf("stl line %d: bad vertex: %v", lineNo, err)
+			}
+			cur = append(cur, v)
+		case "endfacet":
+			if len(cur) != 3 {
+				return nil, fmt.Errorf("stl line %d: facet has %d vertices, want 3", lineNo, len(cur))
+			}
+			w.add(cur[0], cur[1], cur[2])
+			cur = cur[:0]
+		}
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+	if len(w.mesh.Tris) == 0 {
+		return nil, fmt.Errorf("stl contains no triangles")
+	}
+	return &Scene{Meshes: []*Mesh{w.mesh}}, nil
+}
+
+// WriteSTLBinary writes the whole scene as one binary STL solid
+// (STL has no concept of multiple named objects).
+func WriteSTLBinary(w io.Writer, s *Scene) error {
+	m := s.Merged()
+	bw := bufio.NewWriter(w)
+	header := make([]byte, 80)
+	copy(header, []byte("exported by mesht (agent-tools)"))
+	bw.Write(header)
+	binary.Write(bw, binary.LittleEndian, uint32(len(m.Tris)))
+	buf := make([]byte, 50)
+	for i, t := range m.Tris {
+		n := m.FaceNormal(i)
+		le := binary.LittleEndian
+		le.PutUint32(buf[0:], math.Float32bits(float32(n.X)))
+		le.PutUint32(buf[4:], math.Float32bits(float32(n.Y)))
+		le.PutUint32(buf[8:], math.Float32bits(float32(n.Z)))
+		for k := 0; k < 3; k++ {
+			v := m.Verts[t[k]]
+			le.PutUint32(buf[12+k*12:], math.Float32bits(float32(v.X)))
+			le.PutUint32(buf[16+k*12:], math.Float32bits(float32(v.Y)))
+			le.PutUint32(buf[20+k*12:], math.Float32bits(float32(v.Z)))
+		}
+		buf[48], buf[49] = 0, 0
+		bw.Write(buf)
+	}
+	return bw.Flush()
+}
+
+// WriteSTLAscii writes the scene as a text STL solid.
+func WriteSTLAscii(w io.Writer, s *Scene) error {
+	m := s.Merged()
+	bw := bufio.NewWriter(w)
+	fmt.Fprintf(bw, "solid %s\n", sanitizeToken(m.Name))
+	for i, t := range m.Tris {
+		n := m.FaceNormal(i)
+		fmt.Fprintf(bw, "  facet normal %g %g %g\n    outer loop\n", n.X, n.Y, n.Z)
+		for k := 0; k < 3; k++ {
+			v := m.Verts[t[k]]
+			fmt.Fprintf(bw, "      vertex %g %g %g\n", v.X, v.Y, v.Z)
+		}
+		fmt.Fprintf(bw, "    endloop\n  endfacet\n")
+	}
+	fmt.Fprintf(bw, "endsolid %s\n", sanitizeToken(m.Name))
+	return bw.Flush()
+}
+
+func sanitizeToken(s string) string {
+	s = strings.ReplaceAll(strings.TrimSpace(s), " ", "_")
+	if s == "" {
+		return "mesh"
+	}
+	return s
+}

mesh-tool/mesh/transform.go

@@ -0,0 +1,20 @@
+package mesh
+
+// Apply transforms every vertex by mat. Mirroring transforms (negative
+// determinant) flip triangle winding, so it is corrected here to keep
+// normals pointing the same way relative to the surface.
+func (m *Mesh) Apply(mat Mat4) {
+	for i := range m.Verts {
+		m.Verts[i] = mat.Apply(m.Verts[i])
+	}
+	if mat.Det3() < 0 {
+		m.FlipWinding()
+	}
+}
+
+// ApplyAll transforms a set of meshes.
+func ApplyAll(meshes []*Mesh, mat Mat4) {
+	for _, m := range meshes {
+		m.Apply(mat)
+	}
+}

mesh-tool/mesh/vec.go

@@ -0,0 +1,122 @@
+package mesh
+
+import "math"
+
+// Vec3 is a point or direction in 3D space.
+type Vec3 struct{ X, Y, Z float64 }
+
+func (a Vec3) Add(b Vec3) Vec3    { return Vec3{a.X + b.X, a.Y + b.Y, a.Z + b.Z} }
+func (a Vec3) Sub(b Vec3) Vec3    { return Vec3{a.X - b.X, a.Y - b.Y, a.Z - b.Z} }
+func (a Vec3) Mul(s float64) Vec3 { return Vec3{a.X * s, a.Y * s, a.Z * s} }
+func (a Vec3) Dot(b Vec3) float64 { return a.X*b.X + a.Y*b.Y + a.Z*b.Z }
+func (a Vec3) Len() float64       { return math.Sqrt(a.Dot(a)) }
+func (a Vec3) Cross(b Vec3) Vec3 {
+	return Vec3{
+		a.Y*b.Z - a.Z*b.Y,
+		a.Z*b.X - a.X*b.Z,
+		a.X*b.Y - a.Y*b.X,
+	}
+}
+
+// Norm returns the unit vector, or the zero vector for zero-length input.
+func (a Vec3) Norm() Vec3 {
+	l := a.Len()
+	if l == 0 {
+		return Vec3{}
+	}
+	return a.Mul(1 / l)
+}
+
+// Min/Max return the component-wise minimum/maximum.
+func (a Vec3) Min(b Vec3) Vec3 {
+	return Vec3{math.Min(a.X, b.X), math.Min(a.Y, b.Y), math.Min(a.Z, b.Z)}
+}
+func (a Vec3) Max(b Vec3) Vec3 {
+	return Vec3{math.Max(a.X, b.X), math.Max(a.Y, b.Y), math.Max(a.Z, b.Z)}
+}
+
+// Mat4 is a row-major 4x4 transform matrix.
+type Mat4 [16]float64
+
+func Identity() Mat4 {
+	return Mat4{
+		1, 0, 0, 0,
+		0, 1, 0, 0,
+		0, 0, 1, 0,
+		0, 0, 0, 1,
+	}
+}
+
+// Mul returns m * n (n is applied first when transforming points).
+func (m Mat4) Mul(n Mat4) Mat4 {
+	var r Mat4
+	for row := 0; row < 4; row++ {
+		for col := 0; col < 4; col++ {
+			sum := 0.0
+			for k := 0; k < 4; k++ {
+				sum += m[row*4+k] * n[k*4+col]
+			}
+			r[row*4+col] = sum
+		}
+	}
+	return r
+}
+
+// Apply transforms a point (w = 1).
+func (m Mat4) Apply(v Vec3) Vec3 {
+	return Vec3{
+		m[0]*v.X + m[1]*v.Y + m[2]*v.Z + m[3],
+		m[4]*v.X + m[5]*v.Y + m[6]*v.Z + m[7],
+		m[8]*v.X + m[9]*v.Y + m[10]*v.Z + m[11],
+	}
+}
+
+// Det3 is the determinant of the upper-left 3x3. Negative means the
+// transform mirrors space, which flips triangle winding.
+func (m Mat4) Det3() float64 {
+	return m[0]*(m[5]*m[10]-m[6]*m[9]) -
+		m[1]*(m[4]*m[10]-m[6]*m[8]) +
+		m[2]*(m[4]*m[9]-m[5]*m[8])
+}
+
+func Translate(t Vec3) Mat4 {
+	m := Identity()
+	m[3], m[7], m[11] = t.X, t.Y, t.Z
+	return m
+}
+
+func ScaleXYZ(s Vec3) Mat4 {
+	m := Identity()
+	m[0], m[5], m[10] = s.X, s.Y, s.Z
+	return m
+}
+
+func RotateX(deg float64) Mat4 {
+	s, c := math.Sincos(deg * math.Pi / 180)
+	return Mat4{
+		1, 0, 0, 0,
+		0, c, -s, 0,
+		0, s, c, 0,
+		0, 0, 0, 1,
+	}
+}
+
+func RotateY(deg float64) Mat4 {
+	s, c := math.Sincos(deg * math.Pi / 180)
+	return Mat4{
+		c, 0, s, 0,
+		0, 1, 0, 0,
+		-s, 0, c, 0,
+		0, 0, 0, 1,
+	}
+}
+
+func RotateZ(deg float64) Mat4 {
+	s, c := math.Sincos(deg * math.Pi / 180)
+	return Mat4{
+		c, -s, 0, 0,
+		s, c, 0, 0,
+		0, 0, 1, 0,
+		0, 0, 0, 1,
+	}
+}

pixel-sprite-maker/README.md

@@ -0,0 +1,86 @@
+# pixel-sprite-maker (`spritec`)
+
+Turns human/agent-readable `.sprite` text files into pixel art (**PNG, JPG, SVG**)
+and combines several sprites into **sprite sheets / animation strips**.
+Written in Go, zero dependencies, single static binary.
+
+## Build
+
+```bash
+# Arch/Garuda: sudo pacman -S go
+cd pixel-sprite-maker
+go build -o build/spritec .        # or run the VS Code task "build pixel-sprite-maker"
+go test ./...
+```
+
+## The `.sprite` format
+
+One file = one sprite. Designed so an agent can *see* the result in the text:
+
+```
+# comment lines start with '#'
+sprite: coin           # optional name
+palette:
+  k = #1A1205    dark outline
+  y = #FFD700    gold
+  Y = gold       CSS names work too — text after the color is a comment
+grid:
+  ..kkkk..
+  .kyyyYk.
+  kyyyYYyk
+  ..kkkk..
+```
+
+Rules:
+
+- **One character = one pixel.** Every grid row must be the same width.
+- Palette keys are exactly one character (any unicode). `#`, `=`, `:` and
+  whitespace are not allowed as keys — so the number of colors is
+  practically unlimited (a-z, A-Z, 0-9, `!@%&*`, unicode…).
+- `.` is **transparent by default**; override it in the palette if you want.
+- Colors: `#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`, `rgb(r,g,b)`,
+  `rgba(r,g,b,a)` (alpha 0-255 or 0.0-1.0), all CSS named colors, `none`.
+- Max **256x256** pixels per sprite. Sheets may exceed this; single frames may not.
+
+## Commands
+
+```bash
+spritec render coin.sprite -o coin.png --scale 8      # png/jpg/svg from extension
+spritec render coin.sprite --format svg               # -> coin.svg
+spritec render heart.sprite -o heart.jpg --bg '#222034'  # jpg has no alpha: pick bg
+spritec info coin.sprite                              # validate + palette stats
+spritec preview coin.sprite                           # draw in the terminal (truecolor)
+
+# Sprite sheets / animations — row-major (left→right, then top→bottom):
+spritec sheet walk_1.sprite walk_2.sprite walk_3.sprite walk_4.sprite -o walk           # 1 row
+spritec sheet walk_*.sprite --cols 2 -o walkgrid      # 2D: 2 columns x 2 rows
+```
+
+Flags: `-o` output, `--format png|jpg|svg`, `--scale n` (integer nearest-neighbour
+upscale), `--bg color` + `--quality 1-100` (jpg only), `--cols n` (sheet only).
+
+## Sheet output naming — read the layout from the file name
+
+```
+<name>_<cellW>x<cellH>_<cols>x<rows>.<ext>
+
+walk_8x8_4x1.png   = 8x8 px per frame, 4 columns, 1 row (animation strip)
+tiles_16x16_4x2.png = 16x16 px per frame, 4 columns, 2 rows
+```
+
+Frame order is always **row-major**: index = `row * cols + col`, frame 0 is
+top-left. If the frame count doesn't fill the grid, trailing cells are
+transparent. In game code:
+
+```
+frameX = (index % cols) * cellW
+frameY = (index / cols) * cellH
+```
+
+## Exit codes & errors
+
+`0` on success, `1` on any error, `2` on missing command. Parse errors name
+the exact line/row/column and what was expected, so an agent can fix the
+file without guessing.
+
+Examples live in [`examples/`](examples/); generated output in `examples/out/`.

pixel-sprite-maker/examples/coin.sprite

@@ -0,0 +1,17 @@
+# A small gold coin, 8x8.
+# '.' is transparent by default and never needs a palette entry.
+sprite: coin
+palette:
+  k = #1A1205    dark outline
+  y = #FFD700    gold
+  Y = #FFF3A0    highlight
+  s = #B8860B    shadow
+grid:
+  ..kkkk..
+  .kyyyYk.
+  kyyyYYsk
+  kyyYyysk
+  kyYyyysk
+  kYyyyssk
+  .kysssk.
+  ..kkkk..

pixel-sprite-maker/examples/heart.sprite

@@ -0,0 +1,25 @@
+# A 16x16 heart with shading, shows named colors and rgb().
+sprite: heart
+palette:
+  k = #2B0A10          outline
+  r = crimson          main red
+  R = rgb(255, 90, 110) light red
+  d = #8B1A2B          dark red
+  w = #FFFFFFCC        semi-transparent shine
+grid:
+  ................
+  ..kkk....kkk....
+  .krrRk..kRrrk...
+  krrRRrkkrRrrrk..
+  krRwRrrrrrrrdk..
+  krRwwRrrrrrrdk..
+  krRwRrrrrrrddk..
+  krrRrrrrrrrddk..
+  .krrrrrrrrrdk...
+  ..krrrrrrrdk....
+  ...krrrrrdk.....
+  ....krrrdk......
+  .....krdk.......
+  ......kk........
+  ................
+  ................

pixel-sprite-maker/examples/out/coin.svg

@@ -0,0 +1,34 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="64" height="64" viewBox="0 0 8 8" shape-rendering="crispEdges">
+<rect x="2" y="0" width="4" height="1" fill="#1a1205"/>
+<rect x="1" y="1" width="1" height="1" fill="#1a1205"/>
+<rect x="2" y="1" width="3" height="1" fill="#ffd700"/>
+<rect x="5" y="1" width="1" height="1" fill="#fff3a0"/>
+<rect x="6" y="1" width="1" height="1" fill="#1a1205"/>
+<rect x="0" y="2" width="1" height="1" fill="#1a1205"/>
+<rect x="1" y="2" width="3" height="1" fill="#ffd700"/>
+<rect x="4" y="2" width="2" height="1" fill="#fff3a0"/>
+<rect x="6" y="2" width="1" height="1" fill="#b8860b"/>
+<rect x="7" y="2" width="1" height="1" fill="#1a1205"/>
+<rect x="0" y="3" width="1" height="1" fill="#1a1205"/>
+<rect x="1" y="3" width="2" height="1" fill="#ffd700"/>
+<rect x="3" y="3" width="1" height="1" fill="#fff3a0"/>
+<rect x="4" y="3" width="2" height="1" fill="#ffd700"/>
+<rect x="6" y="3" width="1" height="1" fill="#b8860b"/>
+<rect x="7" y="3" width="1" height="1" fill="#1a1205"/>
+<rect x="0" y="4" width="1" height="1" fill="#1a1205"/>
+<rect x="1" y="4" width="1" height="1" fill="#ffd700"/>
+<rect x="2" y="4" width="1" height="1" fill="#fff3a0"/>
+<rect x="3" y="4" width="3" height="1" fill="#ffd700"/>
+<rect x="6" y="4" width="1" height="1" fill="#b8860b"/>
+<rect x="7" y="4" width="1" height="1" fill="#1a1205"/>
+<rect x="0" y="5" width="1" height="1" fill="#1a1205"/>
+<rect x="1" y="5" width="1" height="1" fill="#fff3a0"/>
+<rect x="2" y="5" width="3" height="1" fill="#ffd700"/>
+<rect x="5" y="5" width="2" height="1" fill="#b8860b"/>
+<rect x="7" y="5" width="1" height="1" fill="#1a1205"/>
+<rect x="1" y="6" width="1" height="1" fill="#1a1205"/>
+<rect x="2" y="6" width="1" height="1" fill="#ffd700"/>
+<rect x="3" y="6" width="3" height="1" fill="#b8860b"/>
+<rect x="6" y="6" width="1" height="1" fill="#1a1205"/>
+<rect x="2" y="7" width="4" height="1" fill="#1a1205"/>
+</svg>

pixel-sprite-maker/examples/out/walkgrid_8x8_2x2.svg

@@ -0,0 +1,57 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16" shape-rendering="crispEdges">
+<rect x="2" y="0" width="3" height="1" fill="#101018"/>
+<rect x="10" y="0" width="3" height="1" fill="#101018"/>
+<rect x="2" y="1" width="1" height="1" fill="#101018"/>
+<rect x="3" y="1" width="2" height="1" fill="#f2c09a"/>
+<rect x="10" y="1" width="1" height="1" fill="#101018"/>
+<rect x="11" y="1" width="2" height="1" fill="#f2c09a"/>
+<rect x="2" y="2" width="1" height="1" fill="#101018"/>
+<rect x="3" y="2" width="2" height="1" fill="#f2c09a"/>
+<rect x="10" y="2" width="1" height="1" fill="#101018"/>
+<rect x="11" y="2" width="2" height="1" fill="#f2c09a"/>
+<rect x="1" y="3" width="1" height="1" fill="#101018"/>
+<rect x="2" y="3" width="3" height="1" fill="#2e5fb7"/>
+<rect x="5" y="3" width="1" height="1" fill="#101018"/>
+<rect x="9" y="3" width="1" height="1" fill="#101018"/>
+<rect x="10" y="3" width="3" height="1" fill="#2e5fb7"/>
+<rect x="13" y="3" width="1" height="1" fill="#101018"/>
+<rect x="2" y="4" width="3" height="1" fill="#2e5fb7"/>
+<rect x="10" y="4" width="3" height="1" fill="#2e5fb7"/>
+<rect x="2" y="5" width="3" height="1" fill="#22406e"/>
+<rect x="10" y="5" width="3" height="1" fill="#22406e"/>
+<rect x="2" y="6" width="1" height="1" fill="#22406e"/>
+<rect x="4" y="6" width="1" height="1" fill="#22406e"/>
+<rect x="9" y="6" width="1" height="1" fill="#22406e"/>
+<rect x="13" y="6" width="1" height="1" fill="#22406e"/>
+<rect x="2" y="7" width="1" height="1" fill="#101018"/>
+<rect x="4" y="7" width="1" height="1" fill="#101018"/>
+<rect x="9" y="7" width="1" height="1" fill="#101018"/>
+<rect x="13" y="7" width="1" height="1" fill="#101018"/>
+<rect x="2" y="8" width="3" height="1" fill="#101018"/>
+<rect x="10" y="8" width="3" height="1" fill="#101018"/>
+<rect x="2" y="9" width="1" height="1" fill="#101018"/>
+<rect x="3" y="9" width="2" height="1" fill="#f2c09a"/>
+<rect x="10" y="9" width="1" height="1" fill="#101018"/>
+<rect x="11" y="9" width="2" height="1" fill="#f2c09a"/>
+<rect x="2" y="10" width="1" height="1" fill="#101018"/>
+<rect x="3" y="10" width="2" height="1" fill="#f2c09a"/>
+<rect x="10" y="10" width="1" height="1" fill="#101018"/>
+<rect x="11" y="10" width="2" height="1" fill="#f2c09a"/>
+<rect x="2" y="11" width="3" height="1" fill="#2e5fb7"/>
+<rect x="5" y="11" width="1" height="1" fill="#101018"/>
+<rect x="9" y="11" width="1" height="1" fill="#101018"/>
+<rect x="10" y="11" width="3" height="1" fill="#2e5fb7"/>
+<rect x="13" y="11" width="1" height="1" fill="#101018"/>
+<rect x="1" y="12" width="1" height="1" fill="#101018"/>
+<rect x="2" y="12" width="3" height="1" fill="#2e5fb7"/>
+<rect x="10" y="12" width="3" height="1" fill="#2e5fb7"/>
+<rect x="2" y="13" width="3" height="1" fill="#22406e"/>
+<rect x="10" y="13" width="3" height="1" fill="#22406e"/>
+<rect x="2" y="14" width="1" height="1" fill="#22406e"/>
+<rect x="4" y="14" width="1" height="1" fill="#22406e"/>
+<rect x="10" y="14" width="2" height="1" fill="#22406e"/>
+<rect x="2" y="15" width="1" height="1" fill="#101018"/>
+<rect x="4" y="15" width="1" height="1" fill="#101018"/>
+<rect x="9" y="15" width="1" height="1" fill="#101018"/>
+<rect x="12" y="15" width="1" height="1" fill="#101018"/>
+</svg>

pixel-sprite-maker/examples/walk_1.sprite

@@ -0,0 +1,16 @@
+# Frame 1/4 of a tiny walking guy, 8x8. Legs together.
+sprite: walk_1
+palette:
+  k = #101018    outline / hair
+  s = #F2C09A    skin
+  b = #2E5FB7    shirt
+  d = #22406E    pants
+grid:
+  ..kkk...
+  ..kss...
+  ..kss...
+  .kbbbk..
+  ..bbb...
+  ..ddd...
+  ..d.d...
+  ..k.k...

pixel-sprite-maker/examples/walk_2.sprite

@@ -0,0 +1,16 @@
+# Frame 2/4 - right leg forward.
+sprite: walk_2
+palette:
+  k = #101018    outline / hair
+  s = #F2C09A    skin
+  b = #2E5FB7    shirt
+  d = #22406E    pants
+grid:
+  ..kkk...
+  ..kss...
+  ..kss...
+  .kbbbk..
+  ..bbb...
+  ..ddd...
+  .d...d..
+  .k...k..

pixel-sprite-maker/examples/walk_3.sprite

@@ -0,0 +1,16 @@
+# Frame 3/4 - legs together again (same pose as 1, arms swung).
+sprite: walk_3
+palette:
+  k = #101018    outline / hair
+  s = #F2C09A    skin
+  b = #2E5FB7    shirt
+  d = #22406E    pants
+grid:
+  ..kkk...
+  ..kss...
+  ..kss...
+  ..bbbk..
+  .kbbb...
+  ..ddd...
+  ..d.d...
+  ..k.k...

pixel-sprite-maker/examples/walk_4.sprite

@@ -0,0 +1,16 @@
+# Frame 4/4 - left leg forward.
+sprite: walk_4
+palette:
+  k = #101018    outline / hair
+  s = #F2C09A    skin
+  b = #2E5FB7    shirt
+  d = #22406E    pants
+grid:
+  ..kkk...
+  ..kss...
+  ..kss...
+  .kbbbk..
+  ..bbb...
+  ..ddd...
+  ..dd....
+  .k..k...

pixel-sprite-maker/go.mod

@@ -0,0 +1,3 @@
+module gitea.brasse-pc.eu/brasse/agent-tools/pixel-sprite-maker
+
+go 1.24

pixel-sprite-maker/main.go

@@ -0,0 +1,313 @@
+// spritec turns agent-friendly .sprite text files into PNG/JPG/SVG pixel
+// art, and combines several sprites into sprite sheets / animation strips.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gitea.brasse-pc.eu/brasse/agent-tools/pixel-sprite-maker/sprite"
+)
+
+var version = "dev"
+
+const usage = `spritec - pixel sprite maker for agents
+
+Usage:
+  spritec render <file.sprite> [flags]   render one sprite to png/jpg/svg
+  spritec sheet <a.sprite> <b.sprite> ... [flags]
+                                          combine sprites into one sheet image
+  spritec info <file.sprite>              validate a file and print its stats
+  spritec preview <file.sprite>           draw the sprite in the terminal
+  spritec version                         print version
+
+Render flags:
+  -o <path>        output file; its extension picks the format (.png .jpg .svg)
+  --format <f>     png | jpg | svg (default: from -o, else png)
+  --scale <n>      integer upscale factor, default 1
+  --bg <color>     jpg background color (jpg has no alpha), default #FFFFFF
+  --quality <n>    jpg quality 1-100, default 90
+
+Sheet flags (in addition to the render flags):
+  -o <name>        output base name; layout is appended automatically
+  --cols <n>       number of columns, row-major order (default: one row)
+
+Sheet output naming:
+  <name>_<cellW>x<cellH>_<cols>x<rows>.<ext>
+  e.g. walk_16x16_4x2.png = 16x16 px per frame, 4 columns, 2 rows,
+  frames are read left-to-right then top-to-bottom (row-major).
+
+The .sprite format:
+  # comment
+  sprite: coin           optional name
+  palette:
+    . = none             '.' is transparent by default
+    k = #000000          hex, rgb(...), CSS names ('gold') and 'none' work
+    y = gold             anything after the color is a comment
+  grid:
+    ..kk..
+    .kyyk.
+    .kyyk.
+    ..kk..
+
+Each grid character is one pixel; every row must be the same width.
+Max sprite size: 256x256. Sheets may be bigger, single frames may not.
+`
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Print(usage)
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "render":
+		cmdRender(os.Args[2:])
+	case "sheet":
+		cmdSheet(os.Args[2:])
+	case "info":
+		cmdInfo(os.Args[2:])
+	case "preview":
+		cmdPreview(os.Args[2:])
+	case "version", "--version", "-v":
+		fmt.Println("spritec", version)
+	case "help", "--help", "-h":
+		fmt.Print(usage)
+	default:
+		die("unknown command %q — run 'spritec help'", os.Args[1])
+	}
+}
+
+// parseInterspersed lets flags appear before or after positional args
+// (stdlib flag stops at the first positional otherwise).
+func parseInterspersed(fs *flag.FlagSet, args []string) {
+	var flags, pos []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if len(a) > 1 && a[0] == '-' {
+			flags = append(flags, a)
+			name := strings.TrimLeft(a, "-")
+			if !strings.Contains(name, "=") {
+				f := fs.Lookup(name)
+				isBool := false
+				if f != nil {
+					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
+						isBool = true
+					}
+				}
+				if !isBool && i+1 < len(args) {
+					i++
+					flags = append(flags, args[i])
+				}
+			}
+		} else {
+			pos = append(pos, a)
+		}
+	}
+	fs.Parse(append(flags, pos...))
+}
+
+type renderFlags struct {
+	out     string
+	format  string
+	scale   int
+	bg      string
+	quality int
+}
+
+func addRenderFlags(fs *flag.FlagSet) *renderFlags {
+	rf := &renderFlags{}
+	fs.StringVar(&rf.out, "o", "", "output path")
+	fs.StringVar(&rf.format, "format", "", "png|jpg|svg")
+	fs.IntVar(&rf.scale, "scale", 1, "integer upscale factor")
+	fs.StringVar(&rf.bg, "bg", "#FFFFFF", "jpg background color")
+	fs.IntVar(&rf.quality, "quality", 90, "jpg quality 1-100")
+	return rf
+}
+
+// resolveFormat picks the output format from --format or the -o extension.
+func (rf *renderFlags) resolveFormat() (string, error) {
+	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(rf.out), "."))
+	if ext == "jpeg" {
+		ext = "jpg"
+	}
+	f := strings.ToLower(rf.format)
+	switch {
+	case f == "" && ext == "":
+		return "png", nil
+	case f == "":
+		f = ext
+	case ext != "" && ext != f:
+		return "", fmt.Errorf("--format %s conflicts with output extension .%s", f, ext)
+	}
+	switch f {
+	case "png", "jpg", "svg":
+		return f, nil
+	}
+	return "", fmt.Errorf("unsupported format %q (png, jpg or svg)", f)
+}
+
+func writeGrid(path, format string, g sprite.PixelGrid, rf *renderFlags) error {
+	bg, err := sprite.ParseColor(rf.bg)
+	if err != nil {
+		return fmt.Errorf("--bg: %w", err)
+	}
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	switch format {
+	case "png":
+		err = sprite.WritePNG(f, g, rf.scale)
+	case "jpg":
+		err = sprite.WriteJPG(f, g, rf.scale, bg, rf.quality)
+	case "svg":
+		err = sprite.WriteSVG(f, g, rf.scale)
+	}
+	if err != nil {
+		return err
+	}
+	return f.Close()
+}
+
+func cmdRender(args []string) {
+	fs := flag.NewFlagSet("render", flag.ExitOnError)
+	rf := addRenderFlags(fs)
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("render takes exactly one .sprite file")
+	}
+	in := fs.Arg(0)
+	s, err := sprite.ParseFile(in)
+	if err != nil {
+		die("%v", err)
+	}
+	format, err := rf.resolveFormat()
+	if err != nil {
+		die("%v", err)
+	}
+	out := rf.out
+	if out == "" {
+		out = strings.TrimSuffix(in, filepath.Ext(in)) + "." + format
+	}
+	if err := writeGrid(out, format, s, rf); err != nil {
+		die("%v", err)
+	}
+	w, h := s.Bounds()
+	fmt.Printf("%s  (%dx%d px, scale %d -> %dx%d)\n", out, w, h, rf.scale, w*rf.scale, h*rf.scale)
+}
+
+func cmdSheet(args []string) {
+	fs := flag.NewFlagSet("sheet", flag.ExitOnError)
+	rf := addRenderFlags(fs)
+	cols := fs.Int("cols", 0, "columns in the sheet (default: all sprites in one row)")
+	parseInterspersed(fs, args)
+	if fs.NArg() < 1 {
+		die("sheet needs at least one .sprite file")
+	}
+	var sprites []*sprite.Sprite
+	for _, path := range fs.Args() {
+		s, err := sprite.ParseFile(path)
+		if err != nil {
+			die("%v", err)
+		}
+		sprites = append(sprites, s)
+	}
+	sh, err := sprite.NewSheet(sprites, *cols)
+	if err != nil {
+		die("%v", err)
+	}
+	format, err := rf.resolveFormat()
+	if err != nil {
+		die("%v", err)
+	}
+	base := rf.out
+	if base == "" {
+		base = "sheet"
+	}
+	base = strings.TrimSuffix(base, filepath.Ext(base))
+	out := sh.FileBase(base) + "." + format
+	if err := writeGrid(out, format, sh, rf); err != nil {
+		die("%v", err)
+	}
+	w, h := sh.Bounds()
+	fmt.Printf("%s  (%d frames of %dx%d px in %dx%d grid, total %dx%d px)\n",
+		out, len(sprites), sh.CellW, sh.CellH, sh.Cols, sh.Rows, w*rf.scale, h*rf.scale)
+}
+
+func cmdInfo(args []string) {
+	if len(args) != 1 {
+		die("info takes exactly one .sprite file")
+	}
+	s, err := sprite.ParseFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("sprite:  %s\n", s.Name)
+	fmt.Printf("size:    %dx%d px\n", s.W, s.H)
+	fmt.Printf("palette: %d colors\n", len(s.Keys))
+	usage := s.UsageCount()
+	for _, k := range s.Keys {
+		note := ""
+		if usage[k] == 0 {
+			note = "   (unused)"
+		}
+		fmt.Printf("  %s = %-9s  %5d px%s\n", string(k), sprite.FormatColor(s.Palette[k]), usage[k], note)
+	}
+	if _, defined := usage['.']; defined && !contains(s.Keys, '.') {
+		fmt.Printf("  . = none       %5d px   (implicit transparent)\n", usage['.'])
+	}
+	fmt.Println("valid:   yes")
+}
+
+func contains(keys []rune, k rune) bool {
+	for _, x := range keys {
+		if x == k {
+			return true
+		}
+	}
+	return false
+}
+
+// cmdPreview draws the sprite with truecolor half-blocks, two pixel rows
+// per terminal line. Transparent pixels show the terminal background.
+func cmdPreview(args []string) {
+	if len(args) != 1 {
+		die("preview takes exactly one .sprite file")
+	}
+	s, err := sprite.ParseFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	const reset = "\x1b[0m"
+	var b strings.Builder
+	for y := 0; y < s.H; y += 2 {
+		for x := 0; x < s.W; x++ {
+			top, bot := s.At(x, y), sprite.Transparent
+			if y+1 < s.H {
+				bot = s.At(x, y+1)
+			}
+			topOn, botOn := top.A >= 128, bot.A >= 128
+			switch {
+			case topOn && botOn:
+				fmt.Fprintf(&b, "\x1b[38;2;%d;%d;%dm\x1b[48;2;%d;%d;%dm▀%s", top.R, top.G, top.B, bot.R, bot.G, bot.B, reset)
+			case topOn:
+				fmt.Fprintf(&b, "\x1b[38;2;%d;%d;%dm▀%s", top.R, top.G, top.B, reset)
+			case botOn:
+				fmt.Fprintf(&b, "\x1b[38;2;%d;%d;%dm▄%s", bot.R, bot.G, bot.B, reset)
+			default:
+				b.WriteByte(' ')
+			}
+		}
+		b.WriteByte('\n')
+	}
+	fmt.Printf("%s  %dx%d px\n%s", s.Name, s.W, s.H, b.String())
+}
+
+func die(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, "spritec: "+format+"\n", a...)
+	os.Exit(1)
+}

pixel-sprite-maker/sprite/color.go

@@ -0,0 +1,270 @@
+package sprite
+
+import (
+	"fmt"
+	"image/color"
+	"strconv"
+	"strings"
+)
+
+// Transparent is the color used for pixels that should not be drawn.
+var Transparent = color.NRGBA{0, 0, 0, 0}
+
+// ParseColor accepts:
+//
+//	none | transparent | -           -> fully transparent
+//	#RGB #RGBA #RRGGBB #RRGGBBAA     -> hex
+//	rgb(r,g,b) rgba(r,g,b,a)         -> 0-255 channels, alpha 0-255 or 0.0-1.0
+//	CSS named colors                 -> "red", "rebeccapurple", ...
+func ParseColor(s string) (color.NRGBA, error) {
+	t := strings.ToLower(strings.TrimSpace(s))
+	if t == "" {
+		return Transparent, fmt.Errorf("empty color value")
+	}
+	switch t {
+	case "none", "transparent", "-":
+		return Transparent, nil
+	}
+	if strings.HasPrefix(t, "#") {
+		return parseHex(t)
+	}
+	if strings.HasPrefix(t, "rgb(") || strings.HasPrefix(t, "rgba(") {
+		return parseRGBFunc(t)
+	}
+	if c, ok := cssColors[t]; ok {
+		return c, nil
+	}
+	return Transparent, fmt.Errorf("unknown color %q (use #RRGGBB, rgb(r,g,b), a CSS color name, or 'none')", s)
+}
+
+func parseHex(t string) (color.NRGBA, error) {
+	h := t[1:]
+	var r, g, b, a uint64
+	var err error
+	dup := func(s string) (uint64, error) {
+		v, err := strconv.ParseUint(s, 16, 8)
+		return v*16 + v, err
+	}
+	a = 255
+	switch len(h) {
+	case 3, 4:
+		if r, err = dup(h[0:1]); err == nil {
+			if g, err = dup(h[1:2]); err == nil {
+				b, err = dup(h[2:3])
+			}
+		}
+		if err == nil && len(h) == 4 {
+			a, err = dup(h[3:4])
+		}
+	case 6, 8:
+		if r, err = strconv.ParseUint(h[0:2], 16, 8); err == nil {
+			if g, err = strconv.ParseUint(h[2:4], 16, 8); err == nil {
+				b, err = strconv.ParseUint(h[4:6], 16, 8)
+			}
+		}
+		if err == nil && len(h) == 8 {
+			a, err = strconv.ParseUint(h[6:8], 16, 8)
+		}
+	default:
+		return Transparent, fmt.Errorf("hex color %q must be #RGB, #RGBA, #RRGGBB or #RRGGBBAA", t)
+	}
+	if err != nil {
+		return Transparent, fmt.Errorf("invalid hex color %q", t)
+	}
+	return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}, nil
+}
+
+func parseRGBFunc(t string) (color.NRGBA, error) {
+	open := strings.Index(t, "(")
+	close := strings.Index(t, ")")
+	if close < open {
+		return Transparent, fmt.Errorf("invalid color %q: missing ')'", t)
+	}
+	parts := strings.Split(t[open+1:close], ",")
+	if len(parts) != 3 && len(parts) != 4 {
+		return Transparent, fmt.Errorf("invalid color %q: want rgb(r,g,b) or rgba(r,g,b,a)", t)
+	}
+	var ch [4]uint8
+	ch[3] = 255
+	for i, p := range parts {
+		p = strings.TrimSpace(p)
+		if i == 3 && strings.Contains(p, ".") {
+			// CSS-style fractional alpha 0.0 - 1.0
+			f, err := strconv.ParseFloat(p, 64)
+			if err != nil || f < 0 || f > 1 {
+				return Transparent, fmt.Errorf("invalid alpha %q in %q (want 0.0-1.0 or 0-255)", p, t)
+			}
+			ch[3] = uint8(f*255 + 0.5)
+			continue
+		}
+		v, err := strconv.ParseUint(p, 10, 8)
+		if err != nil {
+			return Transparent, fmt.Errorf("invalid channel %q in %q (want 0-255)", p, t)
+		}
+		ch[i] = uint8(v)
+	}
+	return color.NRGBA{ch[0], ch[1], ch[2], ch[3]}, nil
+}
+
+// FormatColor renders a color the way it should appear in a .sprite file.
+func FormatColor(c color.NRGBA) string {
+	if c.A == 0 {
+		return "none"
+	}
+	if c.A == 255 {
+		return fmt.Sprintf("#%02X%02X%02X", c.R, c.G, c.B)
+	}
+	return fmt.Sprintf("#%02X%02X%02X%02X", c.R, c.G, c.B, c.A)
+}
+
+// cssColors is the full CSS Color Module Level 4 named-color list.
+var cssColors = map[string]color.NRGBA{
+	"aliceblue":            {240, 248, 255, 255},
+	"antiquewhite":         {250, 235, 215, 255},
+	"aqua":                 {0, 255, 255, 255},
+	"aquamarine":           {127, 255, 212, 255},
+	"azure":                {240, 255, 255, 255},
+	"beige":                {245, 245, 220, 255},
+	"bisque":               {255, 228, 196, 255},
+	"black":                {0, 0, 0, 255},
+	"blanchedalmond":       {255, 235, 205, 255},
+	"blue":                 {0, 0, 255, 255},
+	"blueviolet":           {138, 43, 226, 255},
+	"brown":                {165, 42, 42, 255},
+	"burlywood":            {222, 184, 135, 255},
+	"cadetblue":            {95, 158, 160, 255},
+	"chartreuse":           {127, 255, 0, 255},
+	"chocolate":            {210, 105, 30, 255},
+	"coral":                {255, 127, 80, 255},
+	"cornflowerblue":       {100, 149, 237, 255},
+	"cornsilk":             {255, 248, 220, 255},
+	"crimson":              {220, 20, 60, 255},
+	"cyan":                 {0, 255, 255, 255},
+	"darkblue":             {0, 0, 139, 255},
+	"darkcyan":             {0, 139, 139, 255},
+	"darkgoldenrod":        {184, 134, 11, 255},
+	"darkgray":             {169, 169, 169, 255},
+	"darkgreen":            {0, 100, 0, 255},
+	"darkgrey":             {169, 169, 169, 255},
+	"darkkhaki":            {189, 183, 107, 255},
+	"darkmagenta":          {139, 0, 139, 255},
+	"darkolivegreen":       {85, 107, 47, 255},
+	"darkorange":           {255, 140, 0, 255},
+	"darkorchid":           {153, 50, 204, 255},
+	"darkred":              {139, 0, 0, 255},
+	"darksalmon":           {233, 150, 122, 255},
+	"darkseagreen":         {143, 188, 143, 255},
+	"darkslateblue":        {72, 61, 139, 255},
+	"darkslategray":        {47, 79, 79, 255},
+	"darkslategrey":        {47, 79, 79, 255},
+	"darkturquoise":        {0, 206, 209, 255},
+	"darkviolet":           {148, 0, 211, 255},
+	"deeppink":             {255, 20, 147, 255},
+	"deepskyblue":          {0, 191, 255, 255},
+	"dimgray":              {105, 105, 105, 255},
+	"dimgrey":              {105, 105, 105, 255},
+	"dodgerblue":           {30, 144, 255, 255},
+	"firebrick":            {178, 34, 34, 255},
+	"floralwhite":          {255, 250, 240, 255},
+	"forestgreen":          {34, 139, 34, 255},
+	"fuchsia":              {255, 0, 255, 255},
+	"gainsboro":            {220, 220, 220, 255},
+	"ghostwhite":           {248, 248, 255, 255},
+	"gold":                 {255, 215, 0, 255},
+	"goldenrod":            {218, 165, 32, 255},
+	"gray":                 {128, 128, 128, 255},
+	"green":                {0, 128, 0, 255},
+	"greenyellow":          {173, 255, 47, 255},
+	"grey":                 {128, 128, 128, 255},
+	"honeydew":             {240, 255, 240, 255},
+	"hotpink":              {255, 105, 180, 255},
+	"indianred":            {205, 92, 92, 255},
+	"indigo":               {75, 0, 130, 255},
+	"ivory":                {255, 255, 240, 255},
+	"khaki":                {240, 230, 140, 255},
+	"lavender":             {230, 230, 250, 255},
+	"lavenderblush":        {255, 240, 245, 255},
+	"lawngreen":            {124, 252, 0, 255},
+	"lemonchiffon":         {255, 250, 205, 255},
+	"lightblue":            {173, 216, 230, 255},
+	"lightcoral":           {240, 128, 128, 255},
+	"lightcyan":            {224, 255, 255, 255},
+	"lightgoldenrodyellow": {250, 250, 210, 255},
+	"lightgray":            {211, 211, 211, 255},
+	"lightgreen":           {144, 238, 144, 255},
+	"lightgrey":            {211, 211, 211, 255},
+	"lightpink":            {255, 182, 193, 255},
+	"lightsalmon":          {255, 160, 122, 255},
+	"lightseagreen":        {32, 178, 170, 255},
+	"lightskyblue":         {135, 206, 250, 255},
+	"lightslategray":       {119, 136, 153, 255},
+	"lightslategrey":       {119, 136, 153, 255},
+	"lightsteelblue":       {176, 196, 222, 255},
+	"lightyellow":          {255, 255, 224, 255},
+	"lime":                 {0, 255, 0, 255},
+	"limegreen":            {50, 205, 50, 255},
+	"linen":                {250, 240, 230, 255},
+	"magenta":              {255, 0, 255, 255},
+	"maroon":               {128, 0, 0, 255},
+	"mediumaquamarine":     {102, 205, 170, 255},
+	"mediumblue":           {0, 0, 205, 255},
+	"mediumorchid":         {186, 85, 211, 255},
+	"mediumpurple":         {147, 112, 219, 255},
+	"mediumseagreen":       {60, 179, 113, 255},
+	"mediumslateblue":      {123, 104, 238, 255},
+	"mediumspringgreen":    {0, 250, 154, 255},
+	"mediumturquoise":      {72, 209, 204, 255},
+	"mediumvioletred":      {199, 21, 133, 255},
+	"midnightblue":         {25, 25, 112, 255},
+	"mintcream":            {245, 255, 250, 255},
+	"mistyrose":            {255, 228, 225, 255},
+	"moccasin":             {255, 228, 181, 255},
+	"navajowhite":          {255, 222, 173, 255},
+	"navy":                 {0, 0, 128, 255},
+	"oldlace":              {253, 245, 230, 255},
+	"olive":                {128, 128, 0, 255},
+	"olivedrab":            {107, 142, 35, 255},
+	"orange":               {255, 165, 0, 255},
+	"orangered":            {255, 69, 0, 255},
+	"orchid":               {218, 112, 214, 255},
+	"palegoldenrod":        {238, 232, 170, 255},
+	"palegreen":            {152, 251, 152, 255},
+	"paleturquoise":        {175, 238, 238, 255},
+	"palevioletred":        {219, 112, 147, 255},
+	"papayawhip":           {255, 239, 213, 255},
+	"peachpuff":            {255, 218, 185, 255},
+	"peru":                 {205, 133, 63, 255},
+	"pink":                 {255, 192, 203, 255},
+	"plum":                 {221, 160, 221, 255},
+	"powderblue":           {176, 224, 230, 255},
+	"purple":               {128, 0, 128, 255},
+	"rebeccapurple":        {102, 51, 153, 255},
+	"red":                  {255, 0, 0, 255},
+	"rosybrown":            {188, 143, 143, 255},
+	"royalblue":            {65, 105, 225, 255},
+	"saddlebrown":          {139, 69, 19, 255},
+	"salmon":               {250, 128, 114, 255},
+	"sandybrown":           {244, 164, 96, 255},
+	"seagreen":             {46, 139, 87, 255},
+	"seashell":             {255, 245, 238, 255},
+	"sienna":               {160, 82, 45, 255},
+	"silver":               {192, 192, 192, 255},
+	"skyblue":              {135, 206, 235, 255},
+	"slateblue":            {106, 90, 205, 255},
+	"slategray":            {112, 128, 144, 255},
+	"slategrey":            {112, 128, 144, 255},
+	"snow":                 {255, 250, 250, 255},
+	"springgreen":          {0, 255, 127, 255},
+	"steelblue":            {70, 130, 180, 255},
+	"tan":                  {210, 180, 140, 255},
+	"teal":                 {0, 128, 128, 255},
+	"thistle":              {216, 191, 216, 255},
+	"tomato":               {255, 99, 71, 255},
+	"turquoise":            {64, 224, 208, 255},
+	"violet":               {238, 130, 238, 255},
+	"wheat":                {245, 222, 179, 255},
+	"white":                {255, 255, 255, 255},
+	"whitesmoke":           {245, 245, 245, 255},
+	"yellow":               {255, 255, 0, 255},
+	"yellowgreen":          {154, 205, 50, 255},
+}

pixel-sprite-maker/sprite/parse.go

@@ -0,0 +1,186 @@
+package sprite
+
+import (
+	"bufio"
+	"fmt"
+	"image/color"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// MaxSize is the maximum width/height of a single sprite in pixels.
+const MaxSize = 256
+
+// Sprite is a parsed .sprite file: a palette of single-rune keys and a
+// rectangular grid of those keys.
+type Sprite struct {
+	Name    string
+	W, H    int
+	Palette map[rune]color.NRGBA
+	Keys    []rune   // palette keys in file order
+	Rows    [][]rune // H rows of exactly W palette keys
+}
+
+// At returns the color of pixel (x, y). Out-of-range pixels are transparent.
+func (s *Sprite) At(x, y int) color.NRGBA {
+	if x < 0 || y < 0 || x >= s.W || y >= s.H {
+		return Transparent
+	}
+	return s.Palette[s.Rows[y][x]]
+}
+
+// Bounds returns the sprite size in pixels.
+func (s *Sprite) Bounds() (w, h int) { return s.W, s.H }
+
+// ParseFile reads a .sprite file from disk. The sprite name defaults to the
+// file name without extension when the file has no "sprite:" line.
+func ParseFile(path string) (*Sprite, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	s, err := Parse(f)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", path, err)
+	}
+	if s.Name == "" {
+		s.Name = strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
+	}
+	return s, nil
+}
+
+// Parse reads the .sprite text format:
+//
+//	# comment lines start with '#'
+//	sprite: coin              (optional name)
+//	palette:
+//	  . = none                (key '.' is transparent by default)
+//	  k = #000000             text after the color is ignored
+//	  y = gold
+//	grid:
+//	  ..kk..
+//	  .kyyk.
+//
+// Palette keys are exactly one character and may not be '#', '=', ':' or
+// whitespace. Every grid row must be the same width; max size is 256x256.
+func Parse(r io.Reader) (*Sprite, error) {
+	s := &Sprite{Palette: map[rune]color.NRGBA{}}
+	const (
+		secNone = iota
+		secPalette
+		secGrid
+	)
+	section := secNone
+	sc := bufio.NewScanner(r)
+	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	lineNo := 0
+	for sc.Scan() {
+		lineNo++
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue // comment or blank ('#' is not a legal palette key)
+		}
+		lower := strings.ToLower(line)
+		switch {
+		case lower == "palette:":
+			section = secPalette
+			continue
+		case lower == "grid:":
+			section = secGrid
+			continue
+		case strings.HasPrefix(lower, "sprite:"):
+			s.Name = strings.TrimSpace(line[len("sprite:"):])
+			continue
+		}
+		switch section {
+		case secPalette:
+			if err := s.parsePaletteLine(line, lineNo); err != nil {
+				return nil, err
+			}
+		case secGrid:
+			row := []rune(line)
+			s.Rows = append(s.Rows, row)
+		default:
+			return nil, fmt.Errorf("line %d: unexpected %q before a 'palette:' or 'grid:' section", lineNo, line)
+		}
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+	return s, s.validate()
+}
+
+func (s *Sprite) parsePaletteLine(line string, lineNo int) error {
+	eq := strings.Index(line, "=")
+	if eq < 0 {
+		return fmt.Errorf("line %d: palette entry %q must look like '<key> = <color>'", lineNo, line)
+	}
+	keyPart := []rune(strings.TrimSpace(line[:eq]))
+	if len(keyPart) != 1 {
+		return fmt.Errorf("line %d: palette key %q must be exactly one character", lineNo, strings.TrimSpace(line[:eq]))
+	}
+	key := keyPart[0]
+	if key == '#' || key == '=' || key == ':' {
+		return fmt.Errorf("line %d: %q is not allowed as a palette key", lineNo, key)
+	}
+	if _, dup := s.Palette[key]; dup {
+		return fmt.Errorf("line %d: palette key %q defined twice", lineNo, key)
+	}
+	val := strings.TrimSpace(line[eq+1:])
+	// The color is the first token; anything after it is a free-text comment.
+	token := val
+	if strings.HasPrefix(strings.ToLower(val), "rgb") {
+		if close := strings.Index(val, ")"); close >= 0 {
+			token = val[:close+1]
+		}
+	} else if i := strings.IndexAny(val, " \t"); i >= 0 {
+		token = val[:i]
+	}
+	c, err := ParseColor(token)
+	if err != nil {
+		return fmt.Errorf("line %d: %w", lineNo, err)
+	}
+	s.Palette[key] = c
+	s.Keys = append(s.Keys, key)
+	return nil
+}
+
+func (s *Sprite) validate() error {
+	if len(s.Rows) == 0 {
+		return fmt.Errorf("no 'grid:' section with at least one row found")
+	}
+	// '.' is transparent unless the file overrides it.
+	if _, ok := s.Palette['.']; !ok {
+		s.Palette['.'] = Transparent
+	}
+	s.H = len(s.Rows)
+	s.W = len(s.Rows[0])
+	if s.W > MaxSize || s.H > MaxSize {
+		return fmt.Errorf("sprite is %dx%d pixels; the maximum is %dx%d", s.W, s.H, MaxSize, MaxSize)
+	}
+	for y, row := range s.Rows {
+		if len(row) != s.W {
+			return fmt.Errorf("grid row %d is %d pixels wide, expected %d (all rows must match row 1)", y+1, len(row), s.W)
+		}
+		for x, key := range row {
+			if _, ok := s.Palette[key]; !ok {
+				return fmt.Errorf("grid row %d, column %d: %q is not defined in the palette", y+1, x+1, string(key))
+			}
+		}
+	}
+	return nil
+}
+
+// UsageCount returns how many grid pixels use each palette key.
+func (s *Sprite) UsageCount() map[rune]int {
+	n := map[rune]int{}
+	for _, row := range s.Rows {
+		for _, k := range row {
+			n[k]++
+		}
+	}
+	return n
+}

pixel-sprite-maker/sprite/render.go

@@ -0,0 +1,75 @@
+package sprite
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"image/jpeg"
+	"image/png"
+	"io"
+)
+
+// PixelGrid is anything that can be rendered pixel by pixel: a single
+// Sprite or a composed Sheet.
+type PixelGrid interface {
+	Bounds() (w, h int)
+	At(x, y int) color.NRGBA
+}
+
+// Image renders a PixelGrid to an NRGBA image, scaled up by the integer
+// factor scale (nearest neighbour, keeps pixels crisp).
+func Image(g PixelGrid, scale int) *image.NRGBA {
+	if scale < 1 {
+		scale = 1
+	}
+	w, h := g.Bounds()
+	img := image.NewNRGBA(image.Rect(0, 0, w*scale, h*scale))
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			c := g.At(x, y)
+			for dy := 0; dy < scale; dy++ {
+				for dx := 0; dx < scale; dx++ {
+					img.SetNRGBA(x*scale+dx, y*scale+dy, c)
+				}
+			}
+		}
+	}
+	return img
+}
+
+// WritePNG encodes g as PNG with transparency preserved.
+func WritePNG(w io.Writer, g PixelGrid, scale int) error {
+	return png.Encode(w, Image(g, scale))
+}
+
+// WriteJPG encodes g as JPEG. JPEG has no alpha channel, so transparent
+// pixels are composited over bg first.
+func WriteJPG(w io.Writer, g PixelGrid, scale int, bg color.NRGBA, quality int) error {
+	if quality < 1 || quality > 100 {
+		return fmt.Errorf("jpg quality %d out of range 1-100", quality)
+	}
+	src := Image(g, scale)
+	b := src.Bounds()
+	flat := image.NewRGBA(b)
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			flat.Set(x, y, blendOver(src.NRGBAAt(x, y), bg))
+		}
+	}
+	return jpeg.Encode(w, flat, &jpeg.Options{Quality: quality})
+}
+
+// blendOver composites src over an opaque background color.
+func blendOver(src, bg color.NRGBA) color.NRGBA {
+	if src.A == 255 {
+		return src
+	}
+	a := uint32(src.A)
+	inv := 255 - a
+	return color.NRGBA{
+		R: uint8((uint32(src.R)*a + uint32(bg.R)*inv) / 255),
+		G: uint8((uint32(src.G)*a + uint32(bg.G)*inv) / 255),
+		B: uint8((uint32(src.B)*a + uint32(bg.B)*inv) / 255),
+		A: 255,
+	}
+}

pixel-sprite-maker/sprite/sheet.go

@@ -0,0 +1,58 @@
+package sprite
+
+import (
+	"fmt"
+	"image/color"
+)
+
+// Sheet lays out several equally sized sprites in a row-major grid:
+// index 0 is top-left, then left-to-right, then next row. A 1D strip is
+// simply a sheet with one row (or one column).
+type Sheet struct {
+	Sprites      []*Sprite
+	Cols, Rows   int
+	CellW, CellH int
+}
+
+// NewSheet composes sprites into a sheet with the given number of columns.
+// cols <= 0 puts everything in a single row. Every sprite must have the
+// same dimensions so the sheet can be indexed cell by cell.
+func NewSheet(sprites []*Sprite, cols int) (*Sheet, error) {
+	if len(sprites) == 0 {
+		return nil, fmt.Errorf("a sheet needs at least one sprite")
+	}
+	w, h := sprites[0].Bounds()
+	for _, sp := range sprites[1:] {
+		sw, sh := sp.Bounds()
+		if sw != w || sh != h {
+			return nil, fmt.Errorf("sprite %q is %dx%d but %q is %dx%d — all sprites in a sheet must be the same size",
+				sp.Name, sw, sh, sprites[0].Name, w, h)
+		}
+	}
+	if cols <= 0 || cols > len(sprites) {
+		cols = len(sprites)
+	}
+	rows := (len(sprites) + cols - 1) / cols
+	return &Sheet{Sprites: sprites, Cols: cols, Rows: rows, CellW: w, CellH: h}, nil
+}
+
+// Bounds returns the total sheet size in pixels.
+func (sh *Sheet) Bounds() (w, h int) { return sh.Cols * sh.CellW, sh.Rows * sh.CellH }
+
+// At returns the pixel at (x, y). Cells past the last sprite (when the
+// sprite count doesn't fill the grid) are transparent.
+func (sh *Sheet) At(x, y int) color.NRGBA {
+	col, row := x/sh.CellW, y/sh.CellH
+	idx := row*sh.Cols + col
+	if idx >= len(sh.Sprites) {
+		return Transparent
+	}
+	return sh.Sprites[idx].At(x%sh.CellW, y%sh.CellH)
+}
+
+// FileBase appends the layout to an output name so the file itself
+// documents cell size and orientation: <base>_<cellW>x<cellH>_<cols>x<rows>
+// e.g. walk_16x16_4x2 = 16x16 cells, 4 columns, 2 rows, read row by row.
+func (sh *Sheet) FileBase(base string) string {
+	return fmt.Sprintf("%s_%dx%d_%dx%d", base, sh.CellW, sh.CellH, sh.Cols, sh.Rows)
+}

pixel-sprite-maker/sprite/sprite_test.go

@@ -0,0 +1,207 @@
+package sprite
+
+import (
+	"bytes"
+	"encoding/xml"
+	"image/color"
+	"strings"
+	"testing"
+)
+
+const coin = `
+# a tiny coin
+sprite: coin
+palette:
+  k = #000000
+  y = gold
+  Y = #FFF3A0 highlight
+grid:
+  .kk.
+  kyYk
+  kyyk
+  .kk.
+`
+
+func parseOK(t *testing.T, src string) *Sprite {
+	t.Helper()
+	s, err := Parse(strings.NewReader(src))
+	if err != nil {
+		t.Fatalf("parse failed: %v", err)
+	}
+	return s
+}
+
+func TestParseBasics(t *testing.T) {
+	s := parseOK(t, coin)
+	if s.Name != "coin" {
+		t.Errorf("name = %q, want coin", s.Name)
+	}
+	if s.W != 4 || s.H != 4 {
+		t.Errorf("size = %dx%d, want 4x4", s.W, s.H)
+	}
+	if got := s.At(0, 0); got.A != 0 {
+		t.Errorf("(0,0) should be transparent via the implicit '.', got %v", got)
+	}
+	if got := s.At(1, 1); got != (color.NRGBA{255, 215, 0, 255}) {
+		t.Errorf("(1,1) = %v, want gold", got)
+	}
+	if got := s.At(2, 1); got != (color.NRGBA{255, 243, 160, 255}) {
+		t.Errorf("(2,1) = %v, want #FFF3A0", got)
+	}
+}
+
+func TestParseErrors(t *testing.T) {
+	cases := map[string]string{
+		"ragged rows":   "palette:\n a = red\ngrid:\naa\naaa\n",
+		"unknown key":   "palette:\n a = red\ngrid:\nab\naa\n",
+		"bad color":     "palette:\n a = notacolor\ngrid:\na\n",
+		"no grid":       "palette:\n a = red\n",
+		"dup key":       "palette:\n a = red\n a = blue\ngrid:\na\n",
+		"multirune key": "palette:\n ab = red\ngrid:\na\n",
+		"colon key":     "palette:\n : = red\ngrid:\n.\n",
+	}
+	for name, src := range cases {
+		if _, err := Parse(strings.NewReader(src)); err == nil {
+			t.Errorf("%s: expected an error", name)
+		}
+	}
+}
+
+func TestMaxSize(t *testing.T) {
+	row := strings.Repeat("a", 257)
+	src := "palette:\n a = red\ngrid:\n" + row + "\n"
+	if _, err := Parse(strings.NewReader(src)); err == nil {
+		t.Error("257 px wide sprite should be rejected")
+	}
+	ok := "palette:\n a = red\ngrid:\n" + strings.Repeat(strings.Repeat("a", 256)+"\n", 256)
+	s := parseOK(t, ok)
+	if s.W != 256 || s.H != 256 {
+		t.Errorf("size = %dx%d, want 256x256", s.W, s.H)
+	}
+}
+
+func TestParseColorForms(t *testing.T) {
+	cases := map[string]color.NRGBA{
+		"none":              {0, 0, 0, 0},
+		"-":                 {0, 0, 0, 0},
+		"#F00":              {255, 0, 0, 255},
+		"#F00A":             {255, 0, 0, 170},
+		"#00FF00":           {0, 255, 0, 255},
+		"#00FF0080":         {0, 255, 0, 128},
+		"rgb(1,2,3)":        {1, 2, 3, 255},
+		"rgba(1,2,3,64)":    {1, 2, 3, 64},
+		"rgba(1, 2, 3, .5)": {1, 2, 3, 128},
+		"RebeccaPurple":     {102, 51, 153, 255},
+	}
+	for in, want := range cases {
+		got, err := ParseColor(in)
+		if err != nil {
+			t.Errorf("ParseColor(%q): %v", in, err)
+			continue
+		}
+		if got != want {
+			t.Errorf("ParseColor(%q) = %v, want %v", in, got, want)
+		}
+	}
+	for _, bad := range []string{"", "#12345", "rgb(300,0,0)", "purpleish"} {
+		if _, err := ParseColor(bad); err == nil {
+			t.Errorf("ParseColor(%q): expected error", bad)
+		}
+	}
+}
+
+func TestImageAndScale(t *testing.T) {
+	s := parseOK(t, coin)
+	img := Image(s, 3)
+	if b := img.Bounds(); b.Dx() != 12 || b.Dy() != 12 {
+		t.Fatalf("scaled bounds = %v, want 12x12", b)
+	}
+	// pixel (1,1) is gold -> block at (3..5, 3..5)
+	if got := img.NRGBAAt(4, 4); got != (color.NRGBA{255, 215, 0, 255}) {
+		t.Errorf("scaled gold pixel = %v", got)
+	}
+	if got := img.NRGBAAt(0, 0); got.A != 0 {
+		t.Errorf("corner should stay transparent, got %v", got)
+	}
+}
+
+func TestSVGOutput(t *testing.T) {
+	s := parseOK(t, coin)
+	var buf bytes.Buffer
+	if err := WriteSVG(&buf, s, 10); err != nil {
+		t.Fatal(err)
+	}
+	out := buf.String()
+	if !strings.Contains(out, `viewBox="0 0 4 4"`) || !strings.Contains(out, `width="40"`) {
+		t.Errorf("svg header wrong:\n%s", out)
+	}
+	// row 2 (y=1) has runs k, yY?, no: k y Y k -> y and Y differ, so no merge.
+	// row 3 (y=2) k yy k -> the two golds merge into one rect of width 2.
+	if !strings.Contains(out, `<rect x="1" y="2" width="2" height="1" fill="#ffd700"/>`) {
+		t.Errorf("expected RLE-merged gold rect:\n%s", out)
+	}
+	var doc struct{ XMLName xml.Name }
+	if err := xml.Unmarshal(buf.Bytes(), &doc); err != nil {
+		t.Errorf("svg is not valid XML: %v", err)
+	}
+}
+
+func TestSheetLayoutAndNaming(t *testing.T) {
+	a := parseOK(t, coin)
+	b := parseOK(t, coin)
+	c := parseOK(t, coin)
+	sh, err := NewSheet([]*Sprite{a, b, c}, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sh.Cols != 2 || sh.Rows != 2 {
+		t.Errorf("layout = %dx%d, want 2x2", sh.Cols, sh.Rows)
+	}
+	if w, h := sh.Bounds(); w != 8 || h != 8 {
+		t.Errorf("bounds = %dx%d, want 8x8", w, h)
+	}
+	if got := sh.FileBase("walk"); got != "walk_4x4_2x2" {
+		t.Errorf("FileBase = %q, want walk_4x4_2x2", got)
+	}
+	// cell (1,1) in frame 2 (top-right) is gold
+	if got := sh.At(5, 1); got != (color.NRGBA{255, 215, 0, 255}) {
+		t.Errorf("sheet pixel in frame 2 = %v, want gold", got)
+	}
+	// 4th cell (bottom-right) has no sprite -> transparent
+	if got := sh.At(7, 7); got.A != 0 {
+		t.Errorf("empty cell should be transparent, got %v", got)
+	}
+}
+
+func TestSheetSizeMismatch(t *testing.T) {
+	a := parseOK(t, coin)
+	b := parseOK(t, "palette:\n a = red\ngrid:\naa\n")
+	if _, err := NewSheet([]*Sprite{a, b}, 0); err == nil {
+		t.Error("mismatched sprite sizes should be rejected")
+	}
+}
+
+func TestSheetDefaultSingleRow(t *testing.T) {
+	a := parseOK(t, coin)
+	sh, err := NewSheet([]*Sprite{a, a, a}, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sh.Cols != 3 || sh.Rows != 1 {
+		t.Errorf("default layout = %dx%d, want 3x1", sh.Cols, sh.Rows)
+	}
+}
+
+func TestJPGComposite(t *testing.T) {
+	s := parseOK(t, coin)
+	var buf bytes.Buffer
+	if err := WriteJPG(&buf, s, 1, color.NRGBA{255, 255, 255, 255}, 90); err != nil {
+		t.Fatal(err)
+	}
+	if buf.Len() == 0 {
+		t.Error("empty jpg output")
+	}
+	if err := WriteJPG(&buf, s, 1, Transparent, 150); err == nil {
+		t.Error("quality 150 should be rejected")
+	}
+}

pixel-sprite-maker/sprite/svg.go

@@ -0,0 +1,46 @@
+package sprite
+
+import (
+	"fmt"
+	"io"
+)
+
+// WriteSVG encodes g as an SVG where each horizontal run of same-colored
+// pixels becomes one <rect>. shape-rendering="crispEdges" keeps the pixel
+// look at any zoom. scale only affects the document width/height; the
+// viewBox stays in pixel units.
+func WriteSVG(w io.Writer, g PixelGrid, scale int) error {
+	if scale < 1 {
+		scale = 1
+	}
+	gw, gh := g.Bounds()
+	_, err := fmt.Fprintf(w,
+		`<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="%d" viewBox="0 0 %d %d" shape-rendering="crispEdges">`+"\n",
+		gw*scale, gh*scale, gw, gh)
+	if err != nil {
+		return err
+	}
+	for y := 0; y < gh; y++ {
+		for x := 0; x < gw; {
+			c := g.At(x, y)
+			run := 1
+			for x+run < gw && g.At(x+run, y) == c {
+				run++
+			}
+			if c.A > 0 {
+				opacity := ""
+				if c.A < 255 {
+					opacity = fmt.Sprintf(` fill-opacity="%.3f"`, float64(c.A)/255)
+				}
+				_, err = fmt.Fprintf(w, `<rect x="%d" y="%d" width="%d" height="1" fill="#%02x%02x%02x"%s/>`+"\n",
+					x, y, run, c.R, c.G, c.B, opacity)
+				if err != nil {
+					return err
+				}
+			}
+			x += run
+		}
+	}
+	_, err = io.WriteString(w, "</svg>\n")
+	return err
+}

sfx-maker/README.md

@@ -0,0 +1,68 @@
+# sfx-maker (`sfxc`)
+
+Synthesizes **retro game sound effects** (sfxr-style) from `.sfx` text
+files and writes 16-bit mono **WAV**. Sound design becomes text an agent
+can read, tweak and reason about — no DAW needed. Go, zero
+dependencies, single static binary.
+
+## Build
+
+```bash
+# Arch/Garuda: sudo pacman -S go
+cd sfx-maker
+go build -o build/sfxc .        # or the VS Code task "build sfx-maker"
+go test ./...
+```
+
+## Quick start
+
+```bash
+sfxc preset jump -o jump.sfx      # editable text preset
+sfxc build jump.sfx               # -> jump.wav
+mpv jump.wav                      # listen (or aplay/ffplay)
+
+sfxc preset coin -o coin.wav      # straight to WAV
+sfxc preset coin --seed 3 -o coin3.wav    # deterministic variant
+sfxc info laser.sfx               # validate + summary
+```
+
+Presets: `blip, coin, explosion, hurt, jump, laser, powerup`.
+`--seed 0` is the canonical sound; any other seed nudges pitch/length
+deterministically — ask for three seeds, keep the one that sounds best.
+
+## The `.sfx` format
+
+```
+# comment
+sfx: jump            name
+wave: square         square | saw | sine | triangle | noise
+volume: 0.7          0..1
+attack: 0.01         seconds: fade in
+sustain: 0.08        hold at full volume
+decay: 0.18          fade out (total length = a+s+d, max 10 s)
+freq: 330            start pitch, Hz
+freq-slide: 900      Hz/second (positive = rising, negative = falling)
+duty: 0.5            square pulse width 0.05..0.95 (thinner = buzzier)
+vibrato-depth: 25    pitch wobble, Hz
+vibrato-rate: 9      wobbles per second
+arpeggio: 1.335      multiply pitch by this...
+arpeggio-time: 0.06  ...after this many seconds (classic coin blip)
+lowpass: 2200        cutoff Hz (muffle: explosions, thuds)
+highpass: 300        cutoff Hz (thin out: lasers, clicks)
+sample-rate: 44100   8000-96000
+seed: 1              noise randomness — same seed = same sound
+```
+
+Unknown keys are **errors**, so typos surface immediately. Everything is
+deterministic: same file → byte-identical WAV.
+
+## Recipe intuition for agents
+
+- **Jump**: square wave + rising `freq-slide`.
+- **Coin/pickup**: square + `arpeggio` > 1 shortly after the start.
+- **Laser**: saw + steep negative `freq-slide` + `highpass`.
+- **Explosion**: noise + `lowpass` ~2 kHz + long `decay`.
+- **Hurt**: saw, low pitch, quick fall.
+- **Power-up**: rising slide + `vibrato`.
+
+[`examples/`](examples/) contains all presets as `.sfx` + rendered `.wav`.

sfx-maker/examples/blip.sfx

@@ -0,0 +1,9 @@
+# blip preset (seed 0) — edit freely, then: sfxc build examples/blip.sfx
+sfx: blip
+wave: square
+volume: 0.7
+attack: 0.002
+sustain: 0.03
+decay: 0.05
+freq: 660
+duty: 0.4

sfx-maker/examples/coin.sfx

@@ -0,0 +1,10 @@
+# coin preset (seed 0) — edit freely, then: sfxc build examples/coin.sfx
+sfx: coin
+wave: square
+volume: 0.7
+attack: 0.005
+sustain: 0.08
+decay: 0.25
+freq: 988
+arpeggio: 1.335
+arpeggio-time: 0.06

sfx-maker/examples/explosion.sfx

@@ -0,0 +1,9 @@
+# explosion preset (seed 0) — edit freely, then: sfxc build examples/explosion.sfx
+sfx: explosion
+wave: noise
+volume: 0.7
+attack: 0.01
+sustain: 0.15
+decay: 0.55
+freq-slide: -600
+lowpass: 2200

sfx-maker/examples/hurt.sfx

@@ -0,0 +1,9 @@
+# hurt preset (seed 0) — edit freely, then: sfxc build examples/hurt.sfx
+sfx: hurt
+wave: saw
+volume: 0.7
+attack: 0.005
+sustain: 0.04
+decay: 0.14
+freq: 300
+freq-slide: -700

sfx-maker/examples/jump.sfx

@@ -0,0 +1,9 @@
+# jump preset (seed 0) — edit freely, then: sfxc build examples/jump.sfx
+sfx: jump
+wave: square
+volume: 0.7
+attack: 0.01
+sustain: 0.08
+decay: 0.18
+freq: 330
+freq-slide: 900

sfx-maker/examples/laser.sfx

@@ -0,0 +1,10 @@
+# laser preset (seed 0) — edit freely, then: sfxc build examples/laser.sfx
+sfx: laser
+wave: saw
+volume: 0.7
+attack: 0.005
+sustain: 0.05
+decay: 0.12
+freq: 1400
+freq-slide: -6000
+highpass: 300

sfx-maker/examples/powerup.sfx

@@ -0,0 +1,12 @@
+# powerup preset (seed 0) — edit freely, then: sfxc build examples/powerup.sfx
+sfx: powerup
+wave: square
+volume: 0.7
+attack: 0.01
+sustain: 0.25
+decay: 0.25
+freq: 220
+freq-slide: 700
+duty: 0.4
+vibrato-depth: 25
+vibrato-rate: 9

sfx-maker/go.mod

@@ -0,0 +1,3 @@
+module gitea.brasse-pc.eu/brasse/agent-tools/sfx-maker
+
+go 1.24

sfx-maker/main.go

@@ -0,0 +1,212 @@
+// sfxc synthesizes retro game sound effects from .sfx text files
+// (sfxr-style parameters) and writes 16-bit mono WAV.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gitea.brasse-pc.eu/brasse/agent-tools/sfx-maker/sfx"
+)
+
+var version = "dev"
+
+const usage = `sfxc - sound effect maker for agents
+
+Usage:
+  sfxc build <file.sfx> [-o out.wav]      synthesize a .sfx file to WAV
+  sfxc preset <name> [-o out.sfx|out.wav] [--seed n]
+                                          write a preset (editable .sfx text,
+                                          or straight to .wav)
+  sfxc info <file.sfx>                    validate + print parameters
+  sfxc version
+
+Presets: blip, coin, explosion, hurt, jump, laser, powerup
+--seed 0 (default) is the canonical sound; other seeds give variants.
+
+The .sfx format (all keys optional, '#' comments):
+  sfx: jump            name
+  wave: square         square | saw | sine | triangle | noise
+  volume: 0.7          0..1
+  attack: 0.01         seconds: fade in
+  sustain: 0.08        hold
+  decay: 0.18          fade out
+  freq: 330            start pitch, Hz
+  freq-slide: 900      Hz per second (negative = falling)
+  duty: 0.5            square pulse width 0.05..0.95
+  vibrato-depth: 25    Hz
+  vibrato-rate: 9      Hz
+  arpeggio: 1.335      pitch multiplier that kicks in at...
+  arpeggio-time: 0.06  ...this many seconds
+  lowpass: 2200        filter cutoff Hz
+  highpass: 300        filter cutoff Hz
+  sample-rate: 44100
+  seed: 1              noise randomness (deterministic)
+
+Play the result with e.g.:  mpv out.wav   or   aplay out.wav
+`
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Print(usage)
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "build":
+		cmdBuild(os.Args[2:])
+	case "preset":
+		cmdPreset(os.Args[2:])
+	case "info":
+		cmdInfo(os.Args[2:])
+	case "version", "--version", "-v":
+		fmt.Println("sfxc", version)
+	case "help", "--help", "-h":
+		fmt.Print(usage)
+	default:
+		die("unknown command %q — run 'sfxc help'", os.Args[1])
+	}
+}
+
+// parseInterspersed lets flags appear before or after positional args.
+func parseInterspersed(fs *flag.FlagSet, args []string) {
+	var flags, pos []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if len(a) > 1 && a[0] == '-' {
+			flags = append(flags, a)
+			name := strings.TrimLeft(a, "-")
+			if !strings.Contains(name, "=") {
+				f := fs.Lookup(name)
+				isBool := false
+				if f != nil {
+					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
+						isBool = true
+					}
+				}
+				if !isBool && i+1 < len(args) {
+					i++
+					flags = append(flags, args[i])
+				}
+			}
+		} else {
+			pos = append(pos, a)
+		}
+	}
+	fs.Parse(append(flags, pos...))
+}
+
+func writeWAVFile(path string, p *sfx.Params) error {
+	samples := sfx.Render(p)
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := sfx.WriteWAV(f, samples, p.SampleRate); err != nil {
+		return err
+	}
+	return f.Close()
+}
+
+func cmdBuild(args []string) {
+	fs := flag.NewFlagSet("build", flag.ExitOnError)
+	out := fs.String("o", "", "output .wav (default: input name with .wav)")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("build takes exactly one .sfx file")
+	}
+	p, err := sfx.ParseFile(fs.Arg(0))
+	if err != nil {
+		die("%v", err)
+	}
+	path := *out
+	if path == "" {
+		path = strings.TrimSuffix(fs.Arg(0), filepath.Ext(fs.Arg(0))) + ".wav"
+	}
+	if err := writeWAVFile(path, p); err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("%s  (%s, %.2fs, %d Hz)\n", path, p.Wave, p.Duration(), p.SampleRate)
+}
+
+func cmdPreset(args []string) {
+	fs := flag.NewFlagSet("preset", flag.ExitOnError)
+	out := fs.String("o", "", "output file: .sfx (editable text) or .wav (rendered)")
+	seed := fs.Int64("seed", 0, "0 = canonical, other values = variants")
+	parseInterspersed(fs, args)
+	if fs.NArg() != 1 {
+		die("preset takes exactly one preset name (%s)", sfx.PresetNames())
+	}
+	name := fs.Arg(0)
+	p, err := sfx.Preset(name, *seed)
+	if err != nil {
+		die("%v", err)
+	}
+	path := *out
+	if path == "" {
+		path = name + ".sfx"
+	}
+	switch strings.ToLower(filepath.Ext(path)) {
+	case ".wav":
+		if err := writeWAVFile(path, p); err != nil {
+			die("%v", err)
+		}
+		fmt.Printf("%s  (%s preset, seed %d, %.2fs)\n", path, name, *seed, p.Duration())
+	case ".sfx":
+		f, err := os.Create(path)
+		if err != nil {
+			die("%v", err)
+		}
+		defer f.Close()
+		comment := fmt.Sprintf("%s preset (seed %d) — edit freely, then: sfxc build %s", name, *seed, path)
+		if err := p.Write(f, comment); err != nil {
+			die("%v", err)
+		}
+		fmt.Printf("%s  (%s preset, seed %d — edit then 'sfxc build')\n", path, name, *seed)
+	default:
+		die("-o must end in .sfx or .wav")
+	}
+}
+
+func cmdInfo(args []string) {
+	if len(args) != 1 {
+		die("info takes exactly one .sfx file")
+	}
+	p, err := sfx.ParseFile(args[0])
+	if err != nil {
+		die("%v", err)
+	}
+	fmt.Printf("sfx:       %s\n", p.Name)
+	fmt.Printf("wave:      %s\n", p.Wave)
+	fmt.Printf("duration:  %.3fs (attack %.3g + sustain %.3g + decay %.3g)\n",
+		p.Duration(), p.Attack, p.Sustain, p.Decay)
+	if p.Wave != "noise" {
+		fmt.Printf("freq:      %g Hz", p.Freq)
+		if p.FreqSlide != 0 {
+			fmt.Printf("  (slide %+g Hz/s)", p.FreqSlide)
+		}
+		fmt.Println()
+	}
+	if p.ArpFactor != 0 {
+		fmt.Printf("arpeggio:  x%g at %gs\n", p.ArpFactor, p.ArpTime)
+	}
+	if p.VibratoDepth > 0 {
+		fmt.Printf("vibrato:   ±%g Hz at %g Hz\n", p.VibratoDepth, p.VibratoRate)
+	}
+	if p.LowPass > 0 {
+		fmt.Printf("lowpass:   %g Hz\n", p.LowPass)
+	}
+	if p.HighPass > 0 {
+		fmt.Printf("highpass:  %g Hz\n", p.HighPass)
+	}
+	fmt.Printf("volume:    %g\nsamplerate:%d\n", p.Volume, p.SampleRate)
+	fmt.Println("valid:     yes")
+}
+
+func die(format string, a ...any) {
+	fmt.Fprintf(os.Stderr, "sfxc: "+format+"\n", a...)
+	os.Exit(1)
+}

sfx-maker/sfx/params.go

@@ -0,0 +1,223 @@
+// Package sfx synthesizes retro game sound effects (sfxr-style) from
+// text parameter files and renders them to 16-bit mono WAV.
+package sfx
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// Params describes one sound effect. Zero values mean "off" for the
+// optional effects; Defaults() fills the required fields.
+type Params struct {
+	Name string
+	Wave string // square | saw | sine | triangle | noise
+
+	Volume float64 // 0..1 master gain
+
+	// envelope, seconds
+	Attack  float64 // 0 -> Volume
+	Sustain float64 // hold at Volume
+	Decay   float64 // Volume -> 0
+
+	Freq      float64 // start frequency, Hz
+	FreqSlide float64 // Hz per second, may be negative
+	FreqMin   float64 // clamp; sound stops below this (default 20 Hz)
+
+	Duty float64 // square wave duty cycle 0.05..0.95 (default 0.5)
+
+	VibratoDepth float64 // Hz
+	VibratoRate  float64 // Hz
+
+	ArpFactor float64 // frequency multiplier applied at ArpTime (0 = off)
+	ArpTime   float64 // seconds
+
+	LowPass  float64 // cutoff Hz (0 = off)
+	HighPass float64 // cutoff Hz (0 = off)
+
+	SampleRate int   // default 44100
+	Seed       int64 // noise seed (default 1)
+}
+
+// Defaults returns a Params with sensible base values.
+func Defaults() Params {
+	return Params{
+		Wave:       "square",
+		Volume:     0.7,
+		Attack:     0.01,
+		Sustain:    0.1,
+		Decay:      0.15,
+		Freq:       440,
+		FreqMin:    20,
+		Duty:       0.5,
+		SampleRate: 44100,
+		Seed:       1,
+	}
+}
+
+// Duration is the total length of the sound in seconds.
+func (p *Params) Duration() float64 { return p.Attack + p.Sustain + p.Decay }
+
+// Validate checks ranges and returns a helpful error.
+func (p *Params) Validate() error {
+	switch p.Wave {
+	case "square", "saw", "sine", "triangle", "noise":
+	default:
+		return fmt.Errorf("wave %q must be square, saw, sine, triangle or noise", p.Wave)
+	}
+	if p.Volume < 0 || p.Volume > 1 {
+		return fmt.Errorf("volume %g out of range 0-1", p.Volume)
+	}
+	if p.Attack < 0 || p.Sustain < 0 || p.Decay < 0 {
+		return fmt.Errorf("attack/sustain/decay must be >= 0")
+	}
+	if p.Duration() <= 0 {
+		return fmt.Errorf("total duration is 0 — set attack, sustain and/or decay")
+	}
+	if p.Duration() > 10 {
+		return fmt.Errorf("total duration %.2fs is too long (max 10s)", p.Duration())
+	}
+	if p.Wave != "noise" && (p.Freq <= 0 || p.Freq > 20000) {
+		return fmt.Errorf("freq %g out of range 1-20000 Hz", p.Freq)
+	}
+	if p.Duty < 0.05 || p.Duty > 0.95 {
+		return fmt.Errorf("duty %g out of range 0.05-0.95", p.Duty)
+	}
+	if p.SampleRate < 8000 || p.SampleRate > 96000 {
+		return fmt.Errorf("sample-rate %d out of range 8000-96000", p.SampleRate)
+	}
+	return nil
+}
+
+// ParseFile reads a .sfx file; the name defaults to the file name.
+func ParseFile(path string) (*Params, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	p, err := Parse(f)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", path, err)
+	}
+	if p.Name == "" {
+		p.Name = strings.TrimSuffix(filepath.Base(path), filepath.Ext(path))
+	}
+	return p, nil
+}
+
+// Parse reads the .sfx text format: one "key: value" per line,
+// '#' comments. Unknown keys are errors so typos surface immediately.
+func Parse(r io.Reader) (*Params, error) {
+	p := Defaults()
+	sc := bufio.NewScanner(r)
+	lineNo := 0
+	for sc.Scan() {
+		lineNo++
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		i := strings.Index(line, ":")
+		if i < 0 {
+			return nil, fmt.Errorf("line %d: want 'key: value', got %q", lineNo, line)
+		}
+		key := strings.ToLower(strings.TrimSpace(line[:i]))
+		val := strings.TrimSpace(line[i+1:])
+		if j := strings.Index(val, " #"); j >= 0 { // trailing comment
+			val = strings.TrimSpace(val[:j])
+		}
+		var err error
+		switch key {
+		case "sfx", "name":
+			p.Name = val
+		case "wave":
+			p.Wave = strings.ToLower(val)
+		case "volume":
+			p.Volume, err = strconv.ParseFloat(val, 64)
+		case "attack":
+			p.Attack, err = strconv.ParseFloat(val, 64)
+		case "sustain":
+			p.Sustain, err = strconv.ParseFloat(val, 64)
+		case "decay":
+			p.Decay, err = strconv.ParseFloat(val, 64)
+		case "freq":
+			p.Freq, err = strconv.ParseFloat(val, 64)
+		case "freq-slide":
+			p.FreqSlide, err = strconv.ParseFloat(val, 64)
+		case "freq-min":
+			p.FreqMin, err = strconv.ParseFloat(val, 64)
+		case "duty":
+			p.Duty, err = strconv.ParseFloat(val, 64)
+		case "vibrato-depth":
+			p.VibratoDepth, err = strconv.ParseFloat(val, 64)
+		case "vibrato-rate":
+			p.VibratoRate, err = strconv.ParseFloat(val, 64)
+		case "arpeggio":
+			p.ArpFactor, err = strconv.ParseFloat(val, 64)
+		case "arpeggio-time":
+			p.ArpTime, err = strconv.ParseFloat(val, 64)
+		case "lowpass":
+			p.LowPass, err = strconv.ParseFloat(val, 64)
+		case "highpass":
+			p.HighPass, err = strconv.ParseFloat(val, 64)
+		case "sample-rate":
+			p.SampleRate, err = strconv.Atoi(val)
+		case "seed":
+			p.Seed, err = strconv.ParseInt(val, 10, 64)
+		default:
+			return nil, fmt.Errorf("line %d: unknown key %q", lineNo, key)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("line %d: %s: bad value %q", lineNo, key, val)
+		}
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+	if err := p.Validate(); err != nil {
+		return nil, err
+	}
+	return &p, nil
+}
+
+// Write renders the params back to the .sfx text format (used by the
+// preset generator so agents get an editable file).
+func (p *Params) Write(w io.Writer, comment string) error {
+	bw := bufio.NewWriter(w)
+	if comment != "" {
+		fmt.Fprintf(bw, "# %s\n", comment)
+	}
+	fmt.Fprintf(bw, "sfx: %s\nwave: %s\nvolume: %g\n", p.Name, p.Wave, p.Volume)
+	fmt.Fprintf(bw, "attack: %g\nsustain: %g\ndecay: %g\n", p.Attack, p.Sustain, p.Decay)
+	if p.Wave != "noise" {
+		fmt.Fprintf(bw, "freq: %g\n", p.Freq)
+	}
+	if p.FreqSlide != 0 {
+		fmt.Fprintf(bw, "freq-slide: %g\n", p.FreqSlide)
+	}
+	if p.Wave == "square" && p.Duty != 0.5 {
+		fmt.Fprintf(bw, "duty: %g\n", p.Duty)
+	}
+	if p.VibratoDepth > 0 && p.VibratoRate > 0 {
+		fmt.Fprintf(bw, "vibrato-depth: %g\nvibrato-rate: %g\n", p.VibratoDepth, p.VibratoRate)
+	}
+	if p.ArpFactor != 0 {
+		fmt.Fprintf(bw, "arpeggio: %g\narpeggio-time: %g\n", p.ArpFactor, p.ArpTime)
+	}
+	if p.LowPass > 0 {
+		fmt.Fprintf(bw, "lowpass: %g\n", p.LowPass)
+	}
+	if p.HighPass > 0 {
+		fmt.Fprintf(bw, "highpass: %g\n", p.HighPass)
+	}
+	if p.Seed != 1 {
+		fmt.Fprintf(bw, "seed: %d\n", p.Seed)
+	}
+	return bw.Flush()
+}

sfx-maker/sfx/presets.go

@@ -0,0 +1,114 @@
+package sfx
+
+import (
+	"fmt"
+	"math/rand"
+	"sort"
+)
+
+// Preset returns ready-made parameters for classic game sounds.
+// seed 0 gives the canonical version; other seeds vary it slightly so
+// agents can generate alternatives ("give me three coin variants").
+func Preset(name string, seed int64) (*Params, error) {
+	p := Defaults()
+	p.Name = name
+	switch name {
+	case "jump":
+		p.Wave = "square"
+		p.Duty = 0.5
+		p.Freq = 330
+		p.FreqSlide = 900
+		p.Attack = 0.01
+		p.Sustain = 0.08
+		p.Decay = 0.18
+	case "coin":
+		p.Wave = "square"
+		p.Duty = 0.5
+		p.Freq = 988
+		p.ArpFactor = 1.335 // up a fourth: B5 -> E6
+		p.ArpTime = 0.06
+		p.Attack = 0.005
+		p.Sustain = 0.08
+		p.Decay = 0.25
+	case "laser":
+		p.Wave = "saw"
+		p.Freq = 1400
+		p.FreqSlide = -6000
+		p.Attack = 0.005
+		p.Sustain = 0.05
+		p.Decay = 0.12
+		p.HighPass = 300
+	case "explosion":
+		p.Wave = "noise"
+		p.Freq = 900
+		p.FreqSlide = -600
+		p.Attack = 0.01
+		p.Sustain = 0.15
+		p.Decay = 0.55
+		p.LowPass = 2200
+	case "hurt":
+		p.Wave = "saw"
+		p.Freq = 300
+		p.FreqSlide = -700
+		p.Attack = 0.005
+		p.Sustain = 0.04
+		p.Decay = 0.14
+	case "powerup":
+		p.Wave = "square"
+		p.Duty = 0.4
+		p.Freq = 220
+		p.FreqSlide = 700
+		p.VibratoDepth = 25
+		p.VibratoRate = 9
+		p.Attack = 0.01
+		p.Sustain = 0.25
+		p.Decay = 0.25
+	case "blip":
+		p.Wave = "square"
+		p.Duty = 0.4
+		p.Freq = 660
+		p.Attack = 0.002
+		p.Sustain = 0.03
+		p.Decay = 0.05
+	default:
+		return nil, fmt.Errorf("unknown preset %q (available: %s)", name, PresetNames())
+	}
+	if seed != 0 {
+		vary(&p, seed)
+	}
+	if err := p.Validate(); err != nil {
+		return nil, fmt.Errorf("preset %s (seed %d): %w", name, seed, err)
+	}
+	return &p, nil
+}
+
+// vary nudges the tonal parameters deterministically from the seed.
+func vary(p *Params, seed int64) {
+	rng := rand.New(rand.NewSource(seed))
+	jitter := func(v, amount float64) float64 {
+		return v * (1 + amount*(rng.Float64()*2-1))
+	}
+	p.Freq = jitter(p.Freq, 0.15)
+	p.FreqSlide = jitter(p.FreqSlide, 0.25)
+	p.Sustain = jitter(p.Sustain, 0.2)
+	p.Decay = jitter(p.Decay, 0.2)
+	if p.ArpFactor != 0 {
+		p.ArpFactor = jitter(p.ArpFactor, 0.05)
+	}
+	p.Seed = seed // noise variation too
+}
+
+var presetNames = []string{"blip", "coin", "explosion", "hurt", "jump", "laser", "powerup"}
+
+// PresetNames lists the available presets, sorted.
+func PresetNames() string {
+	sort.Strings(presetNames)
+	out := ""
+	for i, n := range presetNames {
+		if i > 0 {
+			out += ", "
+		}
+		out += n
+	}
+	return out
+}

sfx-maker/sfx/sfx_test.go

@@ -0,0 +1,164 @@
+package sfx
+
+import (
+	"bytes"
+	"math"
+	"strings"
+	"testing"
+)
+
+func TestParseAndValidate(t *testing.T) {
+	src := `
+# a jump
+sfx: jump
+wave: square
+freq: 330
+freq-slide: 900
+attack: 0.01
+sustain: 0.08
+decay: 0.18
+duty: 0.4
+`
+	p, err := Parse(strings.NewReader(src))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Name != "jump" || p.Wave != "square" || p.Freq != 330 || p.Duty != 0.4 {
+		t.Errorf("parsed wrong: %+v", p)
+	}
+	if math.Abs(p.Duration()-0.27) > 1e-9 {
+		t.Errorf("duration = %g, want 0.27", p.Duration())
+	}
+}
+
+func TestParseErrors(t *testing.T) {
+	cases := map[string]string{
+		"unknown key":  "wat: 3\n",
+		"bad wave":     "wave: wobble\n",
+		"bad value":    "freq: abc\n",
+		"zero length":  "attack: 0\nsustain: 0\ndecay: 0\n",
+		"volume range": "volume: 2\n",
+		"duty range":   "duty: 0.99\n",
+	}
+	for name, src := range cases {
+		if _, err := Parse(strings.NewReader(src)); err == nil {
+			t.Errorf("%s: expected error", name)
+		}
+	}
+}
+
+func TestRenderBasics(t *testing.T) {
+	p := Defaults()
+	p.Wave = "sine"
+	p.Attack, p.Sustain, p.Decay = 0.01, 0.05, 0.05
+	samples := Render(&p)
+	want := int(0.11 * 44100)
+	if len(samples) != want {
+		t.Errorf("samples = %d, want %d", len(samples), want)
+	}
+	var peak float64
+	for _, s := range samples {
+		if math.Abs(s) > peak {
+			peak = math.Abs(s)
+		}
+		if s > 1 || s < -1 {
+			t.Fatalf("sample %g out of range", s)
+		}
+	}
+	if peak < 0.5 {
+		t.Errorf("peak %g suspiciously quiet", peak)
+	}
+	// end of decay should be silent-ish
+	tail := samples[len(samples)-10:]
+	for _, s := range tail {
+		if math.Abs(s) > 0.1 {
+			t.Errorf("tail sample %g not decayed", s)
+		}
+	}
+}
+
+func TestRenderDeterministic(t *testing.T) {
+	p := Defaults()
+	p.Wave = "noise"
+	p.Seed = 42
+	a := Render(&p)
+	b := Render(&p)
+	for i := range a {
+		if a[i] != b[i] {
+			t.Fatalf("noise render not deterministic at sample %d", i)
+		}
+	}
+}
+
+func TestAllWavesAndPresets(t *testing.T) {
+	for _, w := range []string{"square", "saw", "sine", "triangle", "noise"} {
+		p := Defaults()
+		p.Wave = w
+		if s := Render(&p); len(s) == 0 {
+			t.Errorf("wave %s rendered nothing", w)
+		}
+	}
+	for _, name := range []string{"blip", "coin", "explosion", "hurt", "jump", "laser", "powerup"} {
+		p, err := Preset(name, 0)
+		if err != nil {
+			t.Errorf("preset %s: %v", name, err)
+			continue
+		}
+		s := Render(p)
+		var sum float64
+		for _, v := range s {
+			sum += v * v
+		}
+		rms := math.Sqrt(sum / float64(len(s)))
+		if rms < 0.01 {
+			t.Errorf("preset %s is nearly silent (rms %g)", name, rms)
+		}
+		// variants stay valid
+		if _, err := Preset(name, 7); err != nil {
+			t.Errorf("preset %s seed 7: %v", name, err)
+		}
+	}
+	if _, err := Preset("nope", 0); err == nil {
+		t.Error("unknown preset should error")
+	}
+}
+
+func TestWAVRoundTrip(t *testing.T) {
+	p := Defaults()
+	samples := Render(&p)
+	var buf bytes.Buffer
+	if err := WriteWAV(&buf, samples, p.SampleRate); err != nil {
+		t.Fatal(err)
+	}
+	sr, bits, ch, dataBytes, err := ReadWAVHeader(&buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sr != 44100 || bits != 16 || ch != 1 {
+		t.Errorf("header: sr=%d bits=%d ch=%d", sr, bits, ch)
+	}
+	if dataBytes != len(samples)*2 {
+		t.Errorf("dataBytes = %d, want %d", dataBytes, len(samples)*2)
+	}
+	if buf.Len() != dataBytes {
+		t.Errorf("body length %d != declared %d", buf.Len(), dataBytes)
+	}
+}
+
+func TestParamsWriteRoundTrip(t *testing.T) {
+	p, err := Preset("coin", 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var buf bytes.Buffer
+	if err := p.Write(&buf, "test"); err != nil {
+		t.Fatal(err)
+	}
+	back, err := Parse(&buf)
+	if err != nil {
+		t.Fatalf("re-parse of written .sfx failed: %v\n%s", err, buf.String())
+	}
+	if back.Freq != p.Freq || back.ArpFactor != p.ArpFactor || back.Seed != p.Seed {
+		t.Errorf("roundtrip mismatch: %+v vs %+v", back, p)
+	}
+}

sfx-maker/sfx/synth.go

@@ -0,0 +1,122 @@
+package sfx
+
+import (
+	"math"
+	"math/rand"
+)
+
+// Render synthesizes the effect into float64 samples in [-1, 1].
+func Render(p *Params) []float64 {
+	sr := float64(p.SampleRate)
+	n := int(p.Duration() * sr)
+	out := make([]float64, n)
+	rng := rand.New(rand.NewSource(p.Seed))
+
+	phase := 0.0
+	noiseVal := 0.0
+	noiseCounter := 0.0
+
+	// one-pole filter states
+	lpState := 0.0
+	hpState := 0.0
+	hpPrevIn := 0.0
+	dt := 1 / sr
+	lpAlpha := 0.0
+	if p.LowPass > 0 {
+		rc := 1 / (2 * math.Pi * p.LowPass)
+		lpAlpha = dt / (rc + dt)
+	}
+	hpAlpha := 0.0
+	if p.HighPass > 0 {
+		rc := 1 / (2 * math.Pi * p.HighPass)
+		hpAlpha = rc / (rc + dt)
+	}
+
+	for i := 0; i < n; i++ {
+		t := float64(i) / sr
+
+		f := p.Freq + p.FreqSlide*t
+		if p.ArpFactor != 0 && p.ArpTime > 0 && t >= p.ArpTime {
+			f *= p.ArpFactor
+		}
+		if p.VibratoDepth > 0 && p.VibratoRate > 0 {
+			f += p.VibratoDepth * math.Sin(2*math.Pi*p.VibratoRate*t)
+		}
+		if f < p.FreqMin {
+			f = p.FreqMin
+		}
+
+		var s float64
+		if p.Wave == "noise" {
+			// pitched noise: new random value f*4 times per second
+			noiseCounter += f * 4 * dt
+			if noiseCounter >= 1 || i == 0 {
+				noiseCounter = math.Mod(noiseCounter, 1)
+				noiseVal = rng.Float64()*2 - 1
+			}
+			s = noiseVal
+		} else {
+			phase += f * dt
+			ph := math.Mod(phase, 1)
+			switch p.Wave {
+			case "square":
+				if ph < p.Duty {
+					s = 1
+				} else {
+					s = -1
+				}
+			case "saw":
+				s = 2*ph - 1
+			case "triangle":
+				if ph < 0.5 {
+					s = 4*ph - 1
+				} else {
+					s = 3 - 4*ph
+				}
+			case "sine":
+				s = math.Sin(2 * math.Pi * ph)
+			}
+		}
+
+		s *= envelope(p, t)
+
+		if lpAlpha > 0 {
+			lpState += lpAlpha * (s - lpState)
+			s = lpState
+		}
+		if hpAlpha > 0 {
+			hpState = hpAlpha * (hpState + s - hpPrevIn)
+			hpPrevIn = s
+			s = hpState
+		}
+
+		s *= p.Volume
+		if s > 1 {
+			s = 1
+		} else if s < -1 {
+			s = -1
+		}
+		out[i] = s
+	}
+	return out
+}
+
+// envelope is a linear attack / sustain / decay gain in 0..1.
+func envelope(p *Params, t float64) float64 {
+	switch {
+	case t < p.Attack:
+		return t / p.Attack
+	case t < p.Attack+p.Sustain:
+		return 1
+	default:
+		d := t - p.Attack - p.Sustain
+		if p.Decay <= 0 {
+			return 0
+		}
+		g := 1 - d/p.Decay
+		if g < 0 {
+			g = 0
+		}
+		return g
+	}
+}

sfx-maker/sfx/wav.go

@@ -0,0 +1,54 @@
+package sfx
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"math"
+)
+
+// WriteWAV encodes samples ([-1,1] floats) as a 16-bit mono PCM WAV.
+func WriteWAV(w io.Writer, samples []float64, sampleRate int) error {
+	dataLen := len(samples) * 2
+	var hdr [44]byte
+	copy(hdr[0:4], "RIFF")
+	binary.LittleEndian.PutUint32(hdr[4:8], uint32(36+dataLen))
+	copy(hdr[8:12], "WAVE")
+	copy(hdr[12:16], "fmt ")
+	binary.LittleEndian.PutUint32(hdr[16:20], 16)                   // fmt chunk size
+	binary.LittleEndian.PutUint16(hdr[20:22], 1)                    // PCM
+	binary.LittleEndian.PutUint16(hdr[22:24], 1)                    // mono
+	binary.LittleEndian.PutUint32(hdr[24:28], uint32(sampleRate))   // sample rate
+	binary.LittleEndian.PutUint32(hdr[28:32], uint32(sampleRate*2)) // byte rate
+	binary.LittleEndian.PutUint16(hdr[32:34], 2)                    // block align
+	binary.LittleEndian.PutUint16(hdr[34:36], 16)                   // bits per sample
+	copy(hdr[36:40], "data")
+	binary.LittleEndian.PutUint32(hdr[40:44], uint32(dataLen))
+	if _, err := w.Write(hdr[:]); err != nil {
+		return err
+	}
+	buf := make([]byte, 2*len(samples))
+	for i, s := range samples {
+		v := int16(math.Round(s * 32767))
+		binary.LittleEndian.PutUint16(buf[i*2:], uint16(v))
+	}
+	_, err := w.Write(buf)
+	return err
+}
+
+// ReadWAVHeader sanity-parses a WAV header (used in tests and info).
+func ReadWAVHeader(r io.Reader) (sampleRate, bits, channels, dataBytes int, err error) {
+	var hdr [44]byte
+	if _, err = io.ReadFull(r, hdr[:]); err != nil {
+		return
+	}
+	if string(hdr[0:4]) != "RIFF" || string(hdr[8:12]) != "WAVE" {
+		err = fmt.Errorf("not a WAV file")
+		return
+	}
+	channels = int(binary.LittleEndian.Uint16(hdr[22:24]))
+	sampleRate = int(binary.LittleEndian.Uint32(hdr[24:28]))
+	bits = int(binary.LittleEndian.Uint16(hdr[34:36]))
+	dataBytes = int(binary.LittleEndian.Uint32(hdr[40:44]))
+	return
+}