tile-artist

Tile Artist

Generates tiles.png and tile metadata. GPT Image 2 is the default — one API call per non-SKY tile, each generated at 512×512 then downscaled to 32×32. Falls back to procedural flat-color cells when FAL_KEY is unavailable.

Two modes

Mode	When	Cost	Output
GPT Image 2 (default)	FAL_KEY present	~$0.01–0.05 per tile at low quality	Real pixel-art textures (cobblestone, brick mortar, grass blades, etc.)
Procedural fallback	No API key	Free	Flat-colored cells with a subtle 1-pixel darker border

Both produce identical manifest entries — downstream Preload and Game.js are unaware which was used.

When to use

After game-designer produces a GDD with tilesetPalette. Runs in parallel with sprite-artist and bg-artist.

GDD palette format

Each entry in gdd.tilesetPalette:

{
  "id": "STONE",          // used as tile key in levels and manifest.ids
  "color": "#607070",     // fallback color if GPT call fails
  "passable": false,      // false = solid collision, true = walk-through
  "desc": "gray cobblestone dungeon floor, beveled stone blocks with mortar cracks"
  // ↑ optional but strongly recommended — used as the GPT Image 2 prompt
}

If desc is omitted, the skill falls back to a built-in description map keyed on id (covers common ids: STONE, BRICK, SPIKE, LADDER, PIPE, FLOOR, ACID, GROUND, WALL, PROP, GRASS, WATER, FLOWER, TREE). If the id is not in the map, it constructs a generic prompt from the id and color.

How GPT generation works

For each palette entry (skipping SKY / #FF00FF tiles):

1. Build a prompt: "Pixel art game tile, flat seamlessly tileable surface texture: {desc}. {genre} game aesthetic. Seamlessly tileable, 16-bit retro pixel art, chunky well-defined pixels, clean sharp edges. No text, no characters, no HUD elements, no border frame."
2. Call fal.run/openai/gpt-image-2 at image_size: { width: 512, height: 512 }, quality: low (configurable).
3. Downscale the 512×512 result to tileSize × tileSize (default 32) using sharp.
4. Copy into position i * tileSize in the horizontal output strip.
5. If the call fails, paint the solid color value for that tile (no crash).

SKY tiles are filled with solid magenta (#FF00FF) — Game.js hides them via setAlpha(0) so the parallax background shows through.

Output

• public/assets/tiles.png — horizontal strip: (tileSize × numTiles) × tileSize pixels, one tile per palette entry.
• Manifest entry under tiles:

{
  "tiles": {
    "relSheet": "assets/tiles.png",
    "tileSize": 32,
    "ids":      ["SKY", "STONE", "BRICK", "SPIKE", "LADDER"],
    "passable": [true, false, false, true, true]
  }
}

ids[i] and passable[i] both correspond to tile index i in any level's tiles[][] array.

Implementation

The core function is generateTilesetGPT() in src/lib/sprites.js. It is called by scripts/gen_game.mjs for all example games. For agent-driven pipeline use, invoke it from codesmith or a custom orchestration script:

import { generateTilesetGPT } from '../src/lib/sprites.js';

const tileset = await generateTilesetGPT({
  palette:  gdd.tilesetPalette,   // array of { id, color, passable, desc? }
  outPath:  'public/assets/tiles.png',
  tileSize: 32,
  genre:    gdd.genre,            // added to each tile prompt for style coherence
  tagline:  gdd.tagline,          // added to each tile prompt
  quality:  'low',                // low | medium | high
  log:      console.log,
});
// → { sheet, tileSize, ids }

Fallback scripts (kept for reference / standalone use):

• scripts/paint_tiles.mjs <project-dir> — procedural flat-color strip, no API key needed.
• scripts/generate_tiles_gpt.mjs <project-dir> [--quality low] — thin CLI wrapper around generateTilesetGPT.

Dependencies

• sharp — raw RGBA buffer → PNG, resize.
• FAL_KEY in env or ~/.all-skills/.env — for GPT Image 2 calls. Falls back gracefully if missing.

Why GPT tiles look better than procedural

Procedural tiles are obviously synthetic — flat green for grass, flat brown for dirt. GPT Image 2 produces texture variation: grass blades, dirt speckles, brick mortar lines, pipe rivets. At 32×32 the detail reads clearly. Combined with bg-artist's parallax background, the visual quality jumps from "tech demo" to "real game".

Transparent SKY trick

For platformers and action games, the first palette entry is { id: "SKY", color: "#FF00FF", passable: true }. The tile artist fills it with solid magenta. In Game.js:

const skyIdx = manifest.tiles.ids.indexOf('SKY');
if (skyIdx >= 0) {
  this._tileLayer.forEachTile(t => { if (t.index === skyIdx) t.setAlpha(0); });
}

This makes the sky tile invisible, letting the bg-artist background show through — no extra draw calls, no extra texture.