🚂🤖 LittleJS AI
An AI-assisted toolkit for making HTML5 games with LittleJS — starter templates, helper modules, agent instructions for any coding AI, and a Claude Code plugin. The games built with it live in the LittleJS Arcade.
LittleJS is a fast, lightweight, and fully open source HTML5 game engine designed for simplicity and performance.
This repo is the AI-assisted LittleJS toolkit — everything you need to build games, but not the games themselves:
- starter templates you can fork and remix
- helper modules for menus, sound/FX, and sprites
- docs and prompts to improve LittleJS + AI workflows
The 50+ finished games built with these tools live in their own repo: the LittleJS Arcade (source).
Want to make a game without writing code? Try the LittleJS GPT!
🤖 Claude Code Plugin
Make games with LittleJS, a fast open-source HTML5 engine that's simple to build on, straight from Claude Code. Ask for a game and get a complete, playable project that opens from a file. Because the engine already handles rendering, input, physics, collision and audio, nothing gets rebuilt from scratch: the tokens go into your game, not the plumbing. Templates for menus, sound, sprite art and board games already work. Install once, no clone required:
/plugin marketplace add KilledByAPixel/LittleJS-AI
/plugin install littlejs@littlejs-ai
Then in any empty folder, ask for a game ("make me a breakout game"). Claude scaffolds a complete project — engine included — that opens straight from file:// with no server and no npm install.
The plugin ships five skills:
littlejs-conventions — engine rules and pitfalls, applied automatically to any LittleJS codenew-littlejs-game — scaffolds a complete playable game projectlittlejs-api — exact API signature lookup from the bundled referenceatlas-shape-art — fast recolorable shape sprites from the built-in atlascustom-level-editor — turns the engine's built-in 2D and 3D level editors into an editor for your game
Cloning this repo is only needed for browsing the templates by hand — the plugin bundles everything else.
Developing the plugin itself? Load it from your working tree with claude --plugin-dir . (use forward slashes in the path — backslashes get mangled and silently load nothing), then /reload-plugins after edits. Don't /plugin install your local copy — that installs a frozen snapshot.
Every user-visible change needs two things in the same commit: a bumped version in .claude-plugin/plugin.json and an entry in CHANGELOG.md. The plugin cache is keyed by version, so without a bump, people who already installed the plugin receive nothing. When bumping the engine in dist/, also copy the engine repo's REFERENCE.md over reference.md and its EDITOR.md over skills/custom-level-editor/EDITOR.md.
For other tools, LittleJS also works great with GitHub Copilot, Codex, and Cursor.
LittleJS and everything in this repository is MIT licensed! See LICENSE for details.
📚 Resources
🛠️ Make Your Own
Clone the repo and you have everything you need to build games — from quick prototypes to large, multi-file projects. No external assets and no dependencies to play; the only npm packages are optional build tools.
Start a new game
- Copy the starter folder examples/emptyGame/ to
examples/<yourGame>/.
- Edit
game.js — and add more files (player.js, ui.js, constants.js, …) as the game grows.
- Open
index.html in a web browser. That's it — it runs straight from file://, no server needed.
Games use the global LittleJS API: load dist/littlejs.js with a plain <script> tag and call globals like engineInit, drawText, and vec2 directly. Keep gameplay modular across several .js files for medium and large games.
Ship a single-file build (optional)
A single root build.mjs concatenates the engine + your source, minifies it, and produces one self-contained index.html plus a .zip (great for game jams).
npm install # once, in the repo root — installs terser + bestzip
node build.mjs yourGame # builds examples/yourGame/build/ and yourGame.zip
node build.mjs --all # builds every game that has a build.json
📝 Feature templates
Single-file references to copy patterns from when adding a feature — not full game scaffolds:
- game.html — minimal scaffold (shapes, text, camera)
- boardGame.html — grid-based games (chess, sokoban, match-3)
- menuGame.html — title, pause, options, medals, HUD toolbar
- box2dGame.html — Box2D physics (pool, plinko, pinball)
- textureGame.html — procedural sprite atlases from canvas draw ops
- tweakableGame.html — live-tweak globals with the engine's tweakables panel
- uiGame.html — canvas-drawn UI (menus, sliders, dialogs)
Mix in helper scripts to add features: menus.js (DOM menus + best score + game-over dialog + setPlaying/quitToTitle), gameFx.js (procedural SFX + screen shake), textureGenerator.js (sprite painter). Live value tweaking needs no helper — tweak() is built into the engine's debug build.
🧊 3D games
LittleJS has a built-in 3D renderer that shares the canvas with your 2D game: meshes from shape builders, height map terrain, shadows, lights, fog, particles, cameras, and 3D objects with the same physics, children and timers as 2D ones. It is part of the engine file, so a 3D game still opens straight from file:// with nothing to install or download. See examples/3dGame/ — the engine's own 3D example — for all of it in one scene.
🕹️ Built With These Tools
A few favorites from the LittleJS Arcade — every one made with the templates and helpers in this repo. Fork any of them from the Arcade repo as a starting point for your own.
