🚂🤖 LittleJS AI

An AI-assisted toolkit for making HTML5 games with LittleJS — starter templates, helper modules, docs, and prompts for AI workflows. The games built with it live in the LittleJS Arcade.

🎮 ▶ Play 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, sprites, and live tweaking
• 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

Use LittleJS AI directly inside Claude Code — no clone required. Install once:

/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 four skills:

• littlejs-conventions — engine rules and pitfalls, applied automatically to any LittleJS code
• new-littlejs-game — scaffolds a complete playable game project
• littlejs-api — exact API signature lookup from the bundled reference
• atlas-shape-art — fast recolorable shape sprites from the built-in atlas

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 refresh reference.md by hand.

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

• LittleJS Engine — the main LittleJS repository
• LittleJS Arcade — 50+ finished games built with these tools, in their own repo (source)
• Templates Folder — starting templates and reusable components
• LittleJS GPT AI — use ChatGPT to make games without writing any code (source)

🛠️ 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

1. Copy the starter folder examples/emptyGame/ to examples/<yourGame>/.
2. Edit game.js — and add more files (player.js, ui.js, constants.js, …) as the game grows.
3. 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 via an HTML slider overlay
• uiGame.html — canvas-drawn UI (menus, sliders, dialogs)
• threejsGame.html — three.js 3D scene behind the LittleJS canvas

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), tweakables.js (live value tweaking).

🧊 Three.js 3D games

The engine includes a three.js plugin (ThreeJSPlugin + ThreeJSObject) that renders a 3D scene behind the LittleJS canvas — LittleJS keeps handling the input, physics, and HUD while three.js draws the world. See examples/threejsGame/ for a mini 3D platformer demo (three.js loads from a CDN at startup, everything else works the same as any other game).

🕹️ 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.

• 🤖 Robo Rescue
• 🐸 Froggit
• 🧩 Tetrix
• 🏓 Pong
• 🧛 Emoji Survivors
• 🏙️ Missile Defense
• ⛳ Mini Golf
• 🎱 Pool
• 🃏 Freecell
• 👾 Space Intruders
• 👻 Maze Munch
• 🌑 Astroblast
• 🔴 Checkers