@moonstage/physics

Rigid-body physics for Moonstage. The engine is written in MoonBit (moonbit/engine/engine.mbt), compiled to WebAssembly, and embedded in this package's single module, so it works in folder bundles, .msp packages and single-file games, in browsers and in Node.

• Circles and rotating boxes (polygons collide as their bounding box)
• Contacts with torque, so boxes tumble and circles roll; friction and restitution
• Sensors with collision / collisionEnd events
• Distance joints, and revolute (pin) joints with motors
• Deterministic; one isolated engine instance per runtime
• About 2 ms per tick for 600 rotating bodies on a laptop (npm run bench)

Use

The Moonstage CLI ships with this plugin, so a project just names it:

"physics": { "gravity": [0, 900] },
"plugins": { "@moonstage/physics": { "module": "@moonstage/physics", "config": { "substeps": 4, "iterations": 8 } } }

Then give entities physicsBody, collider and joint components, and drive bodies from behaviors through state vx / vy / av. The contract is in docs/physics.md.

Build

npm run build at the repository root compiles the MoonBit engine (moon build --target wasm) and embeds it into dist/index.js.