Physics Lab

Rigid bodies and deformables in the browser, with no solver to install and nothing to import. Drop a stack of boxes and a ball at it, or hang a cloth and turn the wind up, then step one substep at a time to see what the solver is actually doing. Contact points, their normals, distance links and coil springs all have debug glyphs, and the collider wireframes can be shown over the shaded bodies. Rigid bodies use semi-implicit Euler with impulse response and SAT box-box narrow phase; cloth and jelly use Position-Based Dynamics, which is unconditionally stable and frame-rate independent. Both are dependency-free — no Rapier or Ammo WASM payload. Nothing auto-runs on load and Reset restores the captured initial state, so a published track opens still rather than mid-collapse. Ships empty: the rig is the one you build.