@modoki/engine / index / Physics2D
Variable: Physics2D
constPhysics2D:Trait<{gravityX:number;gravityY:number;pixelsPerMeter:number; }>
Singleton 2D physics world config (one per scene, like Time). If absent, the physics system falls back to these same defaults, so dropping a RigidBody2D "just works" without authoring a Physics2D entity.
gravityX/gravityY are a physical acceleration in m/s² (NOT world units) — independent of pixelsPerMeter — with +Y pointing DOWN (screen frame). The system flips Y when handing gravity to Rapier's Y-up world.
pixelsPerMeter is the scale between world units and Rapier meters. Default 100 (a 100-unit body = 1 m) keeps bodies in the solver's happy 0.1–10 m range. Changing it rebuilds nothing mid-run — existing collider sizes are baked at creation, so change it before Play (Phase 1).