Marble Run is from when I first picked up Three.js — a physics and game-feel exercise. You roll a marble through a procedurally-built course with a camera following behind; Rapier does the real physics work. Nothing clever in the concept — the point was learning to make a physical thing move, and feel right, in a 3D space.

• P1Rapier rigid-body marble + static colliders
• P2Procedural block course (seeded, replayable)
• P3Third-person follow-cam (shared-camera mutation)
• P4Jump — ray-cast ground check
• P5Shadow maps · marble trail · mobile controls