🪀 Spherical Elastic Pendulum: Swing, Stretch and Precession in 3D

Interactive 3D spring pendulum on a Blender-modelled rig: Cartesian RK4 solver cross-checked against the 2D polar solver, exact conical orbits, vertical angular momentum, energy ledger and four numerical checks.

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install