50 spheres (configurable via --spheres N) continuously fall and collide
with a 5x5 plane you can tilt. A colliding sphere switches to moving
along the plane's current normal and draws in wireframe; every 20 ticks
(~2.6s) all spheres respawn at a fresh random position above the plane,
hit or not. Ported faithfully from NGL9Demos/Collisions/SpherePlane,
including its camera -- eye and plane both sit at y=0, so with the
plane untilted you're looking along it edge-on and won't see it as a
filled quad; tilt it with the arrow keys to bring it into view. The
C++ also declares an m_animate flag it never wires up to a key, so
there's deliberately no pause control here either.
up/down : tilt the plane about world X, left/right : tilt about world Z
Left-drag : orbit, Right-drag : pan, Wheel : zoom
main_webgpu.py reproduces the same 50-sphere/tiltable-plane setup
independently. Spheres are a real generated sphere mesh (PrimData.sphere),
the plane is a small hand-built quad; a colliding sphere is tinted red
instead of drawn wireframe.