Two large, static spheres (yellow) and two small spheres (red, blue) that
move toward each other and bounce apart on collision -- with each other
and with the static spheres -- using an analytic sphere/sphere overlap
test (collision_maths.sphere_sphere_collide).
Left-drag : orbit, Right-drag : pan, Wheel : zoom, space : reset
main_webgpu.py reproduces the same 4-sphere setup and collision rules
independently, with spheres drawn as a real generated sphere mesh
(PrimData.sphere) rather than a baked stand-in.