The swept-collision part live — and breakable on purpose. A fast ball, a closed box, and a 4-unit-thin wall in the middle. In Swept mode the ball can never pass it, however fast. Flip to Endpoint (the naive engine every tunneling bug comes from) and kick hard — watch it ghost straight through. Click anywhere to kick toward your click.
What this validates: the sovereign part nx_collide2d passed its gate
8/8 on the hub — tunneling-kill (a 400-unit/tick mover stops at a 4-unit wall), slide (tangent
preserved, normal killed), restitution ≈ e², determinism, 10,000 kicked ticks bounded in a closed box,
save-transparency through nx_gamesave, anti-vacuity, and corner double-contact in one step.
Mutation-proven: substituting exactly the Endpoint mode you can toggle above tunneled the mover
30,000 units past the wall and drove the gate RED. The gate even caught a real bug in its own part on
first run (a zero-time second contact dropped its normal). This page runs a faithful integer port; the
NishiLang part is the verified truth, registered as MCP tool nx_collide2d_gate.
Physics-collision flipped PARTIAL→HAVE on the nx_gamebench board with this proof.