Schroedingers-Hat/jsphys — comment on commit 9098969fb7bf99611ebbeb63d3b8e9bce21ab428
File: jsphys_js/photon.js line 12
By Schroedingers-Hat:

It was intended for causality enforcing checks -- to avoid checking over all objects.
Turned out I didn't need it for speed of light particles.
Could be useful for slower projectiles/adding teleportation, but I think storing things in a separate array would be better in that case.
Probably get rid of it. I can reintroduce something if needed.