Deterministic particle motion simulator.
Has more in common with Conway’s Life than it does with a gravity sim.
Particles are only influenced by the closest particle to them at the beginning of each turn.
Two particle types: nearest and bobo *nearest - these receive an acceleration of -1, 0, or 1 in each of the x and y directions each turn, depending on closest neighbor. *bobo - do not move, on influence passing ’nearest’ particles.