An ant on a grid of 8 colours, one for each q.d state. On each cell it reads the colour, turns left (L) or right (R) as the rule says, bumps the colour up by one (mod 8), and steps. Some rules make chaos, some build highways, some grow symmetric gardens. Click to drop another ant. REVERSE TIME runs every ant backwards; the rule is reversible, so the grid un-grows exactly.
LIT generalised Langton's ant (Langton 1986; Gale, Propp et al.). ANALOGY 8 colours = Dave's 8 q.d states. Self-check: 2,000 steps forward then 2,000 back must restore a blank grid. ← SaPpH{{i}}on