Fisch-Gravner-Griffeath model ā rotating spiral waves from simple local rules
Each cell is in state 0..Nā1. A cell advances to state (s+1) mod N if at least threshold neighbors are in state (s+1) mod N.
Starting from random noise, beautiful rotating spirals (cyclic "waves") spontaneously emerge (Griffeath, 1988).
The waves compete: larger spirals absorb smaller ones. More states ā more colors, more complex patterns.