Non-transitive competition: R beats S, S beats P, P beats R. On a spatial lattice, this produces spiraling waves and coexistence impossible in well-mixed populations.
R: -- | S: -- | P: --
Spatial RPS (Reichenbach et al., Nature 2007): mobility m above a critical threshold drives extinction; below it, spiral waves enable coexistence. Each step: randomly choose a site and a neighbor — either compete (winner replaces loser) or swap (mobility).