Cellular automaton diffusion

Cellular automaton diffusion is a pocket laboratory for the strange beauty of simple rules. Two engines live inside it. The first is the classic cellular automaton: tiny squares on a grid, alive or dead, following one sentence of logic — "a cell is born with three neighbours, survives with two or three." From that single sentence come gliders that crawl across the screen, pulsars that breathe in threes, and guns that fire a stream of patterns forever. The second engine is reaction-diffusion: two invisible chemicals feeding on each other, painting coral reefs, wandering worms and dividing cells out of nothing but mathematics. Draw, seed, and let go. Six brush tools let you place single cells, soft clusters, lines and rectangles. Twenty built-in patterns — from the humble Block to the Gosper Glider Gun — stamp onto the canvas with one tap. Random soups, mirrored symmetrically on four…