Game of Life

The rules fit in two lines — a live cell survives with 2 or 3 neighbors, and a dead cell is born with exactly 3. From that alone emerge traveling gliders, endlessly oscillating pulsars, and guns that fire gliders forever.

Drag to paint cells, or pick a pattern from the brush row and stamp it onto the grid. Cell color encodes age — newborns glow indigo, long-lived survivors fade to slate.