The rule: every region the walls enclose fills, and a wall from edge to edge fills its smaller side. Paint walls on the hexagon field; every cell runs the same small neural network on itself and its six neighbours, step after step, trained rather than written to follow that rule on its fill channel. The badge checks it against the rule computed the ordinary way. Play: Spectacle as a CA · Hand-written CA · Strand NCA: Spectacle's lines · Source on GitHub