Each cell runs a local PID controller regulating its active-neighbour count toward a target. Switch Domain / mechanism to the bioelectrical membrane for excitable media (spiking, refractoriness, propagating waves), or to Dither-CA, where palette colours are the states and each cell steers its neighbourhood’s mean colour toward a target image or gradient. Space = play/pause · S = step · R = reset · click/drag the grid to paint (shift-drag erases, alt-drag paints the negative extreme of a signed state range). Set Neighbourhood to Custom to enable/disable individual relational links within the radius.