Simon has returned to his beloved Cellular Automata theme and created this nice sequence comprising all the 256 elementary rules. You can access his code at https://editor.p5js.org/simontiger/sketches/gECh5tVwa

Simon explains:

Every cell changes according to its color and that of its two neighbors. It starts with all white cells except for a single black cell in the middle. Time is displayed vertically. Sometimes you get just a single color, sometimes you get a repeating pattern, sometimes you get a fractal and other times you get something completely unpredictable.

For a given cell, there are two states. There are three “neighbors”: the cell itself, the cell to its left, and the cell to its right. This means there are 8 possible neighborhoods. For each one we need a different outcome for the cell itself. So there are 2^8 = 256 possible rules. You can also take each of the outcomes and convert them to 1s and 0s: 0 being white and 1 being black. You end up with a binary number which you can convert to decimal, and that’s how the rules are numbered.