Wolfram's elementary automata work in one dimension, with three cells deciding the next. Here is the same idea in two: a cell and its four neighbors (above, below, left, right) make five cells, which can be on or off in 32 ways. Click any pattern in the table to flip what it produces, and the whole picture re-runs. The 32 answers make a 32-bit number, so there are over four billion rules.

Each pattern shows the cell in the middle and the cells above, right, below and left of it; the button under it says what the middle cell becomes in the next generation (blue 1 = on). Two presets show how a simple rule can copy itself: the parity rules turn a single cell into a growing, self-similar lattice of copies of itself. Majority smooths a random start into blobs. Random picks a random rule, which usually freezes or fills the grid, but occasionally does something interesting. The pattern with all five cells off always produces off in this tool, so an empty grid stays empty. The grid wraps around at the edges.

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