A cellular automaton is just a lookup table: every cell looks at its neighborhood and the table says what it becomes next tick. The rule string is that table, compressed. Tap any example to run it.

1D — one row evolves, history scrolls down

110

Elementary (0–255). A cell sees left·self·right — 8 possible patterns. Write the rule number in binary and its 8 bits are the answers: 110 is 01101110, and its top bit says pattern 111 → dead. 256 rules total, and somehow one of them is Turing-complete.

r2:2863311530

Radius-2. The neighborhood widens to 5 cells → 32 patterns → a 32-bit rule number (hex fine: r2:0xAAAA5555). 4.3 billion rules.

k3:912

Totalistic, k states (2–5). The next state depends only on the sum of the 3-cell neighborhood; the code's base-k digits are the lookup table, digit s answering "sum = s". More states = free extra colors.

2D — the whole plane updates at once

B3/S23

Life-like. Each cell counts its 8 neighbors. A dead cell is Born on any listed count; a live cell Survives on any listed count; everything else dies. B3/S23 is Conway's Life. Legacy survival-first notation (23/3) works too.

B2/S/3

Generations. A third number sets the total state count: cells that fail to survive don't vanish — they fade through dying states that block births but count for nothing. B2/S/3 is Brian's Brain; B2/S345/4 is Star Wars. Legacy /2/3 works.

Grids wrap at the edges (a torus), so gliders that leave come back. The 🎲 button rolls random rules from all these families and quietly re-rolls the duds.