How to Play: 37Rdoku is a logic puzzle based on the reversible Rule 37 elementary cellular automaton with periodic boundaries, as described in Wolfram's A New Kind of Science. The grid evolves row by row: each cell in row t+1 is the XOR of the standard Rule 37 output for its neighborhood (left, center, right in row t) and the cell above in row t-1 (0 for the second row). Your goal is to fill the grey (unset) cells with white (0) or black (1) to make the entire grid consistent with this rule and the given clues. There's only one correct solution. Click on grey cells to cycle: grey → white (0) → black (1) → grey. Use the "Check" button to verify if your board is complete and correct. Use "Show Solution" to reveal the answer.
Periodic Boundaries: The board uses periodic (wrap-around) boundaries, meaning the leftmost and rightmost cells in each row are considered adjacent, as if the board wraps upon itself like a cylinder.
The reversible Rule 37 (37R) computes each cell as follows: The standard Rule 37 output for the three-neighborhood (left, center, right in current row) XORed with the cell two rows above (or 0 for the second row).
Below are all 16 possible combinations shown as crosses (above, neighborhood, below):