Calcudoku

How to play

1. Use each of the shown digits once in every row and column. Select a cell and use the number buttons or your keyboard; arrow keys move the selection, and Erase, Backspace, or Delete clears it.
2. Use Notes (or N on the board) to save possible digits. Notes are not correctness hints. Entering a number clears its notes and removes that digit from other notes in its row and column.
3. The digits in each cage must produce its target using the shown operation. For subtraction and division, either order is allowed. A cage without an operation contains its target digit.
4. Repeating a digit in a row or column is rejected. Accepted entries do not confirm cage correctness; the puzzle completes when the whole grid satisfies all its rules.

Head-to-head rules

Complete the number grid and satisfy every cage before your opponent. Both players get the same puzzle and start together, with 5 minutes to finish. Completion time decides the match; fewer moves or a higher solo score do not beat an earlier correct finish. Finishes within 0.1 seconds draw. If neither player finishes before time runs out, the match is a draw.

Your moves and answers stay private. Leaving through the game controls forfeits the match; closing the page does not pause its clock.

Real-player matches update this game's own Elo rating. Daily and practice results keep their separate progress and never change Elo.