Arcade 05 · Exact cover
Sudoku
Fill every row, column and box with 1 to 9. Choose a cell, then a number.
How the generator and solver work
Sudoku is an exact cover problem — 729 candidate placements against 324 constraints — and Knuth's dancing links solves any grid essentially instantly. The generator leans on that: it strips cells one at a time, re-solving after each to guarantee the puzzle still has exactly one answer.
Arrow keys to move · 1–9 to enter · 0 or Backspace to clear · H hint Tap a cell, then tap a number
