Classic Sudoku
The original 9×9 puzzle. Row, column, and 3×3 box must each contain the digits 1–9.
What makes it Stillgrid
Difficulty is graded by the solving technique a puzzle actually requires — not generated by a clue count or stopwatch. An "easy" puzzle solves with naked and hidden singles. "Medium" pulls in pairs and pointing logic. "Hard" needs X-Wing. "Diabolical" needs Swordfish or XY-Wing. You always know what you're walking into.
Rules
- Fill every cell with a digit 1–9.
- No repeats within a row.
- No repeats within a column.
- No repeats within any 3×3 box.
How Stillgrid plays
- Pencil marks (candidates) on every cell.
- Undo/redo with full history.
- Auto-pencil one tap away if you don't want to track candidates by hand.
- Daily challenge with streak tracking — same puzzle for everyone.
- Personal bests for each difficulty.
- No signup. No ads. No microtransactions.