Sudoku
Fill a 9x9 grid with digits so every row, column, and box is complete.
Rules
- Each row must contain the digits 1 through 9 exactly once.
- Each column must contain the digits 1 through 9 exactly once.
- Each 3x3 box must contain the digits 1 through 9 exactly once.
- Pre-filled cells (shown in bold) cannot be changed. Conflicting cells are highlighted in red.
Controls
| Key | Action |
|---|---|
Arrows / wasd / hjkl |
Move cursor |
Mouse left-click |
Focus a cell |
1-9 |
Fill cell with digit |
Backspace |
Clear cell |
Ctrl+H |
Toggle full help |
Ctrl+R |
Reset puzzle |
Escape |
Return to main menu |
Tips
- Scan the most-filled groups first. Rows, columns, or boxes that already have seven or eight digits filled leave very few possibilities for the remaining cells, making them the easiest to solve.
- Look for naked singles. If a cell has only one digit that doesn't conflict with its row, column, and box, that digit is the only option. Check the most constrained cells before guessing anywhere.
- Use the conflict highlighting. When you place a digit, conflicting cells turn red immediately. Catch mistakes early so they don't cascade across the board.