Goal
Fill every empty cell so that each row, column, and 3×3 box contains the numbers 1 through 9 exactly once.
Getting Started
- Choose a difficulty level — Easy, Medium, or Hard — then tap New Game.
- The board will appear with some numbers already filled in. These are given clues and cannot be changed.
Entering Numbers
- Tap or click a cell to select it.
- Use the number pad below the board or press 1–9 on your keyboard.
- Press the erase button (⌫) or Backspace / Delete to clear a cell.
- Use arrow keys to move between cells.
Visual Feedback
- Bold numbers — given clues (locked).
- Blue numbers — your entries.
- Green numbers — hints.
- Red highlight — conflict detected in the same row, column, or box.
- The selected cell and its row, column, and box are softly highlighted to help you scan.
Tools
- Undo — reverses your last move. You can undo multiple times.
- Hint — fills one random empty or incorrect cell with the correct answer (shown in green).
- Solve — reveals the entire solution if you get stuck.
Timer
The clock starts when you place your first number. Try to beat your best time!
Tips
- Start with rows, columns, or boxes that are almost complete.
- Look for numbers that can only go in one place within a row, column, or box.
- Use the conflict highlighting — if a cell turns red, something needs to change.
- Your progress is saved automatically. Close the app and come back anytime.
Difficulty Levels
- Easy — ~42 clues given. Great for beginners.
- Medium — ~32 clues. A balanced challenge.
- Hard — ~25 clues. For experienced players.