How to play
The board is a 9×9 grid split into nine 3×3 boxes. Some cells already have numbers. Your job is to fill every empty cell with a digit from 1 to 9 so that:
- each row contains 1 to 9 exactly once,
- each column contains 1 to 9 exactly once,
- each 3×3 box contains 1 to 9 exactly once.
Tap a cell, then tap a number at the bottom (or type it on a keyboard). The small number under each digit shows how many of that digit are still missing from the board.
- Notes. Turn on Notes to pencil in candidates instead of an answer. When you place a digit, the same note is cleared from the row, column and box automatically.
- Mistakes. A digit that doesn’t match the solution turns red and counts as a mistake. After three mistakes the game ends, but you can take a second chance.
- Hint. Fills in one cell for you. If you have a wrong digit on the board, the hint fixes that first.
- Undo takes back your last move, including notes.
On a keyboard: 1–9 to enter, Backspace or Delete to erase, arrow keys to move, N to switch notes on and off.
Difficulty levels
Every puzzle is generated fresh and checked to have exactly one solution, so you never need to guess.
- Easy puzzles start with 38 numbers and can be finished by looking for cells with only one possible digit.
- Medium puzzles start with about 30 numbers. They still only need single-candidate reasoning, but you’ll have to scan rows, columns and boxes more carefully.
- Hard puzzles start with around 23 to 27 numbers and can’t be solved by single candidates alone. You’ll need notes and techniques like pairs.
Strategy
Start with the digit you see most. If there are already six 7s on the board, the last three are usually easy to place. Tap a 7 on the board to highlight every 7 and look for the boxes that still need one.
Look for the only place a digit can go. Pick a box and a digit it’s missing. Cross out every row and column that already contains that digit. If only one empty cell is left in the box, that’s where it goes. This works for rows and columns too.
Look for the only digit a cell can take. Check a cell against its row, column and box. If eight digits are already used, the ninth is the answer.
Use notes on hard puzzles. When single candidates run out, write every possible digit in the empty cells of one box or row. Two cells in the same row that can only be the same two digits (a pair) mean no other cell in that row can use those digits. That often unlocks the next move.
Don’t guess. Every puzzle here has one solution that can be reached by logic. If you’re stuck, a hint is better than a guess that spreads mistakes.
More logic puzzles. Minesweeper uses the same kind of step-by-step deduction with numbers and hidden mines, and Word Search is a relaxed puzzle for when you want a break from numbers.
If you enjoy Sudoku, try Tower of Hanoi or Five Letters next.
