How to play

Fill the grid so that every row, every column and every 3 × 3 box contains the numbers 1 to 9 once each. Some squares are filled in to start (the dark numbers); the rest are yours. Tap a square, then tap a number below the board, or type 1 to 9 on a keyboard. Tap the same number again to remove it. Squares in the same row, column and box as your choice are shaded, and every square with the same number lights up, which makes it easy to see where a number can still go.

Turn Notes on to write small candidate numbers in a square without committing to them. When you place a number for real, it is taken out of the notes of the squares that share a row, column or box with it. Undo takes back your last moves. Check mistakes highlights numbers that don’t belong, and Hint fills in one square for you; a game with hints doesn’t count for a best time.

Levels and the daily puzzle

Easy gives about 40 squares to start, medium about 32 and hard about 26. Every puzzle has exactly one solution, so you never need to guess. The Daily puzzle is the same for everyone on a given date, at medium difficulty. Your unfinished game is saved on this device, so you can close the page and carry on later.

Tips

Start with numbers that appear most often on the board, and look for a box or row where only one square can hold a certain number. Use notes when two or three numbers are possible, and look for a pair of squares in a row that share exactly the same two candidates: those numbers can be removed from the rest of that row. If you are stuck, scan each number from 1 to 9 in turn rather than staring at one corner.

Is anything sent anywhere? No. Puzzles are made in your browser and your times are saved only on this device.