Rules and controls
Slide a numbered tile into the blank by tapping a tile immediately above, below, left or right of it. Diagonal moves are not allowed. Arrange numbers in increasing order, reading each row left to right from the top, with the blank in the bottom-right corner.
A worked example
For a 3×3 board reading 1 2 3 / 4 5 6 / 7 blank 8, tap 8. It moves left, producing 1 2 3 / 4 5 6 / 7 8 blank, the completed board.
Beginner tips
Arrange the first row before moving down to the next. Plan within the remaining space instead of repeatedly disturbing finished numbers. The last two rows may need to be handled together.
Choose a difficulty
Easy uses a 3×3 board shuffled with 20 legal moves. Medium and hard use 4×4 boards with 80 and 180 shuffle moves. These are shuffle counts, not minimum solution lengths.
Questions and answers
Is every starting position solvable?
Yes. Boards are shuffled from a completed position using only legal moves. Tapping a tile that is not adjacent to the blank neither moves it nor increases the move count.
Can I come back to a puzzle I started?
Yes. Progress is saved in this browser, so open the same puzzle at the same site address on the same device and browser to continue. Clearing site data or changing device, browser or domain means the existing record will not carry over.
How can I enjoy the daily challenge and practice?
The daily challenge gives everyone the same puzzle for a matching game, UTC date and level. Choose “New practice” to play another practice round at your own pace. The same round repeats its puzzle; different rounds can occasionally have the same layout.