Sliding Puzzle
Slide the tiles into the empty space until the numbers are in order, from 1 in the top-left corner to the last number before the gap.
Tap a tile next to the empty space to slide it. On a computer you can also use the arrow keys.
How to play
The board has one empty space. Any tile next to it can slide into it. Keep sliding until every number is in order, left to right and top to bottom, with the empty space in the bottom-right corner. Tiles already in the right place turn green.
A simple method that always works
- Solve the top row first. Bring 1, 2 and 3 into place one at a time. For the last tile of a row, park it below its spot first, then rotate it in.
- Then the left column. Do the same for the tiles that belong down the left side.
- Repeat on the smaller board. What is left is a smaller puzzle. Solve its top row and left column the same way.
- Finish with a 2 × 2 corner. The last few tiles just circle around until they click into place.
A puzzle with a history
The 15 puzzle became a worldwide craze in 1880, when people everywhere tried to slide its little blocks into order. Mathematicians soon proved that exactly half of all possible arrangements can never be solved. Don't worry: every puzzle on this page is shuffled by real moves from the solved position, so it can always be solved.
3 × 3 or 4 × 4?
The 3 × 3 board (the 8 puzzle) takes a minute or two and is perfect for learning the method. The 4 × 4 board is the classic 15 puzzle and a satisfying challenge.