About this game
The sliding puzzle — best known as the 15-puzzle — has been driving people pleasantly crazy since the 1870s. Numbered tiles sit in a frame with one empty space; you can only slide a neighboring tile into that gap. The goal: arrange the numbers in order, from 1 in the top-left to the empty space at bottom-right.
Every shuffle here is generated by legal moves from the solved position, which guarantees the puzzle is always solvable (unlike naive random arrangements, half of which are impossible!). Choose 3×3 to learn, 4×4 for the classic challenge, or 5×5 if you want to suffer beautifully. Tap any tile in the same row or column as the gap to slide the whole group at once.
How to play
- Tap a tile next to the empty space to slide it in.
- Tap a tile in the same row/column as the gap to slide several tiles at once.
- Arrange numbers 1 → 15 (top-left to bottom-right) to win.
- Moves and time are counted; your best move-count is saved per size.
Tips & strategy
- Solve the top row first, then the left column, and repeat on the shrinking board.
- The last two tiles of a row must be rotated in together — learn this one trick and everything clicks.
- Don't count moves early on; smoothness first, efficiency later.
- On 5×5, work in an L-shape: top row, left column, then it's just a 4×4.
Frequently asked questions
Is every shuffle solvable?
Yes. Boards are shuffled by making hundreds of legal random moves from the solved state, so a solution path always exists — exactly the reverse of those moves, or usually something much shorter.
What's the minimum number of moves?
For the 4×4 puzzle, hard positions need up to 80 single-tile moves to solve optimally. Human solvers typically use 100–200 moves — efficiency comes with practice.
Why could old physical puzzles be impossible?
Exactly half of all random tile arrangements are unsolvable — a famous parity proof from 1879. Ours are shuffled by real moves, so you're never handed an impossible board.