How to play the 15-Puzzle
The 15-Puzzle is one of the most famous puzzles in the world: fifteen numbered tiles in a 4×4 frame with one empty space. Slide tiles into the gap until the numbers run from 1 to 15 in rows, with the empty space in the bottom-right corner. Only a tile next to the gap can move – left, right, up or down.
New to it? Start with Beginner (3×3), the 8-Puzzle: same idea, only eight tiles. Then try Classic (4×4).
A method that always works
1. Solve the top row. Place 1 and 2 first. Put 3 and 4 in together: move 4 under the place where 3 belongs, then 3 next to it, and rotate them into the row. 2. Solve the second row the same way (5–8). 3. Solve the last two rows column by column: 9 and 13 together, then 10 and 14, and finally turn 11, 12 and 15 around the gap. After the first two rows you never touch them again.
Why some boards can't be solved
If you take the tiles out of a real puzzle and put them back at random, there is a 50% chance it can never be solved – like the famous board with only 14 and 15 swapped. That is why this game never puts tiles in at random: it mixes the board with legal moves, so every puzzle has a solution.
Good for the brain
Sliding puzzles train planning, spatial thinking and patience. You learn to move tiles away from their place on purpose to bring them back in the right order – a skill that helps in many real problems. A 3×3 round takes a minute; a 4×4 takes a few minutes of real focus.
How do the arrow keys work?
The arrow shows where the tile goes. ← moves the tile right of the gap to the left, → the tile left of the gap to the right, ↑ the tile below the gap up, ↓ the tile above the gap down.
Is the hint the best possible move?
On 3×3 the hint is from a shortest solution. On 4×4 the solver first looks for the shortest solution; if that takes too long it uses a faster search that finds a correct but possibly longer solution. If neither finds one within its limit, the game says so.
Does it work offline?
Yes, after the first visit. Your board, move history and results stay on your device. Settings has backup and restore.