Sliding Puzzle

🕹️ How to play

1. Start playing: The page opens on a scrambled 3×3 — there is no start button. Put the tiles back in order 1, 2, 3… left to right, top to bottom, with the empty space in the bottom-right corner. The board flashes its solved state before it scrambles: that is the goal.
2. Move the tiles: Tap any tile in the same row or column as the empty space and it slides in; tap a tile further along the row and every tile in between is pushed along with it. You can also swipe a tile towards the gap, or use the arrow keys. A tile that can't move just shakes and costs nothing.
3. How time and moves are counted: The clock starts with your first move, so looking at the board is free, and it pauses by itself when you switch tabs or lock the phone. Every tile moved is one move — a three-tile push is 3. Undo takes the moves back but never rewinds the clock.
4. When you get stuck: Undo a few moves and try another order. On 4×4 the tip line tells you when the last two rows start and to finish them column by column. Hint lights up the next tile for you to tap; a hinted round still counts as solved but never sets a best.

📖 Rules & variants

An n×n board holds n²−1 numbered tiles and one empty space. Only tiles in the same row or column as the space can slide into it. Solve it by ordering the tiles 1, 2, 3… row by row with the space in the bottom-right corner. Choose 3×3 (the 8 puzzle), 4×4 (the classic 15 puzzle) or 5×5.

Every board here is solvable because it is made by starting from the solved board and making hundreds of legal random moves. Exactly half of all random arrangements of a 15 puzzle can never be solved — swapping just 14 and 15 is the famous example — so boards are never simply shuffled.

Moves count tiles, so pushing three tiles at once is 3 moves. On 3×3 the result shows that board's optimal solution length; on 4×4 and 5×5 it shows a lower bound. Matching it earns the Optimal badge. Time runs from your first move and stops while paused.

How to solve the 15 puzzle faster: finish the top row, then the second row. Stack each row's last two tiles and turn them into the corner together instead of placing the second-to-last one first. For the last two rows, work column by column in pairs, then rotate the final 2×2.

Picture mode cuts six original illustrations into tiles, with a thumbnail you can enlarge and optional numbers. The daily board is the same 4×4 for everyone. 'Same board again' lets a friend race you on the identical scramble, and the result shows the attempt number and the fastest time.

❓ FAQ