Click a numbered tile next to the empty space to slide it in, putting the shuffled numbers back in order. Solve it and the board automatically grows bigger.
Score: 03x3Moves: 0⏱ 00:00
🧩 Ready?
Tap the button below to start — you'll begin on a 3x3 board
Click a tile next to the empty space to move it. Arrow keys work too.
Best Score
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Largest Board
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🏆 Sliding Puzzle Leaderboard
The History of the Sliding Puzzle
The sliding puzzle (also known as the 15-puzzle) is one of the oldest mechanical puzzles around, with physical versions dating back to the 1870s. The classic 4x4 version has 15 numbered tiles plus one empty space. The rules are simple: only tiles next to the empty space can move, and the goal is to restore the shuffled order back to 1 through the highest number, with the empty space left last. This version adds a rising-difficulty twist — the board keeps growing from 3x3 all the way up to 6x6.
Why the Shuffle Method Matters
The sliding puzzle has a mathematical quirk: if you shuffle the tiles completely at random, roughly half of all possible arrangements can never be solved (mathematicians call this an odd permutation). Instead of a pure random shuffle, this version starts from the solved state and makes a large number of random but legal slides. A shuffle produced this way is always solvable, so you'll never get stuck on a board that has no solution at all.
How to Play
One space on the board is empty. Click any numbered tile directly above, below, left, or right of the empty space, and it slides into that space. Through a sequence of such moves, restore the shuffled numbers back to order: 1, 2, 3... reading left to right, top to bottom, with the empty space ending up in the bottom-right corner. On desktop you can also use the arrow keys (each key moves the empty space in that direction). Once everything lines up, the round ends automatically and you move up to the next, bigger board.
Tips for a Higher Score
A common strategy is to work from the outside in, top to bottom: lock in the entire top row and the entire left column first and stop touching them, then solve the remaining, smaller board one layer at a time. This approach pays off even more on larger boards, helping you avoid the frustrating situation where fixing one tile keeps knocking others out of place. Your score factors in board size, move count, and time — fewer moves and a faster clock both push your score higher.
Frequently Asked Questions
How do you play the sliding puzzle?
One space on the board is empty. Click a numbered tile that's directly adjacent to it (up, down, left, or right), and it slides into the empty space. Repeat this to move the shuffled numbers back into order: 1, 2, 3... from top-left to bottom-right, with the empty space ending up last, in the bottom-right corner.
Is every shuffle guaranteed to be solvable?
Yes. Not every random arrangement of a sliding puzzle can actually be solved — roughly half of all possible arrangements are mathematically impossible. Instead of shuffling purely at random, this version starts from the solved state and performs a large number of random but legal slides, a method that's mathematically guaranteed to always produce a solvable arrangement.
Does the difficulty increase as you play?
Yes. You start on a 3x3 board, and solving it automatically upgrades you to 4x4 (the classic 15-puzzle), then 5x5, then 6x6, after which the board stays at 6x6. Larger boards require noticeably more moves and more planning, and the difficulty curve is deliberately designed to keep climbing.
How can I tell how well I'm doing?
The screen shows your move count and elapsed time in real time. Your score is calculated from board size, move count, and time — bigger boards give a higher base score, but more moves and more time both reduce it, rewarding efficient, fast solving.
Why doesn't anything happen when I click a tile?
Only a tile directly adjacent to the current empty space (up, down, left, or right) can move. Clicking a tile that isn't adjacent to the empty space does nothing and doesn't use up a move. To move a tile that's farther away, first shift the empty space toward it one adjacent move at a time.