Slide it into order: the 15 Puzzle
The Sliding Puzzle — famously the 15 Puzzle — is a pocket-sized classic. Numbered tiles sit in a grid with one space missing; slide tiles into that gap, one at a time, until every number sits in order from 1 to the end. Simple to grasp, surprisingly satisfying to solve.
How to play
Sliding Puzzle in 4 steps
Spot the gap
One cell in the grid is empty. Only tiles directly next to that gap can move.
Slide a tile
Click a tile beside the empty space (or use arrow keys) to slide it into the gap. The gap moves to where the tile was.
Sort the numbers
Keep sliding until the tiles read in order — 1, 2, 3 … — with the empty space in the bottom-right corner.
Beat your record
Solve it in as few moves and as little time as you can, then try a bigger grid.
Controls
- Click / Tap a tile
- Slide it into the adjacent empty space
- Arrow keys
- Slide the tile next to the gap in that direction
- Size buttons
- Choose a 3×3, 4×4 or 5×5 puzzle
- R
- Shuffle and start over
Strategy
Tips to play better
Solve top-down
Lock in the top row completely, then the next row, working downward. Never disturb a row you've already finished.
Finish rows two at a time
On the final two rows, solve them as paired columns instead of row-by-row — it avoids the classic last-tile deadlock.
Use the corner trick
The last two tiles of a row go in together: place them in a little rotation around the corner rather than one at a time.
Half the shuffles are unsolvable
Only even-permutation scrambles can be solved, so this puzzle always deals you a guaranteed-solvable board.
About Sliding Puzzle
The 15 Puzzle swept the world in an 1880 craze, and is often linked to puzzle legend Sam Loyd, who offered a famous (impossible) prize for solving a specially rigged version. That stunt accidentally taught the public a deep idea: exactly half of all tile arrangements can never be solved.
That fact comes from the mathematics of permutation parity — sliding the blank around only ever produces "even" swaps, so a board scrambled into an odd permutation is provably unsolvable. It's a rare case where a children's toy is also a clean lesson in group theory, which is why the sliding puzzle still appears in maths classes today.
This Unicode edition always deals a solvable, well-shuffled board and renders the tiles as crisp numerals. Choose a gentle 3×3, the classic 4×4 fifteen-puzzle, or a brain-bending 5×5, and your best move-count and time for each size are saved locally in your browser.
FAQ
Sliding Puzzle questions
Why is it called the 15 Puzzle?
Is every shuffle solvable?
How do I move a tile?
What's the goal?
Is my best score saved?
Keep playing