Slide Fifteen

Fifteen numbered tiles and one empty square. Slide a tile into the gap, again and again, until the numbers run one to fifteen with the gap at the end.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Slide with the arrow keys. The arrow names the direction the tile moves, so ↑ slides a tile upward into a gap above it.
3. Or click any tile next to the gap.
4. Watch the ticks. A tile that is already in its final place is marked, so you can see progress without recounting the board.
5. Par is 60 moves — the number used to scramble it. Beating par is the achievement.

Why are some sliding-tile puzzles impossible to solve?

Because the puzzle has two separate parity classes, and no legal move crosses between them. Swap any two tiles on a solved board and you land in the other class, where the target arrangement simply cannot be reached — that is the famous "14-15" puzzle, which was offered with a prize precisely because nobody could win it. This game never shuffles: it scrambles by making real moves backwards from the solved board, so every board you get is reachable by construction.

What is a good strategy?

Solve the top row completely, then never disturb it again. Then the next row, and so on, until only a two-by-two corner is left — which is small enough to finish by rotation. Chasing whichever tile looks most out of place feels productive and is how most people end up going in circles.

What does par mean?

It is the number of moves used to scramble the board, which is a genuine upper bound on the shortest solution. Finishing inside it means you found a route at least as good as the one that made the mess.

Does it work offline?

Yes. Once the page has loaded once, the whole game is on your device. There is no server involved in play at any point.

Is there any money, betting or in-app purchase in this?

None, and there never will be. No currency, nothing to buy, no lives to refill, no wager of any kind.

Can I play it with a keyboard or a screen reader?

Both. Arrows slide, and the board publishes a row-and-column description naming each tile, whether it is home, and where the gap is — so the state is fully readable without seeing it.

Four by four, sixty scrambling moves, no timer. The scramble never immediately undoes its own last move, so the depth is real rather than inflated by cancelling pairs.

Light Grid is the other puzzle here where planning beats poking — it rewards working out the whole sequence before you start.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.