Puzzle

Sliding Puzzle

Slide tiles to solve the 15-puzzle

0
Moves
—
Best

Click “New Game” to shuffle and start

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About Sliding Puzzle

The sliding puzzle, often called the fifteen puzzle, presents numbered tiles in a grid with a single empty space. Tiles adjacent to that space can slide into it, and your task is to bring the whole grid into order.

The constraint of a single empty square is what makes it hard. Moving one tile where you want it almost always disturbs tiles you have already placed, so the solution has to proceed in a fixed order.

How to play

  1. 1Click or tap a tile next to the empty space to slide it into that space.
  2. 2Work the tiles into ascending numerical order.
  3. 3Finish with the empty square in its correct position, usually the last slot.

Solving it in order

  • Solve the top row first, then the next row, and so on. Never start on a lower row while an upper one is incomplete.
  • Once a row is finished, avoid disturbing it. All further work happens in the rows beneath.
  • For the last two tiles of any row, place them together using a rotation, rather than trying to slot each one individually.
  • When you reach the final two rows, switch to solving column by column instead of row by row.
  • Plan two or three moves ahead. Sliding tiles reactively will cycle the same few positions indefinitely.

Frequently asked questions

Is every sliding puzzle solvable?

No. Exactly half of all possible tile arrangements are unsolvable, a property determined by the arrangement's parity. Puzzles generated for play are shuffled from a solved state, so they always have a solution.

What is the best way to solve a sliding puzzle?

Solve it row by row from the top, locking each completed row and never disturbing it, then switch to column-by-column for the last two rows.

Why is it called the fifteen puzzle?

The classic version uses a four-by-four grid with fifteen numbered tiles and one empty space, which is where the name comes from.