Sliding puzzle
One tile is missing and everything moves through the gap it leaves. Put the numbers back in order, reading left to right and top to bottom.
Moves0
Size
- Status
- In play
- Tiles home
- 3 / 15
Arrow keys work too.
How to play
- Tap a tile next to the gap to slide it in. Nothing else can move.
- The puzzle is finished when the numbers read in order with the gap at the end.
- Arrow keys slide a tile into the gap from that direction.
- Boards are shuffled by sliding tiles, never by rearranging them, so every board can be solved.
- Three sizes: three by three, four by four, five by five.
Questions
Can I get an unsolvable board?
No. Half of all arrangements of a sliding puzzle cannot be solved, which is why the board is shuffled by making legal moves from the finished state rather than by shuffling tiles. Every move can be undone, so a way back always exists.
How many moves should it take?
A four by four board needs at most eighty moves from any solvable position, but most people take several hundred. The counter is there to beat, not to worry about.
Why is five by five so much harder?
The number of arrangements grows far faster than the board does. Three by three has a few hundred thousand; five by five has more arrangements than there are seconds in the age of the universe.