🧮 15 Puzzle
🧩 Logic · 1 plays15 Puzzle
Slide numbered tiles into order within a frame that has one free space.
About 15 Puzzle
Numbered tiles sit in a frame with one empty space, and are slid into ascending order. The puzzle dates from the 1870s and remains a clean test of sequencing: the first rows come easily, and the difficulty gathers at the end, where the last tiles have to be cycled around one another instead of pushed straight home. Every shuffle is produced from a solvable arrangement, so no board is a dead end. Sizes run from three-by-three to five-by-five, with moves and time recorded for comparison.
How to Play
Slide any tile bordering the empty space by tapping it. Tapping further along a row or column slides the whole line at once. Arrange the numbers in order, reading left to right and top to bottom.
💡 Tips & Strategy
Solve it in layers and never disturb what is finished. Complete the top row, then the left column, and treat the solved cells as walls — that reduces a fifteen tile puzzle to an eight tile one, then to a trivial final square.
The last two tiles of any row need a specific manoeuvre. Rather than placing them one at a time, put the final tile in the corner position and the second-to-last directly beneath it, then rotate the pair into place together. Trying to slot them individually is what makes players undo a completed row.
Think in terms of moving the blank, not the tiles. Every move is really the blank changing places, and planning a route for the gap around a tile you want to keep still is far more reliable than pushing tiles and hoping.
Finish with the bottom two rows solved together as a block of six, since neither can be completed independently. At that size the remaining arrangements are few enough to work out in your head before you move.