How to play the 15 Puzzle

The 15 puzzle is the classic sliding tile game: fifteen numbered tiles and one empty space on a 4x4 board. Slide tiles into the empty space until the numbers read 1 through 15 in order, left to right and top to bottom, with the blank in the bottom-right corner. Click or tap any tile that shares a row or column with the empty space and the whole run of tiles slides over in one go — a handy shortcut that saves taps on mobile. On a keyboard, the arrow keys move the blank space around the board. Every board is shuffled with real legal moves, so each sliding puzzle you get is always solvable.

Strategy tips: solve the puzzle in layers. Place tiles 1 through 4 along the top row first, then 5 through 8, and never disturb a finished row again. The last two tiles of each row are the tricky part — set them up as a pair by parking the row-ending tile below its slot, then rotating both into place together. Once the top two rows are locked in, solve the left column of the remaining 2x4 area, then cycle the final tiles around the empty space. Fewer moves means a better score, so pause and plan runs of multiple tiles instead of shuffling one square at a time.