Home → Curriculum Hub → Interactive Maths Games → The 15 Sliding Puzzle

Slide numbered tiles into order on a square grid, with the blank space finishing in the bottom-right corner. Only tiles adjacent to the blank can move. Press Shuffle to mix the board, then click a tile or use the arrow keys to slide. Choose grid sizes from 3×3 up to 6×6.

The sliding puzzle was popularised in America in the 1870s and became a worldwide craze — so intense that employers reportedly posted signs forbidding employees from playing during work hours. The classic 15 puzzle on a 4×4 grid was proved solvable only for exactly half of all possible tile arrangements: a position is solvable if and only if its permutation has the correct parity relative to the blank square’s row. That is why this game shuffles by making random legal moves from the solved state — guaranteeing every scrambled position can be solved. The puzzle is a concrete introduction to permutations, parity and invariants at KS4 and A-Level.