Fifteen Puzzle: It is a sliding puzzle that consists of a grid of numbered squares with one square missing, and the labels on the squares jumbled up. If the grid is 3×3, the puzzle is called the 8-puzzle (eight) or 9-puzzle (nine). If the grid is 4×4, the Npuzzle is called the 15-puzzle (fifteen puzzle) or 16-puzzle (sixteen puzzle). The goal of this free online puzzle is to un-jumble the squares by only making moves which slide squares into the empty space, in turn revealing another empty space in the position of the moved piece. The n-puzzle is known in various versions, including the eight puzzle, the fifteen puzzle, and with various names. The n-puzzle was "invented" by Noyes Palmer Chapman. Play this free online game.