. . . . . . . . . . . "The \"fifteen puzzle\" or \"slide puzzle\" is a sort of Stock Puzzle where one has to arrange a set of scrambled numbers so that they are all shown in ascending order. One spot is always open, allowing pieces to be moved around, but it is designed in such a way that no piece can ever be removed from the board. More sadistic versions will be bigger than fifteen squares; these larger versions are called \"n-puzzles\", where n is the number of scrambled numbers (always a square number minus one). A more general version of the \"sliding puzzle\" will have the player try to put together an image in the same manner as above. The picture you're trying to reassemble is usually printed on the back of the box to minimize frustration. The puzzle traces back at least to Noyes Palmer Chapman in 1874; later on, Sam Loyd claimed to have invented it. Examples of Fifteen Puzzle include:"@en . "Fifteen Puzzle"@en . . . "The \"fifteen puzzle\" or \"slide puzzle\" is a sort of Stock Puzzle where one has to arrange a set of scrambled numbers so that they are all shown in ascending order. One spot is always open, allowing pieces to be moved around, but it is designed in such a way that no piece can ever be removed from the board. More sadistic versions will be bigger than fifteen squares; these larger versions are called \"n-puzzles\", where n is the number of scrambled numbers (always a square number minus one). Examples of Fifteen Puzzle include:"@en . .