The "Fifteen" (15 Puzzle) is a sliding puzzle that consists of a frame of numbered square tiles in random order with one tile missing.
Invented by Noah Chapman, Fifteen requires moving the tiles on the box using the blank square field, to achieve their ordering by number, preferably by making the least possible moves.You finish the game when you are done placing the knuckles in ascending order from left to right and top to bottom.
The puzzle also exists in other sizes, creating a lot of new possibilities. The easy version has 8 tiles, the medium pack has 15 and the most difficult one has 24. Hundreds of levels are available!
Enjoy!