GOF Puzzle

A few centuries old, the "Game of 15" consists of a frame of numbered square tiles in random order with one tile missing. The object of the puzzle is to place the tiles in order by making tiles move by tapping those that are around the empty space. It has been proved that half of the starting positions for the puzzle are impossible to resolve, no matter how many moves are made. Here it was made sure that users will only get solvable puzzle.