The puzzle was invented by Simon Tatham.
Puzzle is similar to Puzzle 15, but with a different type of move.
There is no hole: all 16 squares on the grid contain numbered squares.
Your move is to shift an entire row left or right, or shift an entire column up or down; every time you do that, the tile you shift off the grid re-appears at the other end of the same row, in the space you just vacated.
To win, arrange the tiles into numerical order (1,2,3,4 on the top row, 13,14,15,16 on the bottom).