It consists of 16 tiles in a 4x4 square. On the left of each row is a plunger, which pushes that row one tile to the right. At the top is a large plunger which pushes the three rightmost columns down one tile.
Springs push back the plungers as soon as they are released.
If the top plunger is pushed in, the first row plunger can no longer move. This limit is not reached since only even permutations are possible. Let T mean the pushing in of the top plunger, and let t mean releasing it. Similarly, let A, B, C, D denote the side plungers from top to bottom, with a capital letter meaning pushing it in and a small letter releasing it. These sequences can also be performed on any other pair of adjacent rows.