After the square has been scrambled, your task is to perform horizontal, vertical, and diagonal shifts to bring the grid back to its original state. Example video: https://www.youtube.com/watch?v=Wy-MaCT_jK0.
Why torus (the shape of an inner tube)?
Torus Boards is a 2-dimensional representation of a game most naturally played on a torus with movable multi-colored bands on its surface (please see the animation at http://oscarseurat.com/TorusBoards/Torus4.html). The bands are assumed to move in three directions: along the smaller radius, the larger radius, and spirally at an angle of 45 degrees to either of the radii.
On the square, these motions correspond to three shifts which wrap around the rows, columns, and diagonals.
The game comes in several sizes/difficulty levels and types of shifts. Enjoy!