Rearrange the tiles again into a square, but this time the tiling should not contain any smaller tiled square of size 2×2, 3×3, 4×4, 5×5, or 6×6.
Select one of 10 challenges from the drop-down menu.
To move a tile, drag it.
You can temporarily store a tile on the large gray margin.
The goal is to reassemble the tiles to a 7×7 square in the center without any smaller square area tiled.
If you study the default setup, you will see that there is a tiled 2×2 square area at the lower right corner and also a tiled 3×3 square area at the top left. Such configurations have to be avoided in order to solve the puzzle.
Checking for correctness
Click the "test" button to let the system check whether you have solved the puzzle. If you have not solved the puzzle, the system will tell you which tiled subsquare you have overlooked by highlighting it. To get rid of the message, simply move a piece.
If your solution is correct, you get a message saying so.
You can reset the tiling at any time to its default configuration by clicking the "reset" button.
This game was first published by the author as the Zillions game Squash in 2007.