Choose and click on a difficulty level button.
Then arrange all of the the numbers on the grid so that:
each vertical, horizontal and diagonal adds to 58,
any four numbers forming a square add to 58,
when the top row is moved to the bottom, or vice versa, the diagonals still add to 58,
when the left hand column is moved to the right hand side, or vice versa, the diagonals still add to 58, and
the four corners always add to 58!