The normal rules for magnets apply: The grid is made up of magnetic and non-magnetic plates. Each magnetic plate has two halves: one positive (+) and one negative (−). Halves with the same symbol can not be horizontally or vertically adjacent. The numbers outside the grid indicate how many magnetic halves of each kind can be found in that row or column.
Additionally, the numbers at the borders have been replaced with letters. Same digits with same letters, different digits with different letters.