The diagram contains magnetic and non-magnetic plates of size 2x1. Each magnetic plate has a positive (+) and a negative (-) pole. Poles with the same charge cannot border on any side as they repel each other. However, their corners can touch. Non-magnetic plates can be placed next to any other plates. The numbers of + and - charges in each row and column are indicated.
MOUSE: Click on a square to draw the '+' sign (the corresponding '-' sign will appear automatically). Click again to invert the polarity. Click again to draw a neutral plate (#). A new click will indicate that there is a magnetic pole with unknown polarity (.) and a new click again will eliminate any symbol.
