This is a puzzle from the old C64 Impossible Mission game. The idea is to combine the 36 tiles in sets of 4, such that each set of 4 makes a solid block. Clicking on the tiles on the left toggles them. A tile can't be turned on if it overlaps with any existing on tiles. The lone rectangle on the right is the combination of all the on tiles. Clicking on that is an easy way to turn all tiles off. When 4 tiles combine to make a solid block, they vanish. The goal is to get rid of all the tiles. There is no score or timer. Just do it for the intellectual exercise. WWW: http://www.linuxmotors.com/puzzle