is fun puzzle game. And it is free.

The goal of the game is to combine all squares of each color in separate groups. You can move squares by swapping them places. But remember that you can swap two squares only, if they contact each other, and if after the move one or both of the squares contact at least one square of the same color. The less moves you use, the better your score.
It may look easy... for humans, but it is quite impressive for monkeys.