Each time you click a gem it will change its color and the color of the 4 (or less) gems around it. You have to try to make all the gems get active using as few moves as you can, or as fast as you can, depending on the game mode. And there is also a bonus mode, where you have to try to make the forms there are showed to gain bonus in the final score.

Check inside the game for instructions on how to play Reversi Gems.