Roll the blue and red smilies so they touch mutually and disappear: when you do it you pass to the next level. As you progress it will be more difficult to put them in contact, and you'll have to rely on the help, or avoid the opposition, of many kind of objects that you will find: magnets that attract the faces, switchers that change their color, or the possibility of fixing them to a point on the ground.
Arrow keys left/right to move the container sphere and make the little faces to roll. To fix the balls to a point, press the space bar. Press the R key to restart the current level.