You have to draw a shape according to what geometrical figured orb you are trying to eliminate by touching and dragging on the screen. So, for a square orb you have to draw a square on the screen. You can move the shape that is drawn, by clicking on it and dragging to where it suits you best. Then when you've got your drawn shape in place, all you have to do is tap on the screen. The shape that you draw must somehow be in contact with the orbs that you are attempting to eliminate. What's the catch? The shapes are constantly moving and might be in the midst of other shapes.