The game invloves obstacles that the bird has to dodge when flying through, you have to tap the screen to make the bird fly. In order for the bird to dodge the obstacles, you have to keep the bird at a reasonable height such as if there is an obstacles high up you have to drop the bird lower. You can control this by realsing the mouse if you want to lower it then continuing to tap the mouse when the bird is at right height. If you keep clicking on the mouse, the bird will fly higher.