Play Copter, a challenging game where you are flying a helicopter through a tunnel with stalactites and stalagmites (clock graphics, actually) that you must either fly over, or fly under. You have no control over your speed, only your height / vertical motion. It seems like gravity is a little stronger especially the lower you fly in the cave as well, because you drop quickly, so be quick and accurate on your mouse button! It seems little bursts do the most good while anticipating the next barrier.
Instructions. Your left mouse button is the helicopter collector. Click and hold your left mouse button to go up, release it to go down.