Level 3: Next to the vibrating circle at each station, there is a dial with 5 different positions it can be in. In each position, the big circle on the track shows a different vibration and plays a different sound. Take note of the different shapes on the dial. Then, try standing inside the circle. You'll notice that even if you don't move your mouse, you still jiggle a little bit. A ball rolling down this track would definately not be able to pass through unharmed...