I used to play this constantly. I think the hardest level I found (that was possible/fun) was one called big ben. To start you had to jump off your segway and grab onto a clock-hand that would spin around. If you jumped off at the right time you would fly through a tunnel and land on a catapult which would fling you at a rope. You had to maneuver your body in order to catch the rope correctly. Afterwards it would use your momentum to start moving a cart that it was attached to. You once again had to jump off at the right point to go around a bunch of spikes before sliding down a ramp, grabbing onto a chandalier, and then letting go to land on the end-point.