There is this addictive little program called Linerider which in the right hands (not mine) can be used to make mesmerizing rube-goldbergesque layouts. The game is based off of simple concepts - gravity, a line (to ride and bounce off), a little guy in a sled.
Since there are actual game physics to contend with it is not a mere fantasy of flight, make the drop too steep and the rider is crushed on impact, lose too much inertial energy and he will not make up the slope. This is all too hard to explain with words, here is an awesome Linerider You Tube video synced with a Nickelback song (double points for the music choice).
Search for Linerider on Youtube, there are a lot of these.