Almost everything is procedurally generated these days. When I look in the mirror every morning, the non-Euclidean angles to which my hair terrifyingly conforms are different every time but always unhelpful, being a clear result of sloppy and overambitious coding. Bust-n-Rush's levels are also variable but they look a lot better than the mess atop my head and they make more sense as well. It works like this: you are a large man running along a series of tunnels/tracks, dodging certain obstacles and smashing through others. If you can jump, sidestep and hold down a 'rush' button, you'll be fine. Try the demo here (or on Mac), or watch a trailer below. Maybe even do both!
I think the trailer does a fairly good job of explaining the game, which is an increasingly rare state of affairs. They could have shown live action footage of a man walking through a cave with Moonlight Sonata playing in the background as water dripped mournfully yet erotically from a cluster of stalactites. You'd be moved, perhaps even brought to tears, but would you know that the game was an arcade-type jumping and dodging extravaganza set in space? Nope.
Unfortunately, the early stages of the demo do a rather less efficient job of showing what the game is all about. They are very much of the tutorial sort and this is the sort of game that starts to shine when there are lots of elements thrown into a level at the same time. The earliest levels are just about holding down a button and watching a counter go up - not exactly a great sales pitch. Persevere and you'll soon have a better idea of what to expect from the full version though. As things become tougher, the procedural generation ensures that reflexes and a little bit of forward planning matter more than memory.