I used to have a level downloaded, but it seems I've lost it. I forgot the name of it, but it involved going through 4 different sections, each leading to a different powerup: one led to double jump, one led to high jump, one led to climbing (I think) and the other to something else. The key feature was that completing one section changed the others and you could complete them in any order.
If anyone knows what level I mean and can tell me the name, I would be most grateful.