mudmask that game looks really cool! Have you got the river generating randomly on every play?
EDIT: reading back through, there is some epically good work posted in this thread...
Thanks so much - while the river isn't COMPLETELY random each time, it's made of random parts that connect together which make different combinations each time. Every time you go X distance it loads another block of level based on the last block's exit point. Not sure if that makes sense! One of those things I came up with laying in bed.. haha
The grass terrain, the trees and bushes, the clouds, and the little water ripples all appear at random though. It definitely gives the illusion of total procedural generation, but I still maintain control of the various parts of the river so that they're both playable and also look nice.