Although this game is already over 10 years old, it still seems to hold up to other, brand new flashgames here. I only came for the medals, but playing with the physics was so much fun that I actually created a fairly good level in the editor myself, I must admit. Although it it quite hard ( about as hard as the last 3 levels), it is still doable, I tested it myself.
In the editor I encountered 2 bugs though.
1. After holding shift a bit to let the acid spread equally over the ground, it also spread into the acid-breakable-blocks. When I tried testing the level there, it didn't load properly (because there was acid inside of blocks, I guess) and I had to reload, luckily it saved my progress.
2. For some odd reason a single blob of acid keeps crawling up the wall it is touching, getting on top of a platform where it's in the way. I had to reduce the placed acid to a puddle that didn't touch the surrounding walls in order to prevent that.
Nevertheless I finished my level, and of course the game itself. All the time I thought that professor was evil because of his looks, the game proves that looks don't reflect the personality. All that suffering was worth it I guess.
By the way, here is my level code, for anyone still checking up on that game (maybe medal-hunting like me) and looking for a little extra challenge. Enter the hardcore parkour :P