That's fair! We wanted to make it more apparent, but couldn't in the timeframe. If it helps, everytime the 'E' or exclamation mark shows up it should activate something when you press it, whether that is talking to an NPC, picking up an item, transitioning levels, or messing around with the radioactive puddle and construction truck. We also didn't have time to show the player that if you pick up an item and talk to Gaz (The Rat in the van) that you can then buy a mutation in his shop! So far the only mutation available is the super jump in the side-scrolling level (activated by pressing 'Q')