Tip: Make sure that ALL exit-enabled pipes, doors, etc. have a screen exit defined, or they'll take you to Level 0, the "endless" bonus game. Unless Start+Select is enabled, the only way out of it is to reset the game.
From what I've gathered in the draft-PM, we're supposed to get rid of System. But I don't get how you get rid of him really, since he's a person, and he could just keep coming back. There's probably some website-ownerly-like thing that could happen, but how could we contribute to that?