Wow. Mark wanted a way to set up a level such that coop players would be forced to bypass the level, but solo players would have to complete it. He asked for advice on the discussion forums at Marathon Central, but didn't get any answers... When he came up with a solution, it was complicated enough to warrant a writeup, so here it is. It's actually a demo map, showing (and telling, with detailed terminals) exactly how he accomplished the feat. (It's way more complicated than you might think...) The technique's biggest drawback is its resource utilization... 26 platforms used to divert players to the proper exit. As I read it, I thought, "There must be a better way..." but if there is, I can't think of it. This is very advanced mapmaking... not for the squeamish. If you're at all interested in player control, though, this is worthwhile reading.