Some people were shitting on the thread at duke4.net, so I'd like to say something here before that happens (not that I really expect it). The Imperium is, for the most part, a good old-fashioned action based episode for Duke 3D. It does utilize some models and coded effects, but it's not trying to be a modern story driven game or anything like that. It's pretty much mindless action with some engrossing atmosphere and level design. So if you are looking for puzzles, or a lot of story (there is some, but not a lot), or new gameplay mechanics, then you will be disappointed. Well that's not completely true, there are a few puzzles and there's some stuff done with the nightvision appearing effect, but no one who played it thought it worth mentioning so obviously it's not a big part of the episode.