The other Expert-level science fiction game from Infocom, Starcross is not as difficult as Suspended, but it is difficult nonetheless. Designed by Dave Lebling generally for people with a scientific background, the majority of this game takes place on a huge alien ship where everything is what it seems, though you may not know what it is. Several of the puzzles have multiple solutions, and there are lots of opportunities to see what Infocom's vivid descriptive prose and parser can really do. This game will require quite a bit of time and work, but it will be worth it if you have a good background in science.