You run in a linear fashion, you shoot stuff, you activate switches to run further and shoot more stuff. Weapons, ammunition and other items just lay around in the usual FPS manner. It's not as bad as, say, Quake 2. There are outdoor areas, friendly alien characters and neutral animals. Occasionally level designer give you some surprise, like collapsing bridge, or a vent that blows you away, but overall levels are quire synthetic. They are designed purely so you can run through them, shooting anything in your way. It's impossible to imagine those creatures actually living there. There are some text messages you can read, like diaries or logs, but I haven't seen much in terms of storyline. Overall, it's a standard and rather repetitive FPS with standards FPS design problems.