Prey's outstanding level design is possibly its strongest asset, but its linear design can take the thrill away.
The portal system is a neat little gimmick in the game, allowing enemies to pop out of no where on walls and ceilings. Some portals don't even show up unless you walk through others, and you might just show up on another aspect of the same room (from floor to wall). The spirit walk is a neat idea, but Prey lacks to use it to it's utmost effectiveness. Most of the time you just use it to walk through a specific wall, and push a button the other side so your body can walk by. Its proven effective for myself from time to time, where I would ambush a couple enemies, and shoot them point blank in the head for a one-shot kill with my bow. The death effect in the game however, is a hit-or-miss attempt, depending on the player you are. If you are like me, and might run through a shooter and use the Quick-Save option just as often as crouch, then it can prove as a useful substitute. However, it lacks the challenge, as dieing is really no consequence. If you die, you appear in the "Spirit World", and shoot some wraiths with your bow to regain life to your body. After about 15 seconds, your body returns to the real world, right where you died.
The weapon designs are pretty creative, and the way you acquire certain weapons is clever. One weapon is an automatic chain gun type gun, with a grenade launcher secondary fire option. You acquire this mid boss fight, where you cut off the hand of your opponent, and eventually pick it up and use it against him. Grenades are little crawler bugs you pickup throughout the game, and in the process of throwing; you rip their little lets off (ah-la grenade pins).
The graphics in Prey are outstanding, and the living levels make it feel creepy, though the game doesn't get too bad in the creepy department. The music is absolutely amazing, done by the same guy who brought you the music in Guild Wars and Oblivion. The weapon sounds are nice, but don't sound too alien oriented (machine gun type weapons still sound like machine guns). Despite that flaw, the sound helps the environment, by letting you hear the walls breathe, enemies walking around the metal corridors, or opponents communicating with each other to take you down.
Prey makes me feel like I'm fighting for something, sometimes. There are times where I would just be running and gunning like a regular FPS, then reminded that I was trying to save my girlfriend, who for some reason, still isn't dead, while almost every other captured human has been. The game is a little short, and can be beaten on normal in 10-12 hours, depending on how fast you blow through the game. After which, you unlock a harder difficulty, which I'm sure can slow the game down a little bit for replay value. Despite a few flaws and oversights, the complex level design and clever use of the environment makes Prey a solid First Person Shooter for those who like shooters for the sake of shooters, without the intensiveness of others, like F.E.A.R. or Half-Life 2.