The dynamic that is set up here is that every time Tommy is "killed", he gets a chance to reclaim health in the spiritual realm by shooting spirits (he can also get back spirity energy here). So there are times when you'll walk into a room full of monsters with low health, and deliberately get yourself killed so you can go to the spirit plane and recharge.

It's functionally the same as using a Quicksave feature, but it's consistent with the game world so you feel much less like you're cheating. It also allows the developers to justifiably put in unavoidable traps and encounters that not even the best players can survive on a single "life".

In close quarters, Prey looks very much like Doom 3, except with greater variety in texturing and types of environments. But Prey also makes use of truly epic scenes, with the player overlooking vast gulfs and flying a vehicle through open space to other parts of the level.

Some parts of the enigmatic alien Sphere have whole asteroids suspended inside them. The game allows you to jump in a vehicle, fly across to the asteroid (whereupon the asteroid's own gravity changes "down" to toward its centre), and run around on the surface.

It's reminiscent of the way games like Black & White allow you to zoom all the way out from the game world, except it's in an FPS!

Of course, what you really want to know about is the portals and gravity manipulation. Both are implemented with considerable success.

Not only do portals exist in important-looking portal generators, they can also appear randomly inside everything from regular doorways to upturned crates. It's almost as if the technology "leaks" portals into random parts of the Sphere.

Running through a portal instantly transports Tommy to another part of the level. No muss, no fuss. It allows for some very intriguing game design, such as running through the door only to appear on a room's ceiling facing the floor... thud.

Since portals allow for the manipulation of gravity, and level support multiple gravity vectors, an obvious extension of this is to allow gravity to be changed dynamically.

Tommy simply shoots a special control panel, and the gravity flips to make the surface on which the panel is mounted the floor. There are plenty of situation in which Tommy must make use of gravity control to get over obstacles or across huge gaps.

There are also time-limited gravity generators which help create some interesting puzzles when combined with Tommy's spirit-walk ability.

The gravity-defying feature in the game is of course wallwalking. Wallwalks "stick" the player to a special surface, allowing you to run all over the walls. Wallwalks are often used to put Tommy in unusual combat situation, where he has to keep an eye on all sorts of visual points that you'd normally be able to dismiss. Great stuff.

What all this means is the game isn't just about shooting monsters, it's also about manipulating the environment to reach Tommy's goal, and that's a big part of what makes it so much fun.

Still, Prey is very much a shooter, so it's a relief that Human Head has included a set of weapons that do it justice. Some folks might not like the way all the weapons are alien in origin and how it's often difficult to tell what the hell kind of ammunition you're even shooting. Just one army-issue, bullet-shooting gun would have made some of the battles even more satisfying, but that doesn't mean the shotgun that fires green goo isn't fun.

Prey has rejuvenated the straight-up shooter. Half-Life Episode 1 is a far different experience, and even if you've played it to death, Prey will still be able to give you something fresh.

It's not subtle, it's not particularly clever, but it is hella fun. It's definitely a game you want to own. That's all the good stuff. For the bad stuff, head down to your local newsagent and grab a copy of PCPP#129 - out now!