Prey is the touching story of how one man comes to accept his spiritual heritage, to the delight of his girlfriend, after being kidnapped by aliens. His girlfriend is considerably less delighted about the aliens, as she's been kidnapped too, but you can't have everything. Most of us never get that kind of impetus to better ourselves, so Tommy's lucky from the start, eh?
It's potentially a bummer that his granddad gets squashed to death and Tommy falls off a bridge and dies after just a few minutes. You might think that was a bit of a spoiler, but it's not - these are the methods by which Tommy's granddad becomes an Obi-Wanish mentor more powerful than you could ever imagine, and how he bestows on the nonbeliever Tommy the already famous Spirit Walk ability.
Prey's world is a mad one. Captured by a giant 'Dyson sphere' in Earth orbit but accidentally freed from the one-way conveyor-belt to death, Tommy navigates a world where up and down are subjective, two-dimensional portals lead to three-dimensional spaces and rooms can change shape around him. To survive you must use these aspects to your own advantage - inverting the gravity to circumvent barriers, spirit-walking through force fields and over ghostly platforms to deactivate protected switches. At times you're even released into the open space inside the sphere, navigating the void in a pod, perhaps to drop onto the heavily curved surface of a captured asteroid and fight the low-gravity fight roaring over the hilariously close horizon.
The technology is stunning; almost too stunning for its own good. The portals are indistinguishable from magic, and while you'll spend a few minutes circling your first encounter in total nope-stillcan't- see-the-seams admiration, after a while they just become routine, the same as any door. Life is unfair.
So the technology is never less than impressive, but the problem is it doesn't really change what you're doing. On the other hand, you are doing it with uncommon style.
Occasionally Prey will remind you how impressive it is, such as the point where a rattling crate topples over to reveal a portal - a creature on the other side (or is it inside?) has knocked it over to rush out and ravage your bits. On a couple of other occasions you exit portals only to glimpse yourself entering the same one... it's like looking in a mirror only to see the back of your head. The collision between looking perfectly real and being clearly impossible is always affecting.
Gravity changes have more direct effects. Though you can't switch it at will, there are blue-lit plates dotted around which, when shot, reset that surface as the floor. At other times you're limited to special walkways which wrap around the floors and ceilings - these need powering, however, as you'll discover the first time a guard turns one off mid-run. Both methods allow you to cross chasms or reach distant platforms when the Spirit Walk is not available (a star symbol etched in the scenery will tell you when that's necessary). You're unlikely to get stuck.
Perhaps the most impressive - and fun - effects of gravitational weirdness come when wandering around on asteroids. One problem involves getting from one asteroid to a smaller one, as only the larger rock has a landing pad. The solution is to walk up, or down, or possibly along the twin oil pipes connecting them, then drop onto the surface, at which point your idea of up finally scrambles completely. Just as it should, considering you're fighting aliens in space. This kind of perception-shifting is inspired.