Prey takes place on a giant organic spaceship, an Omicron with guts, so it's only fitting that the gameplay is cobbled together as well.
The living ship motif was explored in System Shock II, where we saw doors that opened and closed like sphincters and various meaty portions undergoing peristalsis like the background in a Tool video.
The demo leads you through a typically interminable opening sequence, the same way indie films will insist on showing the credits for anyone even remotely connected to the movie. It begins in a bar; That's the scene. Then the player-character is beamed aboard an alien ship along with his girlfriend, his grandfather and everything else, maybe everything else on Earth.
The main character has a name, but he may as well be Duke Nukem with a deflavored Native American mythology to dress up what becomes a typical revenge-rescue-rampage shooter.
The ship hums and whirrs and carries people along assembly lines similar to the Citadel in Half-Life 2. Grandfather ends up on the wrong line, or rather, the right line for the plot. He's speared by a grisly spearing machine and then flattened into a red smear. For what purpose? Raw materials, maybe. Dramatic effect, definitely.
Player-character is visited by Grandfather in a waking hallucination where the mechanics of the spirit-world are explained. Throw an ectoplasmic avatar outside the body and use a special bow for sniping. A contrivance, but it adds enough variety to demand a modicum of tactical planning.
Meanwhile, the girlfriend is whisked along further into the ship, mercifully spared the ginsu treatment. For now. She becomes the carrot on the stick, always just out of reach, pleading with the player to get on with it already.
At every turn the designers of the demo seek to defeat any stable notion of space. This plunges the player into a constant state of helplessness as to orientation or even objective. Gravity switches turn rooms into topsy-turvy puzzle boxes. Portals slash one-way holes through geometry, remixing the usual linearity of tunnel crawls.
Enemies are unremarkable, footsoldiers with the modern equivalent of palette-swaps -- more facial abscesses or a different weapon or a pronounced hunch. There is mystery, too, a possessing specter toying with captive humans and a stranger's voice helping the player-character with explication and aid-from-afar.
Weapon design practices both extremism and economy. Each weapon is powerful and each fulfills a specific niche. The balance is especially noticeable in multiplayer. The basic gun, which appears to fire glowing red-hot rebar bits, doubles duty as a sniper rifle. The acid gun can fire several weak bursts that do close-in damage or a larger area blast that has a longer reload time. Then there is a multipurpose gun that can be charged with different types of ammo -- magma and ice and some kind of golden beam.
The final game could shape up to be inventive and continually disarming, living up to the potential promised by the Doom III engine, provided the giddy sense of momentum can be maintained.