ast week, we got to play through a three-hour BioShock demo. During that time, we saw some amazing and surprising things. Rather than just give you a minute-by-minute account of the entire experience—with agonizing descriptions of every door opened, enemy killed and line of overheard dialogue—we thought we'd cut to the chase and tell you five things you should know about the game.

1. The story…

As a plane-crash survivor who stumbles onto the underwater community of Rapture, you quickly discover that all isn’t well in this would-be utopia. All isn’t well is probably a bit of an understatement. Ghouls roam the rusting hallways in search of Adam, an addictive substance that allows for a variety of physical and mental enhancements. And if the risk of having someone forcibly try to examine what’s in your skull isn’t danger enough, there are also signs of a failed political uprising. As soon as the doors to the underwater elevator open, you’re met with stacks of picket signs proclaiming “Ryan doesn’t own us,” a reference to Rapture’s founder, the paranoid industrialist Andrew Ryan. Your guide throughout the game is the staticky, disembodied voice of a man named Atlas, who also seems to serve as the counterpoint to Ryan's increasingly crazed agenda.

In addition to guiding players through the game, offering guidance in exchange for helping get Atlas’ family out of Rapture, Atlas is also the subject of public-address messages that play periodically over the intercom. These messages portray Atlas and his “gang of bandits” as a menace to Rapture’s safety and security. Whether or not this is an accurate representation of things remains unknown—during our demo we weren’t allowed to see a long stretch of gameplay, preventing us from seeing a couple of promised plot twists. While BioShock mines much of its inspiration from Ayn Rand’s work, it wouldn’t be unheard of for a character like Atlas to actually be a made-up bogeyman designed to keep the populace in check, like Emmanuel Goldstein in Orwell’s 1984.

There’s also that business about having the option of saving the so-called Little Sisters (children who have been infected with Adam-producing sluglike sea creatures) or simply harvesting the Adam for yourself. Your character encounters a mysterious woman who promises an eventual reward for saving the girls, though her ultimate motivations are unknown.

2. …And how it’s told

While you’ll definitely get nudged along a general path while playing BioShock, there’s a great amount of flexibility as to how much of it you digest. Personal recording devices are scattered throughout Rapture, and listening to them provides key background information about what went horribly wrong in Rapture. Unlike in a lot of other adventure games, which typically rely on telling the backstory through written notes and cutscenes, these audio snippets allow BioShock to tell a story without wrenching control out of players’ hands. When you pick up a tape, you’re able to listen to it while you move along—it will continue playing even during combat.

Of course, if you don’t care why the Dr. Steinman character went from being a plastic surgeon to a homicidal psychopath, you’re free to ignore the recordings altogether. In addition to the recordings, BioShock’s environment is an important storytelling device as well. As with the picket signs in the game’s beginning, Rapture is filled with little details that paint a much broader picture of that community’s former life. How far you delve into it is up to you.