BioShock 2

At some stage, this will allow you to spirit the Little Sisters out of Rapture, but in the meantime you can help them do their job: harvesting ADAM from the corpses of dead splicers. When you discover a glowing body, your Little Sister can go to work extracting ADAM with her oversized syringe gun, and while this goes on, Rapture takes notice, and puts you in the firing line.

The section 2K Marin shows off brings everything we've seen before to bear: thuggish splicers, leadheads, nitros, spiders and Houdinis, who attack in mixed waves. The Big Daddy may have little trouble deflecting a few with his interchangeable drill dash and rivet gun, but when they confront you in numbers, they're a serious threat, and dealing with them is a full-time job complicated by the Little Sister's exposure. If she is killed, you lose all that ADAM, so you need to control the crowd, making use of whatever weapons and plasmids you have, including whirlwinds, fire and electricity.

There are other Big Daddies to worry about too, including some "surprising variations you haven't seen before". What's more, "There definitely will be enemies we introduce over the course of the game that feel a little more like they could go toe to toe with a Big Daddy," according to lead designer Zak McClendon. Splicer combat is described as "popcorn between meals". And worse is to come, as Jordan Thomas explains: "[The Big Sister] is incited to attack the player by his interactions with the Little Sisters."

"You take a certain number of them out of the world, and she gets angry, and hunts you down anywhere in a level. And there's a countdown, which gives you a chance to prepare, so you can rush over and hurriedly punch the clown until it gives you goodies, and hack every turret in the room, and blanket it with trapbolts and so on before she comes. Because when she does, you are going to have the fight of your life." It's at this stage that the demo ends, because the player is simply no match for the Big Sister, who terrorises him, just as surely as the Bouncers ripped Jack back to the last Vitachamber when you dared to provoke one in the Medical Pavilion.

Rapture's cultural isolation means that the city itself has evolved ecologically but not stylistically, which 2K Marin combats by creating new locations, rather than returning you to Neptune's Bounty or Fort Frolic. "There will be links to stuff you've seen," says Jeff Weir, "but all the primary environments are totally new places that you've never been to before. Rapture is a huge city. The first game was only a small part." Thanks to your permanent diving suit, BioShock 2 also takes you outside onto the ocean floor, through floral corridors of reefs and vegetation. And you do go back to Fontaine Futuristics.

And thanks to that sucker punch, Rapture has also had to evolve philosophically, although Thomas is adamant that BioShock 2 must reinforce the original's objectivist foundations - and Andrew Ryan himself. "How can I possibly return you to Rapture without having Ryan be a presence?" he asks. "Without objectivism, without the influences both literary and philosophical that gave birth to Rapture, it wouldn't be BioShock. Taking you back to Rapture and showing you how Rapture changes has to begin with the ideas that setting was built out of.

"From there, however, to add a new mystery to Rapture, there has to be a contrast. One of my buzz-phrases for this brand is 'an indictment of extremism', that the interesting thing about BioShock 1 was whether you agree with Ayn Rand or burn her books regularly, you can see it exaggerated massively in the form of Andrew Ryan in the form of Rapture, and you watch how the attempt to bend reality to a fairly rigid set of abstract principles fails and succumbs to this yowl of entropy."