Familiarity in Rapture? Not a good thing,” says BioShock creator Ken Levine, explaining why Irrational Games had to leave Andrew Ryan and his rotting underwater metropolis behind with Infinite. Luckily, the team's come up with another location that looks just as good: the sky city of Columbia, where a network of dirigibles keeps a vivid chunk of turn-of-the-century Americana aloft. It's got all the clapboard, Lincoln masks and bunting you could want.
Columbia is a world's fair crossed with a flying fortress. Fantasy aside, it's the perfect place to construct a game that examines a crucial point in America's development: the period between 1900 and 1914 that saw patriotic ideals curdle into jingoism, while the nation's experiments with power led to labour wars at home and gunship diplomacy overseas. If you're used to the one-two punch of BioShock combat – period weaponry in one hand, more exotic attacks in the other – Infinite's chaotic battles should feel pretty familiar, although some of the open-air environments hint at a new emphasis on ranged fighting.
What has changed, however, is the timing of your arrival on the scene. Unlike Rapture, which had gone to the dogs long before we first stepped from our diving bell, Columbia is tantalisingly perched on the edge of revolution, as the leftist Vox Populi prepare to rise up against the ultra-nationalist Founders. The latter want to keep Columbia aloft, the former want to send it tumbling to the earth, and that means Irrational are throwing us into a city that's hours away from anarchy.
Can games handle a genuine riot? It's certainly not the kind of thing you can convey with the level of set-piece scripting that the original BioShock was so reliant upon. Instead, Levine's team has turned to AI negotiations as the solution, creating a dense mesh of NPCs that will constantly monitor the player's movements, talk among themselves, and juggle a range of different reactions to whatever you're doing. Pedestrians will watch you for the right moment to foil a mugging or buy a soda, while angry mobs may choose to hold themselves in check for the time being, or to start breaking windows.
If that's a lot of pressure to put on behaviour coders, it's nothing compared with Elizabeth, the mysterious girl you've been sent to Columbia to rescue. Part plot device and part combat modifier (she can reach into alternate dimensions to summon everything from ammo to a passing tram for flattening enemies), Infinite's leading lady also sits at the centre of Irrational's greatest challenge: to build a story-driven game that hinges on a convincing human relationship between the player and an AI.