The Xbox 360 is certainly no stranger to violent, run-and-gun shooting games (see: Halo 3, Gears of War, Medal of Honour etc.) so it would be very easy for a game like Bioshock to disappear without a trace as just one of an oversubscribed genre. Interestingly enough, what we have here is a far from a standard first-person shooting game, and a serious contender for the game of year.

Taking the form of a 1950s-styled horror shooter, Bioshock’s environments are dark, claustrophobic and uncomfortable. The action takes place in the city of Rapture, an underwater ‘utopia’, created by a scientist looking for an escape from traditional morality. As a result of this pioneering egghead’s research into human genome modification, the denizens of his brave new world have all turned into genetic mutants who habitually hack each other to bits.

In terms of gameplay, Bioshock takes a fairly standard first-person shooter and adds a couple of nice elements to keep things interesting. The weapons are pretty much what you’d expect from a game set in the 50’s, so the standard set of revolver, shotgun and machinegun sees you through most of the game, although different types of ammunition are available to get you out of specific tricky situations. Much more engaging are the genetic modifications that you accumulate throughout the game, including the ability to create fire, electrified hands and telekinesis.

Aside from the joys of zapping mutants with electricity, Bioshock gets a lot of its character from…well… its characters. There’s loads to enjoy between the disembodied voices of survivors giving you objectives via a crackly two-way radio and the insane ranting of genetically modified humans, but it’s the Big Daddies and Little Sisters who really steal the show. These freakish double-acts consist of a seemingly harmless little girl who wanders around the level accompanied by an armoured giant in a diving suit. They’re perfectly happy to leave you alone as long as you don’t bother them, but since the Little Sisters provide the only way of upgrading your genetic modifications, you’ll eventually find yourself taking on their Big Daddy – and most likely getting brutally beaten, as these behemoths are by far the toughest enemies in the game. Once the bodyguard is out of the way, the Little Sister immediately begins sobbing uncontrollably over his immobile corpse, and you’re offered a choice: ‘harvest’ the little girl’s genetic material, killing her in the process, or release her in exchange for less powerful upgrades.

The Big Daddies and Little Sisters provide a deeply uncomfortable dilemma, and one that demonstrates just how far the developers have gone to make you feel the sense of wrongness that pervades the entire game from start to finish. In summary, Bioshock is an extremely polished, well-balanced and terrifying shooter, and an absolute pleasure from start to finish. Worth buying a 360 just so you can play it.

Bioshock is out now for Xbox 360 and PC