Like its predecessor, Left 4 Dead 2 is a sort of hyper-violent personality test masquerading as a cooperative zombie survival shooter. If you want to know which of your mates you should trust with the water bottle after shipwrecking on a desert island, simply invite them over for a bout and let the game’s dynamic challenge factor weasel out hidden traits and flaws, profiling each player in sickly green strokes of undead gore.

Where other shooters are static, unreactive structures, brittle sandcastles awaiting the casually lobbed football of human intervention, the Left 4 Dead games give exactly as good as they get, altering the quantity, quality and positioning of enemies, weapon drops and obstacles in response to player behavior. Lone wolves will be pounced upon by terrifying cat-like Hunters, cowardly hangers-on showered in Horde-attracting vomit by repulsive Boomers, layabouts lassoed and dragged off by elusive Smokers. After half an hour’s play, you should have a lot of stories to tell and a couple fewer names on your Christmas card list.

Among the game's "Uncommon Infected" are clowns, who can summon the mob.

The Jack-Daniels-swigging sequel is a personality test in another sense, however. Its aim: to divide the gaming population up into those who are prepared to pay a full 30-40 quid for incremental advances on a formula, and those who aren’t. Calling it a glorified expansion pack is several steps too far, but if you’re one of those deeply misguided, patently untrustworthy and smelly individuals who somehow wasn’t blown away by the first game you should probably think twice.

Left 4 Dead 2 introduces us to four new Survivors – slack-jawed teen Ellis, hard-bitten gambler Nick, wannabe TV producer Rochelle and big poppa Coach – and five new campaigns, set in the humid fastness of a post-apocalyptic Deep South – a more colourful environment than the temperate Pennsylvanian suburbia of the first game, and no less abundant in memorable landmarks, from crashed passenger aircraft to mall-top concert arenas. Campaign formats are the same: the first four chapters challenge the Survivors to get from Safehouse to Safehouse with all limbs/organs intact, and the fifth culminates in an all-or-nothing battle against the ravening Infected while rescue takes its sweet goddamn time arriving.