Valve's second stab (and bludgeon) at the multiplayer zombie FPS spans five new campaigns in the Southern USA, from Savannah to New Orleans, and promises a stronger narrative arc across them as we get to know the four new characters - a high-school football coach, a female cable news reporter, a mechanic and a conman.
L4D2 has all our old Infected friends, along with a bunch of new ones, including the Charger, whose giant mutated arm is good for knocking you through the air, and the Wandering Witch, who still doesn't like to be disturbed, but doesn't exactly help herself by stumbling about in a daze rather than sitting down out of the way.
New melee weapons include the frying pan, chainsaw and axe (slice legs offs!), and there's also a new semi-auto shotgun and sniper rifle, all of which should help push the rank-and-file Infected into nice new ragdoll deaths, including a new hazmat-wearing model who's resistant to fire.
As mentioned last night, Valve's updated the AI director so he has discretion over level layout and weather effects, and also sets bits of the game (including the New Orleans campaign RPS played) in daylight.
Elsewhere, one of the more interesting additions is "gauntlet" moments. In New Orleans' case, you're sent across a long, narrow bridge, terrorised by Infected, leaving you to hop between the roofs of cars and vans at breakneck pace to avoid death.
There's more on the game in a podcast with designer Chet Faliszek, and we'll be taking our own look at it tomorrow.