Left 4 Dead

But despite the harrowing memories of Resident Evil Outbreak, it had some cracking ideas too good to leave in the dustbin of history: who wouldn't be excited by the idea of an online four-player co-op game where you're working together to escape from a procession of marauding zombies? Evidently Turtle Rock and Valve loved the concept enough to try and do it properly - albeit with an execution which completely rejects the notion that survival horror should be slow, ponderous and lacking in ammo. Left 4 Dead is more of a noughties reinvention of zombie horror, infused with the terrifying athleticism of 28 Days Later's brand of undead.

Capcom seems to believe that slowing down the pace of combat, and granting the player a strictly limited ammo supply, helps build tension. To a large extent it does, but it's also a very quick way to alienate and frustrate the sort of players who just want to get in there and blast some zombie brains. The first impression of Left 4 Dead is of a game unafraid to reject that notion and make it fast and furious, and generally meddle with the well worn conventions of how zombie shooters should work.

Shoehorned into a dark (gothic) basement bar in the middle of (gothic) Munich on a bitter (possibly gothic) winter evening, we're treated to a fresh build of the game showing off the farmhouse map. Beset with technical hitches, power cuts, and general culinary hocus pocus, we're plied with copious quantities of the finest German blonde beer before we even get a chance to start separating undead heads from rancid bodies. When the show finally does get underway, we do what any inebriated zombie hunters would do: run off in different directions, shoot wildly and dispense with any notion of co-operative play until the game kicks us to the kerb.

As both Tom and Oli have already summed up in our existing previews, everyone in the world is infected with a scary virus which has turned them into slavering zombie death machines of extreme prejudice - except, that is, you and your three buddies. With the basic premise of ah, ha, ha, ha, staying alive, staying alive, all that's between you and a life of sweet safety is a whole pile of undead flesh. How you plan escaping to victory depends on your ability to shoot straight, communicate with one another, stick together and heal one another when things go a bit wrong.

You pick which of the amusing character skins you want to occupy, choose your weapon (think standard, real-world firearms and Molotovs - sorry, no Shaun of the Dead-style vinyl justice allowed here) and get cracking. It's all disarmingly straightforward; you run around large, linear maps, clearing each area of enemies, and the game's mystical 'AI director' decides how much pain it wants to mete out. If you're doing exceptionally well, expect the undead to rain on your head, but if you're a bunch of hapless scaredy-cat losers, it'll back off a bit, so you can expect the whole thing to play out entirely differently every single time. There's nothing remotely scripted about the way it plays, which, of course, should keep us all coming back for more even when we've succeeded in escaping all four of the game's rural and urban scenarios.

Showing off the by-now-familiar urban map, we blast our way through hospital and train station environments, styled in that now-familiar Source Engine look. The visuals don't necessarily wow, but they don't need to. The ebb and flow of the action and tension is palpable, the relief tangible every time you reach the end of one of its terrifying crescendos. When Valve mentions "the AI director is very in touch", you'll know exactly what it means; this invisible guiding hand lends the game a subtle freshness and credibly adaptive challenge. By the time you and your pals get good at the game, goodness only knows what horrors the director will toss into your path.

Valve makes no apology for kicking us off on the easiest of the four difficulty settings, and takes an almost gleeful delight that we still suck at it. It knows only too well that we'll initially screw up, wander off, and get ambushed. Valve's ubiquitous VP of marketing Doug Lombardi and "Mr Awesome" Chet Faliszek wander past now and then, smiling ruefully to themselves as they spot our rubbish tactics a mile off. But everyone does it, so that's okay. As we progress, it's evident that the game revels in presenting a tough challenge - particularly for those foolish enough to reject the notion of team-play. If you decide to play the renegade zombie-killer, expect the AI director to rain zombie death. Even a couple of hours of in, there's a sense that this was a game where you'll enjoy the learning curve, rather than get frustrated with it.

In terms of the first look at the rural map, the atmosphere's notably darker, and creepier - and reminiscent of the way that Half-Life 2 continually changed the look and feel of the locations open to you. From crumbling outhouses to lonely fields, the darker feel, and sense of remote hopelessness feel even more intense. With each map 'Half-Life 2 sized' there's a solid hour and a half of team play expected per scenario - but how much repeat play remains to be seen. We expect plenty.

Eventually, we got a chance to switch sides with one of the team getting to play one of the Infected, with the goal of stalking your human prey and picking them off. It's not simple, and Valve freely admits that there's plenty of balancing work to be done before it's accessible enough to ship. In theory, as a Boomer or Smoker or Tank, you'll be placed somewhere out of sight from the four-man team with the goal of taking them down. Little colour-coded chevrons give you an idea of the survivors' expected path, so you can scale buildings and objects and lay in wait, pouncing on foolish players who stray from the herd, or waiting until everyone's trapped in a confined space and blowing them all up. It's a fantastic concept, but one which has to be a little more accessible than it is right now. Either that, or I'm simply making excuses about how absolutely rubbish I am at the game. I usually do.

Given we were only able to sample a small portion of Left 4 Dead, the possibilities of what lies in store when the game arrives in September position it as one of our most wanted games of the year, just as it was last year when we thought it would be out then. The quality isn't going to fade. It's one of the few online-only games that we can foresee spending stupid amounts of time playing with our friends, and if I get to blow Tom up in an elevator it'll be sweet vengeance for all the times he kicked me off rooftops in Crackdown. I hate him. Read on to see what Doug Lombardi had to say when we quizzed him further about what's in store.