"Left 4 Dead," Valve's Doug Lombardi modestly tells us, "will redefine cooperative games the way Counter Strike redefined competitive multiplayer." He isn't lying. Without hype or hyperbole, Valve's four player first-person shooter is the first of a new era - a co-op game above all else, to the exclusion of a true solo campaign; a co-op game which unapologetically forces strangers to cooperate or die; and a co-op game different every time you play.

"About ten years ago we were living in a world of Deathmatch-only games," says Lombardi. "Counter Strike brought team play to the forefront. Right now, cooperative games are out there, but they're sort of one-shot deals where you play the game once and you start to memorise it.

"We're trying to get over that stagnant second-time experience. Each time you play the game it's different - you enter a room one time and it could be filled with zombies; you enter another time and it could be completely empty."

DEAD MEN RUNNING
The forest campaign begins at a campsite deep in the woods, takes a circuitous path through the trees, across a rickety rope bridge and towards an industrial complex. On each attempt we faced opposition from different sides and in different forms; sometimes attacked on the bridge, other times allowed free passage; sometimes besieged in a small portacabin, other times fighting outside against the horde. There are no spawn points for the game's zombies; instead, an 'AI Director' picks the right enemies based specifically on how you play, scheduling breaks between periods of extreme action.

"I don't know too many people who play a lot of campaign games for months, but people have been playing Counter Strike for years," says Lombardi. "'Co-op' is an out of date phrase. Multiplayer gaming has evolved to the point that it's easy to find your friends and really easy to find a good server, which in the old days just wasn't true. What we're trying to do is evolve game design to feed on that."

Lombardi makes it clear: Left 4 Dead is a cooperative game in a way we've never seen before. Bots can take the place of your three team mates but that's not really the point; it's about surviving with other people; about working together; about finding a weapon stockpile and sharing them amongst the group because that's the only way you'll manage to survive.

Halfway through the forest we stumble upon a small shack; the lights are on but nobody's home. As the first of the survivors enters she's spotted by snarling, raging, zombies - the infected. Even in their most basic form they move like lightning, climbing, leaping anything in their path and rushing at speed towards their target - the rest of us in the open ground between certain death and the cabin's sanctuary.

 
We break into a speedy back-pedal, unloading shotguns and machine guns into the crowd, with every psychotic infected human killed, another taking its place. Some among them lunge towards a straggler landing on the tattooed biker and leaving him defenceless; a shotgun blast from a friend clears the threat but the zombies are upon us, and while Zoey fires from the locked cabin's window the rest of the survivors are torn to pieces out in the open.

It's a lesson learned - not when and how to fight against the zombies, but that moving alone gets you and your friends killed. Stragglers die fast, wannabe hero leaders fearlessly charging into the breach die even quicker. Valve will make you cooperate with total strangers, even if it ends up killing you.

"Counter Strike was multiplayer only with five minute rounds in which you can be killed in the first five seconds and spend the next four minutes and fifty-five seconds sitting and waiting to get back in. In a similar fashion, Left 4 Dead is being completely unapologetic about saying 'if you don't play as a team, you're not gonna make it'.

"It's really about beating people into submission to make them play as a team - to play cooperatively," he adds. Alone, even a single infected can kill you. Hunter zombies leap huge distances, pinning survivors to the ground where only a team mate can rescue them. Wounded survivors fall to the floor, immobile until a friend pulls them to their feet. Dead players don't turn infected, but can be found later in each campaign, sealed in locked rooms until released. Healing takes ten seconds or more and survivors carry only one medikit which can be shared with a wounded comrade if necessary. Better four guns than three, right?

 
MASTER GRIEF
As we chat with Doug, a scream - half shock and half excitement - goes up from four European journos knee-deep in the Hospital campaign. "That," says Doug. "That's what we're trying for, right there. When you play Counter Strike and you just manage to win and you have that watercooler talk about all the things you did afterwards - those are the best gameplay experiences that we have. To get that same high that you get from that perfect Counter Strike game? That's the goal."

Primarily a cooperative game, Left 4 Dead has its own version of the Deathmatch too; a mode which has inadvertently become the perfect counter to the team-killing idiots who threaten to ruin any teamwork-centric game.

Doug explains: "The multiplayer mode allows you to play as the boss infected, and that to me is a griefer's paradise. Your whole thing is to go and cause chaos. Griefers are gonna be the best boss infected to play against, right? They're already causing chaos!" Like the survivors, boss infected come in fours - blood vomiting, morbidly obese Boomers; agile Hunters, climbing and leaping like Spider-Man; Smokers, with a whip-like disturb-o-tongue; and the colossal Hulk-like Tank.

Fighting alongside the regular infected, the boss infected can see players through walls, allowing them to stalk the survivors from afar. No one boss infected is a match for the four survivors in a straight fight, but in the right place at the right time alongside the infected army, they're a nightmare.

The fifth, unplayable boss infected is the game's most terrifying horror. Fleeing through the industrial complex we run across elevated beams and catch sight of a Witch through a floor grating. Only seen once per campaign, she stands crying in the darkness, all pale skin and matted black hair, her agonised moans warning you to extinguish your lights and aim carefully. As strong as the Tank and as fast as the Hunter, she can kill instantly but only becomes agitated when disturbed by gunfire or flashlights.

 
You become quieter when the Witch is around; you tense up and try not to look her in the eye lest a twitch of your finger sends her into a screaming rage. It's that tension which makes the game - a shared tension, alleviated by jokes between you and the other survivors, punctuated by moments of extreme action and all-too-brief periods of calm. At its most thoughtful, Left 4 Dead is a true survival horror game, and at its most frenzied, it's the fastest and most intense first-person shooter you'll probably ever play.

ZED'S DEAD
Consoles are up to the job of survival horror, but that speed is where pad controls just can't match a mouse and keyboard where a full 180 is just a flick of the wrist and a set of hotkeys allow instant access to weapons and equipment. "That's one of the things we'll be working on over the next six months," says Doug, when poked. "We're pretty proud of Half-Life 2 on the Xbox and the 360, and Portal, Episode 2 and Team Fortress 2 are different games which were great experiences on both platforms.

We don't try to kid ourselves that we can just stick in the standard Halo controls and it'll work, which perhaps some other folks are guilty of. "It's all tuning - the speed, how much aiming correction you put in there. There's no secret sauce; it's just doing it over and over again and getting a lot of feedback. "Console testing hasn't gone into external playtest yet, but that'll be going on throughout the summer as we head toward certification," continues Doug.

4-SOME
For now though, it's on the PC where we search for our fallen comrades in locked cupboards and supply rooms. Two men down courtesy of a Molotov accident while fleeing from the Witch, we see the marker denoting where our deceased friends are imprisoned, and in the hurry toward them we split up. The infected smell the weakness and descend upon us like locusts. The third man fallen, one lone survivor clambers over stacks of boxes, scrambling backwards, emptying the final rounds from his two pistols into the ravenous horde, fleeing toward an air duct high above. Too slow, too stupid, too poorly armed, and far too late. When you die, you die alone.

***fingers crossed its not another waste of money on an EA game***

CoD4 zombie mod?  Do tell.