Everything Valve touches seems to turn to gold. Or in this case, zombies. Their latest programming smarts have re-animated from the murky grave the most problematic of sub-genres in videogaming: the co-operative survivor action adventure. Previously seen in the malformed shape of the PS2’s Resident Evil: Outbreak: File #2, Left 4 Dead revamps the whole concept of online co-operative play with the effortless perfection that only Valve seem to be capable of.

 
First impressions are familiar, and yet comfortable. The Source graphics engine, which has powered all Valve’s games since Half-Life 2 in 2004, does a good job of rendering Left 4 Dead’s environments. It’s perhaps not this technology in itself which impresses, but the way in which Valve use it to create the creepy ambience and claustrophobic architecture of the small-town America setting. Dark forests, cramped offices and desolate streets all feature in the game not only to scare you, but also to dictate and direct the action that takes place in them. Valve haven’t merely used the Source engine to distract you with all manner of graphical wonderment; they’ve thought carefully about how the design and architecture of these environments can be put to use in aiding the gameplay. For example, survival tactics actively change according to where you and your buddies are in the city: the outdoor countryside environments force you to watch each other’s backs, whereas urban environments tend to produce all-out stand-offs as zombies are funnelled down streets and alleyways. So, not only do the visuals look attractive, but they also expertly influence the kinds of co-operative gameplay that other games seem to have a trial-and-error approach towards. In Left 4 Dead, you’re using these new tactics in ways which breathe fresh life into the tired and shambling sub genres of co-op adventure and zombie survival horror shooter. The iconic shotgun and SMG become torchlight tools to identify how your teammates are doing, and household smoke detectors can be set up as devices to attract the attention of the zombies, thus redirecting the flow of the horde. These weapons are at their most effective when used in combination with each other, or rather, when they are deployed co-operatively. For example, one player might set the grass on fire to damage the incoming group of enemies, while another simultaneously thins their numbers with precise rifle shots. Valve have made every aspect of the game with co-operative gameplay at its core.

 
The zombies themselves are no exception to this rule, and are a mean bunch to boot. Far away from the traditional bumbling shufflers of early Resident Evil fame, these undead foes are fast on their feet, smart-witted, and will do anything it takes to stop you from surviving. Their Artificial Intelligence is dynamic; in other words, it changes according to your in-game actions. For example, where you are in the map and how much health you have affects the frequency and location of zombie appearances, making for a much more natural (and yet unpredictable) gaming experience than other survival horror games. If you and your buddies are tooled up to the teeth, prepare for an imminent adrenaline-fuelled assault. If you’re low on health and ammo, the game gives you breathing space to regroup and restock, ramping up the tense uneasiness instead. Rather than be restrictively directed by the game’s progress, you and your teammates have the ability to indirectly craft it for yourselves. There are multiple routes though each of the campaign missions, and different narrative elements arise depending on how you’re playing. All this adds up to give Left 4 Dead a highly customisable and fluid movie-like feel, with you in control of what happens. It really does fulfil the much-vaunted but rarely achieved mantra of ‘no two games are the same!’

 
Perhaps the most impressive aspect of the co-operative gameplay is not actually part of the game itself. Confusing? Only at first. Although Valve have placed a lot of emphasis on survival through co-operation, they’ve pretty much left how you do it up to yourself, and much of the fun in Left 4 Dead is being given the freedom to interact with your buddies as you see fit. If you’re playing alone, the fairly competent A.I will follow you around and back you up when you need it, but the game really comes into its own when playing with friends either in local system link or online over Xbox Live. After only a few minutes of play, you and your teammates will be working out your own strategies for survival, sweeping rooms and scouting around all whilst covering each other’s backs and administering first aid when needed. Valve have allowed you to use that part of your brain that doesn’t relate specifically to gaming. Success isn’t just rewarded for good aiming and sharp shooting; it’s also achieved through good communication with your friends: sharing plans and working out as a team what’s the best approach to a situation. They’ve tapped into that unique and under-used set of skills that exist ‘outside’ the game: skills which you might use in teambuilding exercises at school or work. Granted, they’ve done this before in Team Fortress 2: how do you blend into the other team, ‘acting’ like one of them when playing as a Spy? However, Left 4 Dead fully expands upon this skill, basing its gameplay entirely around it. It’s an immensely intelligent, rewarding and social experience, leagues away from the isolated feeling that’s often associated with online shooters.
 
There are some minor drawbacks, however. For clarity’s sake, each of your buddies is highlighted with a blue outline, which identifies them even when they’re on the other side of a door or wall. It’s the equivalent of, say, highlighting a player with their Gamer Tag when they’re trying to hide in the jungle undergrowth in multiplayer Turok. Although it’s a helpful feature in co-op play, it somewhat breaks the realism that Left 4 Dead works so hard to build up. Also, much like Team Fortress 2 and other Valve games, although what’s there is great, there simply isn’t enough of it. Despite the fact that there’s system link and online Versus Modes where one player takes control of an extra-powerful ‘boss’ zombie, there’s only four co-op campaigns in Left 4 Dead’s main game, which you’ll blast through in no time. Perhaps Valve will provide some Downloadable Content over Xbox Live Marketplace: new maps, weapons and characters. But for a full price game, it’s not so much that you’ll be Left 4 Dead, but left waiting 4 more.