The Hunter, a leaping enemy that pins you down and repeatedly smashes your skull in, can only be taken down by one of your team mates once it has you. Smokers grab you round the neck with a long disgusting tongue that drags you to its location while strangling you. The effect is sudden and shocking, and unless you shoot them instantly you're helpless, left to shout out for help and hope your team mates spot your location (which the game does a good job with, thanks to a handy colour coding system and outlines that can be seen through walls). The Tank is a massive beast that appears to have a steroid abuse problem, able to smash you clean off your feet. Taking it down without too much incident requires a team effort. The Boomer, a fat, bile-filled nasty, acts as a as laser targeting system for the infected horde. If it manages to mark you (charmingly done by puking all over you and smearing your vision with green goop), there'll be a sudden scream of: "It got me!", or most likely something far less family friendly. As soon as you hear one it's essential you pinpoint it and take it own before it has a chance to do its business, or you'll be on the end of a sudden torrent of infected coming from everywhere.
Perhaps the best enemy and the one you should be most fearful of is the Witch. This innocent looking crying girl will send chills down your spine when you hear her, and the accompanying soundtrack does little to help. She hates light, so it's vital you don't spook her with your flash lights, and it's best to sneak around her if possible. Don't do what we did on one occasion, and try to be smart with fire. Having spotted her we thought we'd throw a Molotov on her then all pummel as many bullets as possible into her. Bad idea. It seems being set on fire isn't something she enjoys, so she proceeded to go absolutely mental, running around and unleashing fiery hell on us all. It's a moment I won't forget in a long time.
Valve's Director means that you can't approach a level knowing what's coming. Whereas in lots of shooters you can learn what works best in each fire-fight, in L4D you have to react on the fly, using whatever buildings you can to take shelter and hoping you've got the weapons best suited for the job (we found the assault rifle to be a good all-rounder, but the uzi, shotgun and hunting rifle all do well in the right hands, and the pistol is a good secondary weapon especially when doubled up). Your character can also carry one explosive weapon, with the Molotov cocktail and pipe bomb each proving to be great weapons in the right situation. The pipe bomb attracts the brain dead enemies to it before exploding in a shower of blood, but be careful to watch out for flaming infected if any survive a Molotov attack.
The co-op mode is really only half of what L4D has to offer. There's also a versus mode, in which one team play the four survivors, while another four players take on roles as the four most lively special monsters (Hunter, Tank, Boomer and Smoker). With the Director still calling the shots with regard to what it spawns and real people controlling the other nasties, it's a game like nothing you'll have played before. There's an almost sadistic pleasure from sneaking up behind a group of players as a Boomer and puking over them, then retreating and watching as your team mates attempt to pin down other survivors at the most opportune moment. Although not all the co-op campaign maps are available in versus, hopefully more will be released over the coming months - along with new movies to play through too.
Built using an enhanced version of Valve's Source Engine, L4D looks good, but isn't quite up to the standard seen in other high profile shooters released this year - although the PC version can look considerably prettier than the Xbox 360 version when running on a high end PC. Although it lacks the sheer beauty of something like Gears of War 2, it more than makes up for it by throwing an obscene amount of enemies at you and is full of the usual Valve attention to detail - scribbled writing on the wall being a particular highlight. For the most part it runs well too, with the frame rate only dropping during the most crowded scenes that also happen to have a raging fire in shot.
There are games you want everyone to play, just so they can experience what you've such a good time with, and Left 4 Dead is one of them. It's unlike any other game I've ever played and demonstrates the true power of cooperative gameplay. It's worth noting that the experience is somewhat dulled if played alone, but if you've got online friends or are happy to play with randoms, Left 4 Dead is a game you simply can't pass up. Just make sure you've worked out what you'd do in a zombie outbreak before you start playing, as you won't be able to make anything approaching a sane decision with a screaming witch bearing down on you.