Left 4 Dead is finally here and being a true zombie fan (World War Z, The Zombie Survival Guide - I've read them all), imagine my delight at getting the chance to review it. Taking place after a virus has swept the land, turning the populace into mindless zombies - not your average, slow moving shamblers of old but rather the modern 28 Days Later speed freak sprinters - your only aim is to survive. I was in my element! However, the joy of witnessing the largest number of onscreen zombies since Dead Rising isn't the only reason that Valve - the legendary creators of Half-Life and Team Fortress 2 - brought us this game. Valve's intention was that Left 4 Dead should do for co-operative play what Counter-Strike did for competitive multiplayer - does it succeed? Damn right it does, even if the experience is only near perfect.

One major success of Left 4 Dead is the simplicity and, to some extent, believability of the story. A plot filled with complex narratives, evil masterminds and nigh-incomprehensible twists might be expected when a mysterious virus is set lose, but Left 4 Dead has none of these; you are simply one of a group of four survivors with your only concern to carry escape to safety (if such a place still exists in this post-apocalyptic world). That's as far as the story goes (in the time honoured movie tradition of never explaining the cause of the zombie infestation) - and if the world was facing a zombie apocalypse, would you really want to uncover the truth about why the zombies came to exist - they are clearly not the reanimated dead kind - or would you prefer just getting to safety? Finding sanctuary in those few areas of the world that are not yet infected - a 28 Weeks Later style quarantine is in effect - is the objective of each campaign, each of which is split into five maps and features the only real element of story. How you get to these non-infected areas differs - usually it is by radioing for a helicopter or an army evacuation vehicle - but actually just reaching this end point can be fairly taxing, because hordes of mutated ex-humans stand in your way. Just staying alive beyond the beginning is hard enough!

You start off in a safe zone where you can heal up from previous battles in the campaign (unless you jump straight into an individual map), restock your ammo and grab your gear. These items are realistic; guns are never over the top or hugely powerful - the assault rifle is probably the best weapon in the game - and the medkits, which you carry on your back, take time to use - no pausing the game of a single button press that instantly boosts your health here! In addition to convincing items, the realism is further increased by your physical limitations - you only have room for one primary weapon such as a sub-machine gun, your default pistol, one medkit, one explosive such as a Molotov cocktail (you usually only find these after you head out into the killing fields) and one slot for quick health boosting pills (again, only found later).

Tooled up as much as you can, you and the rest of the survivors must head out into the zombie-ridden world of death and start the fun! As soon as you do this - be it opening a door or climbing up a hill - you'll encounter plenty of not-dead-enough zombies. Individually they are easy to handle - pathetically easy, in fact, as they stumble around or spew vomit; three accurate shots and they join their spray of disgusting discharge on the ground. However, these individuals are soon replaced by groups of ten or more, which is far more of a challenge, although some good teamwork usually ensures that you and your three companions aren't eaten alive! Eventually though, even these small groups give way to near unstoppable hordes - prepare for some serious action and hope that your team mates like you! This combat mechanic is best summed up by a poster that I once had about the British Navy, with the phrase "Wet: Never. Soaked: Sometimes. Half-drowned: Always." in big white letters - in Left 4 Dead you are rarely attacked by one enemy; you are usually swamped by them.

However, zombies are the least of your worries (I never thought I'd be writing that - not for a few years at least) as there are several super-infected foes to deal with - big, bad, ugly monstrosities with a unique set of abilities. By far the nastiest of these is the easy to underestimate Boomer, a giant, bloated walking man that can vomit green bile all over you - eww! Despite being quite disgusting, this bile attracts the mindless horde of zombies - in the space of a few seconds you can find yourself the sole target of hundreds of slavering, clawing fiends! Becoming the focus of a thousand terrible things is surely enough for the fat man, but the horror doesn't end there; the bile blurs your vision, leaving you firing blind - and your bullets will hurt your team mates.

The rest of these super-infected are the Tank, the Hunter and the Smoker - and discovering their specific 'talents' is one of the joys of the game, so I won't spoil it for you. Additionally, these four extra-nasty nasties are all fully playable in the online versus mode, though sadly not the offline single player - one of the biggest letdowns of the game. The only unplayable super-infected is the Witch, who on first appearance looks rather puny, sitting in the road, crying in an eerie fashion that seems to get inside your head. However, once disturbed - alarmingly easy to do - she charges at you with incredible speed, ripping out your intestines with unwarranted rage. As she opens your flesh, you fall to the ground leaking blood; you can still shoot but if your team-mates aren't around then you are going to die - never mess with a Witch!

Your team-mates are the other three survivors, controlled by human players or replaced with always proficient AI - you will never get bored waiting for a fourth player before you can start a campaign. Your comrades can all use guns and are so vital when the brown stuff hits the fan that you will always want to be by their side - going it alone usually means certain death! To help you stay in proximity of your friends, they are highlighted when they go behind walls or up stairs. This feature is really useful, as it means you will rarely get separated; you always know where your team-mates are and when other members need help, such as a pull up from a nearly fatal fall, where you need to go becomes apparent immediately.

However, a keen eye will notice that all the survivors are actually the same; they don't have individual skills like the classes in Team Fortress 2, for example - they just look different. For this reason, the game was originally designed not to give players the choice of survivor to play but due to consistent nagging from fans, the ability to choose is now included - presumably no one wanted to play as the fairly attractive girly-girl, Zoey! Keeping all the survivors on even footing just helps to emphasise the wonderfully handled group dynamics; you are a team and you must stop thinking of yourself as the hero that will rise up and save humankind - your team must function as one living (at least at the start), breathing organism if you are to have any hope of surviving. To achieve this, you are free to heal yourself, heal others, give items to other members of the group, call out the location of ammo replenish points and generally watch each others' backs; the health, status and items carried by each survivor is clearly shown at the bottom of the screen, highlighting anyone who is in trouble.

However, the situation is grim and, despite your best efforts, you are going to lose team-mates during a campaign - each one begins with a fairly easy environment that escalates towards a very tough finale. With each survivor that goes down, you would expect your chances of survival to take a severe down turn. Fear not, however as your fallen team-mates eventually respawn in areas of the map, highlighted in bright orange so that their friends can soon rescue them. This respawn and required rescue feature really suits the gameplay; it helps keep the team together and is not completely unbelievable. It is also a godsend in multiplayer; being forced to sit idly by while your friends blasted zombies would be no fun at all!

Maintaining a high level of enjoyment is crucial for a game such as Left 4 Dead, as there are very few moments of true horror or genuine scares - it is pure, fast paced, frantic fun from the off! You may think that I've gone off my rocker by saying that, because zombies are the stuff of nightmares, designed to lunge from shady corners and change the colour of your pants. In some respects this is true - I wouldn't like to meet a 28 Days Later inspired zombie on a dark night (or even in daylight, for that matter) - but horror just isn't the intention of Left 4 Dead. Many horror games such as Dead Space or Resident Evil rely on the player never really having enough ammo, but here, ammo can be refilled to maximum levels at each of the fairly frequent stashes and the pistol has unlimited bullets; you still have to reload your guns though, giving the zombies plenty of windows to gnaw on your limbs, but you'll never find yourself without a working weapon.

Firing these guns and reloading them, running around and jumping are carried out with the usual first person shooter control layout; however, you can also speak to the rest of your team with standard commands like the orders in Unreal Tournament that are used for organising friendly fighters. Lists of these voiced commands, such as asking if everyone is ready to move on or just making your character laugh, are activated with the Z and X keys. Each list is arranged in a convenient radial menu so that you can move the mouse to the direction of the specific command and release the button to activate it - very smooth and wonderfully quick. The problem is that as soon as you press X or Z, which are right under the movement keys, you are forced to say something, which is quite annoying because it's all too easy to press them accidentally. I recommend redefining the speech function to alternative keys, because issuing stupid commands at unnecessary times can really annoy people.

Of course, if this is the worst criticism that could be raised at Left 4 Dead then it would be perfect; however, it isn't, which brings us onto the graphics. Like any game that uses the Source engine (the graphical machine behind the scenes of Half-Life 2), the visuals are definitely high quality but they aren't the ultra high quality of Crysis, Far Cry 2 or Gears of War 2. In fact, the game looks a bit too much like a total conversion of the latest Half-Life 2 episode - not that this is anything to be ashamed of! The usage of the ageing Source engine means that the graphics aren't going to set the world on fire but when you start playing, you just won't care; it's so much fun and you're never going to have time to gaze at rolling vistas anyway. In addition to fairly mundane graphics, there isn't much colour - greys and rusty greens are common, intermixed with the occasional dark red blood splatter - but this just adds to the sombre atmosphere.

Yes indeed, the atmosphere is bleak - you wouldn't feel particularly happy if zombies ate your parents after all (I hope!) - but the sound is a brilliant ray of sunshine that breaks through the dark clouds. The majority of this truly fantastic sound is made up by the blood-curdling screams of the rampaging ghouls, the signature cries of each of the super-infected, which are distinctive enough to warn you of exactly what is approaching, and the near constant gunfire of your fellow survivors. Even better though is the captivatingly well-acted conversations between survivors, which happen automatically when you are performing certain actions like healing a team-mate. They greatly enhance the already brilliant team-work and make those times when you're dead and waiting to be rescued, listening to the high quality, sinister tones of the music, that much creepier and more isolating.

Other than the intense team-based mechanics, the AI Director was a much talked about feature that, just like the incredible co-op, does not fail to meet expectations. If you haven't heard of this before then let me explain: the Director can be thought of as a giant randomiser, not changing the shape of maps but changing where items are located, where enemies are encountered and how many of them you'll bump into at any given point. This randomisation works so well that I have never seen the same map populated the same way twice - and I can't stop playing this game! There is only one minor criticism to raise against the Director - it can sometimes place items in unbelievable places, like a single pipebomb at the top of some stairs in a train station, for example.

My biggest concern about Left 4 Dead is its length; there are only four campaigns, each of which can be completed in an hour. With the game being so short, the randomisation offered by the Director, the achievements on both the PC and Xbox 360 versions - for example, shoving a Boomer back with a gun before killing it - and the additional versus mode that allows you to play take the role of the infected and try to kill the survivors, are very welcome features. However, I would have liked some more gameplay modes, such as rescuing a group of survivors from a zombie onslaught or campaigns that began with your team separated. Unfortunately, the only other mode beyond the standard multiplayer is the exact same campaigns being playable offline with AI controlled team-mates. This single player is definitely a good addition but it's multiplayer with other human players where this game really excels - it's so much more fun when you're depending on imperfect people to watch your back!

Left 4 Dead is a truly monumental achievement, not only for Valve but for the games industry as a whole - this is what the concept of co-operative play is all about and this is the definitive implementation of it thus far. There are a couple of minor problems - the occasional strange item placement and the small number of campaigns - but these do not detract from the sheer joy, entertainment and addictive quality of the gameplay. Even if you generally prefer single player experiences - like me - you will still find this multiplayer rampage nothing less than an absolute treat, so my advice is very simple: if you have a high speed Internet connection (required to install the game) then rush out and buy Left 4 Dead right now - you absolutely will not regret it.

Reviewed by Tom Clark for AceGamez (All Rights Reserved).