I'd say that if you put any group of people into a survival situation and you'd see what they were really like. It's a bit like how people change under pressure, except it's the kind of pressure that can get you killed. Personally, upon reflection it would seem that regardless of how nice a person is, when it comes down to it, we can all be complete bastards. This was certainly something that became evident while playing Valve's Left 4 Dead.

The game's all about survival, so much so that you have to get used to the idea that you might fail a map and still be thirsty for more carnage, bloodshed and violence. Left 4 Dead is a first-person cooperative shooter, where 4 players pit their wits against hordes of zombies. It's all about limited health, limited ammo and a mad dash for the safety room on each level. We'd been playing the demo version for some time and had become completely obsessed with the only 2 available maps, out of a possible 20 we knew existed, so once we got our hands on the full thing... well let's just say we couldn't put it down.

L4D is laid out like a movie set of sorts, with a movie poster depicting which character you're playing as an intro and the AI Director driving the variety and excitement levels, constantly giving you a variety of play like you've never experienced before. While the level structure might remain the same, what the AI Director does is vary how the enemies are presented to you each time you play. The first time you go through a level you might face hundreds of the infected in one go, and the next time you might only see pockets of them keeping the suspense going throughout the entire map but never knowing what's around the next corner.

While you might think that the 4 of you working together might stand a fair chance, they only give you a pistol and a choice of shotgun or sub-machine gun at the start and one health pack. Throughout the level there will be the odd cash of ammo and a handful of pills (temporary health) for you to obtain – but not enough for all of you. The most important thing to keep your eyes out for are the weapon upgrades. Somewhere in the level you'll be able to get your hands on a second pistol, which you can dual wield, and better versions of both the shotgun (Super 90) and sub-machine gun (M16A3 auto-assault rifle) and an additional sniper rifle - which at least helps, but then the levels tend to be longer and so even then it's still possible to run out of ammo. If you run out of ammo for your main then all you'll have to rely on is the pistol which has unlimited ammo or your melee attacks which help knock back zombies for you to get that final shot off – or hopefully someone else if needed.

That one health pack you're running around with will suddenly feel like a little pouch of gold you'll want to covet. While you can use it on yourself, you might decide to heal someone else with it instead. Reason being is that while you can replenish your health, you can also get knocked down after your health reaches zero. If this happens you'll only be able to take pot shots with your pistol until someone can give you a hand up. Should you fall 3 times you're dead for real and the only way to get back into the game is if your team mates find you, locked in a room, and let you out – should they choose to go off path just for your sake. So as you see, sometimes it's better to get them healed up if they're on their last legs.

So while you're running through the level all gung-ho with your team-mates, facing off against multiple hostiles you might think that was it. In step the boss mobs. These guys all have special abilities and while you'll face them in the campaign mode they're also available to play in versus mode. The Boomer is a fat, repulsive looking mutant that can vomit on the survivors that causes all nearby zombies to rush for that person. The Hunter, a stealthy hoody wearing zombie that can pounce on players or even jump from wall-to-wall. If you get pinned by the Hunter, only someone else can get him off you before he rips you to shreds. The Smoker can shoot his tongue out at unsuspecting victims, wrapping it around their throats to reel them in and progressively strangle the player. The Tank is a massive gorilla-like mutant that can pick up bricks to lob at players and can knock them flying with one of his massive fists. Lastly, but most importantly is The Witch who will only attack if startled and will quite literally knock you knock you for six. Best to sneak past her where possible!

Although the game can be played with bots, it's certainly better to try and hook up with friends as with above for example, certain attacks can only be stopped by being helped out by another player – you'll want someone as reliable as possible, that's for certain. It's worth noting that what The Boomer does by vomiting on a player is call The Horde which turns the game into a scene out of 28 Days Later when a massive group of the infected rush towards a player. This, regardless, is something that the AI Director can call on when required and is preceded by the sound of a horn and rolling beats. It can happen, for example, if you set off a car alarm, staying in the same place for too long or completely at random depending on the Directors mood.

There are a few other items scattered around that can help with such crowd control issues – like the occasional Molotov and the more useful if not overly convenient pipe bombs that emit a high frequency and flashing lights, which pisses off the infected no-end as they rush around it before it finally explodes. I'm sure you'll want to shake the hand of the inventor of such a ironically useful weapon if you ever meet them. Molotov's can be thrown and explode as you'd expect – in a big ball of fire! There's the occasional fuel tank that you can shoot for the same trick, and while it's great to see a wall of zombies on fire it can be a little painful if you get too close. Put those marshmallows away...

Left 4 Dead consists of 4 scenarios each with 5 different maps that can be played on 4 different difficulty settings. The first, “No Mercy” scenario will have you winging your way across a suburban environment from a block of apartments trying to make your way to a hospital, topping it all off with a manic rooftop zombie-fest finale. The second “Death Toll”, a dash for a riverside boathouse through the sewer, town and a church. On the third “Dead Air” will have you making your way to an airport for evacuation and you'll have to fight your way through a construction yard and terminal to get there. Lastly in “Blood Harvest” you're trying to head towards rural hideout used by the military for any survivors and you'll be running your arse off through woodland, tunnels, over bridges and through a train station.

It's certainly worth noting that this game is intended to be an intense jump-fest thrill ride throughout. Quite frankly it's true. The sound department can bloody well have a pay-rise if you ask me as having Mike Patton to provide his usual high-standards of weird-as-hell screeching vocal talent for the infected and the use of sounds and music to emphasise a dynamic change in gameplay certainly had my adrenaline pumping more often than not. I'd also recommend, for those of you who are up on playing a lot of FPS games, that playing the game on Expert has to be done. We caned the other settings, but Expect had us downed the first time we tried to play it and that's what we expected. Left 4 Dead's geared towards cooperative gameplay and dying. That's the point. If you're rinsing your way through each level with no real threat, you're on the wrong setting!

Once you're done and dusted with the main campaign, if that ever happens or you just fancy a change then you can head on into 'Versus' mode. In versus mode, while you might fear this as some sort of deathmatch, it's not, it's allowing people to play as the boss mutants while you try to complete the campaign. Albeit slightly different in that you're now not only out for points; trying to complete the level the quickest, with the most health and all limbs intact, but you take turns on each level as both the infected and the survivors. At the end of the round your health will reset and you'll be onto the next level. It has to be said that being the boss mobs in this game are very cool to play as, and even more so that they too have to work cooperatively. Not only do you get to follow the survivors around watching their every move before you spawn, but you can also see your team-mates before and after they spawn. This really helps you coordinated attacks on the survivors, which at the end of the day is a must in order to even hope of winning. These boss mutants don't have much health and a team of survivors working together is going to make your live tough. It's likely that this is what will give Left 4 Dead the longevity it needs.

With the campaign mode, versus mode and even a host of achievements to bag-and-tag, you're up for some seriously late nights of infected zombie mayhem. We had a riot - I'm sure you will too.