Left 4 Dead is not easy; viral armageddons so rarely are. But it makes for some great moments of stress, drama, triumph and overwhelming failure. The dash for the safe holes with a gang of infected athletes chasing you down is pure 28 Days Later, and the degree to which that feeling has been recreated in a game without any real script is incredible. It’s all thanks to an awareness and love of modern zombie movies. And having lots of enemies.

Take one moment, when a Boomer had vomited on our friend, and the regurgitated pheromones had turned him into a zombie magnet. He crouched, allowing us to pick off the zombies without puncturing his cheeks, and between us, we killed them. What we hadn’t noticed was that a queue of zombies had formed behind us, trying to get to our vomit-sodden chum. Our monitor was completely and suddenly full of zombie. Lunging, ash-grey zombies, as close as they could be to our face without the whole thing feeling erotic.

Have we introduced you to The Director? You’ve possibly heard about him; he’s the playful AI mastermind that’ll be toying with your adrenaline levels. Given that zombie hordes don’t have much intelligence to draw on - uncuddly noggin chompers that they are - the cleverness lies in their deployment, which is governed by The Director. No area is safe, and no area is a guaranteed carnage bomb, so you can never be sure around which corner, or from which patch of forest the hordes will come. Instead of scripted moments, the game decides what to do based on preceding events, so you’ll end up forced to trust your sense of dramatic timing, rather than map memory.

If you’ve just had a prolonged onslaught of hell’s overspill, then The Director will loosen the thumbscrews, and give you some dramatic respite. If that sounds generous, it’s not. Your nervous system may have briefly jammed Left 4 Dead’s shredding machine, but the machine’s still plugged in. Once The Director reckons you’ve had time to calm down, on they come. The exact algorithms are, of course, a mystery; all we can pass on is that in its current state, it gives you an excellent sine wave of stress, and is as much like a bloody film as any game without cutscenes, a script or sweeping aerial shots can be.

The music is an important part of that film-like experience, and smart players will take cues from the heralds. The Tank has a particularly dramatic theme tune that warns everyone that the game’s superpowered bullet sponge is on the way. Rather than ruining the surprise (how much fun would that surprise be, anyway?) it gives you and your team a chance to organise, to regroup, and to focus your firepower. The Tank will screw you over unless you’re all working together to chip away at his hit points.