The game's five map campaigns each take around an hour to complete if you know what you're doing. We had the opportunity to play through the Hospital campaign a few times, where the main goal was to clamber through ruined urban areas, access the hospital, then scurry to the roof and get picked up by a rescue chopper. Other than that goal, the game doesn't seem to have any real storyline, it's mainly about shooting. There were a few action set pieces in the campaign, including a rather treacherous elevator ascent where zombies poured into the car through an overhead vent, and the final rooftop defense. During the end battle, the Survivors are set up in a tower and given a stationary gun. Wave after wave of zombie then spawns to try and wipe out the party. If they're successfully taken out, the remaining Survivors will need to bring down two hulking Tank Infected, which is no easy feat.

Moving across each map will, according to Turtle Rock, be different every time as the Infected mob's positions will be randomized. After making multiple trips through each map, we noticed we'd get mobbed at different times, so we had to stay extra frosty when creeping through the dilapidated environments. To survive the onslaught of blood-crazed Infected, you and your team of three will need to stick close together for multiple reasons. First and most obvious, the more bullets you're simultaneously firing at an enemy, the faster they're going to go down. Second, you'll need to revive any fallen squadmates should they take one too many zombie slashes.

Left 4 Dead is built on the most recent version of the Source engine, so players will see plenty of nice animations and effects. The flashlight, for instance, creates some eye-catching lighting which enhances the mood for Survivors as they plunge into the depths of abandoned subway tunnels and warehouses. Combine this with Infected hordes that sprint toward players with frightening ferocity, and you'll get quite a few scares. We certainly did, particularly when we got jumped by Hunters. The Infected hordes have some cool animations relating to the effects of angular momentum. As they run around corners toward your location, you'll see their torsos bow outward and shoulders tilt inward like a real person's would, instead of just robotically turning a corner in stiff, lifeless fashion. When 20 of them are doing this at once as your flashlight is plastering the walls with frantic shadows and teammates are screaming for help, it gets pretty intense, reminiscent of scenes from the film 28 Days Later.