'Left 4 Dead' enlivens co-op play in shooter genre

— -- Many video game studios would envy the stellar reputation cultivated by Valve Software. They've captivated gamers and industry professionals alike with innovative titles like Half-Life and Portal.

Now add zombie thriller Left 4 Dead to the list. The first-person shooter manages to deliver chilling combat while helping to foster camaraderie amongst your fellow online survivors, since you must work as a team to survive.

The game, available on Xbox 360 and PC, is playable in a single-player setting with computer-controlled allies. But Left 4 Dead is best enjoyed when connected online with a team of human counterparts.

You play the role of one of four survivors of a zombie apocalypse: War veteran Bill, biker Francis, computer systems analyst Louis, and college student Zoey. Cast in four unique settings, the team must escape hordes of zombies by reaching safe rooms in each level.

These hordes of Infected are led by four types of zombies with special abilities. Tanks overwhelm you with pure strength. Hunters deftly pounce on survivors and pummel away. Smokers strangle you with their tongue. Boomers, the most disgusting attackers of the group, attract the horde by vomiting on you.

Left 4 Dead evokes an incredible level of panic. Not only are the zombies fast and furious, but they often travel in large numbers. Nothing is more terrifying than watching 20 to 30 zombies immediately converge on your position, sometimes with Hunters or Smokers lurking in the distance.

The anxiety is amplified by the spooky environments. You'll encounter rooms in abandoned homes or buildings where zombies hide behind closed doors. Cars with alarms litter the streets, and one false move can trigger the alarm and attract the hordes. Until you find that safe room, you never feel completely out of danger.

Cooperative gameplay is nothing new to first-person shooters. While you're playing as a team in other games, there's always that urge to fend for yourself.

Left 4 Dead, however, is arguably the best at nurturing the cooperative relationship, in part because you can't survive without them. If you see an injured teammate, you can't help but try to heal them. When an ally is pinned down by a Hunter, your first instinct is to rush over and assist. Left 4 Dead instills a sense of obligation to ensure your whole team survives. What's amazing is how gratifying the experience feels when everyone escapes that final showdown in each campaign.