L4D2 sets a new benchmark for co-operative action games, adding melee combat to enable deeper co-operative gameplay, with items such as a chainsaw, frying pan, axe, baseball bat, and more.

Matthew Lourdelet (2 Evil Eyes) has been working on a new community campaign – Cold Stream. We loved 2 Evil Eyes and Cold Stream looks even more promising with innovative game play arenas and effects. Matthew has really shown that there are still plenty of new ideas in L4D2 modding.

He recently shared it with us and we love it so far but it isn’t done. We were tempted to have him quietly finish it with our help and release it as part of an upcoming DLC.

Tempted… but we decided against that. Instead, we think we have a better idea. We want you the community to be part of the process of taking his unfinished campaign and releasing it as DLC on the Xbox 360, PC and Mac.

The easiest starting point for new campaigns is the three remaining Left 4 Dead 1 campaigns, so the DLC will include those. We also want something brand new and Cold Stream is the perfect fit.

That’s the start of the DLC. We have the basic information but we don't even have a name or release date yet (sometime after the release of Portal 2).

Introducing the AI Director 2.0, L4D's dynamic gameplay is taken to the next level by giving the Director the ability to procedurally change weather effects, world objects, and pathways in addition to tailoring the enemy population, effects, and sounds to match the players' performance. The result is a unique game session custom fitted to provide a satisfying and uniquely challenging experience each time the game is played.

In addition to the new campaign and boss monster L4D2 also includes "Mudmen," the "uncommon common" exclusive to the Swamp Fever campaign, and a few more of the 20-plus new items coming in the full product (cricket bat, AK47, and grenade launcher).

Featuring new Survivors, boss zombies, weapons, and items, Left 4 Dead 2 offers a much larger game than the original with more co-operative campaigns, more Versus campaigns, and maps for Survival mode available at launch.