Pack -- is due for release this spring and introduces a new multiplayer game mode entitled, Survival, plus two complete campaigns for Versus Mode . A Critic's Choice Edition of the game is also heading to retail stores this spring, and will include access to all the content introduced in the L4D: Survival Pack.

In addition, for PC gamers and aspiring developers, the first Left 4 Dead release for the Source Software Development Kit (Source SDK) will allow the creation of custom Left 4 Dead campaigns that will be discoverable via L4D's matchmaking system. The SDK update is also due for release this spring, and is free of charge to all owners of L4D on the PC."