Whiny, self-entitled Left 4 Dead 2 detractors can shut up now, if at least for a little while:

Crash Course, the newly announced DLC campaign for the original Left 4 Dead, arrives in September. A bridge mission between No Mercy and Death Toll, the campaign will include Survival, Co-op, and Versus modes, and will apparently be a more streamlined 30-minute experience.

As if this weren’t enough to assuage the masses that Valve fully intends to support the original game, Gabe Newell released the following statement:

“Since the release of Left 4 Dead last November, the design team has been excited about creating new experiences for this world and allowing players to do the same, by releasing much of our internal toolset, like the Survival Pack and Authoring Tools. We’re working with the fans toward the ongoing entertainment value of the product.”

Crash Course will cost 560 points on the 360, while PC players can snag it for free.