The new, recently announced Crash Course downloadable content (DLC) for Left 4 Dead, Valve’s zombie-infested, team-based horror shooter, will be free to download for PC players of the game, but Xbox 360 owners will need to cough up 560 MS Points if they wish to get their hands on the content, says Valve.

The new DLC, said to be releasing in September, includes new maps for Survival and Cooperative game modes, while also providing a “streamlined version of the game’s existing Versus campaigns,” which seeks to deliver a complete game of Versus in just 30 minutes.

Other features of the new DLC includes “a recharge timer for infected teammates” and balancing of the game’s item spawn behaviour, as well as new dialogue from the original cast and “an explosive finale” to the campaign, bridging the gap between the No Mercy and Death Toll campaigns.

Valve founder, Gabe Newell said of the new content:

“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.”

Unfortunately for Xbox 360 owners, you’re going to have to pay for the “ongoing entertainment value,” which is conceivably less of a decision on Valve’s part than a mandate from Microsoft regarding DLC release practices.

Welp, in the meantime, you can enjoy this official Crash Course poster: