Living up to previously-made claims that Left 4 Dead would receive additional content in the wake of the Left 4 Dead 2 announcement, Valve has sent out word of the upcoming "Crash Course" update, to be available for free on PC and for 560 Microsoft Points ($7) on Xbox 360.

The update is said to contain maps for the game's Cooperative, Survival, and Versus multiplayer modes, with the team giving itself the design goal of allowing for "a complete Versus mode experience in just 30 minutes."

In addition to the maps themselves, various gameplay tweaks have been made to facilitate that end result. The game is set in between Left 4 Dead's existing "No Mercy" and "Death Toll" campaigns, explaining what happened to the four survivors after their ostensible rescue at the end of the first campaign.

Valve has long been a proponent of free content updates for its games, describing that policy as a way of continually promoting sales of full games and keeping its titles relevant among the gaming audience.

However, numerous reports have suggested Microsoft is less amenable to the practice of offering free content through its Xbox Live Marketplace, leading to publicly-revealed disputes between the manufacturer and companies such as Epic, which also has a tradition of free expansion content, over pricing structures.

Said Valve co-founder Gabe Newell, "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 be released this September for both systems.