Valve said yesterday that they're working on a new campaign for Left 4 Dead, and they plan to release it in September. It's called Crash Course, and while it will be free for owners of the PC version, Xbox 360 users will need to purchase it. The new campaign "bridges the gap between the end of the 'No Mercy' campaign and the beginning of 'Death Toll' in the original game, expanding the game universe with new locations, new dialogue from the original cast, and an explosive finale." Crash Course isn't as long as the other campaigns, a deliberate decision by Valve to enable players to finish a Versus-mode game in about 30 minutes. A preview of the new content on Destructoid notes, "Since we've got a shorter campaign, much more has been packed into a smaller space. Lucky players who know where to look can upgrade to second-tier weaponry almost straight away. However, they'll have their work cut out for them, because there's a chance to get swamped by the horde right from the very beginning."

Valve has released a beta version of their authoring tools for Left 4 Dead. The tools will allow you to "create your own campaign maps, character skins, 3D models, sound effects, and music and load them into the game." The kit includes a level editor and command-line compiling utilities, as well as example maps, props, infected, and explosives. It also brings plugins for a 3D modeling program called SketchUp. Valve has updated their development wiki to go along with the release.