As of now, for PC, Left 4 Dead 2 lets players create their own campaigns, share them online, and play others’ levels as well. This feature is available for the original Left 4 Dead as well, but arrived much later after the game’s release. Again, this isn’t some upcoming patch or DLC, this SDK is available now on Steam for free. Just sign in to your account and begin downloading the SDK and authoring tools. The best thing about this is that you can create levels for either the single-player, versus, survival, or scavenge modes, so if a paltry five scenarios just doesn’t satiate your zombie lust, get to work on creating your own.
For those unfamiliar with the game, it’s an action horror title set in a post-apocalyptic world infested with countless zombies. There are five campaigns each set in unique locations based in the southern part of America (like Georgia and Louisiana). You can play alone but if you’re a true socialite it’s best if you play one of the game’s four modes with friends online.
[Thanks L4D Blog]
Article from Gamersyndrome.com