IGN writes: "If you're a Left 4 Dead fan, you've probably played through Valve's four official campaigns about a hundred times over by now. You probably know every corner in No Mercy, as well as the best camping spots in Dead Air, and so on. But if you're looking for something fresh and original, you won't have to wait for Left 4 Dead 2 to ship later this year. Last week, Valve released an update for the PC version of Left 4 Dead that allows you to play user-created maps and campaigns. The software developer kit that allows users to create maps and campaigns was released in beta form earlier this year, so that meant by the team Valve released last week's update, there were dozens upon dozens of campaigns and maps in development".