Valve releases Left 4 Dead 2 PC SDK

Left 4 Dead 2 on PC has just received a massive update, with both authoring tools for custom campaigns and a support package for those who just want to play custom games.  It “allows running ANY map , including custom maps made for the original Left 4 Dead.” All your old favorites like the Mushroom Kingdom  and Lego    in Left 4 Dead 2.