click to Boomer-size Valve took the wraps off Left 4 Dead 2's brand-new competitive multiplayer game type, "Scavenge," at a press event in San Francisco this evening. According to the developer, this mode is built purely for "quick, more frantic gameplay." (Yes, L4D actually can be more frantic).Scavenge has the four survivor characters scrambling to collect gas cans from various spots in a confined location -- in this case a motel, pictured -- in order to fuel up a generator before a two-minute timer expires. There are 16 cans total and 20 seconds are added to the clock for each one that's successfully retrieved. Four other players, controlling Special Infected, must do their best to stop the cans from reaching the goal. The two new Special Infected, Spitters and Jockeys, really excel in this mode. The former can set dropped cans on fire, while the latter can leap onto the shoulders of a survivor, "steering" them away from their goal.These best two-out-of-three matches are broken up into three rounds, during the "half time" of which players switch sides. Valve confirmed that each of L4D2's campaigns has a unique Scavenge map, for a total of six shipping with the game on November 17.