Two weeks after the release of its latest co-operative zom-apocalypse 'em up developer Valve has announced thathas been selling extremely well with worldwide retail sales already topping two million - more than double the sales of the original in the same amount of time.,” commented VP of marketing and general Valve big-wig Doug Lombardi, who's obviously been reading our review of Left 4 Dead 2 where Joe praised its superb level design and wide range of new game modes.What's perhaps even more impressive though is that this sales data doesn't include any sales from Steam, Valve's digital distribution platform. This meanshas undoubtedly sold much more than the quoted two million, although Valve are famously tight lipped when it comes to publishing Steam sales data.These healthy sales come despite a vocal fan boycott of the game earlier this year, following disappointment that Valve were not supporting last year's originalto the same degree as the developer had other titles, like. Obviously the majority of users aren't bothered though, with the game selling faster than brain flavoured cup cakes at a zombie convention.Have you been enjoyingalong with the two million+ other owners? Or are you boarding up the windows and waiting out the zombie apocalypse? Either way, let us know in the forums