"Despite my few complaints, Valve has done exactly what they set out to do: Left4Dead sets a new standard for co-op gameplay. By keeping the campaign lengths under 2 hours, any group of friends can fit a full run-through into their schedule. By keeping the mechanics simple and familiar, anyone can jump in and be part of the fun. It's accessible, edge of your seat zombie massacre fun. Finally, someone has given the survival horror genre the makeover it has so desperately needed, and I couldn't think of a better developer for it than Valve."