Things may have been quiet on the Left 4 Dead 2 front recently, but that doesn't mean Valve isn't toiling away behind the scenes making new content.
The latest bit of downloadable content, Cold Stream, is currently being tested internally at Valve's offices, with the whole company taking time off each day to play the upcoming DLC and submit bugs.
However, since the maps were have been developed with significant input from the Left 4 Dead community Valve is inviting players to help out and put the Cold Stream maps through their paces.
To sweeten the deal it's said If 20,000 people can earn the Stream Crosser achievement, which involves a player 'surviving a campaign of Cold Stream on any difficulty,' it will release Dead Air from the upcoming Cold Stream DLC on July 22, which is a little earlier than previously advertised.
Left 4 Dead co-developer Turtle Rock is currently working on a secret project for THQ. The publisher's core games boss Danny Bilson has said it's 'the coolest design I've ever seen in my life'.