Last week, Valve promised to release the Left 4 Dead 2 version of classic Left 4 Dead episode 'Dead Air' if players helped beta test new community-made map Cold Stream, setting a target for 20,000 playthroughs. Good news! "You started playing at 10am on Wednesday morning. Four and half hours later you surpassed the 20,000 target," Valve revealed in a blog post. "By 5pm you passed 30,000. By this morning at 10am – a mere 24 hours later you hit 60,774!"

"We are going to try and release it as early as possible but will release it on July 22nd the latest," Valve said. "It isn't currently ready for release as we have been working on The Terminal and Finale maps and need to test them more internally."

The developer also mentions working on a new version of the finale in L4D2's 'Dead Carnival' episode, "and some gameplay changes for finales in general." As ever, the changes will hit PC and Mac first.

Once the changes have been given a good testing, and Cold Stream and the rest of the original L4D episodes are finished, it'll all head over to Xbox 360 too. "What date is that?" Valve asks. "Hard to say but with your help it just got closer."