Valve accidentally released a Left 4 Dead prototype

Valve in the new update for Counter-Strike 1.6 apparently accidentally made files available, which were used for early testing of Left 4 Dead’s co-op zombie action. It was created specifically on the basis of Counter-Strike. A couple of videos are attached below. provesthat the players managed to launch this prototype called Terror Strike.

However, we’re not just talking about Left 4 Dead itself. slightly modified classic Counter-Strike, which Valve and developers Turtle Rock used to test the core mechanics. In the fall of 2008, the first Left 4 Dead was finally released. Just a year later it was followed by the second part.