Valve 'accidentally' leaks the earliest Left4Dead prototype, and it was a Counter-Strike mod all along

Valve didn't just update Half-Life for the game's recent 25th anniversary. It also spruced up Counter-Strike 1.6 to take advantage of the features and changes added to Valve's 1998 masterpiece. Yet in doing so, Valve seemingly inadvertently opened the door to a fascinating slice of gaming history – the first prototype of Left 4 Dead...
Read more.