Valve's CS 1.6 update inadvertently reveals Left 4 Dead's early prototype

A recent update for Counter-Strike 1.6 unintentionally included an early prototype of Left 4 Dead, the popular zombie co-op shooter. The prototype, originally built as a mod for Counter-Strike Condition Zero, was discovered by fans who combined it with a previously leaked map called 'Zombie City.' The update was released by Valve to celebrate the 25th anniversary of Half-Life, and while it was meant to make CS 1.6 compatible with Half-Life changes, it accidentally included the Left 4 Dead prototype. The prototype, dubbed 'Terror-Strike,' has been successfully integrated into Condition Zero by fans, providing a glimpse into the earliest versions of Left 4 Dead.