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Left 4 Dead prototype accidentally released in Counter-Strike update

The patch that led to the discovery of the Left 4 Dead map has been fixed, but not before the community preserved it.
Left 4 Dead

A very early prototype for what would become Valve’s beloved cooperative zombie survival game, Left 4 Dead, was accidentally and temporarily released as a part of an update for the now obsolete Counter-Strike 1.6.

The prototype takes the form of a custom map called “Terror-Strike” for Counter-Strike: Condition Zero, a follow-up to the original standalone release of the game. In footage captured by ilovethevopo on YouTube, who specialises in exploring game prototypes, you can see how the map uses assets and systems from Counter-Strike to plot out the flow and tension of Left 4 Dead.

The player starts out by selecting his weapon loadout, wandering through an eerily empty city, and performing an action (in this case, planting a bomb) to move on. Once the bomb is planted, zombies begin swarming them – the ‘zombies’ being represented by player models armed only with knives, moving in various different ways.

The update to Counter-Strike 1.6 was brought on as the game it was originally built on, Half-Life, celebrated its 25th anniversary with its own update that restored some old content, fixed some age-old bugs, and added new multiplayer maps. The company also released a very compelling documentary looking back at the making of her game.

The Terror-Strike map was quickly discovered among the update’s files by the Counter-Strike community, who then performed the work to make it playable. Valve has seemingly removed the files from the update since.

Despite the unintentional release, Terror-Strike is a fascinating bit of history to be uncovered from a company that typically operates as a black box.

Being able to witness the experimental steps that led to a beloved game like Left 4 Dead first-hand is certainly a rare and special moment – and one that will likely be preserved and available to play for years to come, thanks to the community and game history enthusiasts.

Edmond was the founding managing editor of GamesHub. He was also previously at GameSpot for 13 years, where he was the Australian Editor and an award-winning video producer. You can follow him @EdmondTran