Valve accidentally released a very early Left 4 Dead prototype in the latest Counter-Strike update

An “extremely early” Left 4 Dead prototype is now available to play thanks to Counter-Strike’s 1.6 update.

According to content creator Gabe Follower, the prototype – called Terror Strike – was “accidentally compiled” and added to the Counter-Strike update, showing how the zombie game’s DNA lies firmly in the mod for Counter-Strike: Condition Zero and was developed using CS assets, including Counter-Strike weapons.

The files were quickly pulled from the 22nd November update, but not quickly enough to stop them being yoinked and then distributed publicly.

You can see it in action in the video embedded above, or via Gabe Follower’s tweet below.

“What you see is gameplay of Left 4 Dead back when it was a simple project using Counter-Strike: Condition Zero,” explains YouTuber ilovethevopo (thanks, PC Gamer).

“Yes, this is older than zombie_city and the leaked L4D footage that was re-discovered a few weeks ago, both of which were based on Counter-Strike: Source. Zombie_city was originally built for CZ and ported to CSS, but we never got any actual content from the CZ era of L4D until now.

“The code was removed, but not before fans snagged 1.6’s dll files and worked some magic to make a quick ‘mod’ built on Condition Zero. The Terror-Strike code was included because 1.6 has code from CZ in it, and it seems someone forgot to strip the Terror-Strike code from the dlls before originally shipping the update.”

Valve recently suggested we didn’t hold our collective breath for Steam Deck 2.0 anytime soon, as the technology to launch a handheld with an adequately beefy jump in power just doesn’t yet exist.

Speaking to Eurogamer ahead of the recent Steam Deck OLED announcement, Valve engineers discussed the features it is adding to its shinier new handheld model that were not possible to provide back when the original Steam Deck debuted.

The company also said it was working on game projects – plural – right now, which were still targeting current Steam Deck hardware performance levels (which remain unchanged in the OLED).