A new update for Counter-Strike 1.6 accidentally contains an early prototype of Left 4 Dead

For the 25th anniversary of Half-Life, Valve has updated Counter-Strike 1.6, but also seemingly released an early version of Left 4 Dead.

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Left 4 Dead is such a classic that Valve (accidentally) brought it back to life!

An early prototype for Left 4 Dead was released as part of an update to Counter-Strike 1.6, which was updated alongside Half Life as part of its 25th anniversary.

Fans have gone full detective mode to piece together an earlier find, a map called Zombie City, with code released as part of the update. This gives us a snapshot of one of the earliest versions of Left 4 Dead, which you can check out here:

Now we've got this in the wild, what do you think the chances are of Valve making another L4D game? What would you want them to add to a sequel?