Left 4 Dead developer Turtle Rock Studios has released its final, unfinished campaign for the zombie shooter, and you can play it right now. All you need is Left 4 Dead and an internet connection to download the files.

Co-founder Chris Ashton posted a link to the campaign on the Turtle Rock forums, saying that the studio had "just finished putting the Dam campaign ... into a L4D add-on."

"It's gray box, and some code features are missing, but it's playable from beginning to end," he wrote. "It also includes two standalone survival maps that never shipped."

You can download the Dam It campaign here. There are two ways to install the addon, with the "automatic" way consisting of unzipping the .vpk file and double clicking it to launch. The "manual" way, on the other hand, requires you to unzip the same file and copy it over to Left 4 Dead's "addons" folder.

The add-on's page says, "Dam It stitches Dead Air and Blood Harvest together." However, because it's an add-on, code changes are not included. This results in a number of issues, including explosions not triggering panic events in the hangars, zombies not crawling consistently in the orchard, and the covered bridge not collapsing with explosions. In addition to the full issue list, you can see a map of the campaign on Dam It's webpage.

Turtle Rock was recently taken off of development of 2K's monster-hunting shooter Evolve. Despite its ceased development, its servers could still stay active, as long as 2K wants to keep them up.

"[Keeping servers up will] all be up to 2K on out, the same as anything Left 4 Dead related is in Valve's hands," Ashton wrote to a fan on Turtle Rock's forums.