From the news release: Warner Bros. and Turtle Rock Studios announced Back 4 Blood, from the creators and development team behind the critically acclaimed, co-op phenomenon Left 4 Dead. 

 

Back 4 Blood is designed from the ground-up as an original, premium title and marries the best of what made the co-op zombie shooter so successful with new features and state-of-the-art technology.

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I worked with Steamroller on this.