The Complete mod series is a fan-made project that improves nearly every aspect of S.T.A.L.K.E.R.'s third entry, Call of Pripyat, including graphics, sound, AI, and many gameplay elements. The modders even went so far as to recreate the real-world environments based off historical images.
Watch the trailer below, and be sure to check out Artistpavel.com, where you can see a full list of improvements and download the mod.
