Half Life Blue Shift, the beloved expansion pack for Valve's seminal whatever happened to Half-Life 3.
Black Mesa Blue Shift is a rebuild of the Barney Calhoun-based add-on game designed to look and play like the 2012 remake of the FPS original. Three chapters have been released already, but a huge update coming December 10 will bring the next level, Captive Freight, as well as bug fixes and gameplay and visual improvements.
Black Mesa Blue Shift revives what is arguably the best Half-Life expansion to date, dropping you in the boots of lab security guard Barney as he tries to survive the resonance cascade event parallel to Gordon Freeman. Originally developed by Gearbox, later of Borderlands, Battleborn, and Duke Nukem Forever fame, Blue Shift launched all the way back in 2001, and remains one of the best old games you can still play today.
Nevertheless, that original GoldSource engine is starting to look a bit creaky, and the full remake brings a very-welcome dose of smoothness and modernity to the classic shooter. Half-Life Alyx just got a ideas brewing for a Portal 3.
Try some of the other best zombie games, since we all love a good headcrab.