Half-Life: Blue Shift

Half-Life: Blue Shift is an expansion pack for Valve Software's science fiction first-person shooter video game Half-Life. The game was developed by Gearbox Software and published by Sierra Entertainment on June 12, 2001. Blue Shift is the second expansion for Half-Life, originally intended as part of a Sega Dreamcast version of the original game. Although the Dreamcast port was later canceled, the PC version continued development and was released as a standalone product.

As with Gearbox's previous expansion pack Half-Life: Opposing Force, Blue Shift returns to the setting and events of the original game, but portrays the story through the eyes of a security guard, Barney Calhoun, employed by the Black Mesa Research Facility. After a scientific mishap causes Black Mesa to be invaded by aliens, Calhoun must fight his way to safety. The game received mixed although mostly positive reception. Many reviewers were critical of the short length of the game and the lack of new content, although the inclusion of a High Definition pack that upgraded the models and textures in both Blue Shift and the preceding Half-Life games was praised.