Half-Life Blue Shift is a first-person shooter video game developed by Gearbox Software and published by Valve. Half-Life Blue Shift is an expansion pack Half-Life. Half-Life Blue Shift returns to the setting and events of the original game, but portrays the story through the eyes of another person. The protagonist in Blue Shift is 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.

• Half-Life Blue Shift