Like Gearbox's other expansions, Half-Life: Opposing Force and Half-Life: Decay, Blue Shift returns to the setting and timeline of the original story, but with a different player character: the ubiquitous Black Mesa Research Facility security guard Barney Calhoun. Half-Life: Blue Shift, commonly referred to as Blue Shift, is the second stand-alone expansion pack for Half-Life, developed by Gearbox Software and was released on June 12, 2001.
