Sierra has kept Half-Life on countless hard drives by publishing the excellent multiplayer Counter-Strike modification, but Half-Life was originally all about the single-player game--the sci-fi action story of research assistant Gordon Freeman. The first Half-Life expansion pack, Opposing Force, concentrated on the military Special Ops side of the same story, and featured Colonel Adrian Shepherd. The new Half-Life: Blue Shift episode highlights security guard Barney Calhoun's adventure during Black Mesa's extradimensional catastrophe. Like Adrian, Barney encounters much the same creatures as his predecessor, but in different situations and locales than you've seen before, some located as far away from Black Mesa as you can get. Unlike Opposing Force, Blue Shift doesn't feature any new weapons or monsters; oddly, it doesn't even feature the new creatures introduced in Opposing Force.