Half-Life (video game)
Half-Life: Blue Shift is the second Expansion for Half-Life, which was also made by Gearbox Software, and was released on June 12, 2001. Half-Life: Blue Shift happens during the same time as Half-Life and in the same setting, just like Opposing Force. In this expansion, you play as "Barney Calhoun", a security guard who works at Black Mesa during the resonance cascade.