Made by Gearbox Software and originally released in 2001 as an add-on to Half-Life, Blue Shift is a return to the Black Mesa Research Facility in which you play as Barney Calhoun, the security guard sidekick who helped Gordon out of so many sticky situations.
Put "bshift_addon" and "valve_addon" into "C:\Program Files (x86)\Steam\steamapps\common\Half-Life" to get it work works for Half Life and the Blue Shift
Alright Then :)