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.
Another excellent job by the guys at Gearbox Software. This is the second Expansion Pack for Half-Life, and it is great! Playing as a Security Guard is an awesome idea, and it is also cool to see the backstory of Barney Calhoun before the events at Half-Life 2. It's a short Expansion Packs with very little new content, but don't be surprised: originally, it was planned to be a free add on for the Dreamcast version of Half-Life. However, that version was canceled, but Blue Shift was ready to be shipped and Valve decided to release it as a Retail game for PC along with the High Definition pack. This game is short and sweet, you will complete it in a few hours, I managed to complete it in 3 hours after finishing the Opposing Force campaign. There IS something new: you can see Marines using Torches to blow doors like in Opposing Force, however don't expect to see the Opposing Force models, just the standard ones from Half-Life! There is a Training Course like the original one in Half-Life, however adapted for Security Guards. The Holographic Guide is now a Security Guard! There is a new Armor System: you won't use HEV Chargers anymore, but instead pick up Helmets and Vests from the ground. The locations aren't spectacular but they are fun enough. The trip to Xen was probably better than Freeman and Shepard's ones. You will encounter an unique Scientist (Rosenberg) and you will actually have a good ending! You will escape Black Mesa in a SUV with three other Scientists (Rosenberg, Simmons and Walter). No Boss Battles and challenging parts: just standard firefights. The arsenal is just Military Stuff from Half-Life, no content from Opposing Force and no Experimental and Aliens weaponry. You will do many cross paths with Freeman and encounter him while he's being dragged by the Marines in the chapter Apprehension! You will also see some Easter Eggs (Chumtoad's Lair anyone?) and acquire a Pistol even before the Incident! A very nice addition to the series. Recommended!