Half-Life: Blue Shift is the second (after Opposing Force) expansion pack for the original first-person shooter Half-Life. The game setting is the same as the one in the original game: the story takes place in the science laboratory called Black Mesa Research Facility in New Mexico. However, the game portrays the events of Half-Life through the eyes of Barney Calhoun a security guard employed by Black Mesa. Till the things have gone the wrong way the protagonist was responsible for the lab equipment and personnel welfare, but after the accident, his only aim is to protect a high-ranked scientist Dr. Rosenberg. The gameplay is almost similar to the original Half-Life’s: the storyline continues by navigating through the sequence of levels. Each level consists of both combat part and solving puzzles. Although Blue Shift is an expansion to the original Half-Life, both weaponry and enemies range face no changes or additions, so players use same guns to shoot same aliens. The only new mechanics is escorting a character to a specific location.