Half-Life: Blue Shift is a first-person shooter video game developed by Gearbox Software and released in 2001. It is an expansion for the original Half-Life game, allowing players to experience the story from the perspective of Barney Calhoun, a security guard at the Black Mesa Research Facility. The game features similar gameplay mechanics and environments as the original, focusing on exploration and combat against alien creatures and military personnel. In Blue Shift, players navigate through the facility during the same catastrophic events depicted in Half-Life. The expansion includes new levels, puzzles, and challenges, while maintaining the immersive atmosphere and engaging narrative of the original game. It also introduces new weapons and gameplay elements, enhancing the overall experience for players.