Half-Life: Opposing Force is a first-person shooter video game developed by Gearbox Software and released in 1999. It serves as an expansion to the original Half-Life game, allowing players to experience the story from the perspective of Gordon Freeman's adversaries, specifically a soldier named Adrian Shephard. The game features new weapons, enemies, and gameplay mechanics, enhancing the original experience. In Opposing Force, players navigate through the aftermath of the Black Mesa Incident, battling both alien creatures and military forces. The game introduces various challenges and puzzles, requiring players to utilize their skills and strategy to progress through the levels.