Half-Life: Decay

"Half-Life: Decay" is a cooperative first-person shooter video game developed by Gearbox Software and published by Sierra Studios. It was released in 2001 as an expansion for the acclaimed first-person shooter game "Half-Life." Unlike the original game, which follows the story of Gordon Freeman, "Decay" features two new characters, Gina Cross and Colette Green, who are both scientists at the fictional Black Mesa Research Facility.