Question: When was the Half-Life first-person shooter game released by game development community MapCore? 
Sentence (from "Half-Life: Decay"): It is the third expansion pack for "Half-Life", and like its predecessors, "Decay" returns to the setting and timeline of the original story, albeit portraying the story from the viewpoint of a different set of protagonists: two women scientists working in the Black Mesa Research Facility.
Relevant evidence: No