 Most of the game is set in a remote desert area of New Mexico in the Black Mesa Research Facility, a fictional complex that bears many similarities to both the Los Alamos National Laboratory and Area 51, at some point during the 2000s. The game's protagonist is the theoretical physicist Gordon Freeman, who holds a Ph.D. from MIT. Freeman becomes one of the survivors of an experiment at Black Mesa that goes horribly wrong, when an unexpected "resonance cascade" — a fictitious phenomenon — rips dimensional seams, devastating the facility. Aliens from another dimension known as Xen subsequently enter the facility through these dimensional seams (an event known as the "Black Mesa incident").
