Portal introduced players to GLaDOS, the artificial intelligence overseeing the Aperture Science testing facility.
Valve released Portal in 2007 as part of The Orange Box, alongside Half-Life 2: Episode Two and Team Fortress 2. The player controls Chell, who solves spatial puzzles using the Aperture Science Handheld Portal Device.
GLaDOS initially presents the tests as controlled experiments and provides instructions in a calm, computer-generated voice. Her statements gradually become unreliable, turning the puzzle game’s laboratory setting into a distinctive narrative mystery.
GLaDOS is sometimes confused with characters from Valve’s Half-Life series, but she belongs specifically to the Portal storyline. The character became one of gaming’s best-known examples of an unreliable artificial intelligence and returned in Portal 2, released in 2011.