Portal centers on a sequence of physics-based test chambers built to test the Aperture Science Handheld Portal Device. The chambers introduce mechanics progressively, with later tests adding dangers such as automated turrets and hazardous liquids.
You play as Chell, who awakens from stasis without knowing why she is there. GLaDOS, the artificial intelligence overseeing the tests, delivers instructions, warnings and promises of cake. Her announcements and visual clues within the facility gradually reveal the story, while her increasingly threatening behavior casts doubt on the purpose of the experiments.
