About This Game
Waking up in a seemingly empty laboratory, the player is made to complete various physics-based puzzle challenges through numerous test chambers in order to test out the new Aperture Science Handheld Portal Device, without an explanation as to how, why or by whom.
Portal's plot is revealed to the player via audio messages or "announcements" from GLaDOS and visual elements inside rooms found in later levels. According to The Final Hours of Portal 2, the year is established to be "somewhere in 2010"—twelve years after Aperture Science has been abandoned.
The game begins with Chell waking up from a stasis bed and hearing instructions and warnings from GLaDOS, an artificial intelligence, about upcoming tests. Chell enters into distinct chambers that introduce players to the game's mechanics, sequentially.
GLaDOS's announcements serve as instructions to Chell and help the player progress through the game, but also develops the atmosphere and characterizes the AI as a person. Chell is promised cake as her reward if she completes all test chambers.
Chell proceeds through the empty Enrichment Center, with GLaDOS as her only interaction. As the player nears completion, GLaDOS's motives and behavior turn more sinister; although she is designed to appear encouraging, GLaDOS's actions and speech suggest insincerity and callous disregard for the safety and well-being of the test subjects.
The test chambers become increasingly dangerous as Chell proceeds, tests including a live-fire course designed for military androids, as well as some chambers flooded with a hazardous liquid. In another chamber, GLaDOS notes the importance of the Weighted Companion Cube, a waist-high crate with a single large pink heart on each face, for helping Chell to complete the test.
However, GLaDOS declares it must be euthanized in an "emergency intelligence incinerator" before Chell can continue. Some later chambers include automated turrets with childlike voices (also voiced by McLain) that fire at Chell, only to sympathize with her after being destroyed or disabled.
After Chell completes the final test chamber, GLaDOS maneuvers Chell into an incinerator in an attempt to kill her. Chell escapes with the portal gun and makes her way through the maintenance areas within the Enrichment Center.
