The game is different from the rest in the sense that it features two (player controlled silent protagonists) characters namely GLaDOS and Chell. The latter (generic life form and disk operating system) is a computer artificial intelligence designed to help monitor and direct the player. It is important to note that the only available background information presented about Chell is provided for by GLaDOS. The game’s plot is revealed to players through audio messages and announcements from GLaDOS and other visual elements inside rooms found in later levels. The game has since its debut received a lot of praise from gaming enthusiasts who have hailed it for being unpredictable and fun.