Portal 2 — a first-person puzzle computer game, the sequel to the game Portal (2007), developed by Valve Corporation. The sequel expands the gameplay of the first game, which consists of puzzles based on the use of a special device for creating portals — rifts in space — allowing the player to instantly move from one place to another. Among many gameplay innovations in Portal 2 is a cooperative mode for completing the game by two players. Comparing Portal and its sequel, Valve notes that the first part was merely an experiment, while Portal 2 is already a full-fledged game with entirely new gameplay elements and a much greater length (the game is estimated to take about 6 hours in single-player mode and about the same in cooperative mode). Moreover, at the GDC 2010 conference\/<\/span> Valve director Gabe Newell stated that Portal 2 — is the best game in the company's entire history.