Before you lies the threshold to a new world of ultimate adventure — and ultimate challenge. A world where you must think before acting, plan your every move and outsmart your way through devious chambers. In this game, your mental abilities are your best means of survival. Following in the critically acclaimed footsteps of the original Portal, this all-new campaign opens the door to mind-testing puzzles, with an immersive story and never-before-seen environments throwing new obstacles in your path. Are you brave enough to enter?Rejoin GLaDOS, the occasionally murderous computer companion who guided you through the original game as you explore the all-new test chambers of Portal 2. Advanced gaming physics, an intricate storyline and original music immerse you more fully than ever in the addictive gameplay made famous by 2007's Game of the Year Portal. Explore exciting new areas within Aperture Science Labs. Cooperate with an accomplice in a totally unique two-player campaign mode. Get ready to reconsider everything you thought you knew about portals. Success will require you not just to act, but to think with skill.