Portal 2 takes you back to the ruined Aperture Science test center first seen in the original game, and introduces a mind-boggling two-player mode and voice work from Stephen Merchant, J.K. Simmons and Ellen McLain.
Mixing a first person shooter, physics puzzle game and experimental gameplay, 2007's Portal introduced the "portal gun," a device that let players teleport themselves and other objects around levels. While the original game was only a few hours long and grew out of a student project, it hooked casual and pro gamers alike with its ingenious gameplay, smart writing and malevolent, HAL-esque GLaDOS artificial intelligence.
The core portal gameplay is still here -- as is the witty humor that questions your humanity and skill in solving puzzles -- and Valve has introduced bouncy gels, light bridges and other elements to the mix to create delightfully challenging puzzles. IGN writes "Portal 2 makes the original look like the prototype it was. It's filled with a larger cast of characters vividly brought to life through brilliant writing and some of the best voice acting in video games."
'Portal 2' is available now on PlayStation 3, Xbox 360 and Mac/PC (via Steam). Check out the gameplay below: