"Oh, it's you. It's been a long time. How have you been? I've been really busy being dead. You know, after you murdered me. Okay, look. We both said a lot of things that you're going to regret. But I think we can put our differences behind us. For science. You monster."

Both Portal and its slightly unhinged antagonist GLaDOS are back in a sequel that hopes to do more than "just extend the original game" according to Valve's Erik Johnson. "If you ask fans what they wanted, they'd say they want more Portal 1," Johnson said. "But we felt like what they're saying is that they want to be surprised again." While the addition of a co-op experience may surprise you, there's a lot of comfort food here. Not only is GLaDOS back, but so is protagonist Chell, the (slightly worse for wear) Aperture Science facility, and the game's now trademark sense of humor.

While laying out the three major focal points for the game - that's story, gameplay, music if you're keeping track at home - Johnson explained, "The story needed to be funny. It needed to have a lot of the same characters. You're playing as Chell in Portal 2. GladOS is back. And there will also be some new characters, one of which you'll see today."