- Two robots, four portals
- Whole brand-new set of puzzles
- Completely different storyline
- [SPOILER] GlaDOS is running the tests again, but she needs these robots to be more human-like with their thinking and logic. Because, well, Erik actually kind of compared the idea to the Schrödinger's cat experiement. But here GlaDOS is a cold and calculated machine, and she makes cold and calculated decisions. The same goes for the two robots. The results for GlaDOS would be biased and inconclusive. So, she sends them into the bowels of Aperture Science on a team archeological hunt for human relics. Relics as simple as a "#1 Dad!" coffee mug. That human connection with the robots will serve as the catalyst for GlaDOS's tests. Valve will be attending PAX in just a few weeks, and they have more co-op and singleplayer to show us there. Oh, and Erik Johnson also mentioned that "the stake is in the ground" for the recently announced February 9th, 2011 release date. So good news all around, folks.