In his presentation Johnson said that Valve wanted to keep everything that people liked about the first game (the portal puzzles, the humor, the music) and expand on it for the sequel. The storyline for Portal 2's single player campaign has you playing the same character Chell but hundreds of years in the future (Chell's been sleeping apparently). The evil but somewhat goofy AI GLaDOS, who was both your helper and later your enemy in the first game, is also back and apparently rebuilding itself and the Aperture Science testing complex. She also doesn't like Chell very much. In the E3 2010 presentation we also got to see a new AI character, Wheatley, who guides Chell through the slowly rebuilding complex.

The truth is that if Valve just decided to make Portal 2 all about the inter-spacial portals and puzzles that are solved via the Portal gun, the sequel would still likely be successful. However Valve decided to throw in some new aspects that will likely make the puzzles in the first game look simple by comparison. One of them is the use of travel tubes that can be shifted by the effects of the Portal gun to access areas and solve puzzles. Yet another new aspect is the use of jump pads that can boost the player to other aspects of the maps. Other new additions include redirecting lasers via the Portal gun to cut through items and solve puzzles and a tractor beam aspect that, well, you get the picture by now. All of these new elements are seamlessly integrated into the gameplay as you struggle to get through the Aperture Science facility while GLaDOS continues to rebuild the complex and go after you (but in the nicest voice ever).

The biggest new gameplay addition in Portal 2 is the use of paint that can alter the properties of items it touches. This part of the game was brought in by Valve after bringing in the developers of the indie game Tag: The Power of Paint team. The E3 presentation showed the paint being placed on walls and floors. One of the paints makes the surface of items very slick and lets players move extremely quickly (needed when things like walls are about to move and crush you) while another makes surfaces extremely bouncy. All of these additions will likely make the sequel far more complex than the original Portal.

Johnson told us during the E3 2010 presentation that the single player campaign for Portal 2 will be about twice the length of the original game. But that's not all. There's also going to be a second, separate campaign that's designed for two player co-op gameplay. This time the characters you will be playing will be two robots armed with, naturally, portal guns. By the way don't look for any more weapons beyond the Portal gun in the sequel. Johnson told us there just wasn't any need to add any more weapons to the game.

Valve will be using its own Source graphics engine for Portal 2 and Johnson said they had to put in new features in the engine to allow for the game's new features, including the paint altering surfaces. Visually the game doesn't look much different in art style from the original with the exception of the wrecked and overgrowing aspects of the complex.

With a lot of new puzzle-altering features, the addition of a separate two-player co-op campaign and the promise of the dark humor from the original Portal, the sequel looks like it's aiming to exceed the praise that Portal 1 got three years ago. We will likely learn more about the game before Portal 2 is released sometime in 2011.