Portal 2 E3 video demonstration take a look at the mechanics of the game's new gels: Propulsion and Repulsion. As if anything could ever make Portal 2 repulsive! Ahem.
So, these gels: They're yet another new tricky (and likely toxic) product of the Aperture labs that just so happen to open up a variety of new platforming puzzles. Go on and watch the clips after the break -- they'll totally bend your mind. (Or maybe that's just the fumes from the gel. Yeah, probably.)