If you never played the first Portal game, you're missing out.
The awesome physics were the key behind all kinds of crazy mindf*ck puzzles.
You guys definitely need to at least watch these videos. If you're at work, show them to your co-workers.

(Okay, maybe not.)
Anyway, here's a few videos to show what's going on.
Some awesome blue goo that's really bouncy. (No seriously, watch this stuff)
http://www.youtube.com/watch?v=IaZ75vU112QIt's gonna have co-op too.
http://www.youtube.com/watch?v=A88YiZdXugASpringboards!
http://www.youtube.com/watch?v=laxPhiDqTJAThis one has more to do with the story but shows off some cool lighting.
http://www.youtube.com/watch?v=Mz0PvYiHjwEOrange goo, only it propels you as you move along it.
http://www.youtube.com/watch?v=Pcf99_DZZewSweet tubes that suck stuff in and blow it out elsewhere... even through portals.
http://www.youtube.com/watch?v=DOH6BprN9FILazer beams! Ahhhhh!
http://www.youtube.com/watch?v=yFRbGppLaUIAnti-gravity beams of some sort.
http://www.youtube.com/watch?v=1oVpE40V9rE