HHm well... the second is even more twisted than the first. Instead of traps. it seems it plays with time and physics... with the relativity laws, because this time they're in an "Hypercube", that is, a 4D cube, something wich is only an imaginary entity in fact made by mathematicians, but... well you know, it's a movie
. So every room is the same, same colors, and there's no "number" puzzle this time, but, every room has its own gravity, so sometimes, you enter trough a left-door... and that's a top-door in the next room! The gravity is different. And the time-flow is different between rooms, so if you're looking from one room to another, you see the person in the other room walking and talking very quickly, while he sees you very slow... or... well... I don't want to spoil the movie, you know, so better go and watch it
.
The worst thing: the end, IMHO.
I've only read about the third one (It's called "Cube Zero"), but it seems it sucks, because this time it's focused on the guy who is in charge of the cube (another cube... it seems there's a new cube for every movie), so there's really no mistery about "the cube" this time... it spoils everything I think, it would be a big joke compared with the past 2, but I still have to watch it though. But just take a look at the comments at IMDB of the movie... and you'll get the idea.
More info:
http://www.uncubed.com/