How then do they go about making a sequel to this brilliant title? Well, frankly, by doing more of the same and it still works wonderfully.
As fun a villain as GLaDOS is, and due to the way in which she coaxes you through her tests she is fun, the truly great part of the game is the fact that Valve has worked out this simple mechanic—create portal holes to traverse a room—and built level after level after level which constantly test your ingenuity and build on the basic concept. Rather than the levels in the second game feeling like rejects from the first, they are equally clever and will test you just as much if not more.
Please, don't get me wrong, things change dramatically as you go in the title and you're not going to feel like this is a simple rehash of what you did in the first Portal. That being said, I'm not really going to tell you how they change and what may be different, that would ruin so much of the fun. I will tell you that GLaDOS is back; that you learn more about what is going on at Aperture Laboratories and why; and that despite doing more of the same, the game never really feels repetitive.
Portal 2 also comes with the ability to play co-op online in a separate campaign and can be played across different platforms in said campaign. In fact, a huge advantage to buying a PS3 version of Portal 2 is that if you sync your PSN account with your Steam one, you get a free Steam download of Portal 2 for your computer. Sadly, what you can't do is sync a cloud-based save file – save your PS3 game and you can't pick up where you were on your computer. Even so, getting two copies is a pretty great deal and when you consider the fact that the game isn't terribly more expensive on PS3 than on Steam (currently Amazon gets $5.00 more for a PS3 copy than what Steam does for a download) it becomes an even better one.