When Portal 2 was first announced as a full retail release and not just a download, or, like the first game, part of a collection of other games, I was a bit worried that there wouldn't be enough content to sustain a full game. I was gladly mistaken.

Portal 2 keeps the original game's style, but with some changes since it takes place several hundred years after the original game. At first, you will find your old testing grounds, but overrun by plants. Later, you will work your way through new tests, but considering the state of the facilities, even the new locations are in shambles, but that's okay because you will find yourself in much darker and drearier places before the game's Single Player Mode is over.

One of the major aspects of Portal that really sold the original game for me was the dialogue. While there was pretty much just you and GLaDOS, with the occasional lonely-sounding turret thrown in for good measure, the game would have been far less memorable without them. In fact, the game would have felt like just another puzzle title instead of the psychological head-game that it was.

For the most part, that feeling continues in Portal 2. You have a couple more voices to keep you company this time around though. One such character is Wheatley (Stephen Merchant), who can get a bit annoying at times, especially since he was apparently designed to be the most moronic A.I. ever developed. Another is the voice of Aperture Science's founder, Cave Johnson (J.K. Simmons), but I don't want to talk too much about his role in the game as that would reveal a bit too much about the Single Player story. Suffice it to say that the added characters do a lot to add content to the game and allow for a few changes to keep you playing.

Portal 2's core mechanic is still the same, and so, for the most part, is it's gameplay. You reprise your role from the first game and also once again command the Portal Gun that allows you to shoot interconnected portals on any correctly surfaced area.

For those that didn't play the original... well, go play the original. Anyway, for those that didn't try out Portal, this leads to a series of cleverly designed rooms that require a pretty concrete set of steps in order to get past. You will use a lot of the skills you learned in the first game to get through the obstacles thrown at you here, but Portal 2 does introduce a few new problems and mechanics that, when used properly, can be a big help.

The biggest of these new tools is a set of three paints that you can splash across surfaces. One allows you to jump higher, one increases your horizontal speed and the third... well, again, I don't want to give away too much, but it does add a new spin to things, that's for sure.

Of course, one of the biggest additions to Portal 2 is the Co-Op mode. Here, you and a friend (either locally via split-screen or online), control two testing robots that have to work together and communicate really well in order to reach the end of each test chamber. These particular levels are often designed to need two full sets of portals to be active in order to reach the goal. Other variations also require one player stand on a button while the other runs around. It doesn't take long to realize that there is no way you are going to get past these particular testing chambers by working alone.

While Portal 2's Co-Op Mode is best played with a mic and headphone set, there are several built-in communication devices that allow even players without a way to talk to their friends to convey their intentions and desires. These typically come in the manner of HUD overlays you can superimpose on walls you want the other person to put a portal or even start countdowns for events that have to be closely timed.

Portal 2 doesn't seem to be nearly as hard as the first game. I remember spending a good bit of time trying to work through many of the levels in the last half of that game. In Portal 2 on the other hand, I found I would speed through test environments with little to no trouble over and over again before finding one that caused me to stumble a bit. Even those rare tough rooms weren't too much to handle and once you get the feel for some of the game's new features, even those potentially harder levels aren't as bad as they could be.

Basically, while Portal 2 is a lot bigger, it simply doesn't feel as challenging as the original. Then again, maybe I've just finally gotten the hang of "thinking with portals."

Portal 2's portal-hopping gameplay is still the main focus of this game, and as a core mechanic, it still makes for some interesting situations. While there don't seem to be as many puzzles that involve feats like launching yourself in the air and placing portals where you are about to land in order to gain even more momentum, what you have to do is still often a test of timing and luck.

The addition of Co-Op also adds a lot to the game. Not only is the mere idea of a Co-Op Portal game fun sounding, but the kind of situations GLaDOS puts you and your friend through are outrageous. As GLaDOS says to these two characters a lot, its a good thing they don't feel pain... or at least have a way of expressing their pain.

While Portal 2 might not live quite up to the legend that was the first one, it is kind of hard for any sequel of such an innovative game to meet that kind of criteria. Portal 2 is still a fun game that provides much more content than the original, even though the game, both Single Player and Co-Op can be finished in 10 hours or so. Most likely you will find yourself compelled to play through the game's entire experience (minus the commentary track, of course) in as few sittings as possible.