The original Portal is perhaps the iconic "short and sweet" game. It didn't last very long, but while it did, it was mighty close to perfection. It was funny, and there was rarely a dull moment or frustrating sequence. Part of Portal's appeal was that it never overstayed its welcome. You never reached a point where you thought, "Oh, this puzzle again," or wanted to get back to the game instead of the storyline. It would be difficult to make a sequel because there's a risk of giving the player more of the game than the concept could handle. That's why Portal 2 is so impressive. It's longer and more like a full game than Portal was, but it manages to do this without losing any of the traits that made Portal so much fun.

For those who haven't been following along, Portal's ending was actually altered after release. It seemed that you escaped, but the altered ending made it clear that protagonist Chell had been dragged back into the facility by an unknown robot. Portal 2 begins an unknown number of years later. Chell awakens from some kind of stasis to discover the Aperture Science facility crumbling around her, overrun by plants and wildlife. The only other thing active in the facility appears to be the helpful, if dim-witted, robot Wheatley, who is trying to help Chell escape. Unfortunately for her, it isn't long before her old captor, the sadistic AI GlaDOS, returns from the dead. GlaDOS is quite sore at Chell for killing her in the last game and traps her in a new, and deadlier, "testing facility." Now Chell has to escape before GlaDOS can have her revenge.

The writing in Portal 2 is just as sharp and clever as it was in the original. The addition of a few extra characters keeps things from getting old, but it never reaches the point where it gets tiresome. The humor is top-notch and, mercifully, it refrains from the trap of repeating old jokes from the original game. There are a few Companion Cubes and Cake references here and there, but most of the humor feels fresh and new. If I had one complaint, it would be that the plot is fairly predictable, as you have a good idea of what is going to happen from the moment things begin. Fortunately, the writing is so enjoyable that it's all right that you know what is going to happen because how it happens is so darned funny.

The basic gameplay hasn't changed much from the original Portal. You're given a portal gun, a weapon that can project two connected portals on certain surfaces. Using this gun, you must transverse a large number of puzzles and traps to escape from GlaDOS. It's a puzzle game, and it seems very straightforward in that you have two portals and nothing else:  no guns, no superpowers. However, when and where you place the portals can dramatically alter their properties. Two portals on flat surfaces can be a door. Place a portal high up and another on the ground, and you can build up momentum. Place a portal on a slanted surface, and you can send yourself flying through the air. There are boxes and switches you have to activate, deadly fields that can obliterate the objects you're carrying, laser beams that can be used to activate switches … the list goes on and on.

Portal 2 does a very good job of teaching you all the physics and properties of each object. There's a long series of puzzles, both obvious and subtle, which are designed to help you understand how the portals interact with various objects. The game gradually begins to combine them until you're pulling off portal tricks without a second thought. Newcomers will feel right at home with the gameplay, although it's designed well enough that even Portal veterans won't feel like their hands are being held too much through the beginning of the game.

While a lot of the gimmicks are similar, there's a whole host of new and interesting tricks in Portal 2. For example, there are three kinds of gel, each offering certain new properties. Blue gel makes the ground bounce you upward, like you're on a trampoline. Yellow gel gives you a massive speed boost as you run alongside it. White gel turns any surface it touches into one where you can plant a portal. It sounds simple, but figuring out how to correctly use the gels is a total blast. You can use the portals to funnel gel from one location to another, and it's incredibly satisfying to work out the best way to use the gels. The gels seem like a minor feature, but they really alter the portals in dramatic ways. There are also funnels, which are anti-gravity beams that lift you (or anything else) off the ground when you step into them. Like anything else, they can go through portals uninterrupted, allowing you to redirect them around the level. My favorite puzzles involved Light Bridges, which are solid beams of light that can be redirected through portals to let you go to new places in the level or form makeshift barriers against deadly turret bullets.

One of the things I liked best about Portal 2's level design is that it never felt unfair. Whenever a puzzle stumped me for a moment, the solution always seemed obvious in hindsight. My biggest problem was in overthinking the puzzles and making them out to be more complex than they were. Once I solved them, I wanted to slap my forehead because the solution was so obvious. Die-hard Portal players may find some of the new challenges to be too easy, but the game mostly hits a good sweet spot. It wasn't particularly tough, but that also prevented it from being frustrating. Players of any skill level should be able to hop into Portal 2 and have a good time. There are only a few stumbling blocks, and most of those are easily solved by experimenting.

You can probably finish Portal 2 in five to seven hours. This doesn't feel too short because there's very little filler in the game. Aside from a few hallways that seemed to exist so that one of the characters could have a brief monologue, there wasn't a slow moment. Every few minutes, you're introduced to a new puzzle or a new feature, and the game continues to do this until the very end. You may finish the game in less than seven hours, but that will be seven hours of pure fun, not something that's been padded out by cinematic cut scenes and slow moments. It feels like a much longer game simply because it never slows down. It would be easy to spend 20 minutes or more on some of the trickier areas. Like the original Portal, there isn't a ton of replay value. There are some extras to find, and you can try to finish the puzzles faster, but it's the kind of game you'll find yourself replaying on a rainy day.

The single-player mode is not the full extent of Portal 2, though. There's also a somewhat shorter co-op campaign starring two new robots called Atlas and P-Body. Like Chell, Atlas and P-Body have portal guns, and both are capable of projecting two portals each. The level design is altered so that both players have to work together to solve puzzles, and many of the challenges involve things that wouldn't be possible in the single-player game. One challenge, for example, requires you to set up an infinitely looping pair of portals so one robot can build up momentum, followed by the other robot setting up a launcher portal so that his partner can be flung to a distant switch. There are a number of creative puzzles in co-op mode that show off interesting portal properties that you'd never see in the single-player portion. The puzzles in co-op are also tighter on timing than those in the single-player game. With two players working together, you really had to have perfect timing in certain spots to successfully sidestep danger. Fortunately, death is a momentary inconvenience. You respawn pretty much instantly, and the only punishment is a snarky comment from GlaDOS.

The co-op campaign is best played with a friend with whom you can communicate in some fashion. The game offers in-game gestures that allow you to point to specific places or synchronize your timing, but it doesn't work very well without voices. If you don't have a microphone, it would be very easy to get frustrated by what is otherwise a simple puzzle. If you do have a microphone, Portal 2 represents some colossally fun co-op action. The puzzles are clever and encourage both players to work together. It's also a game very much in the vein of Super Mario Bros. Wii, where you'll occasionally blow up each other by accident (or on purpose) in various hilarious ways. The addition of further plot and lines from GlaDOS helps it feel like the co-op campaign isn't an afterthought.

The co-op portion feels like a second half of the game and improves the value of the short and sweet single-player campaign. PlayStation 3 owners also get a rather nice benefit from buying a new copy of Portal 2: the ability to play Portal 2 on the PC or Mac in addition to the PS3. You get a free downloadable version of the game and the ability to play co-op with PlayStation 3 players and your friends who own Portal 2 for the computer through Steam. This cross-platform play worked wonderfully, and being able to play the game along with my pals on the PC really made the co-op feel special.

Portal 2 doesn't look much different from the original game. The visuals are good, but what really stands out is the art design. The original Aperture Science building was solid, clean and white, which made it more shocking when you went behind the scenes to see the dirty depths. Portal 2 takes it further by taking you to a wide variety of locations. Early on, GlaDOS is rebuilding the facility around you. As you complete her tests, you'll see machines actively re-creating the rooms as you go through them. Later on, you visit destroyed ruins of older labs or new and deadlier places, and each spot has a distinctive and memorable design.

The real star of the show, however, is the voice acting. It's difficult to explain how good it is without spoiling some fun surprises, but every voice actor in the game does a wonderful job of portraying his or her character, and they all breathe life and personality into faceless characters. GlaDOS is as sweetly menacing as ever, and Stephen Merchant's Wheatley manages to take a potentially annoying character and make him endearing and likeable. The sound effects combine with the various portal tricks to give rooms a distinctive sound that lets you know what to expect before you even see it.

Portal 2 is more of the same, but only in the best of ways. Valve didn't mess with a winning formula, and the end result is that Portal 2 is a better game than its excellent predecessor. It keeps the same witty humor and high-quality level design but adds a few new tricks to turn the interesting puzzles into exceptional ones. The co-op campaign is a boatload of fun and adds extra value to the package — especially if you're a PS3 owner, who gets the PC/Mac version along with the console copy. Portal 2's only problem is that it's a hair short and lacks replay value. Despite this, it's some of the best gaming I've had in recent memory, and it still manages to be worth the full price. If you remotely enjoyed the original Portal, you'll absolutely love the sequel.

Score: 9.0/10