Once again, you are caught up in thefantastic world of Aperture Science, where hilariousand endearing dialogue is delivered bydisembodied voices and artificial intelligences,and where inventive gameplay mechanics anda smooth difficulty curve make the sublimesatisfaction of puzzle solving accessible to all.

The single-player campaign starts by addressingthe issue of what happens now thatyou’ve destroyed the malevolent AI who triedto incinerate you. “Now” may be a relativeterm in the bowels of Aperture Science, butthe facility you enter is still reeling from youractions at the end of Portal.It’s not long before you find an ApertureScience Handheld Portal Device (colloquiallyknown as a “portal gun”) and start slingingportals like it was 2007. Those unfamiliar with this technology need not fear:

Portal 2 has a nice learning curve that quickly brings youup to speed. The basics are these: Using thisgun, you can create two distinct portals oncertain walls, ceilings, and floors. Go into onehole, and you come out the other. You startoff learning basic navigation and then moveon to transporting objects and experimentingwith more complex moves, like jumping offa ledge into a portal below in order to flingyourself across the room.

Getting the hang ofthis requires you to flex your spatial awareness,but the introduction is so smooth and intuitivethat, before you know it, you’re thinking inportals.This may sound like a slow start to Portalveterans, and from an action standpoint, it is.It’s a while before you encounter challengingpuzzles, but the scenery is so different thatyou won’t mind getting your bearings onceagain. Aperture Science has seen better days,and the broken test chambers, malfunctioningrobotics, and encroaching plant life are an early sign that Portal 2’s environments are much more varied and ambitious than its predecessor’s.

Later levels reveal the true scope of the Aperture facilities to great effect, piquing your curiosity and spurring you onward. As you work your way in and out of the damaged test chambers, you catch some intriguing glimpses behind the scenes. You also see a fair number of empty areas where the scenery fades into nondescript gloom, and these dull areas are a bit disappointing, given the busy industrial vibe of the place. You also encounter a lot of load times throughout the game, and though they rarely feel excessively long, they are often long enough to make you take notice and wish they were shorter.

While you are getting reacquainted with the basics of portals and trying to escape with your new friend, you run into your old testadministrator- slash-nemesis, GLaDOS. Though she isn’t exactly happy to see you, she is glad to have a subject to run through test chambers and pester with sarcastic barbs.

A few hours into the campaign, the narrative focus expands beyond “What happens now?” to include “How did that whole weird situation come to pass?” In your explorations, you encounter new characters who provide

some of the best lines in the game, and your AI companions evolve in surprising and gratifying ways. You also encounter a variety of new testing materials, from catapults to bridges made of light to gelatinous goos that splatter on surfaces and directly affect the way you move through the world. Portal 2 does a great job of introducing you to new tools and then challenging you to use them in clever ways.

Successful navigation requires careful study of your environment and experimentation with the materials and surfaces available to you. There are some very tricky situations that you must puzzle your way out of, and figuring them out is always immensely satisfying. There are some trips off the beaten path, but the action here is more akin to that of the original Portal–lots of clever test chambers that present an increasingly difficult challenge. 

Each player can deploy two portals of his or her own, and having twice as many portals allows a new degree of complexity. Again, the difficulty curve is fairly gentle, teaching you the basics before getting down to the tricky stuff. Teamwork is the name of the game, and some puzzles require some coordinated feats of timing. As you journey through the massive Aperture facility, it becomes clear that Portal 2 does not merely come after Portal. Instead, it radiates outward from its predecessor, simultaneously illuminating the world that gave rise to Portal and continuing the adventure that began there.

The sense of novelty is diminished, but the thrill of exploration and puzzle-solving is still intoxicating, and it’s amazing how Portal 2 manages to tell a better story with disembodied voices and spherical robots than most games can with full-on humans. Your return to Aperture Science is a joyful one in this immensely appealing, laugh-out-loud funny, and thoroughly satisfying sequel.