An Absolutely Fantastic Experience.
If you're a PC player who uses Steam, then it was incredibly hard to miss all the excitement around the Potato Sack and ARG Valve came up with to promote this game. Over the course of weeks players found hidden clues in other games, digging around in various related files and all that. But we're not here to talk about Valve, let's talk Portal 2.
Portal 2, as the name would imply, takes place a long time after the events of Portal 1. You once again are controlling Chell, the human test subject from the first game, as she tries to escape this facility and finally find her way out. This time she's accompanied by Wheatley, an AI core who was assigned to watch over the human subjects. He's planning to escape this facility along with you, and while I'm trying to avoid spoilers here, I'll take the safe way around and just say that things might not go as originally intended.
You'll need to put on your thinking cap in order to guide Chell safely through various tests laid out before her. You'll see a lot more of the Aperture Science facility other then just the test chambers like in the original, you'll explore the very depths of the facility while learning more about Aperture Science itself, and why exactly it went under and has been abandoned like it has. This all culminates in an ending that I felt very happy and satisfied with. Seriously, that was flipping good.
Portal 2 is a richer experience then its original with a bunch of new mechanics involved in the puzzles such as the Propulsion Gel, which makes you run faster, and the Repulsion Gel which bounces you upwards. All of the mechanics combined can create some very tricky puzzles to solve, and with the promise of the Source Developer Kit for Portal 2 coming soon there's no doubt that there will be a bunch of user-created content to enjoy.
Now after you're done with the single player part of the game, you can go over to the co-operative part. A whole new set of levels designed for 2 players which I really like because the puzzles allow me to be an evil bastard and get my bro-op partner killed a bunch of times. But the parts where you're actually solving the harder puzzles together and experimenting to get out, combined with the collective "EUREKA!" moments have to be some of my favorite parts of Portal 2.
Portal 2 is an amazing game, it looks fantastic on the PC, the atmosphere and tone is set perfectly and the characters are just great and well-written. It's probably been a while since I actually cared so much about nearly every character in a game, and Portal 2 did just that: It made me care about the story and I wanted to see the ending of it all.
I myself have clocked in about 12 hours on Portal 2 with the single player and around 2/3rd of the co-op complete, and I can think of a few games with less content then that at the same price. In short I can ONLY recommend getting Portal 2 as soon as you have some spare money lying around. It's something I almost find hard to accurately describe, you have to experience it yourself.