This is one of my favorite games of all time
If it can be called a game at all. Sure, there are game-elements here (platforming, rudimentary puzzles, achievements, etc.), but these all take a back seat to what this game is really about: the experience.
I won't dedicate more than this paragraph to game mechanics; they're dead simple. Left stick - walk, right stick - view, X to jump, O to "speak" - which serves dually as both communication and environment interaction, and that's basically it. Oh, and your jumping power is reflected by how much of your scarf is lit up - the length of which indicates the maximum amount of jumping power you have available. You power up (lengthen your scarf) by picking up glowing symbols that are hidden around the world. The achievements are rather typical: there's the "find the hidden whoziwat" types, the "do the awesome jiggawhizzle" types and a couple of multiplayer related ones. Not many achievements in total, so achievement addicts will not find their fix in this game.
It's hard to write anything abstract about this game, since the game itself is so abstract. It deals with emotions in a way no game I've ever played ever has.
My first playthrough of the game was right when it had launched. It was a kind of chaotic experience - the game was new to me, but also to everyone else who played. I ran into several different people, but the encounters were short lived as we were all so caught up in exploring this wonderful, beautiful world that we'd been given access to. Much like wide-eyed children in an entirely new sandbox, we were giddy with excitement, running around and playing, not really paying attention to one another. Still, the game's excellent mood shifts managed to penetrate my rush of excitement, and incite feelings of joy, trepidation, fear (!) and sorrow. Yes, sorrow. I've never had any game awaken that degree of sorrow and melancholy in me before. It's intensity was only surpassed by the intense feeling of elation and unbridled happiness shortly following it. Upon completion of my first playthrough, I was left with the hands-down best feeling I've ever had, completing a game.
I picked the game back up again a few months down the road, because I missed the scenery and wanted to experience what I had done on my first playthrough. But things had changed somewhat. The most significant change was how the people I met affected my game. You see, the first time around basically everyone else was on their first playthrough as well, so we were all equals. This time around, some of the people were clearly experienced - there are distinct visual clues that tell you how experienced someone is and I met up with a certain individual that was clearly very experienced. It ended up being almost a parent-child relationship, this individual would show me glyphs I hadn't found previously, new sites and new sounds and basically became a caretaker on our journey together. We played from start to finish together and watching the final sequence with the two of us brought on a slightly different set of emotions than my initial playthrough had done.
Since then, I've played games where I was the experienced one, taking responsibility for my companion, making sure they found all the glyphs and whatnot. I've played games were we were both on equal footing, but still way more experienced than what any of us were the first time around all those months ago.
Every playthrough is different. Each and every one is a journey unto itself, because this game is not about the game at all, it's about the experience - and the experience is in large part shaped by your mood on that particular day and perhaps most of all the people you meet and how you interact. It really is a beautiful game, in the deepest sense of the word.