By far, my very favorite game, even though I'm not a fan of indie games in general.
This game is really charming as hell, you start off around some neat hills map where you get to know what this game is about: building. Building up, left, right, down, DOESN'T MATTER. The graphics looks really cute, even though, minimalistic, the sound, the sound is a ♥♥♥♥ing masterpiece, the very best original soundtrack I've heard in my life, every track if filled up with emotions, the author of these (Kyle Gabler) did a great job.
The physics of this game is yet another thing. This is A THING. As you're supposed to build in this game, the main role physics does play. It is just plain immaculate, you won't get disappointed. Yeah, for kids who haven't studied it yet it might be pretty difficult, but if you got some knowledge in that, you can beat it. But, again, you'll have to think.
The whole story looks pretty simple at first: balls sucked by a pipe, wow. But the deeper you dig in the game, the greater the actual plot is, it is full of allegories, metaphors and what not. In the end, it reflects our reality, which is 2D Boy's major feature - a simple childish game with deep sense. No spoilers, of course.
This game makes you think. This game makes you feel. This game lets you be creative. This game is awesome. In my opinion, everyone should play it at least once.