There is nothing bad to say about this game. Nothing.
The soundtrack is a unique, atmospheric montage of skillfully crafted musical sounds. The gameplay is flawless and exciting, and can be quite the challenge to those who think they've seen all the game has to offer! With an intricate overworld, gorgeous scenery, and riveting gameplay, this is a must-have game for anyone who enjoys platformers or video games in general.
There are hidden spots in every level where you can sit and enjoy the scenery for as long as you like, all while relaxing to the fabulous soundtrack. There are hidden secrets which add to the game's depth as you struggle to find at least one in every level of every one of the four worlds. For an indie game, it does everything right.
The controls are responsive and they will not miss an input unless you put in a dash while you're in the air (as that won't happen on any game anyways). Each level is better than the last, and there's a Tome of Levels for you to visit your favorites if you choose not to run through the overworld to get to it. Please play it with a controller, as keyboard takes getting used to.
All in all, this game is wonderful. For me personally not worth 10 bucks or whatever it goes for, but you can get it every few months in a bundle for a dollar with some other games, so there's always that.