Just finished the game, I missed two cristals in the last level, other than that I think I did everything.
It's a very cool experimental game. You find power ups and go exploring a non linear level design form more power ups. It's challenging and forces you to master the game controls. It's clunky, but that's part of mastering it.
I myself have developed a similar game in the past (ikokku bridge to dreamland) and i think you could say it's about "understanding the game rules and solving mechanincal puzzles within it", that means the puzzles are about "how do i make this specific jump?" or "is it better to use this power up now or a couple frames later?" or even "Which parts of the terrain can I use to get higher?" instead of traditional cryptical puzzles.
I recommend it, specially if you want to understand better what makes a game design work. You don't need overcomplicated fighting sistems or fancy graphics, nonthing that the industry makes nowadays. You just need a set of interconected rules and to challenge the player to solve puzzles with those rules. It's a very minimalistic game per say. Yet, a very interesting one.