It's challenging and I had some "aha" moments, which makes me to love this puzzle game! And let's me think of birdsnake and jelly no puzzle (which was recently recommend to me).
Though, it feels like some levels where not at the right position in the game. I know this is might be subjective but, some levels which where easy came after some more challenging ones. Also some few levels are a bit repetitive. I mean levels in later game, which don't add some new idea, understanding or view of the mechanics to the game.
But, besides that it's great!