Unfinished
Of the forty levels only the last four or so were actually interesting.
Ideally a game level is simplistic when you are introducing a new concept, ability or challenge so the player can beat/use it, recognise how it's done and then apply that knowledge in an increasingly difficult environment.
In this game we learn the basics in the first three levels quite quickly. Then there's nothing but padding. No new abilities, no new challenges, just cookie cutter samey-feeling levels up until the last four or so. There is nothing other than the basics to play with.
Good music, nice aesthetic, easy interface. What you need now is either more gameplay ideas or more level ideas. Preferably both.