Very creative entry! Really good ideas! Could use improvements gameplay wise, though.
The flute adds a really unique flair to the game ,and gives each level a distinctive melody which fits it's overall vibe. Well done on that!
The actual gameplay was hit or miss imo. There was no clear objective, rather just play around with the different levels and move on. The levels themselves aren't all that clear on what to do. The cloud level, for example, didn't do a good job distinguishing which clouds are which, other than small lightning effects. The space level could be 'cheesed' entirely simply by holding down the fire button and strafing slightly. The flying level had a similar issue, where i was able to fly all the way to the top without actually moving horizontally, as i had clipped through the tree.
Regarding the previous paragraph, a lot more playtesting should've went in to the game to ensure that the levels are fair, fun and bug-proof. The game has a lot of potential, but it needs a goal, and more well thought out levels, like the water level.