This was fun, and the visuals are gorgeous! The gameplay is simple enough to get hold of, and it is really unique.
I did hit a point where I realized you could camp out in the screen corner to get the enemies to clump, then take them all out before they could spread their positions. This made clearing the levels super easy and somewhat stagnated gameplay, since it didn't matter how many enemies you threw in at that point (up until the boss). If you continue to develop, maybe put something in to discourage this, maybe certain enemies deliberately hang back as opposed to coming up close, or perhaps some limitation on the invulnerability.
Either way, doesn't take away from the fact that for a game jam version, this is great! Well done