I think it would be one of my favourites in the jam, gameplay-wise, if it was a little less clunky. The controls feel sticky for the lack of a better word, it's trivially easy to stun-lock the basic enemy and the hitbox on the boss is entirely broken. It also started to feel repetitive, though just as I was getting that feeling a few new enemies and a trick with the geometry freshened things up a lot. I liked those tricks and I wished they came just a little bit earlier. I really do like the 2.5D aspect, it adds more to the gameplay than I initially thought it would.
I like the art style a lot. The mix of simple 2D and simple 3D actually looks really nice. The effects are primitive, too, but they work. However I did notice some glitching on the edges of the player character, and occasionally the camera would end up in a tree. I liked the music, too, but the sound effects started to become grating.
I actually really like the storyline, too, and I wish it was in the game itself. Was this never planned or did you just run out of time?
Overall I had a lot of fun with this and I'd like to see more adventures of Magical Girl Star Sparkle.