Really neat and adorable prototype!
Even in such a short demo, I could definitely see the work that went into the assets. The sprites and animation for the main character were lovely, and the bright tileset coupled with the sky backdrop made for a truly heavenly atmosphere. The music was fittingly peaceful and soothing as well.
The controls and combat seemed to work quite well, although more sound feedback would definitely be nice. The transformation was also a cool feature, though lasting only 5 seconds felt a bit short. I could definitely see it working as some kind of a buff that you build over time, for example by attacking enemies, to finally unleash it during a boss fight! And then maybe you could even prolong it by attacking continuously and avoiding damage.
I actually wish the game didn't kick you out for finding 3 full stars, as there was more to explore in the level and I ended up restarting a few times just to see everything. I really hope you make a full game in the future!