I love the concept of this, it's pretty insane what you where able to pull off! and Full controller support as well. Few things
1. I think the First Proper boss is a little TOO hard, It was pretty hellish, It took me a bit to figure out how to damage it, and trying to keep track of the small adds, as well as dodge the Way too fast spikes was frustrating, then to be trolled into a Phase 2 when I have no health what so ever was a bit much. So maybe tweaking it down would be a bit better, or swapping it in for a more boss with a bit more ease, that or cut Phase 2 all together.
2. I know Boss 1 is suppose to be a damage sponge to get use to the controls, but giving it an attack or two would help teach the player to dodge and such.
3. This is an absolute Flex, and I love it! Keep it up! Might want to add a Quit option to the Stylish Menu.
That's it, Would love to see this Balanced and expanded upon. Insane you where able to do this in RPG Maker MZ, you guys took that Challenge and ran with it!