Hi and thanks for your feedback!
I'm planning on working on this project for a while, and I'll change a lot of things (on top of my list, there are smaller changes that you listed, SFX, animations and better art) Right now this actually is VS lite, however I want to keep the upgrade system different from VS (it'll be closer to Hades/Death must die).
As for the idea with black image, you're absolutely right! In post-jam version, I'll add it into the game.
Thanks for your long feedback, it gave me lot of ideas. I'm looking forward to your next projects.
~Enit