Interesting idea! The game's art looks great, the movement feels smooth, and I really like the upgrade system.
I do have a few comments that might help, though.
I saw on the game's page that the tutorial was intentionally removed from the demo, but I definitely missed having one. I was a bit confused at first and only understood how everything worked after reading the controls and information on the game page.
I also think it could be helpful to have some kind of wave or level indicator so players know how far they've progressed.
The main mechanic of protecting the character while moving around the circle is interesting, but having the shots come from the center instead of from the player felt a bit confusing to me. It was difficult to aim in one direction while moving the character in another. Maybe it's something that becomes more natural with time, but it felt unintuitive during my first playthrough.
Also, I don't think the options menu is working yet. I tried lowering the volume and changing some other settings, but nothing seemed to happen.
Overall, I think the game has a lot of potential. Nice work!