Thank you so much for the feedback! As for the difficulty scaling, yeah, that was my biggest worry. I playtest my games a BUNCH and that leads to me being really really good at them, but that also means I accidentally make them wayyy harder than they need to be.
As for the health bar and darkness - that's actually just particles! I made a circle sprite and used it as a texture, and set the scale curve so they scale in quickly and scale out slowly. I used the same particle material for both of them, except for the health bar I made the colors a little random!