Good game! It feels more like a platformer than a boss rush, but I think it still fits the category in its own way. The roulette mechanic is very interesting and original. I feel like the combat could be improved, maybe a bit more attack range. Another important detail is the invincibility time after taking damage; I think it should last a bit longer. Sometimes, if an enemy hits you while being very close, you don’t have time to react, and you die even if you have full health.
P.S. I imagine you’re using GM’s Glow filter. This filter is quite heavy, though I guess people with more modern PCs won’t notice it. My computer isn’t very powerful, so in the areas where you use the effect, the game runs extremely slow. Everything in the menu and the opening story runs at like 4 FPS. I’m just mentioning this so you can consider it in the future if you want your game to be playable for all kinds of audiences. There are much more optimized shaders for this effect that you can download, or you could make your own.
Either way, great game!