Thanks for playing! The character floats because he is a winged angel. I do think I should have lowered the scaling on the easy bosses for sure. Maybe you had trouble on the next bosses because you didn't buy items in between the fights? The bosses scale to get stronger the higher round you get because you can buy seals, blessings, and pacts which can increase your stats dramatically. The better you do against a boss, the more money you get (if you win without taking damage, kill it under 60 seconds, etc). The seals are the main upgrade and they spin around the player oftentimes giving stats or shooting out projectiles on rotation.
Another spin element is the stage and shop which are currently both purely aesthetic but in the future obstacles that fall from the sky will adhere the spinning ceiling that way it is less random as it is now.