I really like the background art and the visual effects, but I felt the character art was slightly off-style to them in some way, I have to admit though I can't pinpoint exactly how.
The spinning mechanic to block and heal is a nice idea and controls for it feel really good, but often times I didn't have to move at all if I timed it right and got the boss in a corner. Maybe there's a way to encourage using more movement to win the fight, the dashing-like attack of the second boss was a good example for that.
Biggest plus point is definately the visual effects, those are gorgeous!