Overall I really liked your game, the graphics are simple but soulful.
The theme is very well respected, I however did not feel any horror vibe despite the skulls and other horror designs (maybe because of the music which was a bit repetitive?).
Also maybe you could add some contrast between the background and the monster as they were difficult to tell apart. And put the dragon a bit more to the left, as the constellations are difficult to reach if we see them too late.
I encountered a few freezes, but otherwise, your game is very smooth.
Congratulations!