I think the bat/enemies are too hard to see against the background. I died first try and I thought it was the coin that killed me.
I had to work out how to play this. The icons had me believe it was one touch to jump, hold to jump high. Instead, it's jump and press again to double jump. Even with this, I find the default jump is too large for small gaps. A more controlled jump would help.
Since you can jump using your keyboard, I would like a keyboard shortcut to restart too please.
The music is okay at first but it's too short and becomes grating.
One futher nitpick: The game over image is supposed to be what? It looks like she's bowing as if to say "Sorry I failed you master."