This is one of my favourites so far! I love rhythm games and this one felt really satisfying with really good music that fit a rhythm game perfectly!
It also is a great addition to have the red enemies which take two hits, and the rocks too, as then the game engages you for longer and you still have to pay attention.
My only issues are that I couldn't really tell how close an enemy had to be to hit them, maybe a line to show that, like the line on the bottom of the fretboard on guitar hero, would be a nice addition (or maybe i had to hit them when they lined up with the arrows? idk),
and because your eyes are focused on the enemies, you often dont notice when you lose health, maybe something like the screen flashing red or shaking could add more indication to that.
Well done with this game and good luck!!