The audio and visuals feel very consistent with each other in this game, well done! I also like the variety of enemies, My high score is 5.
Some feedback:
-first play session, I immediately accidentally clicked an upgrade (as I was trying to shoot), so I couldn't read what I picked
-On WebGL, to fix the mouse drag blue overlay visual bug, in the css file set the canvas to user-select:none
-I found the health draining ability a bit too punishing, I preferred to use the normal attack.