I think you shouldn't have put all the controls on the mouse because it ended up feeling kinda weird and combining that with the enemies short reaction times to shoot made the game felt harder than it needed to be. Maybe you could add an option to move with the keyboard.
Ps: Don't know if you remember me but I'm the guy that was talking with you about action games, You seem really knowledgeable in that genre so I would like if you could check out my game and give me advice on how to make it feel better, or perhaps reference some games I should check out and take notes.