I will say that I rushed the music, expect for the credits song. The credits song was something I made before this for something not related to gamedev while I made the other tracks in a very short amount of time. I'll read up more on good melodies to use for future music.
I think having two keys for fireballs would be a great idea. Maybe a key to shoot the fireballs in the direction of the cursor and fireballs stop when not holding down a key. Maybe having something for HP to allow for multiple hits for the player and enemies outside of the boss would work well. I have to consider a bunch of things if I do make a sequel to this.
Thanks for the feedback.