Very cool! I got to fireball status. I like the idea of permanent upgrades with the wave-style game.
One thing I will say is that the health system was very confusing to me. I thought the health bar in the top was mine, but it kept going down, and I would die in one hit anyways despite constant upgrades.
Also, I would recommend to wait to give the controls for shield and fireball until after the player unlocks those. Giving those controls at the very beginning and the player not having them can seem confusing.
Awesome game!