Solid work and good use of music themes. The fireball traveling speed is a bit slow, though.
Couple bugs: It is possible to shoot a fireball, and then walk in front of it since the projectile is slower than the player. When you do, you block its movement and make a permanent light source. This is also why sometimes fireballs don't work - collision with the player is enabled so they end up hitting the player as they spawn.
Second, the boss music played over top the normal music. I really liked both themes, but hearing both at the same time was a bit disorienting.