This is very dull...
As a SHMUP, the particular gameplay is incredibly mundane. And is overall too simple. The enemies are boring, and the gameplay is incredibly repetitive. Something you must consider in making a game is that GAMEPLAY is king. This would have served much better as a movie, given your skills in that arena of drawing and I can most certainly see this as something like that.
Your art is very good; it is without a doubt the best part about this entire submission and I do applaud you for putting a lot of effort into the effects as well as the backgrounds. But reusing the same background for every level, compounded by a single shot mechanism for holding it down, bullets are really too slow and too easy to dodge. I only played through two levels and I had enough.
If you are ever to make a second part to this game, or a remastered version; I would suggest this:
Give it a story to follow, maybe a few cutscenes dealing with that.
Scenery change is definitely a good thing. People get bored of looking at the same thing over and over. There are definitely infinite ways you can go abou this.
Same goes with the enemies, have a few different kinds of bosses, each with varying abilities and bullet patterns. This is a SHMUP, they are MEANT to be hair-tearing hard. Just remember, you can make bullet paths beautiful and deadly too.
Have different kinds of weapons, I would suggest three basic spells, and the longer you would charge it, the stronger it becomes. Like... Fire, Lightning, and Ice. Very basic. Maybe like... 3 charge levels by how long she chants the spell.