I have been thinking about something like this for a while but never thought seriously on trying it out because of how hard it seemed to make. So I am really happy about seeing an implementation of the Danmaku as boss that is realistic to make.
The patterns aren't particularly well balanced (rotations have made it impossible to hit anything) and I've had a hard time deciding what to choose because the options have little to no explanation (a preview to the right would've been perfect).
The balance of beating the player is also a little broken, you can either accidentally get a horrible combo or beat the player rather quickly because of a good combo (and I kinda don't wanna beat the player when I have a pretty combo).
Something I didn't expect at all was the usage of the Spell-Timer as a countdown when to change your attack without loosing an HP. That is a really nice concept and could probably make for some balancing that could work in a larger release.
I also really like how the game is presented, it's just missing some fancy background elements for the real shmup experience, but otherwise I love the sprites and dialogue. even if they're not much they're great.
The most fun I've had with the game was when I tried out a few combos by just waiting in the corner to farm some points (seemed like the best way to do it) and it allowed for some fun stacking of combi. might revisit the game some other time to let it run in the background for longer so I can make some seriously idiotic combos.
(also for review unimportant crash: the game crashes when you change the window size while the battle is running, the menu resizing works fine though)