This has great promise but it was too difficult for me to enjoy. Some of my thoughts:
Good:
Great fundamental mechanics. Cancelling enemy bullets is a simple mechanic that I think builds well into the bullet hell genre and allows for a unique variant of strategy that does not swing into the touhou-style of hardcore bullet hell.
Simple to play, simple to understand and also, the special attack is so satisfying to use.
Very classic bullet hell with loads of enemies and LOADS of bullets to boot!
To improve:
I have a few pointers but I think the most important one is the accesibility of the game. While I did previously make note of being excited at trying this out (and I was!), the difficulty did put me off way much more than I liked.
Granted, I'm not a dedicated bullet hell player (I've only won Touhou games at the Easy difficulty at best), so do take this with a grain of salt.
It is clear to me that you've developed this with a particular audience in mind, so that's good. But I believe the casual difficulty, even with the checkpoint systems, still makes the difficulty curve too steep to properly enjoy and players may become too frustrated before they get into the groove and start enjoying the game.