I like the bullet density - considering the slower pace of gameplay, the amount of bullets is very appropriate, and the game definitely feels very much like Touhou in the sense of "Dodging finesse > Reaction times".
Although, I believe the enemies and the boss could use some nerfing of their HP level - they feel very high, and I honestly felt a bit frustrated at the first boss fight due to how long it takes to hit him into the other phases, thus I sadly didn't finish it. Although to be fair, the lack of audio and sfx was the main contributor to this, to me personally it just doesn't feel the same to turn on a theme in the background instead of listening to what's in the game, even if it's just a nice royalty-free track, along with some basic sounds, it'd help me immerse myself into the game and enjoy it more.
Visually, the switch between yellowy and blueish lighting felt too abrupt, and for me it made it harder to look at the bullets. I've also experienced a bug in which the background would also tear at times.
Still, I'm sure that with some more work and tuning you'd end up with a neat touhou-like game!