I'm not really crazy about shmups, especially the unessicary difficulty of 90s ones. But i get thats exactly what you're going for soo...
It annoys me that I have to toggle my move speed, I'm used to a "focus" button. Maybe that could be an option
I dislike how continuing doesnt give you a max powerup, or you limit continues like you are actually trying to rob me of quarters. Its fine having a steep difficulty curve but you don't have to stomp on the dicks of those trying to gain a mastery of the system.
I hate how you can die on terrain and it moves in certain sections
Some of the patterns seem impossible to dodge and require a burst to get by. Especially ones with tracking shots if you don't know they're coming. Seems like bad design to me.
The art, sound and general style is all on point though, keep it up and clean up your timelines.