Nice opening screen!
One of us is an avid Touhou enthusiast so she'll be writing the feedback with that in mind.
I feel the character movement is too fast and don't give the player the precision they need to properly avoid the bullets. The walking side to side was too fast but the jump was especially imprecise and hard to control.
The enemy bullet graphics felt well matched to their hitboxes, the bullets also had nice patterns and good speeds!
A somewhat longer grace period after getting hit would be good, as well as stronger feedback when taking damage. I would also suggest making a short invincibility period after getting hit so that the player can reposition themselves.
On another point consider having the character automatically always shooting, there's no particular reason not to be shooting all the time so right now the player is simply forced to hold down a button to play the game.
Cool main character design and nice audio! The dimension modes felt nice and juicy!