So who's the Touhou fan... :D
I've never really played many bullet hell games but this one felt really fun to swing the sun around your player while dodging projectiles. Detaching the sun to become the moon was really rewarding if you could time it to bounce horizontally dealing damage satisfyingly. Perhaps this method may be seen as a bit overpowered and I can see that there is a limit on DPS which is understandable, one thing I might suggest if you were to work on this game more is that allowing the player to pull off lots of damage could keep that satisfaction in place but perhaps to make the game not fly by so easily the "boss" could react to higher DPS with moves more focused on putting the player in tricky dodging situations as they do not have to worry as much about dishing out damage.
The music was also great and I loved the atmosphere of the game!