I really liked the hints and different end cards, they looked great.
The gameplay was pretty good, and the rank-system kept making me want to keep playing and get the higher ranks.
Given it's a bullet-hell-like, it is pretty tough to get higher than a C. I think the combat system needed some kind of longer "grace-period", for only half a second-ish, to activate when the player gets hit so that the player has a fighting chance if they end up in a crowd of trash.
The different weapons types and pick-ups are also really nice, although the single fire gun seemed a bit underpowered compared to the shotgun fire.