Pretty cool idea, I think with a bit more work it could be a really nice idle-like clicker game.
A fairly quick change I would make if you plan to work on it any more would be making it more clear what equipment/amour the player has crafted, as at the moment it is quite hard to tell.
I thought the goal was pretty clear and intuitive, and the movement mechanism is hilarious! An automatic reset if the player or ball fall down the pit in level 3 would be nice, along with a chair-reset hotkey as someone else suggested.
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.
