Credits page, cool!
I just reached the shop and found another bug. Before the shop appears there is a ~1s window for the player to take another shot. If the player begins taking aim and the shop appears, then after the shop is closed the ball is automatically shot. If you buy an item then the ball is shot not where you were aiming previously but in the direction of the purchased item.
Have you thought about using different shapes for enemies. Maybe a boss that is a square, minions that are triangles. Maybe even an enemy that's too big to be scored and you need to do something to score it(a giant circle with a small weak spot which when hit reduces size, it could be a boss fight where you need to hit that weak spot multiple times).
Here's another idea, Maybe you can also have shields enemies with tiny shields which face you when your ball is still. Forcing you to make a bounce shot.