A lot of other comments here mentioned some of the feedback I was planning to, so I won't go into them too much.
For gravity flipping, having hazards that completely cover one side could be a way to incentivize the flip. Alternatively, requiring the player to collect items that are mid air
Having indication of where attacks are coming from a little before they show would be helpful as well. The first time I was killed by arrows from the bottom, I instantly died since I was on top of them, so I didn't even see the arrow until I retried and then figured out that's what had happened. Same thing happened with the ball a few times near the corner of the screen.
The soundtrack was very nice.
Also, that's a lot of cookies ◉_◉