That's what I call a great review.
I was aware problem with the bombs not looking like bombs, I have to rework them, definitely. Very cool that you noticed the spins. I didn't really think of stacking the boxes, but now that you mention it, it makes a lot of sense (although it requires some extra working).
The theme could have been boosted by changing the rewind boxes to a time-base rewind instead of order-based, maybe (but that would have taken more effort, of course).
I was thinking of improving replayability by theming the quadrants (the top could have 0 gravity, the bottom could be a hell) but I need to think about it. The flipping-gravity boxes (or even flipping gravity bombs) look like a good idea, thanks for that.
Thank you so much for your thorough review!