Wow, what a great concept. I love niche puzzle games, and You def made one.
I would definitely buy this on Steam if it had:
Bumpy music & eye-catching graphics. Not fancy, or anything. An animated background, And making the player look a bit better would go a long way. I do have to say though, both level design, & mechanics are great, Good prototype.
Also one the downsides to such a mechanic is that the player has to also manipulate the physics pretty well. + the game is unforgiving in a way that the player needs to go around the whole map/rotate the whole thing, to try on the physics part again. Which isn't smooth/elegant. One way would be to let player control the speed of the rotation, but that could also destroy level design in some maps possibly, etc.

Make the bullets bigger so the game becomes less about precision, and more about puzzling, as it should be.
Loved the sound effects though
This kind of set of mechanics can become a good niche indie game for sure.