I never played anything with similar mechanics so I think is very original.
I found the game a bit difficult. I think that the game would be much more fun if when you died you could restart from the same level. In that way players could adjust the angle as they want. Otherwise, getting the exact direction you want is very hard and you have to retry the whole game multiple times just because you failed one shot.
Question (Curiosity): Did you used the gravitational law or just applied an acceleration with constant magnitude when the object is in the area? (I feel like shooting one time makes the body get affected too much by the gravity of the planets but others it does nothing)