Interesting idea! I have to admit at first I was confused by whether bouncing the rocks up to the planet would lose me points until I realised that was just a visualisation of the planet's health under the health bar.
I think it might be cool to try a Pong like bouncing movement where the repulsor's movement adds some direction to the rocks. If you also allow rocks to collide with each other I think you could be onto a full game. If you can hit 2 rocks into each other you gain 3 points (1 per rock and 1 bonus for the stylish dispatching of them) and perhaps they could break into smaller pieces which also need reflecting OR destroy even more rocks further increasing the score multiplier.
You would probably need more rocks to keep the challenge up.