Hi there! Cool game. I like that you can push planets around and the controls are good, responsive. The rotation feels nice, and you can do pretty cool manoeuvres too.
You could add some more effects, like som kinda fire after the rocket, or something like that. When you hit an asteroid, it doesn't really feel like you take damage, so you can add some affects and like the spaceship could flash red or even the entire screen could flash red or something.
I also found a bug where the materials got stuck inside asteroids, and you got to restart because it was impossible to win.
Other than that, good game!