As already mentioned, the graphics and control feel good. However, you should remove the driving reverse part because rockets usually can't do that ;) And maybe using a force-based control would feel more realistic than using velocity-based control.
Appart from adding music to your game, I would change three things:
- The background to give the player a better understanding of his movement direction and speed.
- The spawning of the asteroids. I guess you spawn on a random position in your area. After you calculated your new spawn position, check the distance to the player (spawnPostion - playerPosition).magnitude and if this value is too low, calculate a new value. This way it is impossible that an asteroid spawns inside the player (which is super annoying).
- Increase the play area when the player growth. That way you will always have enough room to spawn asteroids ;)
However, good idea for a game.
I would really appreciate it if you play and rate my game too.