My highscore was 8900 before I decided to quit. I found it hard to move around the planet and aim at asteroids, and ended up spam shooting most of the time to get rid of most far out asteroids, all while trying to aim for the ones that actually got close to the planet. I'm glad the ship is invulnerable to asteroids, which gives a bit more time to react and hit. Artwise, the planet and asteroids designs are really good. There's a lot of fine details on the planet, nice colours and a bit of humour in that the cities are monstrously huge in relation to that tiny planet - or so it seems.

Couple more nitpicks:

- Some details in the "space" area could be used. Maybe some white dots of differing sizes to give a "starry" look, thus evoking more of the idea that this takes place in space.
- I'm not really a huge fan of the sounds - the shooting sounds are much louder than the sound of asteroids getting destroyed, which gets quite annoying after playing for a while. Maybe something more Sine wave or Tom sounding could be more suitable. The asteroid sound effect is a bit clicky and could use some more punch, but it wasn't as prevalent of an irritant.
- A button to restart directly into the game rather than bringing the player to the menu screen would elevate this game's replayability a lot, especially since the only other option on the menu is to quit, which you give as an option on the Game Over screen anyway.

Overall, it's an all right, workable game with some nice graphics. You also nailed the theme pretty well too.

Nice little game! I included it in my Ludum Dare 38 compilation video series, if you’d like to take a look :)
https://www.youtube.com/watch?v=JSWOUTubUBM