Fun, for awhile
First of all, this is a nice change of pace from your traditional brick breaker. "Brick Galaxy" didn't leave me with a lot of confidence until the moment I discovered that the bricks were behind me.
Things you did right:
1) The core ludeme of the game is a nice twist on the classic Arkanoid: protect the bricks, break the rest of the stuff.
2) Much of the game has very well-balanced difficulty: It's not hard for the casual gamer to advance, but getting the bonus by having more of your planet left is reserved for the more skilled player.
3) The graphics are pleasantly retro, no matter what the calamity below me said.
4) The music doesn't hurt to listen to.
Things that need improvement:
1) The screen is tiny. There's no reason the screen can't be larger, and every reason it should be. We're not playing on 640x480 screens anymore, and the graphics DO hurt to look at after a while due to eyestrain. For your next project, think about zooming in or making the sprites larger to begin with.
2) The meteors always need to come from the top of the screen. Players need to feel in control; whenever they lose because of something beyond their control, they feel cheated. In this game, having time to react to the meteor is key to play; if you take away that time, it feels cheap. The meteors coming from the side of the screen make it impossible to prevent them from hitting the planet on occasion, and they need to go away.
3) There could stand to be a few more musical tracks, or at least a longer single track. It's not unpleasant, but it would vary it up and make me less likely to hit mute after awhile. Just remember, if The Who came on the radio once, you'd be like "Yeah!" Twice, you'd be like, "Encore!" The seventh time, you'd shut that off. Even good music needs to go away after a while.
Overall good work.