That was fun! The mechanics are solid, and the art and soundtrack contribute to the moody atmosphere. The asteroid proximity indicators were very helpful.
My only note on the gameplay is that, although the camera was highly proficient in terms of showing the most relevant area, it did have a lot of fairly distracting shake to it.
Good job on including volume options! That being said, the default volume (maximum) is a tad loud; the audio regularly peaked above 0.0 dB. Consider setting the default Master Volume three or four notches lower. Also, the "menu back" and "enemy destroyed" sounds are a bit louder than the other sounds.
Great work!