Playability:
Got a score of 1140 on my first run and didn't understand what the unique game mechanic was until I bled an enemy ship through. Absolutely awesome use of the background on this and entirely unexpected.
Theme:
Fits the theme well and directly ties it to gameplay in a compelling way. Good work.
Cleverness:
Incredibly clever use of the Earth in the background. Would love to see this game expanded to more planets or more enemy types.
Artistic Style:
Consistent and simple art style. Good overall.