This is a lot of fun! I'm a big fan of games with floaty space movement like asteroids, lunar lander, etc., I think it works really well here and adds to the difficulty in a good way. I think the acceleration could be increased a bit, and the knockback decreased a bit but otherwise I really enjoyed it! I like the detail of being able to damage earth yourself though it felt a little unfair when enemy ships wound up ontop of the earth (though they thankfully don't seem to stay there too long which is nice).
Also love the simple design of your main menu conveying the controls, it makes it very easy to understand at a glance and jump right in!