Nice game, great effort! It's good to see people picking up and exploring the space games like SSR brought to us.
If I'm allowed to nitpick on a couple of things it'd be the chunky pixel art (more detail would have helped a lot in reading the levels and their elements) and the grouping of the levels (having, for example, a block of 9 levels in which aliens are present or mirrors are present would have made the game design look more coherent).
In any case: very nice, thanks for this!
P.S. We got Jonathan Blow to try the game out on stream and we had a small discussion about it, so check it out: https://www.twitch.tv/videos/710688626?t=2h46m1s if you're interested.