Cool game ^^ First I had issues because I clicked on the full screen button and that destroyed the tutorial (no messages appeared) probably because of my ultrawide screen resolution.
Then I read your instructions and it was much more clearer! I don't know if the upgrades you could get were random or not, but you could have a cool roguelike idea there.
One thing though, at first it wasn't really clear to me that the other planes had to be in the whole circle to be able to attack them, first I tried to keep them in the outer ring (because it is so wide that it made sense) and it was nearly impossible to manage them lol. So maybe just having a circle around the player or making the one you have a lot thinner would be a good change.
Nice idea for the theme as well, so all in all good job :D