Did couple of playthroughs, unlocked 6 skins, the best run had me at 750 kills, ran into boss the second time. Overall pretty decent swing at the genre, I played worse shovelware shumps on Steam (not that I recommend to put it out), no bugs or weird beahavior. Boss had a decent laser weapon and missiles, latter could be telegraphed better as I barely noticed them closing in to my plane.
Regarding balance, enemies stay on the playfield too long and waves come too often, we're being swarmed with enemies within seconds and usually we have to navigate pretty thin lane and do small jumps to areas full with enemies just to make it a little wider. There's also problem with planes looking same-y. Only with my continous replays I was starting to notice the differences between the aircrafts. In my first run I saw a big plane and a small plane, differences aren't popping out at the first glance so I'd recommend changing the colors of different planes.
Bomb attacks are weird, the way it's presented it feels like we're dropping it on the ground (and it's pretty slow) but it somehow damages planes? Also more than once the clouds were obscuring my view, it hampers manuveuring. Explosions were meh, and you have to know, explosions are very important.
For me - bigger planes, easier to destroy, waves that come and go, enemies that aren't staying too long on the screen, different colors for enemies, different weapons (you probably wanna say that this plane didn't have spread shot, but it should have, at least in games), proper level end and more levels.