This is impressive !
I really like how you perfectly nailed down the arcade feel, be it gameplay wise, or in the music and menu sounds.
The action is really good and keeps the pace up without reaching frustrating levels of insanity, which is awesome, the effects and explosions are really good, not to mention the plane models :o i really like their designs in general, with that realistic plausible look, but whacky alternate reality type of designs.
I like the giant version of the flying pancake plane as a boss XD
My only real issue playing this is about gameplay readability, the spark effect on player shots i feel is a bit too much and can obscure enemy fire, and enemy bullets are sometimes a bit bright and don't contrast all that well with the backgrounds at times.
But other than that it's quite a great bit of fun to play, with solid elements already there, this would be awesome as a full version with more content.
Congrats, especially since you did this solo, and Good job :)