This game is amazing, i am glad that i scrolled all the way down to the bottom of submissions to find it. It's just cool, and with a bit of polish it would be very solid indie-game. Music, graphics, gameplay, everything is spot on.
That's being said, there is two things i would like to see changed in a full game:
– Physics. I had a-lot of damage done to the ship not because of enemies, but because i got inside of the wall and was getting damage until i flew out of it. I think there should be some sort of collision system, preventing you from getting inside the walls (Balloon seems to have it). Ship movement feels a little clunky, but this is a good thing, i felt like i was operating a real balloon.
– Overall speed of the game. Prologue and first 3 chapters felt very slow, and whole tutorial could have been packed in one level. But when bullets start flying, game became much more interesting, so i propose a shorter prologue.