I really like your game. The vibe is cute and unique. The audio, visuals and gameplay work really nicely together. Congrats! It's funny to play this kind of fly, upgrade, fly further game, because our game loop is very similar. Nice to see that I really enjoy it here as well. What I love as well is the extremely simple but extremely fun/challenging way of flying with only A and D. This makes the gameplay. If I have to give some improvements I think it starts out a bit slow and there isn't really a challenge to it. I didn't loose any lives and the fun started to amp when I got more speed.
Congrats for making such a nice game!