An actually nice complete experience for a jam game.
I think it was a bit odd to allow players to retry without fixing and refilling the balloon first, I just plummeted immediately. While I didn't encounter this myself, I assume it'd be possible to spend so much money on upgrades that you can't afford to fix/refill and get stuck. And there's no reason anyone WOULDN'T fix/refill before trying again, so why not make it automatic?
The birds blend in with clouds, not sure if that was intentional.
I think more thought could be put into how/where hazards/powerups are spawned. Create a difficulty curve, prevent overlap, etc.
You should get in the habit of not using a red cross as health as the American Red Cross has asked developers not to.
The music was nice but not very fitting. Seemed like boss music, for a game that felt pretty lighthearted.