It is a really cool game.
I finished it and I liked how you implemented the mechanics all along the new levels.
There was some issue however that hampered the gameplay and found it frustrating.
I think you arealdy know it, but it's the grace period at the edge of any platform before jumping.
The hitbox of your character is very small, you don't know if it's on the first leg or second leg where you can jump. But I often had to jump while my whole body was on the platform because if I had 1 or 2 pixel at the edge, my character will fall.
This is very frustrating unfortunately and several times I wanted to stop playing. But the game itself made me go to the end :)
Despite this little issue, I enjoyed the artistic side of it, the gameplay mechanics with balloons (it's pretty fun), and the challenge.
Well done.