I like the idea, it makes good use of the theme as you both "scale" the balloon and the tower. You may also say that the tower itself was "built to scale". Good puzzle design and art. I think I would change the controls a bit, for example you could make the balloon inflate when you hold [Space] and deflate when you don't. As for the rest I would do a bit more standard keybinds like [Q] to drop and [E] to use. Apart from that this is a good entry for the jam.