This is a neat and polished game.
The biggest issue is that unless you maximize the window, the upgrade bar might not show up, which makes it easy to miss out on the mechanic entirely. It might be fixable by messing with the viewport settings in itch.io
Balance wise, bounciness seems like the most dangerous upgrade. I was able to get to the point where all upgrades were fully maxed out without upgrading bounciness once without much trouble. Once I got that first bounce, I was almost immediately deleted.
Good work.