What is here is impressive! I like that the balls all have different rules for how to get the most out of them!
It needs some kind of visible incentive to get the player hooked on improving their bounce per second gains. What is here is very functional, and I did enjoy figuring out the different ball rules and strategies for max bounces. But without an "end" goal after the 7th ball is unlocked any optimizing feels a bit pointless. I would consider adding a final goal, and maybe a time summary for how long it took to reach it. That way players want to improve their efficiency and start strategizing around the ball abilities.