Another way to do it, is using the Bullet Behavior on your Balls. I know that sounds painful... Hear me out.
Set "Bounce off Solids" to enabled in the "Bullet Behavior" properties, and adjust the "Speed", "Acceleration", and "Gravity" in the same properties window to adjust how fast they will fall & how high they will bounce.
If you are spawning fresh smaller balls after the big one gets taken out, like in the game you linked to. You could adjust the properties for those as well, if you want them to bounce differently, compared to the larger balls.
At least this is the easiest way I've found to handle my balls. Always... be gentle.
EDIT: Spelling Erroirs, Grammar, and added more text