That's a fair question since there's a way to mess up your build. But you need to shrink balls and get them to the bottom. That means you can't just put all your towers in the top row.
Oh, I see. So putting all my shrink rays in top row is not a good idea? Is getting the balls on the bottom how you make money?
I get the idea that you buy weapons and apply those to the balls, but I wasn’t really sure how to make money.