I eventually understood what was going on, I think. Every time I put the ball in the hole, I score a point (also a ball), that also counts for the bridge. However, you can pay with these points for extra balls and/or multiplier bonus, by pressing the cubes. So you build the bridge faster, but you pay parts of the bridge to increase the speed of building.
It took me a bit to figure out what was going on, but I just pressed all buttons and ran around. That could need some improvement I think. I also don't know the details and the numbers, which were unclear (why are there three boxes?).
However, as far as incrementals go, there might be something here. I would still just give one ball each time, since multiple balls just make it harder to gain points, as they bounce off each other. And then make different courses, items, power-ups, automatic-golf-paddles, etc.

