[stavros]

Hm what's the problem with that? I understand that the bumper extends down, but what else needs to be on the underside that makes this unbuildable?

[BadBadJellyBean]

I think it's because the bumpers on top (the white things with the blue dot in the middle) need a lot of space underneath and the line runs through the space that they would need.

[stavros]

Hm I understand the bumper part, but what does the line represent? Why does it need to run on the underside?

[jjmarr]

The line represents a physical tunnel through which the ball can travel.

[stavros]

Oh, there's a hole at the top of the line that leads to an underground lane? That makes sense, I couldn't make that out in the photo, thanks.

[toast0]

If you drain to the far left, and kickback is lit, the ball gets sent along the line and comes out the top (and IIRC, refills your fuel?)

[stavros]

Oh that whole thing is a higher level! I see now, I thought that top section is actually a ground section, thanks.