kangaroo - loop?

Hello,

I created this very simple definition with gh+kangaroo. Rectangles are moving with diffrent speed and in diffrent directions. What I am trying to achieve is:

when each rectangle's centroind reaches "boundary" curve it reverses rectangles vector direction. So basically when rectangle reaches a curve it turns back.

I am stuck here. I THINK that this is a loop case. I have absolutely no experience in using these. I watched a video about hoopsnake basics and tried to achieve what i wanted to with no positive results.

I ask you to help me with this one - It would be great if you could give me a tip how to get this result.

I attach rhino and gh files.

Thank you in advance,

Wujo