Centering everything – again

Hi everyone. I’m trying to centre the circles. This seems reasonably simple, and I found the thread (this one)from a month or so ago that asked this exact question, which was very helpful.

But, I’m a little stuck because although the circles become centred when the sidebar is closed, when the sidebar is opened up (or open by default) the circles revert back to left. And for the life of me, I can’t figure out which is causing that to happen.

I feel certain that there is one particular line I need to change to margin: auto; , but I feel like I’ve experimentally tried just about all of them.

Any ideas?

Thanks!