How do you make a reasonable tablet mode, was my first question.

That sidebar takes up part of the page, but if you scroll past it, you're also losing all the hyperlinks.
So, solution to always have access to hyperlinks was:

• as you're scrolling down the "graph/referrals" the nav links stick to the top of the page.
• when you get close to the bottom of the sidebar, a top menu appears with the same nav links. The whole top menu sticks to the top.

Otherwise, all fairly standard.