There's one small issue with this:
When you press the sidebar menu and then tap outside it to close it, if you're scrolled down the page it will jump back up to the header.
Unfortunately, this is an issue with the mobile version of sigma-9 and BHL as well. There's not any way around it, as far as I am aware. It is kind of an accepted flaw in the mobile version since there's not really another good way of styling the collapsible sidebar on mobile. As a result, this extends that flaw to the desktop version.
This is a big reason why I made the collapsible sidebar component work via hovering since it avoids this issue. I'd honestly suggest doing the same here. Though I know the hover mechanic is disliked by some. I, personally, find it preferable to the inconvenience caused by this method.
Anyway, it looks good otherwise just wanted to give my input on the above. :]
