A fairly standard strip bar menu, allowing sub menus to cascade either to the left or right.
Decrease the size of the view port, click on the hamburger menu icon to see the main menu. Clicking on those items having children, indicated by the 'plus' icon + allows sub-menus to concertina in, in-line. A further click on the item will close it.
A free standing version of this example is available for download here.