A CodePen by JenniKate Wallace. CSS nav auto resize to off canvas - Nav that uses JS to detect width of screen
 - if screen wide enough nav shows horizontally with hover over for submenu
 - otherwise nav collapses to the offcanvas nav and submenu shows/hides on click of global menu item

When off canvas nav is shown JS is used to detect the height of the nav container & page container and auto resize them so background colors are consistent & so nav is always fully visable.