Based on an idea stolen from StartBootstrap.
All original features were preserved:
- off canvas, full height, vertical menu
- responsive design
...and also added:
- expand/collapse buttons
- auto-collapse menu for 'small' screens (when click a link in menu)
- no horizontal scrollbar when the menu is manually expanded
- sticky header
All in pure HTML, CSS, JS (no JQuery dependency).
For simplicyty, I've putted together all parts (HTML, CSS, JS) in the
index.html file so that you can access them via 'View Source' in live demo.