* Use `.active` on nav link to denote current page/state in navigation
* If you have a solid dark color or black background, add `.theme-alt` at the same level as `.side-navigation` to get white navigation links.
* `.side-navigation` begins as `display: none;` at `$vp1` and becomes visible at `$vp3`
* `a.navigation-btn` is visible on `$vp1` and `$vp2` to enable toggling visibility of `.side-navigation`
* Use your own JavaScript to show/hide navigation on `$vp1` and `$vp2`, though you can use ours below as a reference