Simple scroll logic - just detects if page has scrolled from the top

gistfile1.js

/* 
 *  Scroll Logic
 */

var active = false;
var lastElement, nextElement;
window.addEventListener( 'scroll', onScroll, false)

function onScroll( event ) {

  top = ( doc && doc.scrollTop  || body && body.scrollTop  || 0 );

	if ( active === false && (top.scrollY > 0 || top > 0) ) {

		header.className = 'fixed-title active';
		active = true;

	} else if ( top.scrollY === 0 || top ===0 ) {
		active = false;
		header.className = 'fixed-title';
	}
}