parallax.js

jQuery(document).ready(function(){

	jQuery(window).on('scroll', function(){
		var scrollTop = jQuery(window).scrollTop();
		var windowHeight = jQuery(window).height();
		var windowAxis = scrollTop + (windowHeight / 2);

		jQuery('[data-bubble]').each(function(){
			var height = jQuery(this).height();
			var top = jQuery(this).offset().top;
			var axis = top + ( height / 2);
			var ratio = parseFloat(jQuery(this).attr('data-ratio'));
			var calculus = (windowAxis - axis) * ratio;
			jQuery(this).css('transform', 'translateY(' + parseInt(calculus) + 'px)');
		});
	});
});