(function ($)
{

	// Public: jScroll Plugin
	$.fn.jScroll = function (options)
	{

		var opts = $.extend({}, $.fn.jScroll.defaults, options);

		return this.each(function ()
		{
			var $element = $(this);
			var $window = $(window);
			var locator = new location($element);

			$window.scroll(function ()
			{
				$element
					.stop()
					.animate(locator.getMargin($window), opts.speed);
			});
		});

		// Private 
		function location($element)
		{
			this.min = $element.offset().top;
			this.originalMargin = parseInt($element.css("margin-top"), 10) || 0;

			this.getMargin = function ($window)
			{
				var max = $element.parent().height() - $element.outerHeight();
				var margin = this.originalMargin;

				if ($window.scrollTop() >= this.min)
					margin = margin + opts.top + $window.scrollTop() - this.min;

				if (margin > max)
					margin = max;

				return ({ "marginTop": margin + 'px' });
			}
		}

	};

	// Public: Default values
	$.fn.jScroll.defaults = {
		speed: "slow",
		top: 10
	};

})(jQuery);