// Create a self-invoking anonymous function. That way, 
// we're free to use the jQuery dollar symbol anywhere within.
(function($) {

// We name our plugin "newscroll". When creating our function, 
// we'll allow the user to pass in a couple of parameters.
$.fn.newsScroll = function(options) {

	// For each item in the wrapped set, perform the following. 
	return this.each(function() {	
	  
		var
			// Caches this - or the ul widget(s) that was passed in.
			//  Saves time and improves performance.
			$this = $(this), 
		  
			// If the user doesn't pass in parameters, we'll use this object. 
			defaults = {
				speed: 400, // How quickly should the items scroll?
				delay: 3000, // How long a rest between transitions?
				list_item_height: $this.children('li').outerHeight() // How tall is each list item? If this parameter isn't passed in, jQuery will grab it.
			},
			
			// Create a new object that merges the defaults and the 
			// user's "options".  The latter takes precedence.
			settings = $.extend({}, defaults, options);
		 
		// This sets an interval that will be called continuously.
		setInterval(function() {
			// Get the very first list item in the wrapped set.
			$this.children('li:first')
	  	    		// Animate it
	  	    		.animate({ 
						marginTop : '-' + settings.list_item_height, // Shift this first item upwards.
						opacity: 'hide' }, // Fade the li out.
						// Over the course of however long is 
						// passed in. (settings.speed)
						settings.speed, 
						// When complete, run a callback function.
						function() {
							// Get that first list item again. 
							$this.children('li:first')
							.appendTo($this) // Move it the very bottom of the ul.
							// Reset its margin top back to 0. Otherwise, 
							// it will still contain the negative value that we set earlier.
							.css('marginTop', 0) 
							.fadeIn(300); // Fade in back in.
						}
					); // end animate
		}, settings.delay); // end setInterval
	});
}

})(jQuery);