window.addEvent('domready', function() {

      var effect = $('pre').effect('color', {duration: 3400});
      var periodical;
       
      var fx = function() {
	      effect.start('#eeeeee').chain(function() {
		      effect.start('#000000');
	      });
      }
       
      $('start').addEvent('domready', function() {
	      fx();
	      periodical = fx.periodical(4300);
      });
       
      $('stop').addEvent('click', function() {
	      $clear(periodical);
      });
    
});