function randOrdArray(){
  return (Math.round(Math.random())-0.5); 
} 
window.addEvent('domready',function() {
  /* preloading */
  var imagesDir = base + 'images/stories/galerie/slideshow/';
  var images = ['slide1.jpg','slide2.jpg','slide3.jpg','slide4.jpg','slide5.jpg','slide6.jpg','slide7.jpg','slide8.jpg'];
  var holder = $('slideshow-holder');
  images.sort( randOrdArray );
  images.each(function(img,i){ images[i] = imagesDir + '' + img; }); //add dir to images
  var progressTemplate = 'Loading image {x} of ' + images.length;
  var updateProgress = function(num) {
    progress.set('text',progressTemplate.replace('{x}',num));
  };
  var progress = $('progress');
  updateProgress('text','0');
  var loader = new Asset.images(images, {
    onProgress: function(c,index) {
      updateProgress('text',index + 1);
    },
    onComplete: function() {
      var slides = [];
      /* put images into page */
      images.each(function(im) {
        slides.push(new Element('img',{
          src:im,
          width: 569,
          height: 335,
          styles: {
            opacity:0,
            top:0,
            left:0,
            position:'absolute',
            'z-index': 10
          }
        }).inject(holder));
      });
      var showInterval = 5000;
      var index = 0;
      progress.set('text','Načítám obrázky.');
      (function() {slides[index].tween('opacity',1); }).delay(1000);
      var start = function() {
        (function() {
          holder.setStyle('background','');
          slides[index].fade(0);
          ++index;
          index = (slides[index] ? index : 0);
          slides[index].fade(1);
        }).periodical(showInterval);
      };

      /* start the show */
      start();
    }
  });
});