Event.observe(window, 'load', function() {

  var fx1 = 0.0;
  var fx2 = 0.25;
  var t = 0.5;


  /* ZAMEK */
  
  if( $('zamek-url')!=null ) {

    Element.setOpacity('zamek-url', fx1);
    
    Event.observe('zamek-url', 'mouseover', function() {
      new Effect.Opacity('zamek-url', {duration:t, from:fx1, to:fx2});
    });
  
    Event.observe('zamek-url', 'mouseout', function() {
      new Effect.Opacity('zamek-url', {duration:t, from:fx2, to:fx1});
    });

  }  

  /* RATUSZ */
    
  if( $('ratusz-url')!=null ) {

    Element.setOpacity('ratusz-url', fx1);
    
    Event.observe('ratusz-url', 'mouseover', function() {
      new Effect.Opacity('ratusz-url', {duration:t, from:fx1, to:fx2});
    });
    
    Event.observe('ratusz-url', 'mouseout', function() {
      new Effect.Opacity('ratusz-url', {duration:t, from:fx2, to:fx1});
    });

  }
  
  /* TOWER */

  if( $('tower-url')!=null ) {

    Element.setOpacity('tower-url', fx1);
  
    Event.observe('tower-url', 'mouseover', function() {
      new Effect.Opacity('tower-url', {duration:t, from:fx1, to:fx2});
    });
  
    Event.observe('tower-url', 'mouseout', function() {
      new Effect.Opacity('tower-url', {duration:t, from:fx2, to:fx1});
    });

  }
  
  /* EIFFEL */

  if( $('eiffel-url')!=null ) {

    Element.setOpacity('eiffel-url', fx1);
  
    Event.observe('eiffel-url', 'mouseover', function() {
      new Effect.Opacity('eiffel-url', {duration:t, from:fx1, to:fx2});
    });
  
    Event.observe('eiffel-url', 'mouseout', function() {
      new Effect.Opacity('eiffel-url', {duration:t, from:fx2, to:fx1});
    });

  }

});