<div id="debugging_mouse_axis"></div>
<div id="debugging_status"></div>
<div id="sidebar">
<ul id="menu">
<li><a href="#">MENU 1 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 2 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 3 <span> / 2007</span></a></li>
<li><a href="#">MENU 4 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 5 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 6 <span> / 2007</span></a></li>
<li><a href="#">MENU 7 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 8 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 9 <span> / 2007</span></a></li>
<li><a href="#">MENU 10 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 11 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 12 <span> / 2007</span></a></li>
<li><a href="#">MENU 13 <span> / 2007</span></a></li>
<li><a href="#">SUPER LONG MENU MENU MENU MENU SIZE 14 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 15 <span> / 2007</span></a></li>
<li><a href="#">MENU 16 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 17 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 18 <span> / 2007</span></a></li>
<li><a href="#">MENU 19 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 20 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 21 <span> / 2007</span></a></li>
<li><a href="#">MENU 22 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 5 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 23 <span> / 2007</span></a></li>
<li><a href="#">MENU 24 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 25 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 26 <span> / 2007</span></a></li>
<li><a href="#">MENU 27 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 28 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 29 <span> / 2007</span></a></li>
<li><a href="#">MENU 30 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 31 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 32 <span> / 2007</span></a></li>
<li><a href="#">MENU 33 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE 34 <span> / 2007</span></a></li>
<li><a href="#">MENU SIZE LONG 35 <span> / 2007</span></a></li>
</ul>
</div>

body {
padding:0;
margin:0 20px;
}

#sidebar {
height:400px;
overflow:hidden;
position:relative;
background-color:#eee;
} 

#menu {
width:100%;
list-style:none;
padding:0;
margin:0;
top:0;
position:relative;
height:100%;
width:300px;
}

#menu li {
padding:10px 0;
text-align:right;
display:block;
cursor:hand;
cursor:pointer;
}

#menu li a {
background:url() repeat #1f1f1f;

color:#ddd;
font-family:helvetica, arial, verdana;
font-size:9px;
font-weight:900;
display:inline;
padding:20px 8px 5px 20px;
text-decoration:none;
}

#menu li span {
font-family:georgia, arial;
font-size:9px;
color:#464646;
}

$(document).ready(function() {  

  //Background color, mouseover and mouseout
  var colorOver = '#31b8da';
  var colorOut = '#1f1f1f';

  //Padding, mouseover
  var padLeft = '20px';
  var padRight = '20px';
  
  //Default Padding
  var defpadLeft = $('#menu li a').css('paddingLeft');
  var defpadRight = $('#menu li a').css('paddingRight');
    
  //Animate the LI on mouse over, mouse out
  $('#menu li').click(function () { 
    //Make LI clickable
    window.location = $(this).find('a').attr('href');
    
  }).mouseover(function (){
    
    //mouse over LI and look for A element for transition
    $(this).find('a')
    .animate( { paddingLeft: padLeft, paddingRight: padRight}, { queue:false, duration:100 } )
    .animate( { backgroundColor: colorOver }, { queue:false, duration:200 });

  }).mouseout(function () {
  
    //mouse oout LI and look for A element and discard the mouse over transition
    $(this).find('a')
    .animate( { paddingLeft: defpadLeft, paddingRight: defpadRight}, { queue:false, duration:100 } )
    .animate( { backgroundColor: colorOut }, { queue:false, duration:200 });
  }); 
  
  //Scroll the menu on mouse move above the #sidebar layer
  $('#sidebar').mousemove(function(e) {

    //Sidebar Offset, Top value
    var s_top = parseInt($('#sidebar').offset().top);   
    
    //Sidebar Offset, Bottom value
    var s_bottom = parseInt($('#sidebar').height() + s_top);
  
    //Roughly calculate the height of the menu by multiply height of a single LI with the total of LIs
    var mheight = parseInt($('#menu li').height() * $('#menu li').length);
  
    //I used this coordinate and offset values for debuggin
    $('#debugging_mouse_axis').html("X Axis : " + e.pageX + " | Y Axis " + e.pageY);
    $('#debugging_status').html(Math.round(((s_top - e.pageY)/100) * mheight / 2));
      
    //Calculate the top value
    //This equation is not the perfect, but it 's very close  
    var top_value = Math.round(( (s_top - e.pageY) /100) * mheight / 2);
    
    //Animate the #menu by chaging the top value
    $('#menu').animate({top: top_value}, { queue:false, duration:500});
  });

  
});