index.html

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
<head>
  <script src="javascripts/prototype.js" type="text/javascript" charset="utf-8"></script>
  <script src="javascripts/lines.js" type="text/javascript" charset="utf-8"></script>
</head>
<body>

<style type="text/css" media="screen">
  body {background-color:#ccccff;}
  .line {position:absolute;}
</style>


<script type="text/javascript">
  var lines = [];
  var mouseX=0, 
      mouseY=0;
  function mousemove( evt )
  {
  	if( !evt )
  		evt = event

  	mouseX = evt.clientX
  	mouseY = evt.clientY
  }
  document.onmousemove	= mousemove

  function updateLine()
  {
    if(lines.length==0)
    {
      lines[0] = new Line(mouseX,mouseY,mouseX,mouseY);
      return
    }
    
    lastLine = lines[lines.length-1];
    lines[lines.length] = new Line(lastLine.stop()[0],lastLine.stop()[1],mouseX,mouseY);
    
    if(lines.length>10)
    {
      lines[0].destroy();
      lines = lines.without(lines[0])
    }
  }

  setInterval( updateLine, 25)
  
</script>
</body>
</html>