function $(e){return document.getElementById(e);}
function animate() {
  var elt = $("header");
  var pos = elt.offsetTop,
      newPos = Math.floor(pos*3/4);

  elt.style.marginTop = newPos+"px";
  if (newPos>0) {
    setTimeout(animate, 50);
  } else {
    $("page").style.display="block";
    document.cookie = "visited=true";
  }
}
function init() {
  var doIntro = document.cookie.indexOf("visited=true")==-1;

  if (doIntro) {
    $("header").style.marginTop = Math.round(document.body.clientHeight/2-22.5)+"px";
    $("page").style.display="none";
    setTimeout(animate, 2000);
  }
}