var i = k = 0,
  f = false,
  t = bg_Name = "",
  browser_shit = !(typeof document.createElement("div").style.opacity != 'undefined');
window.onload = function() {
  var bg = document.getElementById('bg'),
      pageX = function() { return (html && html.scrollLeft || body && body.scrollLeft || 0) - (html.clientLeft || 0) },
      pageY = function() { return (html && html.scrollTop || body && body.scrollTop || 0) - (html.clientTop || 0) };
  if( navigator.userAgent.match(/iP[hone|od|ad]/i) ){
    bg.style.backgroundImage = "url(img/ios_main_fon.png)";
    bg.style.transition = "all .2s ease-out";
    window.ondevicemotion = function(event) {
      var w = document.documentElement.offsetWidth/2,
          h = document.documentElement.offsetHeight/2;
      var x = w + ((event.accelerationIncludingGravity.x / 10) * w) - 450,
          y = h + ((event.accelerationIncludingGravity.y / 10) * h) - 450;
      bg.style.backgroundPosition = ""+ x+"px "+y+"px";
    }
  } else {
    function MMove(e) {
      e = e || window.event
      if (e.pageX == null && e.clientX != null ){ 
        var html = document.documentElement
        var body = document.body
        e.pageX = e.clientX + pageX()
        e.pageY = e.clientY + pageY()
      }
      bg.style.backgroundPosition = t = " "+(e.pageX-450)+"px "+(e.pageY-450)+"px";
    }
    if (document.layers) {document.captureEvents(Event.MOUSEMOVE);}
    document.onmousemove=MMove;
  }
  var aObjects = document.getElementsByTagName('a');
  for( var i = 0; i < aObjects.length; i++) {
    aObjects[i].onmouseover = function() { 
      f=true; 
      var a_id = this.getAttribute("id");
      bgOver(a_id);
    }
  }
}

function bgOver(s) {
  f=false;
  i=100; 
  bg_Name = s;
  k=10;
  bgDel_scroll_d();
}
function bgDel() {
  f=false;
  i=100;
  bg_Name = "none";
  k=4;
  bgDel_scroll_d();
}
function bgDel_scroll_d() {
  if (f == false) {
    if(browser_shit) {
      i-=k*2;
      document.getElementById('bg').style.filter = 'alpha(opacity='+i+')';
    } else {
      i-=k;
      document.getElementById('bg').style.opacity = (i/100)
    }
    if (i > 0) setTimeout(bgDel_scroll_d,2);
    else {
      document.getElementById('bg').className=bg_Name; 
      i=0;
      bgDel_scroll_u();
    }
  }
}
function bgDel_scroll_u() { 
  if (f == false) {
    if(browser_shit) {
      i+=10;
      document.getElementById('bg').style.filter = 'alpha(opacity='+i+')';
    }else {
      i+=5;
      document.getElementById('bg').style.opacity = (i/100)
    }
    if ( (i < 100) && (f==false) ) setTimeout(bgDel_scroll_u,2);
    else if (browser_shit) document.getElementById('bg').style.filter = 'alpha(opacity=100)';
    else document.getElementById('bg').style.opacity = "1"
  }
}