function SetTower() {
    var t = document.getElementById('tower');
    var screenwidth = (window.innerWidth) ? window.innerWidth : document.body.clientWidth + 2;
    var left = (screenwidth - 771) / 2 + 751;

    t.style.visibility = 'visible';
    t.style.left = left + 'px';

    t.style.top = "312";
}

function positionBox() {
    var obj = document.getElementById("tower");
    if (parseInt(document.body.scrollTop) > 297) {
        if (obj) {
            if (document.documentElement && document.documentElement.scrollTop)
                obj.style.top = parseInt(document.documentElement.scrollTop) + 0 + "px";
            else if (document.body)
                obj.style.top = parseInt(document.body.scrollTop) + 0 + "px";
        }
    }
    else {
        obj.style.top = "312px";
    }
}