animation(moon,1,20,200);
function animation(elem,speed,delay,distance) {
var x = 0;
var s = speed * Math.PI / 180;
setInterval(function() {
x += s;
elem.style.left = distance * Math.sin(x) + 'px';
elem.style.top = distance * Math.cos(x) + 'px';
}, delay);
}