var saguaro = document.getElementById("saguaro"),
	glasses = document.getElementById("glasses"),
	saguaroImg = saguaro.getElementsByTagName("img")[0],
	boundingRect = saguaro.getBoundingClientRect(),
   glassesSize = glasses.getBoundingClientRect();

	saguaro.addEventListener( "mousemove", moveGlasses, false);
	saguaro.addEventListener( "touchstart", moveGlasses, false);
	saguaro.addEventListener( "touchmove", moveGlasses, false);

	function moveGlasses(e) {
			glasses.style.left = (e.pageX - boundingRect.left)+"px";
			glasses.style.top = (e.pageY - boundingRect.top)+"px";
		}