$(document).ready(function() {
var movementStrength = 25;
var height = movementStrength / $(window).height();
var width = movementStrength / $(window).width();
	$("#first").mousemove(function(e){
     var pageX = e.pageX - ($(window).width() / 2);
     var pageY = e.pageY - ($(window).height() / 2);
     var newvalueX = width * pageX * -1 - 50;
     var newvalueY = height * pageY * -1 - 50;
     $('#first').css("background-position", newvalueX+"px          " + newvalueY + "px");
});
});