$(document).ready(function() {

    var block = $(".block");

​

    (function() {

        $(document).mousemove(function(event) {

            var X = event.pageX;

            var Y = event.pageY;

            block.css({

                transform: 'translateX(' + (event.pageX / 4) + 'px )', // Not working <-----

                transform: 'translateY(' + (event.pageY / 4) + 'px )',

            });

        });

    })();

​

​

});