(function() {

    var mX, mY, distance,
        $distance = $('#distance span'),
        $element  = $('#element');

    function calculateDistance(elem, mouseX, mouseY) {
        return Math.floor(Math.sqrt(Math.pow(mouseX - (elem.offset().left+(elem.width()/2)), 2) + Math.pow(mouseY - (elem.offset().top+(elem.height()/2)), 2)));
    }

    $(document).mousemove(function(e) {
        mX = e.pageX;
        mY = e.pageY;
        distance = calculateDistance($element, mX, mY);
        $distance.text(distance);
    });

})();