/**
 * Zachary Johnson
 * http://www.zachstronaut.com
 * I place the following code in the public domain.
 */
 
var text = null;
var spot = null;
var box = null;
var boxProperty = '';
 
init();
 
function init() {
    text = document.getElementById('tsb-text');
    spot = document.getElementById('tsb-spot');
    box = document.getElementById('tsb-box');
    
    if (typeof box.style.webkitBoxShadow == 'string') {
        boxProperty = 'webkitBoxShadow';
    } else if (typeof box.style.MozBoxShadow == 'string') {
        boxProperty = 'MozBoxShadow';
    } else if (typeof box.style.boxShadow == 'string') {
        boxProperty = 'boxShadow';
    }
 
    if (text && spot && box) {
        document.getElementById('text-shadow-box').onmousemove = onMouseMove;
        document.getElementById('text-shadow-box').ontouchmove = function (e) {e.preventDefault(); e.stopPropagation(); onMouseMove({clientX: e.touches[0].clientX, clientY: e.touches[0].clientY});};
    }
    
    onMouseMove({clientX: Math.floor(window.innerWidth / 2), clientY: Math.floor(window.innerHeight / 2.75)});
}
 
function onMouseMove(e) {
    var xm = (e.clientX - Math.floor(window.innerWidth / 2)) * 0.4;
    var ym = (e.clientY - Math.floor(window.innerHeight / 3)) * 0.4;
    var d = Math.round(Math.sqrt(xm*xm + ym*ym) / 5);
    text.style.textShadow = -xm + 'px ' + -ym + 'px ' + (d + 10) + 'px black';
    
    if (boxProperty) {
        box.style[boxProperty] = '0 ' + -ym + 'px ' + (d + 30) + 'px black';
    }
    
    xm = e.clientX - window.innerWidth;
    ym = e.clientY - window.innerHeight;
    spot.style.backgroundPosition = xm + 'px ' + ym + 'px';
}