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                <div id="container">
	<svg id="svg" xmlns="" xmlns:xlink="">
<!-- 	FF throws an error if I try to get the bbox of an element inside of a symbol -->
<!-- 		<symbol id="Source"> -->
<!-- 			<image id="image" xlink:href="" x="0" y="0" height="2448" width="3264"/> -->
<!-- 		</symbol> -->
		<mask id="mask">
			<g id="grid"></g>

		<g mask="url(#mask)">
			<image id="image" xlink:href="" x="0" y="0" height="2448" width="3264"/>
<!-- 			<use x="0" y="0" xlink:href="#Source" /> -->



                html, body {
	background: hsla(240, 0%, 80%, 1);
	min-height: 100vh;

body {
	display: flex;
	align-items: center;
	justify-content: center;

#container {
	width: 80%;
	background: hsla(240, 0%, 70%, 1);
	box-shadow: 0px 0px 3px 3px hsla(240, 0%, 60%, 0.8);
/* 	visibility: hidden; */

svg {
	width: 100%;
	height: 100%;
	fill: white;



                // wait until DOM is ready
document.addEventListener("DOMContentLoaded", function(event) {

// wait until window, stylesheets, images, links, and other media assets are loaded
window.onload = function() {

 // All ready, start!



// We manipulate a few of the DOM elements via JavaScript in order to minimise the amount of editing that would otherwise have to be done to the DOM elements every time the ratio/size of the image is altered

// TODO add a resize event

function init() {

	// Get the image size
	var img = document.querySelector("#image").getBBox();
	// Update the <symbol> tag's viewbox based on the image size
	// document.getElementById("Source").setAttribute("viewBox", "0 0 " + img.width + " " + img.height);

	// Calculate the ratio of the image
	var ratio = calculateRatio(img.width, img.height);

	// Get the main SVG tag
	var svg = document.getElementById("svg");
	svg.setAttribute("viewBox", "0 0 " + img.width + " " + img.height);

	var container = document.getElementById("container");

	// Update its height to match the image ratio = updateHeight(container.offsetWidth, ratio) +"px";

	// Calculate the aspect ratio of the image.
	function calculateRatio(w,h) {
		return Math.max(w,h) / Math.min(w,h);

	// Return an updated height based on  width/ratio
	function updateHeight(width, ratio) {
		return Math.round(width / ratio);

	// Create X squares of a size along a grid the size of the image
	var squares = {
		ttlHorz: 10,
		ttlVert: 10,
	var squareSize = calculateSquareSize(img.width, squares.ttlHorz);
	// Originally, I had it up so that the user would only had to set the size of the square but, because we are now setting the viewBox on the whole SVG, this no longer works as designed and has been replaced with the above
	// var squareSize = 20;
	// var squares = {
	// 	ttlHorz: squaresPerLength(svg.getBBox().width, squareSize),
	// 	ttlVert: squaresPerLength(svg.getBBox().height, squareSize),
	// }
	// function squaresPerLength(width, size) {
	// 	return width / size;
	// }

	function calculateSquareSize(totalWidth, numOfSquares) {
		return totalWidth / numOfSquares;

	var g = document.getElementById("grid");
	var arr = [];

	// Loop thru the total squares and create the grid
	for(var i = 0; i < squares.ttlHorz; i++) {
		for(var j = 0; j < squares.ttlVert; j++) {
		var square = document.createElementNS("", "rect");
		square.setAttribute("width", squareSize);
		square.setAttribute("height", squareSize);
		square.setAttribute("x", i * squareSize);
		square.setAttribute("y", j * squareSize);


	function shuffle(array) {
			var currentIndex = array.length, temporaryValue, randomIndex;

			// While there remain elements to shuffle...
			while (0 !== currentIndex) {

					// Pick a remaining element...
					randomIndex = Math.floor(Math.random() * currentIndex);
					currentIndex -= 1;

					// And swap it with the current element.
					temporaryValue = array[currentIndex];
					array[currentIndex] = array[randomIndex];
					array[randomIndex] = temporaryValue;

			return array;

	function randomIntFromInterval(min,max)
					return Math.floor(Math.random()*(max-min+1)+min);

	var newArr = shuffle(arr)

	// Animate the squares
	TweenMax.staggerTo(newArr, 1.5, {
			x:function() {
				// Firefox does not seem to animate elements inside of a mask
				return randomIntFromInterval(-100,100);
			y:function() {
				// Firefox does not seem to animate elements inside of a mask
				return randomIntFromInterval(-100,100);
	});, 0.3, {autoAlpha:1});