var refreshDuration = 50000;
var refreshTimeout;
var numPointsX;
var numPointsY;
var unitWidth;
var unitHeight;
var points;

function onLoad()
{
var svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
svg.setAttribute('width',window.innerWidth);
svg.setAttribute('height',window.innerHeight);
//document.querySelector('#bg').appendChild(svg);

var unitSize = (window.innerWidth+window.innerHeight)/20;
numPointsX = Math.ceil(window.innerWidth/unitSize)+1;
numPointsY = Math.ceil(window.innerHeight/unitSize)+1;
unitWidth = Math.ceil(window.innerWidth/(numPointsX-1));
unitHeight = Math.ceil(window.innerHeight/(numPointsY-1));

points = [];

for(var y = 0; y < numPointsY; y++) {
for(var x = 0; x < numPointsX; x++) {
points.push({x:unitWidth*x, y:unitHeight*y, originX:unitWidth*x, originY:unitHeight*y});
}
}

randomize();

for(var i = 0; i < points.length; i++) {
if(points[i].originX != unitWidth*(numPointsX-1) && points[i].originY != unitHeight*(numPointsY-1)) {
var topLeftX = points[i].x;
var topLeftY = points[i].y;
var topRightX = points[i+1].x;
var topRightY = points[i+1].y;
var bottomLeftX = points[i+numPointsX].x;
var bottomLeftY = points[i+numPointsX].y;
var bottomRightX = points[i+numPointsX+1].x;
var bottomRightY = points[i+numPointsX+1].y;

var rando = Math.floor(Math.random()*2);

for(var n = 0; n < 2; n++) {
var polygon = document.createElementNS(svg.namespaceURI, 'polygon');

if(rando==0) {
if(n==0) {
polygon.point1 = i;
polygon.point2 = i+numPointsX;
polygon.point3 = i+numPointsX+1;
polygon.setAttribute('points',topLeftX+','+topLeftY+' '+bottomLeftX+','+bottomLeftY+' '+bottomRightX+','+bottomRightY);
} else if(n==1) {
polygon.point1 = i;
polygon.point2 = i+1;
polygon.point3 = i+numPointsX+1;
polygon.setAttribute('points',topLeftX+','+topLeftY+' '+topRightX+','+topRightY+' '+bottomRightX+','+bottomRightY);
}
} else if(rando==1) {
if(n==0) {
polygon.point1 = i;
polygon.point2 = i+numPointsX;
polygon.point3 = i+1;
polygon.setAttribute('points',topLeftX+','+topLeftY+' '+bottomLeftX+','+bottomLeftY+' '+topRightX+','+topRightY);
} else if(n==1) {
polygon.point1 = i+numPointsX;
polygon.point2 = i+1;
polygon.point3 = i+numPointsX+1;
polygon.setAttribute('points',bottomLeftX+','+bottomLeftY+' '+topRightX+','+topRightY+' '+bottomRightX+','+bottomRightY);
}
}
polygon.setAttribute('fill','rgba(0,0,0,'+(Math.random()/25)+')');
var animate = document.createElementNS('http://www.w3.org/2000/svg','animate');
animate.setAttribute('fill','freeze');
animate.setAttribute('attributeName','points');
animate.setAttribute('dur',refreshDuration+'ms');
animate.setAttribute('calcMode','linear');
polygon.appendChild(animate);
svg.appendChild(polygon);
}
}
}

//refresh();

}

function randomize() {
for(var i = 0; i < points.length; i++) {
if(points[i].originX != 0 && points[i].originX != unitWidth*(numPointsX-1)) {
points[i].x = points[i].originX + Math.random()*unitWidth-unitWidth/2;
}
if(points[i].originY != 0 && points[i].originY != unitHeight*(numPointsY-1)) {
points[i].y = points[i].originY + Math.random()*unitHeight-unitHeight/2;
}
}
}

function refresh() {
    randomize();
    for(var i = 0; i < document.querySelector('#bg svg').childNodes.length; i++) {
	var polygon = document.querySelector('#bg svg').childNodes[i];
        var animate = polygon.childNodes[0];
        if(animate.getAttribute('to')) {
	    animate.setAttribute('from',animate.getAttribute('to'));
	}
        animate.setAttribute('to',points[polygon.point1].x+','+points[polygon.point1].y+' '+points[polygon.point2].x+','+points[polygon.point2].y+' '+points[polygon.point3].x+','+points[polygon.point3].y);
	animate.beginElement();
    }
    refreshTimeout = setTimeout(function() {refresh();}, refreshDuration);
}

function onResize() {
document.querySelector('#bg svg').remove();
clearTimeout(refreshTimeout);
onLoad();
}

window.onload = onLoad;
window.onresize = onResize;