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HTML 

              
                <canvas id="canvas"></canvas>
<div id="note" class="note">Click to shuffle</div>
!

CSS 

              
                html,
body {
  margin: 0;
  overflow: hidden;
  font-family: Arial;
  cursor: pointer;
  background-color: black;
}

.note {
  position: absolute;
  color: white;
  right: 20px;
  bottom: 20px;
  margin: auto;
  text-align: center;
  user-select: none;
  font-family: Arial;
  opacity: .2
}
!

JS 

              
                var canvas  = document.getElementById('canvas');
	ctx = canvas.getContext('2d'),
	WIDTH = 0,
	HEIGHT = 0,
	worms = [];

var c1 = 43,
	c1S = 1,
	c2 = 205,
	c2S = 1,
	c3 = 255,
	c3S = 1,
	colorspeed1, colorspeed2, colorspeed3,
	maxColor1, maxColor2, maxColor3,
	minColor1, minColor2, minColor3,
	iteration = 0,
	maxIteration = 9999,
	baseGCO,
	resetAlpha = 0,
	symmetryType;

function initVariables(){
	population = Math.floor(Math.random()*150)+30;
	colorspeed1 = Math.random()*2;
	colorspeed2 = Math.random()*2;
	colorspeed3 = Math.random()*2;
	maxColor1 = Math.floor(Math.random()*100)+155;
	maxColor2 = Math.floor(Math.random()*100)+155;
	maxColor3 = Math.floor(Math.random()*100)+155;
	minColor1 = Math.floor(Math.random()*100);
	minColor2 = Math.floor(Math.random()*100);
	minColor3 = Math.floor(Math.random()*100);
	symmetryType = 2//Math.floor(Math.random()*3);
}

initVariables();

function Worm(id, x, y) {
	this.id = id;
	this.x = x;
	this.y = y;
	this.r = Math.floor(Math.random()*8)+3;
    this.radiusReductionSpeed = (Math.ceil(Math.random()*5)+4) / 1000;
	this.breathingDir = 1;
	this.speed = Math.floor(Math.random()*10)/10;
	this.direction = Math.floor(Math.random()*360);
	this.stepCounter = 0;
	this.changeDirectionFrequency   = getRandomInt(1,200);
	this.turner                     = getRandomInt(0,1) == 0 ? -1 : 1;
	this.turnerAmp                  = getRandomInt(1,2);
    this.a = Math.random()/2;
	this.color = "rgba("+c1+","+c2+","+c3+", "+this.a+")";
    this.style = Math.random() > .5 ? "fill" : "stroke";
    this.isAlive = true;
    if (symmetryType == 0) this.isSymmetrical = false;
    else if (symmetryType == 1) this.isSymmetrical = Math.random() > .5 ? true: false;
    else if (symmetryType == 2) this.isSymmetrical = true;
}

Worm.prototype.move = function() {
	var next_x = this.x + Math.cos(degToRad(this.direction))*this.speed,
        next_y = this.y + Math.sin(degToRad(this.direction))*this.speed;

    // Limites du canvas
    if (next_x >= (WIDTH - this.r)) {
        maxIteration = iteration;
        next_x = WIDTH - this.r;
        this.direction = getRandomInt(90,270,this.direction);
    }
    else if (next_x <= this.r) {
        maxIteration = iteration;
        next_x = this.r;
        var except = [90,270];
        this.direction = getRandomInt(0,360,except);
    }
    if (next_y >= (HEIGHT - this.r)) {
        maxIteration = iteration;
        next_y = HEIGHT - this.r;
        this.direction = getRandomInt(180,360,this.direction);
    }
    else if (next_y <= this.r) {
        maxIteration = iteration;
        next_y = this.r;
        this.direction = getRandomInt(0,180,this.direction);
    }

    this.x = next_x;
    this.y = next_y;

    this.stepCounter++;

    if (this.changeDirectionFrequency && this.stepCounter == this.changeDirectionFrequency ) {
        this.turner *= -1;
        this.turnerAmp = getRandomInt(1,2);
        this.stepCounter = 0;
        this.changeDirectionFrequency = getRandomInt(1,200);
    }

    this.direction+=this.turner*this.turnerAmp;

    this.r -= this.radiusReductionSpeed;
    if (this.r <= 0) {
        this.r = 0;
        this.isAlive = false;
    }
	this.draw();
};

Worm.prototype.draw = function() {

	ctx.beginPath();
	ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
    if (this.style == "fill") {
	   ctx.fillStyle = this.color;
	   ctx.fill();
    } else {
        ctx.strokeStyle = this.color;
        ctx.stroke();
    }
	ctx.closePath();
	this.color = "rgba("+c1+","+c2+","+c3+","+this.a+")";

    if (this.isSymmetrical) {
        var distFromCenter_X = Math.abs(WIDTH/2 - this.x);
        distFromCenter_X *= this.x >= WIDTH/2 ? -1 : 1;

        var distFromCenter_Y = Math.abs(HEIGHT/2 -this.y);
        distFromCenter_Y *= this.y >= HEIGHT/2 ? -1 : 1;

        ctx.beginPath();
        ctx.arc(WIDTH/2 + distFromCenter_X, HEIGHT/2 + distFromCenter_Y, this.r, 0, 2 * Math.PI, false);
        if (this.style == "fill") {
           ctx.fillStyle = this.color;
           ctx.fill();
        } else {
            ctx.strokeStyle = this.color;
            ctx.stroke();
        }
        ctx.closePath();
        this.color = "rgba("+c1+","+c2+","+c3+","+this.a+")";
    }
};

setCanvasSize();

function setCanvasSize() {
	WIDTH = document.documentElement.clientWidth,
    HEIGHT = document.documentElement.clientHeight;                      

	canvas.setAttribute("width", WIDTH);
	canvas.setAttribute("height", HEIGHT);
}

window.onresize = setCanvasSize;

function init(){
	defineGCO();
	for (var i = 0; i < population; i++) {
		worms[i] = new Worm(i, WIDTH/2, HEIGHT/2);
	}
	animate();
}

function defineGCO() {
	var gco = Math.random();
	if (gco <= 1) ctx.globalCompositeOperation = "screen";
	if (gco <= .25) ctx.globalCompositeOperation = "luminosity";
	baseGCO = ctx.globalCompositeOperation;
	console.log(ctx.globalCompositeOperation);
}

init();

function animate() {
	iteration++;
	requestAnimationFrame(animate);

	var allAreDead = true;
	for (var i in worms) {
		if (worms[i].isAlive) {
			worms[i].move(); 
			allAreDead = false;
		}
	}
	if (allAreDead && maxIteration == 9999) maxIteration = iteration;

	if (iteration >= maxIteration) {
		ctx.globalCompositeOperation = "source-over";
		ctx.fillStyle = "rgba(0,0,0,"+resetAlpha+")";
		resetAlpha+=.01;
		ctx.fillRect(0,0,WIDTH,HEIGHT);		
		ctx.globalCompositeOperation = baseGCO;
	}
	if (resetAlpha > 1.2) {
		reset();
		return;	
	}

	changeColor();
	
}

function reset() {
	ctx.clearRect(0,0,WIDTH,HEIGHT);
	resetAlpha = 0;
	defineGCO();
	iteration = 0;
	maxIteration = 9999;
	for (var i = 0; i < population; i++) {
		delete worms[i];
	}
	worms = [];
	initVariables();

	for (var i = 0; i < population; i++) {
		worms[i] = new Worm(i, WIDTH/2, HEIGHT/2);
	}

}

function getRandomInt(min, max, except) {
    var i = Math.floor(Math.random() * (max - min + 1)) + min;
    if (typeof except == "undefined") return i;
    else if (typeof except == 'number' && i == except) return getRandomInt(min, max, except);
    else if (typeof except == "object" && (i >= except[0] && i <= except[1])) return getRandomInt(min, max, except);
    else return i;
}

function degToRad(deg) {
	return deg * (Math.PI / 180);
}

function changeColor(){
	if (c1 <= 0 || c1 >= maxColor1) {
	 	c1S *= -1;
		if (c1 > maxColor1) c1 = maxColor1;
		if (c1 < minColor1) c1 = minColor1;
	}
	if (c2 <= minColor2 || c2 >= maxColor2) {
		c2S *= -1;
		if (c2 > maxColor2) c2 = maxColor2;
		if (c2 < minColor2) c2 = minColor2;
	}
	if (c3 <= 0 || c3 >= maxColor3) {
		c3S *= -1;
		if (c3 > maxColor3) c3 = maxColor3;
		if (c3 < minColor3) c3 = minColor3;
	}
	c1 += Math.floor(colorspeed1 * c1S);
	c2 += Math.floor(colorspeed2 * c2S);
	c3 += Math.floor(colorspeed3 * c3S);
}

document.addEventListener("click", function (e) {
	document.getElementById('note').style.display = "none";
	maxIteration = iteration;
});
!
999px

Console