<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Canvas Bubble Animation</title>
</head>
<body>
  <canvas>
    
  </canvas>
</body>
</html>
body {
  margin: 0;
  padding: 0;
}

canvas {
  width: 100%;
  height: 100%;
}
var canvas = document.querySelector('canvas');

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

var canvasContext = canvas.getContext('2d');

function Circle (x, y, dx, dy, radius, color) {
  this.x = x;
  this.y = y;
  this.dx = dx;
  this.dy = dy;
  this.radius = radius;
  this.color = color;
  
  this.draw = function () {
    canvasContext.beginPath();
    canvasContext.arc(this.x, this.y, this.radius, 0, 2*Math.PI, false);
    canvasContext.lineWidth = 2;
    canvasContext.strokeStyle = this.color;
    canvasContext.stroke();
  }
  
  this.update = function () {
    if (this.x + this.radius > innerWidth || this.x - this.radius < 0) {
    this.dx = -this.dx;
  }
  
  if (this.y + this.radius > innerHeight || this.y - this.radius < 0) {
    this.dy = -this.dy;
  }
  
   this.x+=this.dx;
   this.y+=this.dy;
    
   this.draw();
  }
}

var colorPalette = ["#e55039", "#78e08f", "#f6b93b", "#60a3bc", "#A3CB38", "#B53471", "#EE5A24", "#12CBC4"];
var circleArray = [];

for (var i = 0; i < 20; i++) {
  var x = Math.random()*(innerWidth-200)+100;
  var y = Math.random()*(innerHeight-200)+100;
  var radius =60;
  var dx = (Math.random() - 0.5) * 8;
  var dy = (Math.random() - 0.5) * 8;
  var color = colorPalette[Math.round(Math.random()*(colorPalette.length-1))];
  
  circleArray.push(new Circle(x, y, dx, dy, radius, color));
}

function animate() {
  requestAnimationFrame(animate);
  
  canvasContext.clearRect(0, 0, innerWidth, innerHeight);
  
  for (var i = 0; i < circleArray.length; i++) {
    circleArray[i].update();
  }
 
  
}

animate();

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.