random_circles.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Circles</title>
    <style>
      html {
        width: 100%;
        height: inherit;
      }
      canvas {
        display: block;
      }
      body {
        margin: 0;
      }
      button {
        position: absolute;
        top: 10px;
        left: 10px;
      }
    </style>
  </head>
  <body>

  <button>Redraw</button>

  <canvas></canvas>

    <script>
    const btn = document.querySelector('button');
    const canvas = document.querySelector('canvas');
    const ctx = canvas.getContext('2d');
    let WIDTH = document.documentElement.clientWidth;
    let HEIGHT = document.documentElement.clientHeight;
    canvas.width = WIDTH;
    canvas.height = HEIGHT;
    function random(number) {
      return Math.floor(Math.random()*number);
    }
    function draw() {
      ctx.clearRect(0,0,WIDTH,HEIGHT);
      for(let i = 0; i < 100; i++) {
        ctx.beginPath();
        ctx.fillStyle = 'rgba(255,200,30,0.5)';
        ctx.arc(random(WIDTH), random(HEIGHT), random(50), 0, 2 * Math.PI);
        ctx.fill();
      }
    }
    btn.addEventListener('click',draw);
    </script>
"circles.html" 55L, 1180C     