text: const balls = document.getElementsByClassName('ball');
  
  document.onmousemove = (event) => {
    // mouse position relative
    // to screen width and height
    const rx = event.clientX / window.innerWidth;
    const ry = event.clientY / window.innerHeight;
  
    // convert to percentages
    const x = (rx * 100) + '%';
    const y = (ry * 100) + '%';
  
    for (let i = 0; i < balls.length; i++) {
      balls[i].style.left = x;
      balls[i].style.top = y;
      balls[i].transform = 'translate(-' + x + ',-' + y + ')';
    }
  };
  