let beer = document.querySelector('.beer');

function spawnBubble() {
  let bubble = document.createElement('span');
  let rand = parseInt(Math.random() * (100 - 0) - 0);
  bubble.classList.add('bubble');
  bubble.classList.add('start');
  bubble.style.left = `${rand}%`;
  let timer = setTimeout(() => {
    beer.appendChild(bubble);
    setTimeout(() => {
      bubble.classList.remove('start');
    }, 50);
    setTimeout(() => {
      bubble.remove();
      clearTimeout(timer);
    }, 5000);
  }, parseInt(Math.random() * 1500));
}

setInterval(() => {
  let rand = parseInt(Math.random() * (10 - -10) - 10);
  beer.style.webkitTransform = "rotate(" + rand + "deg)";
  [...Array(20).keys()].forEach(spawnBubble);
}, 1000);