<div id="balloon-container">
</div>

body {
  margin: 0;
}

#balloon-container {
  height: 100vh;
  padding: 1em;
  box-sizing: border-box;
  display: flex;
  flex-wrap: wrap;
  overflow: hidden;
  transition: opacity 500ms;
}

.balloon {
  height: 125px;
  width: 105px;
  border-radius: 75% 75% 70% 70%;
  position: relative;
}

.balloon:before {
  content: "";
  height: 75px;
  width: 1px;
  padding: 1px;
  background-color: #FDFD96;
  display: block;
  position: absolute;
  top: 125px;
  left: 0;
  right: 0;
  margin: auto;
}

.balloon:after {
    content: "▲";
    text-align: center;
    display: block;
    position: absolute;
    color: inherit;
    top: 120px;
    left: 0;
    right: 0;
    margin: auto;
}

@keyframes float {
  from {transform: translateY(100vh);
  opacity: 1;}
  to {transform: translateY(-300vh);
  opacity: 0;}
}

const balloonContainer = document.getElementById("balloon-container");

function random(num) {
  return Math.floor(Math.random() * num);
}

function getRandomStyles() {
  var r = random(255);
  var g = random(255);
  var b = random(255);
  var mt = random(200);
  var ml = random(50);
  var dur = random(5) + 5;
  return `
  background-color: rgba(${r},${g},${b},0.7);
  color: rgba(${r},${g},${b},0.7); 
  box-shadow: inset -7px -3px 10px rgba(${r - 10},${g - 10},${b - 10},0.7);
  margin: ${mt}px 0 0 ${ml}px;
  animation: float ${dur}s ease-in infinite
  `;
}

function createBalloons(num) {
  for (var i = num; i > 0; i--) {
    var balloon = document.createElement("div");
    balloon.className = "balloon";
    balloon.style.cssText = getRandomStyles();
    balloonContainer.append(balloon);
  }
}

function removeBalloons() {
  balloonContainer.style.opacity = 0;
  setTimeout(() => {
    balloonContainer.remove()
  }, 500)
}

window.addEventListener("load", () => {
  createBalloons(30)
});

window.addEventListener("click", () => {
  removeBalloons();
});