<div class="container">
  <div class="shadow-animation"></div>
  <div class="fireworks"></div>
</div>

.shadow-animation {
  transform: skew(20deg);
  font-size: 10px;
  height: 5em;
  width: 5em;
  background-color: #f9cb30;
  color: #333;
  animation: animationExample 1s ease 0s infinite alternate both;
  margin-bottom: 15em;
}

@keyframes animationExample {
  0% {
    box-shadow: 0 0 0 0 currentColor, 0 0 0 0 currentColor;
  }

  25% {
    box-shadow: 0 0 0 0 currentColor, 0 0 0 0 currentColor;
  }

  50% {
    box-shadow: 10em 0 0 0 currentColor, 10em 0 0 0 currentColor;
  }

  75% {
    box-shadow: 10em 10em 0 0 currentColor, 10em 0 0 0 currentColor;
  }

  100% {
    box-shadow: 10em 10em 0 0 currentColor, 10em 0 0 0 currentColor;
  }
}

.fireworks {
  font-size: 5px;
  margin-top: 50px;
  margin-right: 20em;
  border-radius: 50%;
  height: 1em;
  width: 1em;
  color: #333;
  animation: explodeCircles 1s ease 0s infinite normal both;
}

@keyframes explodeCircles {
  80% {
    box-shadow: 20em 0 0 1em currentColor, -20em 0 0 1em currentColor,
      0 20em 0 1em currentColor, 0 -20em 0 1em currentColor,
      -14.14em -14.14em 0 1em currentColor, -14.14em 14.14em 0 1em currentColor,
      14.14em -14.14em 0 1em currentColor, 14.14em 14.14em 0 1em currentColor;
  }

  100% {
    box-shadow: 30em 0 0 -1em currentColor, -30em 0 0 -1em currentColor,
      0 30em 0 -1em currentColor, 0 -30em 0 -1em currentColor,
      -21.215em -21.215em 0 -1em currentColor,
      -21.215em 21.215em 0 -1em currentColor,
      21.215em -21.215em 0 -1em currentColor,
      21.215em 21.215em 0 -1em currentColor;
  }
}


.container {
  display: flex;
  justify-content: space-between;
  padding: 100px 0 0;
  width: 90%;
  margin: 30px auto;
  max-width: 500px;
}