<div class="container">
  <div id="cloud-intro"></div>
</div>
html, body, .container{
  width: 100%;
  height: 100%;
  min-width: 500px;
  min-height: 500px;
  margin: 0;
  padding: 0;
  overflow: hidden;
}
.container{
  background-color: #007ced;
	background: linear-gradient(to bottom, #007ced 1%,#cce7ff 100%);
}
#cloud-intro{
  position: relative;
  height: 100%;
  background: url(https://static.radulescu.me/examples/clouds/clouds1000.png);
  background: url(https://static.radulescu.me/examples/clouds/clouds1000.png) 0 200px,
              url(https://static.radulescu.me/examples/clouds/clouds1200_1.png) 0 300px,
              url(https://static.radulescu.me/examples/clouds/clouds1000_blur3.png) 100px 250px;
	animation: wind 20s linear infinite;
}
@keyframes wind{
  0% {
    background-position: 0 200px, 0 300px, 100px 250px;
  }
  100% {
    background-position: 1000px 200px, 1200px 300px, 1100px 250px;
  }

}

External CSS

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External JavaScript

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