JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<body>
<div class="container">
  <div class="sun">
  </div>
</div>
</body>
</html>

CSS

body {
  background: #8DBECC;
}

.container {
  position: relative;
  height: 100%;
  width: 100%;
}

.sun {
  position: absolute;
  width: 30px;
  height: 200px;
  animation: x-motion 3s ease-in-out 0s infinite alternate;
 
}

.sun:before {
  content: '';
  width: 30px;
  height: 30px;
  position: absolute;
  top: 100%;
  background: #F18C3E;
  animation: y-motion 3s ease-in-out 0s infinite alternate;
  border-radius: 15px;
}

@keyframes x-motion {
  0% {
    left: 0;
  }
  
  100% {
    left: calc(100% - 30px);
  }
}

@keyframes y-motion {
  0%, 100% {
    top: 100%;
  }
  
  50% {
    top: 0%;
  }
}