JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html>

<html>
  <head>
    <meta charset="utf-8" />
  </head>
  <body>
    <div class="container">
      <div class="box1"></div>
      <div class="box2"></div>
    </div>
  </body>
</html>

CSS

.container {
  border-radius: 50px;
  height: 200px;
  position: relative;
  overflow: hidden;
  width: 500px;
}

.box1 {
  background-color: white;
  height: 100%;
  position: relative;
  width: 100%;
  z-index: 1;
}

.box2 {
  background-color: black;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
}