JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrap">
  <div id="content">
    <div id="nav"></div>
    <div id="popup"> </div>
  </div>
</div>

CSS

#wrap {
  width: 400px;
  height: 300px;
  background-color: #eee;
  position: relative;
}
#content {
  width: 100%;
  height: 100%;
  background-color: #111;
  z-index: 4;
}
#nav {
  position: absolute;
  top: 10px;
  left: 10px;
  width: 100px;
  height: 100px;
  background-color: #ddd;
  z-index: 5;
}
#popup {
  position: absolute;
  top: 25px;
  left: 50px;
  width: 10px;
  height: 300px;
  background-color: #0ff;
  z-index: 6;
}