JSFiddle - React, Tailwind, and code Playground

HTML

<body>
  <div id="view-port">
    <div id="top-toolbar"></div>
    <div id="contents">
        <div id="fullscreen"></div>
    </div>
    <div id="bottom-toolbar"></div>
  </div>
  
</body>

CSS

body{
  position: absolute;
  top:0;
  bottom:0;
  left:0;
  right:0;
  width:100%;
  height:100%;
  border:0;
  margin:0;
}
#view-port {
  position:relative;
  width:100%;
  height:100%;
  background: green;
}
#top-toolbar {
  top: 0;
  background: orange;
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 10%;
}

#contents {
  top: 3em;
  background: brown;
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 80%;
  display: block;
  transform: translate3d(0%,0,0px);
}

#fullscreen {
  top:0;
  position:fixed;
  z-index: 999;
  background: purple;
  width: 100%;
  height: 100%;
}

#bottom-toolbar{
  background: orange;
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 10%;
  bottom: 0;
}