JSFiddle - React, Tailwind, and code Playground

HTML

<article class='glass down'>
  <h1 class='toggle' onclick='toggle()'>Pelican</h1>
  <p class='unimportant'><em>Pel"i*can</em>, n. Etym: [F. p&eacute;lican, L. pelicanus, pelecanus, Gr. para&ccedil;u.] [Written also pelecan.] 1. (Zo&ouml;l.)</p>

  <p><em>Defn:</em> Any large webfooted bird of the genus of Pelecanus, of which about a dozen species are known. They have an enormous bill, to the lower edge of which is attached a pouch in which captured fishes are temporarily stored.

    <p class='unimportant'><em>Note:</em> The American white pelican (Pelecanus erythrorhynchos) and the brown species (P. fuscus) are abundant on the Florida coast in winter, but breed about the lakes in the Rocky Mountains and British America.</p>
</article>
<!-- Image by Yair Hazout via unsplash.com -->
<!-- Text from Webster's Unabridged Dictionary via Project Gutenberg -->

CSS

html, body, article, .glass::before {
  width: 100%;
  height: 100%;
  overflow: hidden;
}

.glass {
  position: relative;
}

.glass::before {
  z-index: -1;
  display: block;
  position: absolute;
  content: ' ';
}

/* BACKGROUNDS */
body {
  background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/28727/pelican.jpg');
  background-size: cover;
}

.glass::before {
  background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/28727/pelican-blurred.jpg');
  background-size: cover;
  opacity: 0.4;
}

.glass {
  background-color: white;
}

/* TRANSFORMATIONS */
.glass.down {
  /* Fallback for browsers that don't support 3D Transforms */
  transform: translateY(100%) translateY(-7rem);
  transform: translateY(100%) translateY(-7rem) translateZ(0);
}

.glass.down::before {
  transform: translateY(-100%) translateY(7rem);
  transform: translateY(-100%) translateY(7rem) translateZ(0);
}

.glass.up, .glass.up::before {
  transform: translateY(0);
  transform: translateY(0) translateZ(0);
}

/* TRANSITIONS */
.preload * {
  transition: none !important;
}

.glass, .glass::before {
  transition: transform 0.5s ease-out;
}

/* TYPOGRAPHY, ETC */
body {
  font-family: 'Source Sans Pro', Verdana, sans-serif;
  font-size: 100%;
}

h1 {
  font-size: 5rem;
  line-height: 1.4;
  font-weight: bold;
  text-align: center;
  padding: 0 7rem;
  border-bottom: 2px solid rgba(0, 0, 0, 0.1);
  cursor: pointer;
}

h1::before {
  position: absolute;
  left: 0;
  top: 0;
  background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/28727/double-chevron-up.svg');
  content: ' ';
  display: block;
  width: 7rem;
  height: 7rem;
  transition: transform 0.2s ease-out 0.5s;
}

.up h1::before {
  transform: rotate(180deg);  
}

em {
  font-style: normal;
  font-weight: bold;
}

p {
  font-size: 1.8rem;
  line-height: 1.4;
  max-width: 30em;
  margin: 1.4em auto;
  padding: 0 1em;
}

@media (max-width: 500px), (max-height: 300px) {
  p.unimportant {
    display: none;
 ...

JavaScript

function toggle() {
  var button = document.querySelector('.toggle');
  var overlay = document.querySelector('.glass');
  if (overlay.className === 'glass down') {
    overlay.className = 'glass up';
  } else {
    overlay.className = 'glass down';
  }
}

window.onload = function() {
  /* transition support ~= classList support */
  var preload = document.querySelector('.preload');
  preload.classList.remove('preload');
}