style.css

body { 
  font-family: Avenir, sans-serif; margin: 0; 
  background-color: #121;
}

div#quad { 
  background-color: #000; 
  font-size: 0; width: 60%; 
  margin: 0 auto;
  box-shadow: 0 0 12px rgba(0,0,0,0.8);
}

div#quad figure { 
  margin: 0; width: 50%; 
  height: auto; transition: 1s; 
  display: inline-block; 
  position: relative; overflow: hidden; 
}

div#quad figure:hover { cursor: pointer; z-index: 4; }
div#quad figure img { width: 100%; height: auto; }

div#quad figure:nth-child(1) { transform-origin: top left; }
div#quad figure:nth-child(2) { transform-origin: top right; }
div#quad figure:nth-child(3) { transform-origin: bottom left; }
div#quad figure:nth-child(4) { transform-origin: bottom right; }

div#quad figure figcaption { 
  margin: 0; opacity: 0; 
  background: rgba(0,0,0,0.3); 
  color: #fff;
  padding: .3rem; 
  font-size: 1.2rem; 
  position: absolute; 
  bottom: 0; width: 100%;
	transition: 1s 1s opacity; 
}

.expanded {
  transform: scale(2);
  z-index: 5;
}
div#quad figure.expanded figcaption { opacity: 1; }
div.full figure:not(.expanded) { pointer-events: none; }

h1, h5 {
  color: #fff;
  padding: .3rem;
  text-align: center;
}