Edit in JSFiddle

<div class="cube-container spin">
  <div class="cube">
    <figure class="side front">1</figure>
    <figure class="side back">2</figure>
    <figure class="side left">3</figure>
    <figure class="side right">4</figure>
    <figure class="side top">5</figure>
    <figure class="side bottom">6</figure>
  </div>
</div>

body {
  color: #fff;
  font: 600 24px/24px "Open Sans", "HelveticaNeue-Light", "Helvetica Neue Light", "Helvetica Neue", Helvetica, Arial, "Lucida Grande", Sans-Serif;
  margin: 12px 45px;
}
.spin {
  cursor: pointer;
  transform-style: preserve-3d;
}
.spin:hover {
    animation: spin 5s linear infinite;
}
@keyframes spin {
  0% {
    transform: rotateY(0deg);
  }
  100% {
    transform: rotateY(360deg);
  }
}
.cube-container {
  height: 200px;
  -webkit-perspective: 300;
  perspective: 300;
  position: relative;
  width: 200px;
}
.cube {
  height: 100%;
  position: absolute;
  transform: translateZ(-100px);
  transform-style: preserve-3d;
  width: 100%;
}
.side {
  background: rgba(45, 179, 74, .3);
  border: 2px solid #2db34a;
  height: 196px;
  line-height: 196px;
  position: absolute;
  text-align: center;
  width: 196px;
}
.front {
  transform: translateZ(100px);
}
.back {
  transform: rotateX(180deg) translateZ(100px);
}
.left {
  transform: rotateY(-90deg) translateZ(100px);
}
.right {
  transform: rotateY(90deg) translateZ(100px);
}
.top {
  transform: rotateX(90deg) translateZ(100px);
}
.bottom {
  transform: rotateX(-90deg) translateZ(100px);
}