.cd {
    width: 100%;
    height: 100%;
    position: absolute;
    -webkit-transform-style: preserve-3d;
    -webkit-transition: -webkit-transform 1s;
    transform-style: preserve-3d;
    transition: transform 1s;
    margin-top: 15px;
}

.cd div {
  display: block;
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
}

.cd .back {
    -webkit-transform: rotateY(180deg);
    transform: rotateY(180deg);
}

.cd.flipped {
  -webkit-transform: rotateY(180deg);
  transform: rotateY(180deg);
}