#flip-card {
  perspective: 2000px;
}

#flip-card-inner {
  transition: transform 1s;
  transform-style: preserve-3d;
  perspective: 1000px;
}

#flip-card-front, #flip-card-back {
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
}

#flip-card-back {
  transform: rotateY(180deg);
}

.rotated {
  transform: rotateY(-180deg);
}