html {
  height: 100%;
}
body {
  min-height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background: #EEE;
}
.flip-clock {
  text-align: center;
  perspective: 400px;
  margin: 20px auto;
}
.flip-clock *,
.flip-clock *:before,
.flip-clock *:after {
  box-sizing: border-box;
}
.flip-clock__piece {
  display: inline-block;
  margin: 0 5px;
}
.flip-clock__slot {
  font-size: 2vw;
}
.card {
  display: block;
  position: relative;
  padding-bottom: 0.72em;
  font-size: 9vw;
  line-height: 0.95;
}
.card__top,
.card__bottom,
.card__back::before,
.card__back::after {
  display: block;
  height: 0.72em;
  color: #ccc;
  background: #222;
  padding: 0.25em 0.25em;
  border-radius: 0.15em 0.15em 0 0;
  backface-visiblity: hidden;
  transform-style: preserve-3d;
  width: 1.8em;
  transform: translateZ(0);
}
.card__bottom {
  color: #FFF;
  position: absolute;
  top: 50%;
  left: 0;
  border-top: solid 1px #000;
  background: #393939;
  border-radius: 0 0 0.15em 0.15em;
  pointer-events: none;
  overflow: hidden;
}
.card__bottom::after {
  display: block;
  margin-top: -0.72em;
}
.card__back::before,
.card__bottom::after {
  content: attr(data-value);
}
.card__back {
  position: absolute;
  top: 0;
  height: 100%;
  left: 0%;
  pointer-events: none;
}
.card__back::before {
  position: relative;
  z-index: -1;
  overflow: hidden;
}
.flip .card__back::before {
  -webkit-animation: flipTop 0.3s cubic-bezier(0.37, 0.01, 0.94, 0.35);
          animation: flipTop 0.3s cubic-bezier(0.37, 0.01, 0.94, 0.35);
  -webkit-animation-fill-mode: both;
          animation-fill-mode: both;
  transform-origin: center bottom;
}
.flip .card__back .card__bottom {
  transform-origin: center top;
  -webkit-animation-fill-mode: both;
          animation-fill-mode: both;
  -webkit-animation: flipBottom 0.6s cubic-bezier(0.15, 0.45, 0.28, 1);
          animation: flipBottom 0.6s cubic-bezier(0.15, 0.45, 0.28, 1);
}
@-webkit-keyframes flipTop {
  0% {
    transform: rotateX(0deg);
    z-index: 2;
  }
  0%,
  99% {
    opacity: 0.99;
  }
  100% {
    transform: rotateX(-90deg);
    opacity: 0;
  }
}
@keyframes flipTop {
  0% {
    transform: rotateX(0deg);
    z-index: 2;
  }
  0%,
  99% {
    opacity: 0.99;
  }
  100% {
    transform: rotateX(-90deg);
    opacity: 0;
  }
}
@-webkit-keyframes flipBottom {
  0%,
  50% {
    z-index: -1;
    transform: rotateX(90deg);
    opacity: 0;
  }
  51% {
    opacity: 0.99;
  }
  100% {
    opacity: 0.99;
    transform: rotateX(0deg);
    z-index: 5;
  }
}
@keyframes flipBottom {
  0%,
  50% {
    z-index: -1;
    transform: rotateX(90deg);
    opacity: 0;
  }
  51% {
    opacity: 0.99;
  }
  100% {
    opacity: 0.99;
    transform: rotateX(0deg);
    z-index: 5;
  }
}