.cards {
  display: flex;
  gap: 10px;
}

.card {
  position: relative;
  width: 20px;
  height: 30px;
  perspective: 500px;
  animation: flip 2s infinite;
}

.card:nth-child(2) {
  animation-delay: 0.2s;
}
.card:nth-child(3) {
  animation-delay: 0.4s;
}
.card:nth-child(4) {
  animation-delay: 0.6s;
}

.face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: 4px;
}

.front {
  background: #e67e22;
}

.back {
  background: #d35400;
  transform: rotateY(180deg);
}

@keyframes flip {
  0%,
  100% {
    transform: rotateY(0deg);
  }
  50% {
    transform: rotateY(180deg);
  }
}