animate.css/source/flippers/flip.css

@keyframes flip {
  0% {
    transform: perspective(400px) translateZ(0) rotateY(-360deg) scale(1);
    animation-timing-function: ease-out;
  }

  40% {
    transform: perspective(400px) translateZ(150px) rotateY(-190deg) scale(1);
    animation-timing-function: ease-out;
  }

  50% {
    transform: perspective(400px) translateZ(150px) rotateY(-170deg) scale(1);
    animation-timing-function: ease-in;
  }

  80% {
    transform: perspective(400px) translateZ(0) rotateY(0deg) scale(.95);
    animation-timing-function: ease-in;
  }

  100% {
    transform: perspective(400px) translateZ(0) rotateY(0deg) scale(1);
    animation-timing-function: ease-in;
  }
}

.animated.flip {
  backface-visibility: visible;
  animation-name: flip;
}