<div class="flip-card" tabIndex="0">
  <div class="flip-card-inner">
    <div class="flip-card-front">
      <h3>Hover, please!</h3>
    </div>
    <div class="flip-card-back">
      <h3>Whoaaa!!!</h3>
    </div>
  </div>
</div>
body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.flip-card {
  background-color: transparent;
  width: 300px;
  height: 300px;
  perspective: 1000px;
}

.flip-card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  transition: transform 0.6s;
  transform-style: preserve-3d;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
  backface-visibility: hidden;
  -moz-backface-visibility: hidden;
}

.flip-card:focus {
    outline: 0;
}

.flip-card:hover .flip-card-inner,
.flip-card:focus .flip-card-inner{
  transform: rotateY(180deg);
}

.flip-card-front,
.flip-card-back {
  position: absolute;
  width: 100%;
  height: 100%;
}

.flip-card-front {
  background: linear-gradient(to left, #4364f7, #6fb1fc);
  color: black;
  z-index: 2;
  display: flex;
  justify-content: center;
  align-items: center;
}

.flip-card-back {
  background: linear-gradient(to right, #4364f7, #6fb1fc);
  color: white;
  transform: rotateY(180deg);
  z-index: 1;
  display: flex;
  justify-content: center;
  align-items: center;
}
h3 {
  font-size: 20px;
  font-family: Verdana, sans-serif;
  font-weight: bold;
  color: #fff;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.