<div class="flip-card">
  <div class="flip-card-inner">
    <div class="flip-card-front">hover, please</div>
    <div class="flip-card-back">hello</div>
  </div>
</div>
body {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
}
.flip-card {
  width: 300px;
  height: 300px;
  perspective: 1000px;
}
.flip-card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  text-align: center;
  transition: 500ms;
}
.flip-card:hover .flip-card-inner,
.flip-card:focus .flip-card-inner {
  transform: rotateY(180deg);
}
.flip-card-front,
.flip-card-back {
  display: flex;
  align-items: center;
  justify-content: center;
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  color: #FFF;
  font-size: 30px;
  border-radius: 4px;
}
.flip-card-front {
  background: linear-gradient(to right, skyblue, blue);
}
.flip-card-back {
  background: linear-gradient(to left, skyblue, blue);
  transform: rotateY(180deg);
}

External CSS

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External JavaScript

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