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body {
  width: 30%;
  min-width: 300px;
  height: 80vh;
  margin: 20vh auto 0;
  background: linear-gradient(to left, #FF512F , #DD2476); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
  color: #282828;
}

h1 {
  color: white;
}




//Demo styles
.task {
  position: relative;

  overflow: hidden;
  cursor: pointer;
  
  perspective: 800px;
  transform-style: preserve-3d;
}

.abstract,
.details {
  $bg: rgba(white, 1);
  width: 100%;
  padding: 15px 30px;
  position: relative;
  background: $bg;

  .task:hover & {
    background: darken($bg, 2%);
  }
}

.abstract {
  //z-index: 10;
  transition: .3s ease all;
}

.details {
  max-height: 0;
  padding: 0;
  
  overflow: hidden;
  visibility: hidden;
  
  transform: rotateX(-180deg);
  transform-origin: top center;
  backface-visibility: hidden;
  transition: .3s transform ease;
  
  &:before {
    content: '';
    display: block;
    position: absolute;
    top: 0;
    left: 10%;
    right: 10%;
    height: 1px;
    background: grey;
  }
  
  .task:hover & {
    max-height: none;
    overflow: visible;
    visibility: visible;
    transform: rotateX(0deg);
  }
}

.details__inner {
  padding: 15px 30px;
}

<div class="wrap">
  <h1>Hover card</h1>
  <div class="task">
    <div class="abstract">
      <h3>Abstract</h3>
      <p>This is what you see by default.</p>
    </div>
    <div class="details">
      <div class="details__inner">
        <h3>Details</h3>
        <p>This additional content gets revealed on hover.</p>
      </div>
    </div>
  </div>
</div>