<div class="background">
<div class="card">
</div>
</div>
div.background {
  background: #262626;
  height: 300px;
  width: 300px;
  display: flex;
}

div.card {
  background: #262626;
  margin: auto;
  height: 100px;
  width: 100px;
  box-shadow:
    #000000 4px 4px 8px,
    #4d4d4d -4px -4px 8px;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.