CodePen

HTML

            
              <div class="wrapper w1">
  <h1><code>perspective: 1000px</code></h1>
  <div class="cube">
    <div class="side  front">1</div>
    <div class="side   back">6</div>
    <div class="side  right">4</div>
    <div class="side   left">3</div>
    <div class="side    top">5</div>
    <div class="side bottom">2</div>
  </div>
</div>
<div class="wrapper w2">
  <h1><code>perspective: 250px</code></h1>
  <div class="cube">
    <div class="side  front">1</div>
    <div class="side   back">6</div>
    <div class="side  right">4</div>
    <div class="side   left">3</div>
    <div class="side    top">5</div>
    <div class="side bottom">2</div>
  </div>
</div>
            
          
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↑ Insert the most common viewport meta tag

CSS

            
              .wrapper {
  width: 50%;
  float: left;
}

.w1 {
  perspective: 1000px;
}

.w2 {
  perspective: 250px;
}

.wrapper h1 {
  text-align: center;
}

.cube {
  font-size: 4em;
  width: 2em;
  margin: 1.5em auto;
  transform-style: preserve-3d;
  transform: rotateX(-40deg) rotateY(32deg);
}

.side {
  position: absolute;
  width: 2em;
  height: 2em;
  
  background: rgba(tomato, .6);
  border: 1px solid rgba(0,0,0,.5);
  
  color: white; 
  text-align: center;
  line-height: 2em;
}

.front  { transform:                  translateZ(1em); }
.top    { transform: rotateX( 90deg)  translateZ(1em); }
.right  { transform: rotateY( 90deg)  translateZ(1em); }
.left   { transform: rotateY(-90deg)  translateZ(1em); }
.bottom { transform: rotateX(-90deg)  translateZ(1em); }
.back   { transform: rotateY(-180deg) translateZ(1em); }
            
          
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JS

            
              
            
          
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