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HTML

            
              .box
            
          
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↑ Insert the most common viewport meta tag

CSS

            
              @mixin box( $color ) {
  background-color: blue; // I pity the fool who doesn't make boxes blue!
  position: absolute;
  height: 60%;
  width: 60%;
  left: 20%;
  top: 20%;
}

.box {
  @include box( red ); 
}
            
          
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JS

            
              
            
          
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