title: CSS property as SASS mixin value
body: <p>I try to build some universal margin/padding mixin... </p>
  
  <p>This is my code:</p>
  
  <pre><code>[class*="shift"] {
    $sft-o: 10px;
    @mixin shift_stp($val) {
      &amp;[class*="_sml"]{ $val: $sft-o; }
      &amp;[class*="_mid"]{ $val: $sft-o * 2; }
      &amp;[class*="_big"]{ $val: $sft-o * 3; }
    }
    &amp;[class*="_m"]{
      @include shift_stp(margin);
    }
    &amp;[class*="_p"]{
      @include shift_stp(padding);
    }
  }
  </code></pre>
  
  <p>Something is not right, so I wonder if it is possible to set some CSS property as a mixin value? Can anybody help?</p>