title: What is wrong with my box-shadow SASS @Mixin?
body: <p>I am trying to find a working box-shadow @mixin for SASS.</p>
  
  <p><strong>My CodePen: <a href="http://codepen.io/leongaban/pen/nCDos" rel="nofollow noreferrer">http://codepen.io/leongaban/pen/nCDos</a></strong>
  <br/><br/><br/>
  On stackoverflow I <a href="https://stackoverflow.com/questions/10435056/creating-a-box-shadow-mixin-using-sass">found this question</a> and used it and the answer exactly, however I'm still getting the following error:</p>
  
  <p><img src="https://i.stack.imgur.com/GMSHP.png" alt="enter image description here"></p>
  
  <pre><code>@mixin box-shadow($top, $left, $blur, $color, $inset:"") {
      -webkit-box-shadow:$top $left $blur $color #{$inset};
      -moz-box-shadow:$top $left $blur $color #{$inset};
      box-shadow:$top $left $blur $color #{$inset};
  }
  
  .login_window {
      width: 200px; height: 100px; background: red;
  
      @include box-shadow(inset 0 1px 1px rgba(0, 0, 0, 0.5));
  }
  </code></pre>
  
  <p>How would you write it?</p>