title: Sass mixin and include not working
body: <p>I am using the basic example of the mixin and include, but I can't get it to work. </p>
  
  <p>This is the code I am using.</p>
  
  <pre><code>    @mixin border-radius($radius) {
    -webkit-border-radius: $radius;
       -moz-border-radius: $radius;
        -ms-border-radius: $radius;
            border-radius: $radius;
  } 
  
      .test {
      @include border-radius(10px);
      padding: 20px;
      background: red;
      font-size: 12px;
  
      h2 {
          font-size: 24px;
          color: yellow;
      }
      p {
          color: #333333;
      }
  }
  </code></pre>