media

In Sass, the @media directive may be nested and contain expressions.
$v: 1.5;
.sidebar {
   width: 300px;
   @media screen {
      width: 500px;
      @media  (orientation: landscape) and (-webkit-min-device-pixel-ratio: round($v + 0.2)) {
         height: 200px;
      } 
   }
}

.sidebar {
  width: 300px;
}
@media screen {
  .sidebar {
    width: 500px;
  }
}
@media screen and (orientation: landscape) and (-webkit-min-device-pixel-ratio: 2) {
  .sidebar {
    height: 200px;
  }
}