title: Combining layout breakpoints in Compass Susy?
body: <p>I am just atarting to use Susy</p>
  
  <p>I have defined my layouts, I needed to start with the desktop version and add 2 more: one for tablets and one for phones:</p>
  
  <pre><code>$total-columns  : 12;
  $column-width   : 4em;
  $gutter-width   : 1.4em;
  $grid-padding   : $gutter-width;
  
  $phone: 4 35em;
  $tablet: 35em 8 70em;
  </code></pre>
  
  <p>Seems to be working.  My issues arise when there's a change I need to make to something that should appear in the desktop but not in EITHER of the other 2, I find myself repeating myself:</p>
  
  <pre><code>#my-div {
  @include span-columns(3 omega,7);
       @include at-breakpoint($tablet) {
      display:none;
      }
   @include at-breakpoint($phone) {
      display:none;
      }
  }
  </code></pre>
  
  <p>How can I simplify this?</p>