te-up-right</h2>
      <button ng-click="dn_rotate_up_right=!dn_rotate_up_right">Toggle Class</button>
      <div class="element" ng-class="{'dn-rotate-up-right':dn_rotate_up_right}">
        ...
      </div>
    </section>

    <section>
      <h2>.dn-rotate-down-right</h2>
      <button ng-click="dn_rotate_down_right=!dn_rotate_down_right">Toggle Class</button>
      <div class="element" ng-class="{'dn-rotate-down-right':dn_rotate_down_right}">
        ...
      </div>
    </section>


    <section>
     