 <h2>.dn-lightspeed</h2>
      <button ng-click="dn_lightspeed=!dn_lightspeed">Toggle Class</button>
      <div class="element" ng-class="{'dn-lightspeed':dn_lightspeed}">
        ...
      </div>
    </section>

    <section>
      <h2>.dn-roll</h2>
      <button ng-click="dn_roll=!dn_roll">Toggle Class</button>
      <div class="element" ng-class="{'dn-roll':dn_roll}">
        ...
      </div>
    </section>

    <section>
      <h2>.dn-hinge</h2>
      <button ng-click="dn_hinge=!dn_hinge">Toggle Class</