<script src="http://www.polymer-project.org/platform.js"></script>

<script src="http://www.polymer-project.org/polymer.js"></script>

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<polymer-element name="my-element">

  <template>

    <content></content>

  </template>

  <script>

    Polymer('my-element', {

      hiddenChanged: function() {

        alert(this.hidden)

      }

    });

  </script>

</polymer-element>

​

<my-element onclick="this.hidden=!this.hidden">Click me to hide</my-element>