I have tried to understand core-animated-pages, but i don't uderstand where i fail. I have implemented both demo examples that first demo in <http://www.polymer-project.org/docs/elements/core-elements.html#core-animated-pages>

But the transitions don't work! Which is the problem?? This is the code

```
        <!doctype html>
        <html>
        <head>

        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

      <script src="components/platform/platform.js"></script>
      <link href="components/core-animated-pages/core-animated-pages.html" rel="import">
      <link href="components/core-animated-pages/transitions/cross-fade.html" rel="import">
      <link href="components/core-animated-pages/transitions/slide-from-right.html" rel="import">
      <link href="components/core-animated-pages/transitions/hero-transition.html" rel="import">

      <style>
      #hero1 {
        position: absolute;
        top: 0;
        left: 0;
        width: 300px;
        height: 300px;
        background-color: orange;
      }
      #hero2 {
        position: absolute;
        top: 200px;
        left: 300px;
        width: 300px;
        height: 300px;
        background-color: orange;
      }
      #bottom1, #bottom2 {
        position: absolute;
        bottom: 0;
        top: 0;
        left: 0;
        height: 50px;
      }
      #bottom1 {
        background-color: blue;
      }
      #bottom2 {
        background-color: green;
      }
    </style>
    <!-- // hero-transition and cross-fade are declared elsewhere -->
        <core-animated-pages transitions="hero-transition cross-fade">
          <section id="page1">
            <div id="hero1" hero-id="hero" hero></div>
            <div id="bottom1" cross-fade></div>
          </section>
          <section id="page2">
            <div id="hero2" hero-id="hero" hero></div>
            <div id="bottom2" cross-fade></div>
          </section>
        </core-animated-pages>

      <script>
        document.addEventListener('click', function(e) {
        var pages = document.querySelector('core-animated-pages');
        pages.selected = (pages.selected + 1) % pages.children.length;
      });
      </script>
    </body>
    </html>

```

Thanks