title: Polymer1.0 - How to change Boolean in Child when Boolean in Parent changes
body: <p>I need a child element to know when a value in the parent element changes. I have tried using curly braces, square brackets, the dollar sign, and every combination of those, but nothing works. When you click the button in the parent the child element doesn't get the updated value.</p>
  
  <p>What do I need to do to </p>
  
  <pre><code>&lt;dom-module id="parent-element"&gt;
    &lt;template&gt;
      &lt;child-element childBoolean="[[parentBoolean]]"&gt;&lt;/child-element&gt;
      &lt;button on-tap="_toggle"&gt;toggle&lt;/button&gt;
    &lt;/template&gt;
  
    &lt;script&gt;
      Polymer({
        is: 'parent-element',
        properties:{
          parentBoolean:{
            type:Boolean
            value:false
          }
        },
        _toggle:function(){
          this.parentBoolean = !this.parentBoolean;
        }
      &lt;/script&gt;
  &lt;/dom-module&gt; 
  
  
  
  &lt;dom-module id="child-element"&gt;
    &lt;template&gt;
      the value is [[childBoolean]]
    &lt;/template&gt;
  
    &lt;script&gt;
      Polymer({
        is: 'child-element',
        properties:{
          childBoolean: Boolean
          }
        }
      &lt;/script&gt;
  &lt;/dom-module&gt;
  </code></pre>