the
          <code>movable</code> attribute. The movable attribute and the checkbox
          below are bound to the <code>lock</code> field, so that when
          the box is checked, the movable attribute is removed causing the
          Movable behavior to be detached and the <code>div</code>s to no longer
          be movable. This demonstrates that behaviors are dynamically attached
          and detached to elements as the DOM changes.
        </p>
        <p>
          Lock: <input type="checkbox" c