title: sort parents vertically and child horizontally
body: <p>sortable on <code>part</code> works fine - <code>single</code> are sorted horizontally.</p>
  
  <p>Why <code>parent</code> is not sortable - to sort <code>part</code> vertically ?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code> $('.parent').sortable({
    items: ".part",
    containment: "parent",
    tolerance: "pointer",
    axis: "y",
   });
  
  
   $('.part').sortable({
    containment: "parent",
    tolerance: "pointer",
    axis: "x",
   });</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.parent{
  background:silver;
  position:fixed;
  width:90%;
  left:5%;
  height:50px;
  overflow-y:scroll;
  }
  .part{
  background:lightgreen;
  margin:5px;
  display:grid;
  grid-template-columns:50% 50%;
  }
  .single{
  background:gold;
  cursor:cell;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"&gt;&lt;/script&gt;
  &lt;div class='parent'&gt;
  &lt;div class='part'&gt;
  &lt;div class='single'&gt;lorem1&lt;/div&gt;
  &lt;div class='single'&gt;ipsum1&lt;/div&gt;
  &lt;/div&gt;
  &lt;div class='part'&gt;
  &lt;div class='single'&gt;lorem2&lt;/div&gt;
  &lt;div class='single'&gt;ipsum2&lt;/div&gt;
  &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>