title: flexbox vertical center with 100% height
body: <p>Is it possible to use flexbox to center vertically and horizontally for background color purposes?</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-css lang-css prettyprint-override"><code>.wrapper {
    display: flex;
    width: 100vw;
    height: 100vh;
    text-align: center;
  }
  
  .item {
    flex: 1;
    background-color: green;
    align-self: center;
    justify-content: center;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class='wrapper'&gt;
    &lt;div class='item'&gt;
      sdafsdfs
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>If I add a <code>height: 100%</code> the text moves back to the top.</p>