title: Flex items wrapping even with box-sizing border-box
body: <p>In my code below, when I add padding it should add to width since I am using <code>border-box</code>. But it is not working why? Can anyone help me.</p>
  
  <p>If I add some margin or padding my <code>child__wrapper</code> is pushed into new line why?</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>* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  .wrapper {
    display: flex;
    flex-wrap: wrap;
    margin: 0;
    padding: 0;
    width: 100%;
  }
  
  .child__wrapper {
    height: 300px;
    flex: 0 0 33.3%;
    margin: 10px;
    box-sizing: border-box;
    background: rebeccapurple;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="wrapper"&gt;
    &lt;div class="child__wrapper"&gt;1&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;2&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;3&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;4&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;5&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;6&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;7&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;8&lt;/div&gt;
    &lt;div class="child__wrapper"&gt;9&lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>