title: 2x2 grid in Flexbox with fixed width column
body: <p>Is it possible to create this grid with Flexbox:</p>
  
  <pre><code>----------
  A1 | B1
  ----------
  A2 | B2
  ----------
  </code></pre>
  
  <p>A1&amp;A2 have a fixed width (50px) and B1&amp;B2 fill the remaining space. I don't want to create wrappers for the columns, because I would like to reorder the cells on mobile.</p>