title: Flexbox margin between boxes
body: <p>I know margins between flexboxes can be set automatically thanks to the the <code>align-content</code> property, but I need it to be fixed margin set in px. I am looking for something similar to <code>column-gap</code> for multi-columns.</p>
  
  <p>Here is what I need to do:</p>
  
  <p><img src="https://i.stack.imgur.com/ho92d.png" alt="demo"></p>
  
  <p>Here the space between 1,2,3 and 4,5 is equal, let’s say 30px. Any idea?</p>