title: css flexbox wrapping: analogue of pseudo-classes to select start/end items on main/cross axis?
body: <p>Flexbox is a great thing. But for more versatility, when flex wrapping used: it needs pseudo classes, analogues of first-child  or last-child or nth-child. </p>
  
  <p>It will be very comfortably to know, if item on the end by main-axis, or it was wrapped and now it is on the begin of main axis.</p>
  
  <p>For example, I want this:</p>
  
  <pre><code>.flexbox
  {
      display: flex;
      flex-flow:row wrap;
  }
  
  .flexbox .item:flex-start
  {
      /*items in the left of container selector*/
  }
  
  .flexbox .item:flex-end
  {
      /*items in the right of container selector*/
  }
  
  .flexbox .item:flex-cross-start
  {
      /*items on the top of container selector*/
  }
  .flexbox .item:flex-cross-end
  {
      /*items on the bottom of container selector*/
  }
  </code></pre>
  
  <p>But sad - there are no <a href="http://www.w3schools.com/Css/css_pseudo_classes.asp" rel="noreferrer">pseudo classes</a> with a flex subject. </p>
  
  <p><strong>Question</strong>: can I write css selector(without JS), determines elements in wrap-flex-container, that are in start/end of the main/cross axis, or no?</p>
  
  <p>subquestion: why there are no pseudo-classes for flexbox, are there some conceptual contradictions? </p>