Pure CSS Alternating Left Right

<section class="pure-g">
  <figure class="pure-u-1-3">
    Image
  </figure>
  <article class="pure-u-2-3">
    Article
  </article>
</section>
<section class="pure-g">
  <figure class="pure-u-1-3">
    Image
  </figure>
  <article class="pure-u-2-3">
    Article
  </article>
</section>
<section class="pure-g">
  <figure class="pure-u-1-3">
    Image
  </figure>
  <article class="pure-u-2-3">
    Article
  </article>
</section>