Sidebar

  <div class="o-site__header">...</div>
  <main class="o-site__content">
    <div class="o-container o-container--collapse">
      <div class="o-container__sidebar u-size-width-25@md">
        ...
      </div>
      <div class="o-container__body u-size-width-75@md">
        ...
      </div>
    </div>
  </main>
  <div class="o-site__footer">...</div>