Mega Nav

  <nav class="c-mega-nav">
    <ul class="c-nav c-nav--vertical c-nav--horizontal@lg c-nav--accordion c-nav--dropdown@lg u-position-relative" data-module="Nav">
      <li class="c-nav__item is-accordion-nav-parent is-dropdown-nav-parent u-position-static">
        <a class="c-nav__link is-active" href="...">...</a>
        <button class="c-button is-accordion-button">
          <span class="o-icon o-icon--chevron-down">
            [icon]
          </span>
        </button>
        <div class="is-accordion-nav is-dropdown-nav">
          <div class="o-flex-grid u-size-width-100">
            <div class="o-flex-grid__cell o-flex-grid__cell--span-6@sm">
              <ul class="c-nav c-nav--vertical">
                <li class="c-nav__item">
                  <a href="..." class="c-nav__link">...</a>
                </li>
                <li class="c-nav__item">
                  <a href="..." class="c-nav__link">...</a>
                  <ul class="c-nav c-nav--nested">
                    <li class="c-nav__item">
                      <a class="c-nav__link is-active" href="...">...</a>
                    </li>
                    ...
                  </ul>
                </li>
                <li class="c-nav__item">
                  <a href="..." class="c-nav__link">...</a>
                </li>
                ...
              </ul>
            </div>
            <div class="o-flex-grid__cell o-flex-grid__cell--span-6@sm">
              <ul class="c-nav c-nav--vertical">
                <li class="c-nav__item">
                  <a href="..." class="c-nav__link">...</a>
                </li>
                ...
              </ul>
            </div>
          </div>
        </div>
      </li>
      <li class="c-nav__item">
        <a class="c-nav__link" href="...">...</a>
      </li>
      ...
    </ul>
  </nav>