l-6 col-md-4">.col-6 .col-md-4</div>
      </div>
      <div class="row">
        <div class="col-6">.col-6</div>
        <div class="col-6">.col-6</div>
      </div>

      <hr>

      <h3>Mixed: mobile, tablet, and desktop</h3>
      <p></p>
      <div class="row">
        <div class="col-12 col-sm-6 col-lg-8">.col-12 .col-sm-6 .col-lg-8</div>
        <div class="col-6 col-lg-4">.col-6 .col-lg-4</div>
      </div>
      <div class="row">
        <div class="col-6 col-sm-4">.col-6 .col-sm-4</div>
        <