 container.
        -->
        <div class="target"
             data-offset-x=0 data-offset-y=0
             data-expected-width=0 data-expected-height=0></div>
      </div>
      <div class="spacer" style="height: 80px"></div>
      <!--
        The containing block of this target is the multicol container.
      -->
      <div class="target"
           data-offset-x=10 data-offset-y=20
           data-expected-width=40 data-expected-height=20></div>
    </div>
    <!--
      The containing block of this 