nk;
  font-size: 20px;
  writing-mode: horizontal-tb;
}
#target > :nth-child(3) {
  background: cyan;
  width: 40px;
  height: 40px;
}
</style>
<div id="target">
  <div>line1<br>line2</div>
  <div>line1<br>line2</div>
  <div></div>
</div>
