<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Reference</title>
<style>
.clamp {
  display: -webkit-box;
  -webkit-box-orient: vertical;
  font: 16px / 32px serif;
  white-space: pre;
  padding: 0 4px;
  background-color: yellow;
}
.child {
  display: flex;
  font: 24px / 48px serif;
  color: blue;
}
</style>
<div class="clamp"><div>Line 1
Line 2<div class="child">Line 3
Line 4</div>Line 5…</div></div>