<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#first-text-line">
<link rel="match" href="reference/first-line-with-inline-block-ref.html">
<style>
.fl:first-line {
  color: red;
}
.fl-atomic {
  display: inline-block;
}
.fl-atomic:first-line {
  color: lime;
}
</style>
<div class="fl">
FIRST <div class="fl-atomic">first</span><br>second</div> FIRST
</div>