<html>
  <meta chartset=utf-8>
  <title>Test Reference</title>
  <link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net">
<style>
html {
  writing-mode: vertical-rl;
}
body {
  writing-mode: vertical-rl;
  width: 0; height: 0;
}
html::before {
  content: "This text must be vertical.";
}
html::after {
  content: "This text must be horizontal.";
  display: block;
  writing-mode: horizontal-tb;
}
</style>
<body></body>
