chromium/third_party/blink/web_tests/external/wpt/css/css-anchor-position/position-anchor-001.html

<!DOCTYPE html>
<title>Tests the 'position-anchor' property</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#position-anchor">
<link rel="author" href="mailto:[email protected]">
<link rel="match" href="position-anchor-ref.html">
<style>
.anchor {
  width: 100px;
  height: 100px;
  background: orange;
}

.target {
  position: fixed;
  background: lime;
  position-try-fallbacks: --pf;
  left: 999999px; /* force fallback */
}

@position-try --pf {
  top: anchor(bottom, 0px);
  left: anchor(left, 0px);
  width: anchor-size(width, 0px);
  height: anchor-size(height, 0px);
}

body {
  margin: 0;
}

#anchor1 {
  anchor-name: --a1;
  margin-left: 100px;
}

#target1 {
  position-anchor: --a1;
}

#anchor2 {
  anchor-name: --a2;
  margin-left: 300px;
  margin-top: 100px;
}

#target2 {
  position-anchor: --a2;
}
</style>

<div id="anchor1" class="anchor">anchor1</div>
<div id="anchor2" class="anchor">anchor2</div>

<div id="target1" class="target">target1</div>
<div id="target2" class="target">target2</div>