<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-align-3/#align-abspos">
<link rel="help" href="https://drafts.csswg.org/css-align-3/#justify-abspos">
<style>
body {
  margin: 0;
}

.container {
  writing-mode: vertical-rl;
  display: inline-block;
  position: relative;
  margin: 20px;
  border: solid 4px;
  width: 60px;
  height: 60px;
}

.item {
  writing-mode: vertical-rl;
  position: absolute;
  background: green;
  inset: 5px 10px 5px 10px;
}

.item::before {
  aspect-ratio: 1/1;
  m