ntal element inside a verticalLR container computes properly its percentage margins against the container's inline size (the container's height in this test), and the element is sized accordingly subtracting those margins from the available size.">
<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
<style>
.container {
  background: cyan;
  border: solid thick;
  height: 200px;
  width: 500px;
  writing-mode: vertical-rl;
}
.element {
  background: magenta;
  font: 50px/1 Ahem;
  margin: 10%; 