<div class="notice">
  👋 Hey, looks like your browser does not support <code>margin-block</code>. Try viewing this demo in Firefox or Chrome.
</div>

<div class="wrapper">
  <h1>Hello Dolly!</h1>
</div>
:root {
  --start: 25%;
  --end: 100px;
}

body {
  padding: 1.5rem;
}

.wrapper {
  background: #100e17;
  border-radius: 8px;
  height: 250px;
  margin-bottom: 2rem;
  padding: 1rem;
  position: relative;
  width: clamp(300px, 90%, 800px);
  writing-mode: vertical-lr;
}

h1 {
  color: #fff;
  margin-block: var(--start) var(--end);
  position: relative;
}

.notice {
  background: #fff9c4;
  border-radius: 8px;
  color: #827717;
  margin-bottom: 1.5rem;
  padding: 1rem;
  text-align: center;
  width: clamp(300px, 90%, 800px);
}

@supports (margin-block: 0) {
  .notice {
    display: none;
  }
}

External CSS

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External JavaScript

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