details element open/close animation (CSS)

<details>
  <summary>
    What is the answer to the ultimate question of life, the universe, and everything?
  </summary>
  <p>42.</p>
</details>

<div class="unsupported">The transition does not work in your browser! 🙁 This is because the <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/interpolate-size" target="_blank"><code>interpolate-size</code></a> property is not supported.</div>

details {
  interpolate-size: allow-keywords;

  margin-inline: 0.5rem;
  padding: 0.25rem 1rem;
  max-width: 50rem;

  border-radius: 1rem;
  box-shadow: 0 0 2px 0 currentColor;
}

/* open state */
details[open]::details-content {
  height: auto;
}

/* closed state */
details::details-content {
  height: 0;
  overflow: hidden;

  transition: content-visibility, height;
  transition-duration: 750ms;
  transition-timing-function: ease-in-out;

  /* this is requred for content-visibility to transition at 100% mark */
  transition-behavior: allow-discrete;
}

summary {
  cursor: pointer;
}

/* general styles */

* {
  box-sizing: border-box;
  margin: 0;
}

html {
  color-scheme: dark light;
}

body {
  width: 100%;
  height: 100dvh;

  font-family: system-ui, sans-serif;
  font-size: clamp(1rem, 0.3043rem + 3.4783vw, 2.5rem);

  display: grid;
  grid-template-rows: auto 1fr;
  place-items: center;
}

/* Provide a warning if interpolate-size is not suppored in the browser */
.unsupported {
  grid-row: 1;

  color: red;
  background-color: hsl(0, 100%, 90%);
  border: 1px red solid;
  font-size: 0.8rem;

  margin: 1rem 0.25rem;
  padding: 0.2rem;
  max-width: 600px;

  a:visited {
    color: blue;
  }
}

@supports (interpolate-size: allow-keywords) {
  .unsupported {
    display: none;
  }

  body {
    grid-template-rows: 1fr;
  }
}