body {
  display: grid;
  place-items: center;
}

main {
  aspect-ratio: var(--std-ar);
  block-size: 100vh;
  display: flex;
  flex-direction: column;
  max-inline-size: 100vw;
  overflow: hidden;

  & > .scrollable {
    flex: 1 1 auto;
    margin-block: var(--size-sm);
  }
}