.x-group:where(.vertical) {
  flex-direction: column;

  > :where(*) {
    border-radius: inherit;

    &:where(:not(:first-child)) {
      margin-block-start: calc(var(--x-control-border-width) * -1);
      border-start-start-radius: 0;
      border-start-end-radius: 0;
      margin-inline-start: 0;
    }

    &:where(:not(:last-child)) {
      border-end-start-radius: 0;
      border-end-end-radius: 0;
    }
  }
}