:is(.popover) {
  --speed: 150ms;

  opacity: 0;
  transition:
      display var(--speed) allow-discrete,
      opacity var(--speed),
      overlay var(--speed) allow-discrete,;

  &[open] {
    opacity: 1;
  }

  @starting-style {
    &[open] {
      opacity: 0;
    }
  }
}