details > summary {
  cursor: pointer;
  list-style: none;
}

details > summary::-webkit-details-marker {
  display: none;
}

details > summary::before {
  content: "▶";
  display: inline-block;
  margin-right: .35rem;
  transition: transform var(--dur-fast);
}

details[open] > summary::before {
  transform: rotate(90deg);
}