/* 折角箭头：左 + 下两条边旋转而成，收起朝下、展开朝上 */
.root {
  display: inline-block;
  flex-shrink: 0;
  width: 6px;
  height: 6px;
  border-left: 1px solid currentColor;
  border-bottom: 1px solid currentColor;
  opacity: 0.4;
  transform: rotate(315deg);
  transition:
    transform var(--su-duration-base) var(--su-ease-in-out),
    opacity var(--su-duration-base) var(--su-ease-in-out);
}

.open {
  opacity: 0.7;
  transform: rotate(135deg);
}

@media (prefers-reduced-motion: reduce) {
  .root {
    transition: none;
  }
}