.tnstack-toc {
  --toc-bg: #f8fafc;
  --toc-surface: #fff;
  --toc-text: #172033;
  --toc-muted: #64748b;
  --toc-border: #dbe3ee;
  --toc-link: #334155;
  --toc-hover: #4f46e5;
  --toc-line: #cbd5e1;
  --tnstack-toc-max-height: 360px;
  margin: 1.5em 0;
  overflow: hidden;
  border: 1px solid var(--toc-border);
  border-radius: 12px;
  background: var(--toc-bg);
  color: var(--toc-text);
  box-shadow: 0 4px 18px rgba(15, 23, 42, 0.05);
}

.tnstack-toc--dark {
  --toc-bg: #111827;
  --toc-surface: #182235;
  --toc-text: #f8fafc;
  --toc-muted: #94a3b8;
  --toc-border: #334155;
  --toc-link: #dbeafe;
  --toc-hover: #a5b4fc;
  --toc-line: #475569;
  color-scheme: dark;
}

@media (prefers-color-scheme: dark) {
  .tnstack-toc--auto {
    --toc-bg: #111827;
    --toc-surface: #182235;
    --toc-text: #f8fafc;
    --toc-muted: #94a3b8;
    --toc-border: #334155;
    --toc-link: #dbeafe;
    --toc-hover: #a5b4fc;
    --toc-line: #475569;
    color-scheme: dark;
  }
}

.tnstack-toc__summary,
.tnstack-toc__header {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  min-height: 52px;
  margin: 0;
  padding: 0.8rem 1rem;
  background: var(--toc-surface);
  color: var(--toc-text);
}

.tnstack-toc__summary {
  cursor: pointer;
  list-style: none;
  user-select: none;
}

.tnstack-toc__summary::-webkit-details-marker {
  display: none;
}

.tnstack-toc__summary:focus-visible {
  outline: 2px solid var(--toc-hover);
  outline-offset: -3px;
}

.tnstack-toc__title {
  font-size: 1rem;
  font-weight: 700;
  line-height: 1.3;
}

.tnstack-toc__count {
  margin-left: auto;
  color: var(--toc-muted);
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}

.tnstack-toc__chevron {
  width: 0.55rem;
  height: 0.55rem;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(45deg) translateY(-2px);
  transition: transform 0.18s ease;
}

.tnstack-toc[open] .tnstack-toc__chevron {
  transform: rotate(225deg) translate(-2px, -2px);
}

.tnstack-toc__nav {
  max-height: var(--tnstack-toc-max-height);
  overflow-x: hidden;
  overflow-y: auto;
  scrollbar-color: var(--toc-line) transparent;
  scrollbar-width: thin;
  padding: 0.9rem 1rem 1rem;
  border-top: 1px solid var(--toc-border);
  overscroll-behavior: contain;
}

.tnstack-toc__nav::-webkit-scrollbar {
  width: 6px;
}

.tnstack-toc__nav::-webkit-scrollbar-thumb {
  border-radius: 999px;
  background: var(--toc-line);
}

.tnstack-toc__list {
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: toc-item;
}

.tnstack-toc__list .tnstack-toc__list {
  position: relative;
  margin: 0.3rem 0 0.2rem 0.45rem;
  padding-left: 1rem;
}

.tnstack-toc__list .tnstack-toc__list::before {
  content: "";
  position: absolute;
  top: 0.15rem;
  bottom: 0.3rem;
  left: 0;
  width: 1px;
  background: var(--toc-line);
}

.tnstack-toc__item {
  position: relative;
  margin: 0.25rem 0;
  counter-increment: toc-item;
}

.tnstack-toc__link {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 0.55rem;
  align-items: baseline;
  padding: 0.2rem 0;
  color: var(--toc-link);
  font-size: 0.92rem;
  line-height: 1.45;
  text-decoration: none;
  transition:
    color 0.15s ease,
    transform 0.15s ease;
}

.tnstack-toc__link::before {
  content: counters(toc-item, ".") ".";
  min-width: 1.35rem;
  color: var(--toc-muted);
  font-size: 0.78em;
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  text-align: right;
}

.tnstack-toc__link:hover,
.tnstack-toc__link:focus {
  color: var(--toc-hover);
  transform: translateX(2px);
}

.tnstack-toc__item--h2 > .tnstack-toc__link {
  font-weight: 700;
}

.tnstack-toc__item--h3 > .tnstack-toc__link {
  font-size: 0.9rem;
  font-weight: 600;
}

.tnstack-toc__item--h4 > .tnstack-toc__link,
.tnstack-toc__item--h5 > .tnstack-toc__link,
.tnstack-toc__item--h6 > .tnstack-toc__link {
  font-size: 0.86rem;
}

.tnstack-toc__item--h5 > .tnstack-toc__link,
.tnstack-toc__item--h6 > .tnstack-toc__link {
  color: var(--toc-muted);
}

@media (max-width: 640px) {
  .tnstack-toc__summary,
  .tnstack-toc__header {
    padding: 0.75rem 0.85rem;
  }

  .tnstack-toc__nav {
    padding: 0.8rem 0.85rem 0.9rem;
  }

  .tnstack-toc__list .tnstack-toc__list {
    margin-left: 0.2rem;
    padding-left: 0.75rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .tnstack-toc__chevron,
  .tnstack-toc__link {
    transition: none;
  }
}