:root {
  --toc-ribbon-bg: rgba(7, 11, 22, 0.9);
  --toc-ribbon-border: rgba(76, 157, 245, 0.35);
  --toc-ribbon-shadow: 0 24px 60px rgba(2, 6, 16, 0.55);
  --toc-chip-bg: rgba(255, 255, 255, 0.05);
  --toc-chip-border: rgba(255, 255, 255, 0.12);
  --toc-chip-hover: rgba(76, 157, 245, 0.16);
  --toc-chip-active: rgba(76, 157, 245, 0.28);
  --toc-chip-text: #f7fbff;
  --toc-chip-muted: rgba(247, 251, 255, 0.7);
  --toc-submenu-bg: rgba(4, 8, 20, 0.96);
  --toc-submenu-border: rgba(76, 157, 245, 0.2);
  --toc-scroll-btn-bg: rgba(255, 255, 255, 0.08);
  --toc-scroll-btn-hover: rgba(76, 157, 245, 0.25);
  --toc-scroll-btn-icon: rgba(255, 255, 255, 0.8);
  --toc-eyebrow: rgba(255, 255, 255, 0.7);
  --toc-transition: 0.25s ease;
}

body.light .toc-ribbon,
body.light .toc-track-shell,
body.light .toc-submenu,
body.light .toc-scroll-btn {
  --toc-ribbon-bg: rgba(255, 255, 255, 0.92);
  --toc-ribbon-border: rgba(13, 25, 48, 0.12);
  --toc-ribbon-shadow: 0 20px 55px rgba(14, 23, 45, 0.18);
  --toc-chip-bg: rgba(15, 23, 36, 0.05);
  --toc-chip-border: rgba(15, 23, 36, 0.15);
  --toc-chip-hover: rgba(15, 23, 36, 0.1);
  --toc-chip-active: rgba(76, 157, 245, 0.25);
  --toc-chip-text: #0f1724;
  --toc-chip-muted: rgba(15, 23, 36, 0.7);
  --toc-submenu-bg: rgba(255, 255, 255, 0.98);
  --toc-submenu-border: rgba(15, 23, 36, 0.1);
  --toc-scroll-btn-bg: rgba(15, 23, 36, 0.05);
  --toc-scroll-btn-hover: rgba(76, 157, 245, 0.25);
  --toc-scroll-btn-icon: rgba(15, 23, 36, 0.7);
  --toc-eyebrow: rgba(15, 23, 36, 0.65);
}

.page-index.toc {
  width: min(1100px, 100%);
  margin: 0 auto 2.5rem;
  padding: 0 1rem;
  position: sticky;
  top: calc(var(--navbar-h, 64px) + 12px);
  z-index: 20;
}

.toc-ribbon {
  border-radius: 26px;
  border: 1px solid var(--toc-ribbon-border);
  background: var(--toc-ribbon-bg);
  box-shadow: var(--toc-ribbon-shadow);
  padding: 1rem 1.25rem 1.35rem;
  backdrop-filter: blur(18px);
}

.toc-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.toc-eyebrow {
  font: 600 0.78rem/1 "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--toc-eyebrow);
  margin: 0;
}

.toc-scroll-controls {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.toc-scroll-btn {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  border: 1px solid transparent;
  background: var(--toc-scroll-btn-bg);
  color: var(--toc-scroll-btn-icon);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background-color var(--toc-transition), color var(--toc-transition), opacity var(--toc-transition);
}

.toc-scroll-btn::before {
  content: '';
  width: 12px;
  height: 12px;
  border-bottom: 2px solid currentColor;
  border-left: 2px solid currentColor;
  transform: rotate(45deg);
}

.toc-scroll-btn[data-dir="1"]::before {
  transform: rotate(-135deg);
}

.toc-scroll-btn:disabled {
  opacity: 0.35;
  cursor: default;
}

.toc-scroll-btn:not(:disabled):hover,
.toc-scroll-btn:focus-visible {
  background: var(--toc-scroll-btn-hover);
  outline: none;
}

.toc-track-shell {
  position: relative;
  margin-top: 0.85rem;
  padding-bottom: 0.2rem;
}

.toc-track-shell::before,
.toc-track-shell::after {
  content: '';
  position: absolute;
  top: 0.35rem;
  bottom: 0.35rem;
  width: 42px;
  pointer-events: none;
  z-index: 2;
  transition: opacity 0.2s ease;
}

.toc-track-shell::before {
  left: 0;
  background: linear-gradient(90deg, var(--toc-ribbon-bg), rgba(0, 0, 0, 0));
}

.toc-track-shell::after {
  right: 0;
  background: linear-gradient(-90deg, var(--toc-ribbon-bg), rgba(0, 0, 0, 0));
}

.toc-track-shell[data-scroll-state='start']::before,
.toc-track-shell[data-scroll-state='end']::after,
.toc-track-shell[data-scroll-state='full']::before,
.toc-track-shell[data-scroll-state='full']::after {
  opacity: 0;
}

.toc-track-shell[data-scroll-state='start']::after,
.toc-track-shell[data-scroll-state='end']::before,
.toc-track-shell[data-scroll-state='middle']::before,
.toc-track-shell[data-scroll-state='middle']::after {
  opacity: 0.95;
}

.toc-track {
  list-style: none;
  margin: 0;
  padding: 0.1rem 0.1rem 0.35rem;
  display: flex;
  gap: 0.65rem;
  overflow-x: auto;
  overscroll-behavior-inline: contain;
  scroll-snap-type: inline proximity;
  scrollbar-width: none;
}

.toc-track::-webkit-scrollbar {
  display: none;
}

.toc-item {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  flex: 0 0 auto;
}

.toc-chip,
.toc-link.toc-chip {
  scroll-snap-align: start;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--toc-chip-border);
  background: var(--toc-chip-bg);
  color: var(--toc-chip-text);
  font: 600 0.92rem/1.3 "Inter", system-ui, sans-serif;
  text-decoration: none;
  transition: background-color var(--toc-transition), color var(--toc-transition), border-color var(--toc-transition);
  white-space: nowrap;
}

.toc-chip:hover,
.toc-chip:focus-visible {
  background: var(--toc-chip-hover);
  outline: none;
}

.toc-chip.toc-link-active {
  background: var(--toc-chip-active);
  border-color: rgba(76, 157, 245, 0.45);
  color: var(--toc-chip-text);
}

.toc-chip-shell {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

.toc-sub-trigger {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  border: 1px solid var(--toc-chip-border);
  background: var(--toc-chip-bg);
  color: var(--toc-chip-muted);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background-color var(--toc-transition), color var(--toc-transition), transform var(--toc-transition);
}

.toc-sub-trigger-icon {
  width: 0.75rem;
  height: 0.75rem;
  border-radius: 2px;
  background:
    linear-gradient(currentColor 0 0) center/100% 2px no-repeat,
    linear-gradient(currentColor 0 0) center/2px 100% no-repeat;
}

.toc-sub-trigger[aria-expanded='true'] .toc-sub-trigger-icon {
  background:
    linear-gradient(currentColor 0 0) center/100% 2px no-repeat;
  transform: rotate(90deg);
}

.toc-sub-trigger:hover,
.toc-sub-trigger:focus-visible,
.toc-item[data-open='true'] .toc-sub-trigger {
  background: var(--toc-chip-hover);
  color: var(--toc-chip-text);
  outline: none;
}

.toc-submenu {
  display: none;
  z-index: 10;
}

.toc-item[data-open='true'] > .toc-submenu {
  display: block;
}

.toc-submenu {
  position: absolute;
  left: 0;
  top: calc(100% + 14px);
  min-width: max(260px, 40vw);
}

.toc-submenu::before {
  content: '';
  position: absolute;
  top: -10px;
  left: 32px;
  width: 18px;
  height: 18px;
  background: var(--toc-submenu-bg);
  border: 1px solid var(--toc-submenu-border);
  border-right: none;
  border-bottom: none;
  transform: rotate(45deg);
  z-index: -1;
}

.toc-submenu .toc-sub-list {
  list-style: none;
  margin: 0;
  padding: 0.9rem;
  border-radius: 18px;
  border: 1px solid var(--toc-submenu-border);
  background: var(--toc-submenu-bg);
  box-shadow: 0 18px 45px rgba(2, 6, 16, 0.5);
  display: grid;
  gap: 0.35rem;
}

.toc-submenu .toc-link {
  text-decoration: none;
  color: var(--toc-chip-muted);
  font: 500 0.88rem/1.4 "Inter", system-ui, sans-serif;
  padding: 0.35rem 0.65rem;
  border-radius: 999px;
  transition: background-color var(--toc-transition), color var(--toc-transition);
}

.toc-submenu .toc-link:hover,
.toc-submenu .toc-link:focus-visible {
  background: var(--toc-chip-hover);
  color: var(--toc-chip-text);
  outline: none;
}

.toc-submenu .toc-link.toc-link-active {
  background: var(--toc-chip-active);
  color: var(--toc-chip-text);
}

@media (max-width: 900px) {
  .page-index.toc {
    padding: 0 0.75rem;
    top: calc(var(--navbar-h, 60px) + 8px);
  }

  .toc-scroll-controls {
    display: none;
  }

  .toc-track-shell::before,
  .toc-track-shell::after {
    width: 30px;
  }

  .toc-track {
    gap: 0.5rem;
  }

  .toc-chip,
  .toc-link.toc-chip {
    padding: 0.4rem 0.85rem;
    font-size: 0.88rem;
  }

  .toc-submenu {
    position: static;
    min-width: 100%;
  }

  .toc-submenu::before {
    display: none;
  }

  .toc-submenu .toc-sub-list {
    box-shadow: none;
    border-radius: 16px;
    padding: 0.75rem;
    background: rgba(255, 255, 255, 0.02);
    border-color: rgba(255, 255, 255, 0.1);
  }
}

@media (max-width: 520px) {
  .toc-ribbon {
    padding: 0.85rem 0.9rem 1rem;
    border-radius: 22px;
  }

  .toc-track {
    scroll-snap-type: x mandatory;
  }

  .toc-track-shell {
    margin-top: 0.75rem;
  }
}