/* ═══════════════════════════════════════════════════════════════
   Chapter Navigation — Minimal Sidebar
   ═══════════════════════════════════════════════════════════════ */

/* ── Navigation Toggle ── */
.nav-toggle {
  position: fixed;
  top: var(--space-md);
  right: var(--space-md);
  z-index: 100;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  padding: 8px;
  opacity: 0.4;
  transition: opacity var(--duration-fast) var(--ease-out);
}

.nav-toggle:hover {
  opacity: 1;
}

.nav-toggle__line {
  width: 20px;
  height: 1px;
  background: var(--parchment-dim);
  transition: all var(--duration-fast) var(--ease-out);
}

.nav-toggle.is-active .nav-toggle__line:nth-child(1) {
  transform: rotate(45deg) translate(4px, 4px);
}

.nav-toggle.is-active .nav-toggle__line:nth-child(2) {
  opacity: 0;
}

.nav-toggle.is-active .nav-toggle__line:nth-child(3) {
  transform: rotate(-45deg) translate(4px, -4px);
}

/* ── Navigation Panel ── */
.chapter-nav {
  position: fixed;
  top: 0;
  right: 0;
  width: min(320px, 85vw);
  height: 100vh;
  background: var(--abyss-deep);
  border-left: 1px solid var(--mud);
  z-index: 99;
  transform: translateX(100%);
  transition: transform var(--duration-normal) var(--ease-out);
  overflow-y: auto;
  padding: var(--space-xl) var(--space-md) var(--space-lg);
  scrollbar-width: none;
}

.chapter-nav::-webkit-scrollbar {
  display: none;
}

.chapter-nav.is-open {
  transform: translateX(0);
}

/* ── Nav Header ── */
.chapter-nav__header {
  font-family: 'Cormorant Garamond', Georgia, serif;
  font-size: var(--fs-xs);
  font-weight: 400;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--parchment-ghost);
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-sm);
  border-bottom: 1px solid var(--mud);
}

/* ── Nav Parts ── */
.chapter-nav__part {
  margin-bottom: var(--space-md);
}

.chapter-nav__part-title {
  font-family: 'Cormorant Garamond', Georgia, serif;
  font-size: var(--fs-sm);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--parchment-dim);
  margin-bottom: var(--space-xs);
}

/* ── Nav Links ── */
.chapter-nav__list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.chapter-nav__link {
  display: block;
  padding: var(--space-xs) 0;
  font-family: 'Crimson Pro', Georgia, serif;
  font-size: var(--fs-sm);
  color: var(--parchment-ghost);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out);
  border-left: 2px solid transparent;
  padding-left: var(--space-sm);
}

.chapter-nav__link:hover {
  color: var(--parchment);
}

.chapter-nav__link.is-active {
  color: var(--parchment-bright);
  border-left-color: var(--blood);
}

.chapter-nav__link.is-read {
  color: var(--parchment-dim);
}

/* ── Chapter Counter ── */
.chapter-nav__counter {
  font-size: var(--fs-xs);
  color: var(--parchment-ghost);
  font-variant-numeric: tabular-nums;
  margin-right: var(--space-xs);
}

/* ── Backdrop ── */
.nav-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(4, 4, 4, 0.7);
  z-index: 98;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--duration-normal) var(--ease-out);
}

.nav-backdrop.is-visible {
  opacity: 1;
  pointer-events: auto;
}

/* ── Current Chapter Indicator (mini, always visible) ── */
.current-chapter {
  position: fixed;
  bottom: var(--space-md);
  right: var(--space-md);
  font-family: 'Cormorant Garamond', Georgia, serif;
  font-size: var(--fs-xs);
  color: var(--parchment-ghost);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  opacity: 0;
  transition: opacity var(--duration-normal) var(--ease-out);
  z-index: 50;
  pointer-events: none;
}

.current-chapter.is-visible {
  opacity: 0.5;
}

/* ── Responsive ── */
@media (max-width: 480px) {
  .nav-toggle {
    top: var(--space-sm);
    right: var(--space-sm);
  }

  .chapter-nav {
    width: 100vw;
  }

  .current-chapter {
    bottom: var(--space-sm);
    right: var(--space-sm);
    font-size: 0.65rem;
  }
}