/* ── App shell ─────────────────────────────────────────── */

.app-shell {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  grid-template-rows: 100vh;
  min-height: 100vh;
}

.app-shell--collapsed {
  grid-template-columns: var(--sidebar-collapsed) 1fr;
}

.app-shell--no-book {
  grid-template-columns: 1fr;
}

/* ── Sidebar ───────────────────────────────────────────── */

.sidebar {
  display: flex;
  flex-direction: column;
  background: var(--color-bg-sidebar);
  color: var(--color-text-on-brand);
  z-index: var(--z-sidebar);
  overflow: hidden;
}

.sidebar__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-5) var(--space-4);
  border-bottom: 1px solid rgba(247, 243, 236, 0.1);
  min-height: var(--topbar-height);
}

.sidebar__logo {
  flex-shrink: 0;
  width: 2.25rem;
  height: 2.25rem;
  display: block;
  border-radius: var(--radius-sm);
  object-fit: cover;
}

.sidebar__title {
  font-size: var(--text-base);
  font-weight: var(--weight-semibold);
  letter-spacing: -0.01em;
  white-space: nowrap;
  overflow: hidden;
}

.sidebar__subtitle {
  font-size: var(--text-xs);
  color: var(--color-text-on-brand-muted);
  white-space: nowrap;
}

.app-shell--collapsed .sidebar__title,
.app-shell--collapsed .sidebar__subtitle,
.app-shell--collapsed .nav-section__label,
.app-shell--collapsed .nav-link__text,
.app-shell--collapsed .sidebar__book-meta {
  display: none;
}

.sidebar__nav {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-4) var(--space-3);
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

.nav-section__label {
  padding: 0 var(--space-3);
  margin-bottom: var(--space-2);
  font-size: 0.6875rem;
  font-weight: var(--weight-semibold);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-on-brand-muted);
}

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  color: var(--color-text-on-brand-muted);
  text-decoration: none;
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  transition: background var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out);
}

.nav-link:hover {
  background: var(--color-bg-sidebar-hover);
  color: var(--color-text-on-brand);
  text-decoration: none;
}

.nav-link.is-active {
  background: var(--color-bg-sidebar-active);
  color: var(--color-text-on-brand);
}

.nav-link.is-disabled {
  opacity: 0.4;
  pointer-events: none;
}

.nav-link__icon {
  flex-shrink: 0;
  width: 1.25rem;
  height: 1.25rem;
  display: grid;
  place-items: center;
  font-size: var(--text-sm);
  opacity: 0.9;
}

.nav-group {
  display: flex;
  flex-direction: column;
  gap: 0.125rem;
}

.nav-group__row {
  display: flex;
  align-items: stretch;
  gap: 0.125rem;
}

.nav-group__row .nav-link--parent {
  flex: 1;
  min-width: 0;
}

.nav-group__toggle {
  flex-shrink: 0;
  width: 1.75rem;
  border: none;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-text-on-brand-muted);
  cursor: pointer;
  font-size: 0.7rem;
  line-height: 1;
  transition: background var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out),
              transform var(--duration-fast) var(--ease-out);
}

.nav-group__toggle:hover:not(:disabled) {
  background: var(--color-bg-sidebar-hover);
  color: var(--color-text-on-brand);
}

.nav-group__toggle:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.nav-group.is-open .nav-group__toggle {
  transform: rotate(180deg);
}

.nav-group__children {
  display: flex;
  flex-direction: column;
  gap: 0.125rem;
  padding: 0.15rem 0 0.35rem 0.5rem;
  margin-left: 1.1rem;
  border-left: 1px solid rgba(247, 243, 236, 0.12);
}

.nav-group__children[hidden] {
  display: none;
}

.nav-sublink {
  display: block;
  padding: 0.35rem 0.65rem;
  border-radius: var(--radius-sm);
  color: var(--color-text-on-brand-muted);
  text-decoration: none;
  font-size: 0.8125rem;
  font-weight: var(--weight-medium);
  transition: background var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out);
}

.nav-sublink:hover {
  background: var(--color-bg-sidebar-hover);
  color: var(--color-text-on-brand);
  text-decoration: none;
}

.nav-sublink.is-active {
  background: var(--color-bg-sidebar-active);
  color: var(--color-text-on-brand);
}

.nav-sublink.is-disabled {
  opacity: 0.4;
  pointer-events: none;
}

.app-shell--collapsed .nav-group__toggle,
.app-shell--collapsed .nav-group__children {
  display: none;
}

.sidebar__footer {
  padding: var(--space-3);
  border-top: 1px solid rgba(247, 243, 236, 0.1);
}

.sidebar__book {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3);
  border-radius: var(--radius-sm);
  background: rgba(247, 243, 236, 0.06);
  cursor: pointer;
  border: none;
  width: 100%;
  text-align: left;
  color: inherit;
  transition: background var(--duration-fast) var(--ease-out);
}

.sidebar__book:hover {
  background: rgba(247, 243, 236, 0.12);
}

.sidebar__book-icon {
  flex-shrink: 0;
  width: 2rem;
  height: 2rem;
  display: grid;
  place-items: center;
  border-radius: var(--radius-sm);
  background: rgba(247, 243, 236, 0.1);
  font-size: var(--text-sm);
}

.sidebar__book-name {
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.sidebar__book-fy {
  font-size: var(--text-xs);
  color: var(--color-text-on-brand-muted);
}

/* ── Main column ───────────────────────────────────────── */

.main-column {
  display: flex;
  flex-direction: column;
  min-width: 0;
  overflow: hidden;
}

.topbar {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  height: var(--topbar-height);
  padding: 0 var(--space-6);
  background: rgba(255, 252, 247, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
  z-index: var(--z-topbar);
}

.topbar__toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.25rem;
  height: 2.25rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg-elevated);
  color: var(--color-text);
}

.topbar__crumb {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  min-width: 0;
}

.topbar__crumb-current {
  color: var(--color-text);
  font-weight: var(--weight-medium);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.topbar__actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.topbar__backup {
  display: flex;
  align-items: center;
  gap: 0.15rem;
}

.topbar__icon-btn {
  display: inline-grid;
  place-items: center;
  width: 2.25rem;
  height: 2.25rem;
  padding: 0;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg-elevated);
  color: var(--color-text-muted);
  cursor: pointer;
}

.topbar__icon-btn:hover {
  color: var(--color-text);
  border-color: var(--color-brand);
  background: var(--color-bg-muted);
}

.topbar__icon-btn:disabled {
  opacity: 0.55;
  cursor: wait;
}

.topbar__icon {
  display: block;
}

.content {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-6);
}

.content__inner {
  max-width: var(--content-max);
  margin: 0 auto;
  animation: content-in var(--duration-normal) var(--ease-out);
}

@keyframes content-in {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.page-header {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
  margin-bottom: var(--space-6);
}

.page-header__title {
  font-size: var(--text-2xl);
  letter-spacing: -0.02em;
}

.page-header__desc {
  margin-top: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  max-width: 36rem;
}

.page-header__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ── Book gate (no active book) ────────────────────────── */

.book-gate {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.book-gate__header {
  padding: var(--space-6) var(--space-8);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.book-gate__logo {
  width: 2.5rem;
  height: 2.5rem;
  display: block;
  border-radius: var(--radius-sm);
  object-fit: cover;
}

.book-gate__brand {
  font-size: var(--text-lg);
  font-weight: var(--weight-semibold);
  letter-spacing: -0.01em;
}

.book-gate__body {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
}

.book-gate__panel {
  width: 100%;
  max-width: 32rem;
}

.book-gate__headline {
  font-size: var(--text-3xl);
  letter-spacing: -0.03em;
  margin-bottom: var(--space-3);
}

.book-gate__lede {
  color: var(--color-text-muted);
  margin-bottom: var(--space-8);
  line-height: var(--leading-relaxed);
}

/* ── Mobile overlay & drawer ───────────────────────────── */

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(26, 28, 27, 0.45);
  z-index: calc(var(--z-sidebar) - 1);
  opacity: 0;
  transition: opacity var(--duration-normal) var(--ease-out);
}

.sidebar-overlay.is-open {
  display: block;
  opacity: 1;
}

@media (max-width: 900px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: var(--sidebar-width);
    transform: translateX(-100%);
    transition: transform var(--duration-normal) var(--ease-out);
  }

  .app-shell--nav-open .sidebar {
    transform: translateX(0);
  }

  .app-shell--nav-open .sidebar-overlay {
    display: block;
    opacity: 1;
  }

  .topbar__toggle {
    display: inline-flex;
  }

  .content {
    padding: var(--space-4);
  }

  .book-gate__header {
    padding: var(--space-4);
  }

  .book-gate__headline {
    font-size: var(--text-2xl);
  }
}