:root {
  --bg: #eef2f7;
  --panel: #fff;
  --panel-soft: #f8fafc;
  --border: #dbe3ef;
  --text: #1e293b;
  --muted: #64748b;
  --accent: #2563eb;
  --accent-soft: #eff6ff;
  --nav-soft: #f0fdf4;
  --nav-prefix: #047857;
  --shadow: 0 8px 24px rgba(15, 23, 42, 0.08);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

.hidden { display: none !important; }

.demo-badge {
  position: fixed; top: 10px; left: 10px; z-index: 200;
  padding: 5px 10px; border-radius: 8px; background: #0f172a; color: #f8fafc;
  font-size: 11px; font-weight: 600;
}

.demo-back {
  position: fixed; top: 10px; right: 10px; z-index: 200;
  padding: 6px 12px; border-radius: 8px; border: 1px solid var(--border);
  background: var(--panel); color: var(--text); text-decoration: none; font-size: 12px;
  box-shadow: var(--shadow);
}

.toast {
  position: fixed; bottom: 20px; left: 50%;
  transform: translateX(-50%) translateY(12px);
  padding: 10px 16px; border-radius: 8px; background: #0f172a; color: #fff;
  font-size: 13px; opacity: 0; pointer-events: none; transition: opacity 0.2s, transform 0.2s; z-index: 300;
}

.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

.shell { display: grid; grid-template-rows: 48px 1fr; min-height: 100vh; }

.shell-header {
  display: flex; align-items: center; gap: 12px; padding: 0 16px;
  border-bottom: 1px solid var(--border); background: var(--panel);
}

.shell-header h1 { margin: 0; font-size: 16px; }
.shell-header span { font-size: 12px; color: var(--muted); }

.shell-body { display: grid; grid-template-columns: 180px 1fr; min-height: 0; }

.sidebar {
  border-right: 1px solid var(--border); background: var(--panel-soft);
  padding: 12px; display: flex; flex-direction: column; gap: 4px;
}

.sidebar-label {
  font-size: 10px; font-weight: 700; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--muted); margin-bottom: 4px;
}

.sidebar-item {
  padding: 8px 10px; border-radius: 8px; font-size: 13px; color: var(--muted);
}

.sidebar-item.active { background: var(--nav-soft); color: var(--nav-prefix); font-weight: 600; }

.workspace {
  padding: 0; overflow: auto;
  display: flex; flex-direction: column; align-items: stretch;
}

/* —— Stage & path header —— */
.nav-stage {
  width: 100%; min-height: 100%;
  display: flex; flex-direction: column;
}

.nav-path-header {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  padding: 9px 16px; border-bottom: 1px solid var(--border);
  background: var(--nav-soft);
}

.nav-subsection-select {
  flex: 0 0 auto; max-width: min(220px, 42vw);
  padding: 5px 28px 5px 10px; border: 1px solid var(--border);
  border-radius: 8px; background: var(--panel); font-size: 12px; font-weight: 600;
  color: var(--text); cursor: pointer;
}

.nav-breadcrumbs {
  display: flex; align-items: center; flex-wrap: wrap; gap: 4px;
  font-size: 12px; min-width: 0; flex: 1;
}

.nav-crumb-prefix {
  font-weight: 700; color: var(--nav-prefix); margin-right: 4px;
}

.nav-crumb { color: var(--muted); }
.nav-crumb-sep { color: #cbd5e1; user-select: none; }

/* —— Hub —— */
.nav-hub {
  display: flex; flex-direction: column; gap: 24px;
  padding: 20px 24px 32px; max-width: 860px; margin: 0 auto; width: 100%;
}

.nav-block-title {
  margin: 0 0 12px; font-size: 12px; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.06em; color: #475569;
}

/* —— Subsection cards (gallery) —— */
.nav-sub-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 12px;
}

.nav-sub-card {
  display: flex; flex-direction: column; border: 1px solid var(--border);
  border-radius: 12px; overflow: hidden; cursor: pointer;
  transition: border-color 0.15s, box-shadow 0.15s, transform 0.15s;
  background: var(--panel);
}

.nav-sub-card:hover, .nav-sub-card:focus-visible {
  border-color: color-mix(in srgb, var(--sub-color) 70%, var(--border));
  box-shadow: 0 6px 18px color-mix(in srgb, var(--sub-color) 24%, transparent);
  transform: translateY(-1px); outline: none;
}

.nav-sub-cover {
  height: 96px; display: flex; align-items: center; justify-content: center;
  font-size: 36px;
  background: linear-gradient(135deg, var(--sub-color), color-mix(in srgb, var(--sub-color) 42%, #fff));
}

.nav-sub-foot {
  padding: 12px; border-top: 1px solid rgba(15, 23, 42, 0.06);
}

.nav-sub-foot strong {
  font-size: 13px; font-weight: 700; color: #475569; line-height: 1.35;
}

.nav-sub-card:hover .nav-sub-foot strong { color: var(--sub-text); }

/* —— Subsection chips —— */
.nav-sub-chips { display: flex; flex-wrap: wrap; gap: 8px; }

.nav-sub-chip {
  border: 1px solid var(--border); background: var(--panel-soft);
  padding: 8px 14px; border-radius: 999px; font-size: 13px; font-weight: 600;
  cursor: pointer; color: var(--text);
}

.nav-sub-chip:hover { background: var(--sub-color); border-color: color-mix(in srgb, var(--sub-color) 80%, var(--border)); }

/* —— Subsection rows —— */
.nav-sub-list { display: flex; flex-direction: column; gap: 8px; }

.nav-sub-row {
  display: grid; grid-template-columns: 40px 1fr 20px; gap: 12px; align-items: center;
  width: 100%; padding: 12px 14px; border: 1px solid var(--border); border-radius: 10px;
  background: var(--panel); cursor: pointer; text-align: left; font: inherit; color: inherit;
}

.nav-sub-row:hover { border-color: #93c5fd; background: var(--accent-soft); }
.nav-sub-row-icon { font-size: 22px; text-align: center; }
.nav-sub-row-title { font-weight: 600; font-size: 14px; }
.nav-sub-row-chevron { color: var(--muted); font-size: 18px; }

/* —— Compact subs —— */
.nav-sub-compact-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); gap: 8px;
}

.nav-sub-compact {
  display: flex; flex-direction: column; align-items: center; gap: 6px;
  padding: 12px 8px; border: 1px solid var(--border); border-radius: 10px;
  background: var(--panel-soft); cursor: pointer; font: inherit; color: inherit;
}

.nav-sub-compact-cover {
  width: 44px; height: 44px; border-radius: 10px; display: flex; align-items: center; justify-content: center;
  font-size: 22px; background: var(--sub-color);
}

.nav-sub-compact-title { font-size: 12px; font-weight: 600; text-align: center; }

/* —— Document flow —— */
.nav-document {
  font-size: 14px; line-height: 1.6; color: var(--text);
}

.nav-doc-part + .nav-doc-part {
  margin-top: 1.25em; padding-top: 1.25em; border-top: 1px solid #e8edf2;
}

.nav-preview h2 { margin: 0 0 0.5em; font-size: 1.25em; }
.nav-preview h3 { margin: 1em 0 0.35em; font-size: 1.05em; }
.nav-preview p { margin: 0 0 0.75em; }
.nav-preview ul { margin: 0 0 0.75em; padding-left: 1.25em; }

/* —— External TOC —— */
.nav-ext-toc { display: flex; flex-direction: column; gap: 0; }

.nav-ext-section { margin: 0 0 0.85em; }
.nav-ext-section:last-child { margin-bottom: 0; }

.nav-ext-title {
  margin: 0 0 0.35em; padding: 0; font-size: 1em; font-weight: 600;
  background: none; border: none; color: inherit;
}

.nav-ext-list { margin: 0 0 0.5em; padding: 0; list-style: none; }

.nav-ext-list li { padding: 0.15em 0; }

.nav-ext-list a {
  color: var(--accent); text-decoration: none; font-size: inherit;
}

.nav-ext-list a:hover { text-decoration: underline; }

/* —— External cards —— */
.nav-ext-cards {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 10px;
}

.nav-ext-card {
  display: flex; flex-direction: column; gap: 4px; padding: 12px;
  border: 1px solid var(--border); border-radius: 10px; text-decoration: none;
  color: var(--text); background: var(--panel-soft);
}

.nav-ext-card:hover { border-color: #93c5fd; background: var(--accent-soft); }
.nav-ext-card-folder { font-size: 10px; font-weight: 700; text-transform: uppercase; color: var(--muted); }
.nav-ext-card strong { font-size: 13px; }

/* —— Tabular —— */
.nav-tabular-wrap { overflow-x: auto; margin: 0; }

.nav-tabular {
  width: 100%; border-collapse: collapse; font-size: 13px;
}

.nav-tabular th, .nav-tabular td {
  border: 1px solid var(--border); padding: 8px 12px; text-align: left;
}

.nav-tabular th { background: var(--panel-soft); font-weight: 600; }

.nav-tabular tbody tr:hover td { background: var(--accent-soft); }

/* —— Media —— */
.nav-media-list {
  list-style: disc; margin: 0.5em 0 0 1.25em; padding: 0;
}

.nav-media-list li { margin: 0.2em 0; }

.nav-media-list a { color: var(--accent); text-decoration: none; word-break: break-all; }
.nav-media-list a:hover { text-decoration: underline; }

.nav-media-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(100px, 1fr)); gap: 10px;
}

.nav-media-thumb {
  display: flex; flex-direction: column; align-items: center; gap: 6px;
  padding: 14px 8px; border: 1px solid var(--border); border-radius: 10px;
  text-decoration: none; color: var(--text); background: var(--panel-soft); font-size: 28px;
}

.nav-media-thumb small { font-size: 10px; color: var(--muted); text-align: center; word-break: break-all; }
.nav-media-thumb:hover { border-color: #93c5fd; background: var(--accent-soft); }

@media (max-width: 640px) {
  .shell-body { grid-template-columns: 1fr; }
  .sidebar { display: none; }
  .nav-hub { padding: 16px; }
}