* {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      -webkit-font-smoothing: antialiased;
    }

    body {
      background-color: var(--bg);
      color: var(--text);
      font-family: var(--font-sans);
      line-height: 1.6;
      padding: 24px 20px 80px;
      transition: background-color 0.2s ease, color 0.2s ease;
    }

    /* Outer Presentation Canvas */
    .overview-container {
      max-width: 1360px;
      margin: 0 auto;
    }

    .doc-header {
      margin-bottom: 36px;
      padding-bottom: 20px;
      border-bottom: 1px solid var(--border);
      display: flex;
      flex-wrap: wrap;
      justify-content: space-between;
      align-items: flex-end;
      gap: 16px;
    }

    .doc-badge {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      color: var(--accent);
      margin-bottom: 6px;
      display: inline-block;
    }

    .doc-title {
      font-family: var(--font-serif);
      font-size: clamp(2rem, 3.5vw, 2.75rem);
      font-weight: 500;
      color: var(--text);
      line-height: 1.15;
      letter-spacing: -0.02em;
    }

    .doc-desc {
      color: var(--text-muted);
      font-size: 14px;
      max-width: 720px;
      margin-top: 8px;
    }

    .theme-toggle-btn {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      padding: 8px 14px;
      border-radius: var(--radius-sm);
      border: 1px solid var(--border);
      background: var(--surface);
      color: var(--text);
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      min-height: 44px;
    }

    .theme-toggle-btn:focus-visible {
      outline: 2px solid var(--accent);
      outline-offset: 2px;
    }

    .section-title-wrap {
      margin: 48px 0 20px;
    }

    .section-tag {
      font-size: 12px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.05em;
      color: var(--accent);
    }

    .section-heading {
      font-family: var(--font-serif);
      font-size: 24px;
      font-weight: 500;
      color: var(--text);
      margin-top: 2px;
    }

    .section-sub {
      font-size: 13px;
      color: var(--text-muted);
      margin-top: 4px;
    }

    /* Grid for Mobile screens */
    .mobile-row {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(360px, 390px));
      gap: 32px;
      margin-bottom: 40px;
      align-items: start;
    }

    .frame-wrapper {
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    .frame-meta {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 12px;
      font-weight: 600;
      color: var(--text-muted);
      padding: 0 4px;
    }

    .status-badge {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      padding: 2px 8px;
      border-radius: 4px;
      font-size: 11px;
      background: var(--surface-raised);
      border: 1px solid var(--border);
    }

    /* 390px Mobile Phone Shell */
    .mobile-screen {
      width: 390px;
      min-height: 844px;
      background: var(--bg);
      border: 1px solid var(--border);
      border-radius: 36px;
      box-shadow: 0 12px 36px rgba(0, 0, 0, 0.08);
      overflow: hidden;
      display: flex;
      flex-direction: column;
      position: relative;
    }



    /* Device status bar */
    .phone-status-bar {
      height: 44px;
      padding: 0 20px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 12px;
      font-weight: 600;
      color: var(--text);
      z-index: 10;
      background: var(--bg);
    }

    .phone-notch {
      width: 120px;
      height: 24px;
      background: var(--surface-raised);
      border-radius: 0 0 14px 14px;
      border: 1px solid var(--border);
      border-top: none;
    }

    /* App Shell Header (Collapsing Top Bar) */
    .app-header {
      padding: 8px 16px 12px;
      background: var(--bg);
      border-bottom: 1px solid var(--border-subtle);
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
    }

    .brand-group {
      display: flex;
      align-items: center;
      gap: 10px;
    }

    .brand-mark {
      width: 32px;
      height: 32px;
      background: var(--accent);
      color: var(--accent-contrast);
      font-weight: 700;
      font-size: 16px;
      border-radius: 8px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-family: var(--font-serif);
      flex-shrink: 0;
    }

    .brand-text {
      display: flex;
      flex-direction: column;
    }

    .brand-title {
      font-size: 15px;
      font-weight: 700;
      line-height: 1.15;
      color: var(--text);
      letter-spacing: -0.01em;
    }

    .brand-sub {
      font-size: 10px;
      font-weight: 600;
      color: var(--text-muted);
      letter-spacing: 0.04em;
    }

    .header-actions {
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .lang-pill {
      font-size: 11px;
      font-weight: 600;
      padding: 4px 6px;
      border-radius: 4px;
      color: var(--text-muted);
      background: var(--surface-raised);
      border: 1px solid var(--border-subtle);
    }

    .lang-pill.active {
      color: var(--accent);
      font-weight: 700;
      background: var(--surface);
      border-color: var(--accent);
    }

    .theme-icon-slot {
      width: 32px;
      height: 32px;
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      border: 1px solid var(--border);
      background: var(--surface);
      color: var(--text-muted);
      font-size: 12px;
    }

    /* Screen Scrollable Body */
    .screen-content {
      flex: 1;
      overflow-y: auto;
      padding: 16px 16px 24px;
      display: flex;
      flex-direction: column;
      gap: 20px;
    }

    /* Welcome / Purpose Micro-Header */
    .screen-greeting {
      padding: 0 2px;
    }

    .greeting-title {
      font-family: var(--font-serif);
      font-size: 22px;
      font-weight: 500;
      color: var(--text);
      line-height: 1.25;
    }

    .greeting-sub {
      font-size: 13px;
      color: var(--text-muted);
      margin-top: 2px;
    }

    /* Priority Block 1: Continue / Resume Session */
    .continue-card {
      background: var(--surface);
      border: 1.5px solid var(--accent);
      border-radius: var(--radius-md);
      padding: 16px;
      position: relative;
      box-shadow: 0 4px 14px rgba(87, 94, 207, 0.08);
      display: flex;
      flex-direction: column;
      gap: 12px;
    }



    .continue-badge-row {
      display: flex;
      justify-content: space-between;
      align-items: center;
    }

    .active-session-label {
      font-size: 11px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.05em;
      color: var(--accent);
      display: flex;
      align-items: center;
      gap: 6px;
    }

    .pulse-dot {
      width: 6px;
      height: 6px;
      border-radius: 50%;
      background: var(--accent);
    }

    .session-source-stamp {
      font-size: 11px;
      color: var(--text-subtle);
      font-variant-numeric: tabular-nums;
    }

    .continue-topic {
      font-family: var(--font-serif);
      font-size: 18px;
      font-weight: 500;
      color: var(--text);
      line-height: 1.3;
    }

    .continue-meta-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 12px;
      color: var(--text-muted);
      border-top: 1px solid var(--border-subtle);
      padding-top: 10px;
    }

    .progress-track {
      width: 100%;
      height: 4px;
      background: var(--surface-raised);
      border-radius: 2px;
      overflow: hidden;
      margin-top: 2px;
    }

    .progress-fill {
      height: 100%;
      background: var(--accent);
      border-radius: 2px;
    }

    .btn-primary-action {
      background: var(--accent);
      color: var(--accent-contrast);
      font-family: var(--font-sans);
      font-weight: 600;
      font-size: 14px;
      border: none;
      border-radius: var(--radius-sm);
      height: 44px;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      cursor: pointer;
      transition: background 0.15s ease;
      text-decoration: none;
    }

    .btn-primary-action:hover {
      background: var(--accent-hover);
    }

    .btn-primary-action:focus-visible {
      outline: 2px solid var(--text);
      outline-offset: 2px;
    }

    /* First-run variant of Block 1 */
    .start-fresh-card {
      background: var(--surface);
      border: 1.5px dashed var(--accent);
      border-radius: var(--radius-md);
      padding: 18px 16px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .start-fresh-header {
      display: flex;
      align-items: flex-start;
      gap: 12px;
    }

    .start-fresh-icon {
      width: 36px;
      height: 36px;
      border-radius: 8px;
      background: var(--accent-light);
      color: var(--accent);
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 18px;
      flex-shrink: 0;
    }

    .start-fresh-text h3 {
      font-family: var(--font-serif);
      font-size: 17px;
      font-weight: 500;
      color: var(--text);
      line-height: 1.25;
    }

    .start-fresh-text p {
      font-size: 12px;
      color: var(--text-muted);
      margin-top: 3px;
      line-height: 1.45;
    }

    /* Priority Block 2: Quick Start (10 questions) */
    .block-section {
      display: flex;
      flex-direction: column;
      gap: 10px;
    }

    .block-heading-row {
      display: flex;
      align-items: baseline;
      justify-content: space-between;
      padding: 0 2px;
    }

    .block-heading {
      font-size: 13px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.05em;
      color: var(--text-muted);
    }

    .block-meta {
      font-size: 11px;
      color: var(--text-subtle);
    }

    .quick-start-selector {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-md);
      padding: 14px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .quick-chips-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 8px;
    }

    .quick-chip {
      min-height: 44px;
      padding: 8px 10px;
      border: 1px solid var(--border);
      border-radius: var(--radius-sm);
      background: var(--bg);
      color: var(--text);
      font-size: 12px;
      font-weight: 600;
      display: flex;
      align-items: center;
      justify-content: space-between;
      cursor: pointer;
      text-align: left;
      transition: border-color 0.15s ease, background 0.15s ease;
    }

    .quick-chip:hover {
      border-color: var(--accent);
      background: var(--surface-raised);
    }

    .quick-chip.selected {
      border-color: var(--accent);
      background: var(--accent-light);
      color: var(--accent);
    }

    .quick-chip-name {
      white-space: nowrap;
      overflow: hidden;
      text-overflow: ellipsis;
    }

    .quick-chip-count {
      font-size: 10px;
      font-weight: 500;
      color: var(--text-subtle);
      margin-left: 4px;
      flex-shrink: 0;
    }

    .quick-chip.selected .quick-chip-count {
      color: var(--accent);
      font-weight: 700;
    }

    .btn-secondary-action {
      background: var(--surface-raised);
      color: var(--text);
      border: 1px solid var(--border);
      font-weight: 600;
      font-size: 13px;
      border-radius: var(--radius-sm);
      height: 44px;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      cursor: pointer;
      transition: background 0.15s ease, border-color 0.15s ease;
    }

    .btn-secondary-action:hover {
      background: var(--border-subtle);
      border-color: var(--accent);
    }

    /* Priority Block 3: Disciplines Overview (10 disciplines) */
    .disciplines-list {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-md);
      overflow: hidden;
    }

    .discipline-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 12px 14px;
      min-height: 48px;
      border-bottom: 1px solid var(--border-subtle);
      text-decoration: none;
      color: var(--text);
      transition: background 0.12s ease;
    }

    .discipline-row:last-child {
      border-bottom: none;
    }

    .discipline-row:hover {
      background: var(--surface-raised);
    }

    .discipline-row:focus-visible {
      outline: 2px solid var(--accent);
      outline-offset: -2px;
    }

    .discipline-info {
      display: flex;
      align-items: center;
      gap: 10px;
    }

    .discipline-dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
      background: var(--border);
      flex-shrink: 0;
    }

    .discipline-dot.active {
      background: var(--accent);
    }

    .discipline-name {
      font-size: 13px;
      font-weight: 500;
    }

    .discipline-counts {
      display: flex;
      align-items: center;
      gap: 6px;
      font-size: 12px;
      font-variant-numeric: tabular-nums;
    }

    .count-seen {
      color: var(--text);
      font-weight: 600;
    }

    .count-divider {
      color: var(--text-subtle);
    }

    .count-total {
      color: var(--text-muted);
    }

    .row-arrow {
      color: var(--text-subtle);
      font-size: 14px;
      margin-left: 6px;
    }

    /* Empty state notice for Disciplines */
    .empty-state-banner {
      background: var(--surface-raised);
      border: 1px dashed var(--border);
      border-radius: var(--radius-sm);
      padding: 10px 12px;
      font-size: 12px;
      color: var(--text-muted);
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 6px;
    }

    /* Priority Block 4: Exam Mode Entry (Heavier, distinct commitment) */
    .exam-mode-card {
      background: linear-gradient(180deg, var(--surface) 0%, var(--surface-raised) 100%);
      border: 2px solid var(--text);
      border-radius: var(--radius-lg);
      padding: 18px 16px;
      display: flex;
      flex-direction: column;
      gap: 14px;
      position: relative;
    }



    .exam-card-header {
      display: flex;
      justify-content: space-between;
      align-items: flex-start;
      gap: 8px;
    }

    .exam-badge {
      display: inline-flex;
      align-items: center;
      gap: 4px;
      font-size: 10px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      padding: 3px 8px;
      border-radius: 4px;
      background: var(--text);
      color: var(--bg);
    }



    .exam-rules-tag {
      font-size: 11px;
      color: var(--text-subtle);
    }

    .exam-title {
      font-family: var(--font-serif);
      font-size: 19px;
      font-weight: 600;
      color: var(--text);
      line-height: 1.25;
    }

    .exam-specs-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
      background: var(--surface);
      border: 1px solid var(--border-subtle);
      border-radius: var(--radius-sm);
      padding: 10px;
      text-align: center;
    }

    .spec-item {
      display: flex;
      flex-direction: column;
      gap: 2px;
    }

    .spec-val {
      font-size: 14px;
      font-weight: 700;
      color: var(--text);
    }

    .spec-lbl {
      font-size: 10px;
      color: var(--text-muted);
      text-transform: uppercase;
      letter-spacing: 0.04em;
    }

    .btn-exam-action {
      background: var(--text);
      color: var(--bg);
      font-weight: 600;
      font-size: 14px;
      border: none;
      border-radius: var(--radius-sm);
      min-height: 48px;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      cursor: pointer;
      transition: opacity 0.15s ease;
    }



    .btn-exam-action:hover {
      opacity: 0.92;
    }

    .btn-exam-action:focus-visible {
      outline: 2px solid var(--accent);
      outline-offset: 2px;
    }

    /* Fixed Bottom Tab Bar */
    .app-tabbar {
      position: sticky;
      bottom: 0;
      left: 0;
      right: 0;
      height: 60px;
      background: var(--surface);
      border-top: 1px solid var(--border);
      display: grid;
      grid-template-columns: repeat(5, 1fr);
      z-index: 20;
    }

    .tab-item {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 2px;
      text-decoration: none;
      color: var(--text-muted);
      min-height: 44px;
      padding: 4px 0;
      position: relative;
    }

    .tab-item.active {
      color: var(--accent);
    }

    .tab-icon {
      font-size: 18px;
      line-height: 1;
    }

    .tab-label {
      font-size: 10px;
      font-weight: 600;
    }

    .tab-item.active::after {
      content: '';
      position: absolute;
      top: 0;
      width: 24px;
      height: 2px;
      background: var(--accent);
      border-radius: 0 0 2px 2px;
    }

    /* Special Status Banners */
    .banner-offline {
      background: var(--surface-raised);
      border-bottom: 1px solid var(--border);
      padding: 6px 14px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 11px;
      color: var(--text-muted);
    }

    .banner-offline .dot {
      width: 7px;
      height: 7px;
      border-radius: 50%;
      background: var(--orange);
      display: inline-block;
      margin-right: 6px;
    }

    .locked-overlay-wrap {
      position: relative;
      opacity: 0.65;
      pointer-events: none;
    }

    .lock-notice-box {
      margin-top: 10px;
      background: var(--surface-raised);
      border: 1px solid var(--border);
      border-radius: var(--radius-sm);
      padding: 12px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 12px;
    }

    .lock-notice-link {
      color: var(--accent);
      font-weight: 600;
      text-decoration: none;
    }

    /* Skeleton Loading State */
    .skeleton-box {
      background: linear-gradient(90deg, var(--surface-raised) 25%, var(--border-subtle) 50%, var(--surface-raised) 75%);
      background-size: 200% 100%;
      animation: shimmer 1.6s infinite;
      border-radius: var(--radius-sm);
    }

    @keyframes shimmer {
      0% { background-position: 200% 0; }
      100% { background-position: -200% 0; }
    }

    @media (prefers-reduced-motion: reduce) {
      .skeleton-box {
        animation: none;
        background: var(--surface-raised);
      }
    }

    /* DESKTOP 1280px Arrangement */
    .desktop-showcase {
      margin-top: 40px;
      border: 1px solid var(--border);
      border-radius: 16px;
      background: var(--surface);
      box-shadow: 0 16px 48px rgba(0, 0, 0, 0.06);
      overflow: hidden;
    }



    .browser-bar {
      height: 40px;
      background: var(--surface-raised);
      border-bottom: 1px solid var(--border);
      padding: 0 16px;
      display: flex;
      align-items: center;
      gap: 12px;
      font-size: 12px;
      color: var(--text-muted);
    }

    .window-dots {
      display: flex;
      gap: 6px;
    }

    .window-dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      background: var(--border);
    }

    .browser-url {
      background: var(--surface);
      border: 1px solid var(--border-subtle);
      border-radius: 6px;
      padding: 2px 16px;
      font-size: 11px;
      color: var(--text-subtle);
      font-family: monospace;
    }

    .desktop-layout {
      display: grid;
      grid-template-columns: 240px 1fr;
      min-height: 800px;
      background: var(--bg);
    }

    /* Left Sidebar 240px */
    .desktop-sidebar {
      background: var(--surface);
      border-right: 1px solid var(--border);
      display: flex;
      flex-direction: column;
      padding: 20px 16px;
    }

    .sidebar-brand {
      display: flex;
      align-items: center;
      gap: 10px;
      margin-bottom: 32px;
    }

    .sidebar-nav {
      display: flex;
      flex-direction: column;
      gap: 4px;
      flex: 1;
    }

    .sidebar-link {
      display: flex;
      align-items: center;
      gap: 12px;
      padding: 10px 12px;
      border-radius: var(--radius-sm);
      text-decoration: none;
      color: var(--text-muted);
      font-size: 13px;
      font-weight: 500;
      min-height: 44px;
      transition: background 0.12s ease, color 0.12s ease;
    }

    .sidebar-link:hover {
      background: var(--surface-raised);
      color: var(--text);
    }

    .sidebar-link.active {
      background: var(--accent-light);
      color: var(--accent);
      font-weight: 600;
    }

    .sidebar-footer {
      border-top: 1px solid var(--border-subtle);
      padding-top: 16px;
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .desktop-theme-selector {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 4px;
      background: var(--surface-raised);
      border: 1px solid var(--border-subtle);
      padding: 3px;
      border-radius: 6px;
    }

    .theme-opt-btn {
      font-size: 11px;
      font-weight: 600;
      padding: 4px 6px;
      border: none;
      background: transparent;
      color: var(--text-muted);
      border-radius: 4px;
      cursor: pointer;
      text-align: center;
    }

    .theme-opt-btn.active {
      background: var(--surface);
      color: var(--text);
      box-shadow: 0 1px 3px rgba(0,0,0,0.08);
    }

    /* Desktop Main Content Area */
    .desktop-main {
      padding: 36px 48px;
      max-width: 1120px;
      width: 100%;
      margin: 0 auto;
      overflow-y: auto;
    }

    .desktop-hero-header {
      margin-bottom: 28px;
    }

    .desktop-hero-header h1 {
      font-family: var(--font-serif);
      font-size: 28px;
      font-weight: 500;
      color: var(--text);
    }

    .desktop-hero-header p {
      font-size: 14px;
      color: var(--text-muted);
      margin-top: 4px;
    }

    .desktop-two-col {
      display: grid;
      grid-template-columns: 1.4fr 1fr;
      gap: 24px;
      align-items: start;
    }

    .desktop-col-left {
      display: flex;
      flex-direction: column;
      gap: 24px;
    }

    .desktop-col-right {
      display: flex;
      flex-direction: column;
      gap: 24px;
    }

    /* Comparison Legend Block */
    .legend-box {
      margin-top: 50px;
      padding: 24px;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-md);
    }

    .legend-title {
      font-family: var(--font-serif);
      font-size: 18px;
      font-weight: 600;
      margin-bottom: 12px;
      color: var(--text);
    }

    .legend-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
      gap: 20px;
      font-size: 13px;
      color: var(--text-muted);
    }

    .legend-item strong {
      color: var(--text);
      display: block;
      margin-bottom: 4px;
    }