/* ==========================================================================
   RevRevPlus — Clean, Minimal, Purple-Themed Design System (Light & Dark)
   ========================================================================== */

:root,
[data-theme="light"] {
  --bg-app: #F8F7FC;
  --bg-surface: #FFFFFF;
  --bg-subtle: #F3F1FA;
  --bg-hover: #EDE9FE;
  --bg-elevated: #FFFFFF;

  --text-primary: #181326;
  --text-secondary: #524C66;
  --text-muted: #7C7591;

  --border: #E5E1F0;
  --border-strong: #CFC7E6;

  --purple-50: #F5F3FF;
  --purple-100: #EDE9FE;
  --purple-200: #DDD6FE;
  --purple-500: #8B5CF6;
  --purple-600: #7C3AED;
  --purple-700: #6D28D9;

  --accent: #7C3AED;
  --accent-hover: #6D28D9;
  --accent-soft: #F3EEFF;
  --accent-border: #D8B4FE;

  --success: #16A34A;
  --success-soft: #ECFDF5;
  --success-border: #A7F3D0;

  --warning: #D97706;
  --warning-soft: #FFFBEB;
  --warning-border: #FDE68A;

  --danger: #DC2626;
  --danger-soft: #FEF2F2;
  --danger-border: #FECACA;

  --shadow-xs: 0 1px 2px rgba(24, 19, 38, 0.04);
  --shadow-sm: 0 2px 8px rgba(24, 19, 38, 0.05);
  --shadow-md: 0 8px 24px rgba(24, 19, 38, 0.08);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --sidebar-width: 260px;
  --topbar-height: 64px;
}

[data-theme="dark"] {
  --bg-app: #0F0D17;
  --bg-surface: #171424;
  --bg-subtle: #201C30;
  --bg-hover: #2A2440;
  --bg-elevated: #1E1A2E;

  --text-primary: #F5F3FF;
  --text-secondary: #C4BBD9;
  --text-muted: #8E84A8;

  --border: #2C2640;
  --border-strong: #3E3659;

  --purple-50: rgba(139, 92, 246, 0.1);
  --purple-100: rgba(139, 92, 246, 0.18);
  --purple-200: rgba(139, 92, 246, 0.28);
  --purple-500: #A78BFA;
  --purple-600: #8B5CF6;
  --purple-700: #7C3AED;

  --accent: #8B5CF6;
  --accent-hover: #7C3AED;
  --accent-soft: rgba(139, 92, 246, 0.15);
  --accent-border: rgba(167, 139, 250, 0.38);

  --success: #22C55E;
  --success-soft: rgba(34, 197, 94, 0.14);
  --success-border: rgba(34, 197, 94, 0.35);

  --warning: #F59E0B;
  --warning-soft: rgba(245, 158, 11, 0.14);
  --warning-border: rgba(245, 158, 11, 0.35);

  --danger: #EF4444;
  --danger-soft: rgba(239, 68, 68, 0.14);
  --danger-border: rgba(239, 68, 68, 0.35);

  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.25);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.32);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.45);
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background-color: var(--bg-app);
  color: var(--text-primary);
  line-height: 1.55;
  min-height: 100vh;
  transition: background-color 0.2s ease, color 0.2s ease;
  overflow-x: hidden;
}

.hidden {
  display: none !important;
}

/* ==========================================================================
   1. INITIAL LOADING SCREEN & AI TASK OVERLAY
   ========================================================================== */

.loading-screen {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background-color: var(--bg-app);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  transition: opacity 0.35s ease, visibility 0.35s ease;
}

.loading-screen.fade-out {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.loading-screen-card {
  width: 100%;
  max-width: 360px;
  text-align: center;
  padding: 36px 28px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

.loading-logo-wrap {
  width: 84px;
  height: 84px;
  margin: 0 auto 16px;
  border-radius: 20px;
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 10px;
}

.loading-logo {
  width: 100%;
  height: 100%;
  object-fit: contain;
  animation: gentlePulse 2s infinite ease-in-out;
}

.loading-title {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  margin-bottom: 6px;
}

.loading-subtitle {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

.loading-bar-track {
  width: 100%;
  height: 6px;
  background: var(--bg-subtle);
  border-radius: 999px;
  overflow: hidden;
}

.loading-bar-fill {
  height: 100%;
  width: 35%;
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.35s ease;
}

@keyframes gentlePulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.task-overlay {
  position: fixed;
  inset: 0;
  z-index: 9000;
  background: rgba(15, 13, 23, 0.55);
  backdrop-filter: blur(3px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.task-overlay-card {
  width: 100%;
  max-width: 400px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px 24px;
  text-align: center;
  box-shadow: var(--shadow-md);
}

.task-overlay-icon {
  width: 56px;
  height: 56px;
  object-fit: contain;
  margin-bottom: 12px;
}

.task-spinner {
  width: 28px;
  height: 28px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  margin: 0 auto 14px;
  animation: spin 0.75s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.task-overlay-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 6px;
}

.task-overlay-subtitle {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

/* ==========================================================================
   2. TYPOGRAPHY, BUTTONS, INPUTS, ALERTS, BADGES
   ========================================================================== */

h1, h2, h3, h4 {
  color: var(--text-primary);
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.3;
}

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

.text-xs {
  font-size: 0.78rem;
}

.text-sm {
  font-size: 0.875rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 16px;
  font-size: 0.9rem;
  font-weight: 500;
  font-family: inherit;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background-color 0.16s ease, border-color 0.16s ease, color 0.16s ease, transform 0.1s ease;
  text-decoration: none;
  white-space: nowrap;
}

.btn:active {
  transform: translateY(1px);
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.btn-primary {
  background-color: var(--accent);
  color: #FFFFFF;
  border-color: var(--accent);
}

.btn-primary:hover:not(:disabled) {
  background-color: var(--accent-hover);
  border-color: var(--accent-hover);
}

.btn-secondary {
  background-color: var(--accent-soft);
  color: var(--accent);
  border-color: var(--accent-border);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--purple-100);
}

.btn-ghost {
  background-color: transparent;
  color: var(--text-primary);
  border-color: var(--border);
}

.btn-ghost:hover:not(:disabled) {
  background-color: var(--bg-subtle);
  border-color: var(--border-strong);
}

.btn-danger {
  background-color: var(--danger-soft);
  color: var(--danger);
  border-color: var(--danger-border);
}

.btn-danger:hover:not(:disabled) {
  background-color: var(--danger);
  color: #FFFFFF;
}

.btn-success {
  background-color: var(--success-soft);
  color: var(--success);
  border-color: var(--success-border);
}

.btn-warning {
  background-color: var(--warning-soft);
  color: var(--warning);
  border-color: var(--warning-border);
}

.btn-sm {
  padding: 6px 12px;
  font-size: 0.825rem;
}

.btn-lg {
  padding: 12px 22px;
  font-size: 0.975rem;
}

.btn-block {
  width: 100%;
}

.btn-icon {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-primary);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1rem;
}

.btn-icon:hover {
  background: var(--bg-subtle);
}

.btn-text-xs {
  background: none;
  border: none;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  padding: 2px 6px;
  border-radius: 4px;
}

.btn-text-xs:hover {
  background: var(--accent-soft);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 16px;
}

.form-group label {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-primary);
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: 10px 12px;
  font-size: 0.925rem;
  font-family: inherit;
  color: var(--text-primary);
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.form-textarea {
  min-height: 110px;
  resize: vertical;
}

.form-hint {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 3px 9px;
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 999px;
  border: 1px solid transparent;
}

.badge-purple {
  background: var(--accent-soft);
  color: var(--accent);
  border-color: var(--accent-border);
}

.badge-success {
  background: var(--success-soft);
  color: var(--success);
  border-color: var(--success-border);
}

.badge-warning {
  background: var(--warning-soft);
  color: var(--warning);
  border-color: var(--warning-border);
}

.badge-danger {
  background: var(--danger-soft);
  color: var(--danger);
  border-color: var(--danger-border);
}

.badge-neutral {
  background: var(--bg-subtle);
  color: var(--text-secondary);
  border-color: var(--border);
}

.alert {
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  margin-bottom: 16px;
  border: 1px solid transparent;
}

.alert-error {
  background: var(--danger-soft);
  color: var(--danger);
  border-color: var(--danger-border);
}

.alert-success {
  background: var(--success-soft);
  color: var(--success);
  border-color: var(--success-border);
}

.alert-info {
  background: var(--accent-soft);
  color: var(--accent);
  border-color: var(--accent-border);
}

/* ==========================================================================
   3. AUTHENTICATION VIEW
   ========================================================================== */

.auth-view {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-app);
}

.auth-topbar {
  height: 64px;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border);
  background: var(--bg-surface);
}

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

.brand-icon-sm {
  width: 32px;
  height: 32px;
  object-fit: contain;
}

.brand-name {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
}

.auth-container {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 32px 16px;
}

.auth-card {
  width: 100%;
  max-width: 440px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  box-shadow: var(--shadow-sm);
}

.auth-header {
  text-align: center;
  margin-bottom: 24px;
}

.auth-logo {
  width: 68px;
  height: 68px;
  object-fit: contain;
  margin-bottom: 12px;
}

.auth-header h1 {
  font-size: 1.4rem;
  margin-bottom: 6px;
}

.auth-tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 4px;
  background: var(--bg-subtle);
  padding: 4px;
  border-radius: var(--radius-sm);
  margin-bottom: 20px;
}

.auth-tab {
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 500;
  padding: 8px 6px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.auth-tab.active {
  background: var(--bg-surface);
  color: var(--accent);
  font-weight: 600;
  box-shadow: var(--shadow-xs);
}

/* ==========================================================================
   4. APP SHELL, SIDEBAR & TOPBAR
   ========================================================================== */

.app-shell {
  display: flex;
  min-height: 100vh;
}

.app-sidebar {
  width: var(--sidebar-width);
  background: var(--bg-surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: 200;
  transition: transform 0.22s ease;
}

.sidebar-header {
  height: var(--topbar-height);
  padding: 0 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border);
}

.sidebar-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: inherit;
}

.sidebar-logo {
  width: 36px;
  height: 36px;
  object-fit: contain;
}

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

.sidebar-brand-title {
  font-weight: 700;
  font-size: 1.05rem;
  line-height: 1.15;
}

.sidebar-brand-badge {
  font-size: 0.7rem;
  color: var(--accent);
  font-weight: 600;
}

.sidebar-nav {
  padding: 14px 12px 8px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-item {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  text-align: left;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.nav-item:hover {
  background: var(--bg-subtle);
  color: var(--text-primary);
}

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

.nav-icon {
  width: 20px;
  text-align: center;
  font-size: 1rem;
}

.sidebar-section {
  flex: 1;
  padding: 12px 14px;
  overflow-y: auto;
  border-top: 1px solid var(--border);
  margin-top: 8px;
}

.sidebar-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  font-weight: 600;
  margin-bottom: 8px;
}

.sidebar-subjects-list {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.sidebar-subject-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 7px 10px;
  border-radius: 6px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.84rem;
  font-family: inherit;
  cursor: pointer;
  text-align: left;
  transition: background-color 0.15s ease;
}

.sidebar-subject-btn:hover {
  background: var(--bg-subtle);
  color: var(--text-primary);
}

.sidebar-subject-btn.active {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

.sidebar-subject-name {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.sidebar-footer {
  padding: 14px;
  border-top: 1px solid var(--border);
  background: var(--bg-surface);
}

.user-Summary {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}

.user-avatar {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid var(--accent-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.88rem;
  flex-shrink: 0;
}

.user-meta {
  overflow: hidden;
}

.user-name {
  font-size: 0.86rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.user-email {
  font-size: 0.74rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.app-main {
  flex: 1;
  margin-left: var(--sidebar-width);
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.app-topbar {
  height: var(--topbar-height);
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  position: sticky;
  top: 0;
  z-index: 100;
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.topbar-breadcrumb {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}

.model-pill {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 6px 12px;
  border-radius: 999px;
  background: var(--bg-subtle);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.model-pill:hover {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
}

.model-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
}

.model-dot.verified {
  background: var(--success);
}

.view-container {
  flex: 1;
  max-width: 1220px;
  width: 100%;
  margin: 0 auto;
  padding: 28px 24px 64px;
  animation: fadeIn 0.2s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ==========================================================================
   5. CARDS, GRIDS, PROGRESS BARS, WORKSPACE TABS
   ========================================================================== */

.page-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.page-header h1 {
  font-size: 1.55rem;
  margin-bottom: 4px;
}

.page-header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-bottom: 28px;
}

.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  box-shadow: var(--shadow-xs);
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
  margin-bottom: 6px;
}

.stat-value {
  font-size: 1.65rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-sub {
  font-size: 0.78rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 22px;
  box-shadow: var(--shadow-xs);
  margin-bottom: 20px;
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.card-title {
  font-size: 1.1rem;
  font-weight: 600;
}

.subjects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 18px;
}

.subject-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 20px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 16px;
  cursor: pointer;
  transition: border-color 0.16s ease, transform 0.16s ease, box-shadow 0.16s ease;
}

.subject-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-sm);
  transform: translateY(-2px);
}

.subject-card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
}

.subject-card-title {
  font-size: 1.12rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.subject-topic-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
}

.topic-pill {
  font-size: 0.75rem;
  padding: 3px 8px;
  border-radius: 6px;
  background: var(--bg-subtle);
  color: var(--text-secondary);
  border: 1px solid var(--border);
}

.progress-row {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.progress-label-line {
  display: flex;
  justify-content: space-between;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.progress-track {
  width: 100%;
  height: 8px;
  background: var(--bg-subtle);
  border-radius: 999px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.3s ease;
}

.progress-fill.success {
  background: var(--success);
}

/* ==========================================================================
   6. SUBJECT WORKSPACE TABS & ADAPTIVE REVISION BANNER
   ========================================================================== */

.workspace-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 24px;
  overflow-x: auto;
  padding-bottom: 2px;
}

.workspace-tab {
  padding: 10px 18px;
  border: none;
  border-bottom: 2px solid transparent;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.92rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  white-space: nowrap;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.workspace-tab:hover {
  color: var(--text-primary);
}

.workspace-tab.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
  font-weight: 600;
}

.adaptive-banner {
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  margin-bottom: 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.adaptive-options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.adaptive-option-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  cursor: pointer;
  text-align: left;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.adaptive-option-card:hover {
  border-color: var(--accent);
}

.adaptive-option-card.active {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.adaptive-option-title {
  font-weight: 600;
  font-size: 0.92rem;
  margin-bottom: 4px;
  color: var(--text-primary);
}

.adaptive-option-desc {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* ==========================================================================
   7. LEARN MODE (STEP-BY-STEP INTERACTIVE TEACHING)
   ========================================================================== */

.learn-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 20px;
  align-items: start;
}

.topic-sidebar-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.topic-select-btn {
  width: 100%;
  padding: 11px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-surface);
  color: var(--text-primary);
  text-align: left;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  font-family: inherit;
  font-size: 0.88rem;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.topic-select-btn:hover {
  border-color: var(--accent);
}

.topic-select-btn.active {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
  font-weight: 600;
}

.learn-step-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 24px;
  margin-bottom: 18px;
}

.learn-step-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 14px;
  gap: 10px;
}

.term-highlight-box {
  background: var(--bg-subtle);
  border-left: 3px solid var(--accent);
  padding: 12px 14px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 14px 0;
}

.check-question-box {
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-sm);
  padding: 16px;
  margin-top: 18px;
}

.option-btn {
  width: 100%;
  text-align: left;
  padding: 10px 14px;
  margin-top: 8px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-surface);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.option-btn:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--bg-hover);
}

.option-btn.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
  font-weight: 600;
}

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-soft);
  color: var(--success);
  font-weight: 600;
}

.option-btn.wrong {
  border-color: var(--danger);
  background: var(--danger-soft);
  color: var(--danger);
}

/* ==========================================================================
   8. REVISE MODE: INTERACTIVE FLASHCARDS & STRUCTURED MINDMAPS
   ========================================================================== */

.revise-subtabs {
  display: inline-flex;
  background: var(--bg-subtle);
  padding: 4px;
  border-radius: var(--radius-sm);
  gap: 4px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.revise-subtab {
  border: none;
  background: transparent;
  color: var(--text-secondary);
  padding: 8px 14px;
  border-radius: 6px;
  font-size: 0.86rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
}

.revise-subtab.active {
  background: var(--bg-surface);
  color: var(--accent);
  font-weight: 600;
  box-shadow: var(--shadow-xs);
}

.flashcard-stage {
  max-width: 680px;
  margin: 0 auto;
}

.flashcard-box {
  background: var(--bg-surface);
  border: 2px solid var(--border);
  border-radius: var(--radius-lg);
  min-height: 270px;
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: border-color 0.18s ease, transform 0.18s ease;
  user-select: none;
}

.flashcard-box:hover {
  border-color: var(--accent);
}

.flashcard-box.revealed {
  border-color: var(--accent);
  background: var(--bg-elevated);
}

.flashcard-content {
  font-size: 1.18rem;
  font-weight: 500;
  text-align: center;
  margin: auto 0;
  padding: 16px 0;
}

.flashcard-answer-divider {
  border-top: 1px dashed var(--border-strong);
  margin: 16px 0;
  padding-top: 16px;
  color: var(--text-primary);
  font-size: 1.05rem;
}

.flashcard-rating-bar {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-top: 18px;
}

.rating-btn {
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  font-family: inherit;
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: transform 0.1s ease, filter 0.15s ease;
}

.rating-btn:hover {
  filter: brightness(0.97);
}

.kbd-tag {
  display: inline-block;
  padding: 2px 6px;
  font-size: 0.74rem;
  border-radius: 4px;
  background: rgba(0, 0, 0, 0.08);
  font-family: monospace;
}

/* SIMPLE, CLEAN, EXPANDABLE HIERARCHICAL MINDMAP */
.mindmap-container {
  overflow-x: auto;
  padding: 16px 4px;
}

.mindmap-node-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.mindmap-root-box {
  background: var(--accent);
  color: #FFFFFF;
  padding: 16px 20px;
  border-radius: var(--radius-md);
  max-width: 520px;
  box-shadow: var(--shadow-xs);
}

.mindmap-root-box h3 {
  color: #FFFFFF;
  font-size: 1.1rem;
  margin-bottom: 4px;
}

.mindmap-root-box p {
  font-size: 0.85rem;
  opacity: 0.92;
}

.mindmap-branches {
  margin-left: 24px;
  padding-left: 22px;
  border-left: 2px solid var(--accent-border);
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-top: 12px;
}

.mindmap-branch-item {
  position: relative;
}

.mindmap-branch-item::before {
  content: '';
  position: absolute;
  left: -22px;
  top: 22px;
  width: 22px;
  height: 2px;
  background: var(--accent-border);
}

.mindmap-box {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  max-width: 680px;
  transition: border-color 0.15s ease;
}

.mindmap-box:hover {
  border-color: var(--accent);
}

.mindmap-box-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  cursor: pointer;
}

.mindmap-box-title {
  font-weight: 600;
  font-size: 0.96rem;
  color: var(--text-primary);
}

.mindmap-box-desc {
  font-size: 0.84rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.mindmap-subbranches {
  margin-left: 18px;
  padding-left: 18px;
  border-left: 2px solid var(--border-strong);
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 10px;
  margin-top: 10px;
}

.mindmap-leaf-box {
  background: var(--bg-subtle);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
}

.mindmap-leaf-title {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--accent);
  margin-bottom: 3px;
}

.mindmap-leaf-desc {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* ==========================================================================
   9. UPLOAD DROPZONE & MODAL
   ========================================================================== */

.dropzone {
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius-md);
  padding: 28px 20px;
  text-align: center;
  background: var(--bg-subtle);
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.dropzone:hover,
.dropzone.dragover {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 5000;
  background: rgba(15, 13, 23, 0.55);
  backdrop-filter: blur(2px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  overflow-y: auto;
}

.modal-card {
  width: 100%;
  max-width: 640px;
  max-height: 90vh;
  overflow-y: auto;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 26px;
  box-shadow: var(--shadow-md);
}

/* ==========================================================================
   10. TOAST NOTIFICATIONS & MARKDOWN OUTPUT
   ========================================================================== */

.toast-container {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 9500;
  display: flex;
  flex-direction: column;
  gap: 8px;
  max-width: 360px;
}

.toast {
  background: var(--bg-surface);
  color: var(--text-primary);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
  font-size: 0.875rem;
  animation: fadeIn 0.2s ease;
}

.toast.success { border-left-color: var(--success); }
.toast.error { border-left-color: var(--danger); }

.markdown-body h3,
.markdown-body h4 {
  margin-top: 14px;
  margin-bottom: 6px;
}

.markdown-body p {
  margin-bottom: 10px;
}

.markdown-body ul,
.markdown-body ol {
  margin-left: 20px;
  margin-bottom: 12px;
}

.markdown-body li {
  margin-bottom: 4px;
}

.markdown-body blockquote {
  border-left: 3px solid var(--accent);
  padding-left: 12px;
  color: var(--text-secondary);
  margin: 10px 0;
}

/* ==========================================================================
   11. RESPONSIVE DESIGN (DESKTOP, TABLET, MOBILE)
   ========================================================================== */

.mobile-only {
  display: none;
}

.sidebar-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  z-index: 150;
}

@media (max-width: 1024px) {
  .learn-layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .mobile-only {
    display: inline-flex;
  }

  .app-sidebar {
    transform: translateX(-100%);
    width: 280px;
  }

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

  .app-main {
    margin-left: 0;
  }

  .app-topbar {
    padding: 0 14px;
  }

  .view-container {
    padding: 20px 14px 56px;
  }

  .subjects-grid {
    grid-template-columns: 1fr;
  }

  .flashcard-rating-bar {
    grid-template-columns: 1fr;
  }

  .auth-card {
    padding: 24px 18px;
  }

  .modal-card {
    padding: 20px 16px;
  }
}

@media (max-width: 480px) {
  .topbar-right .model-pill span#active-model-label {
    max-width: 110px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .page-header h1 {
    font-size: 1.3rem;
  }
}