/* ==========================================================================
   AI Classroom Assistant - Custom CSS Variables & Core Design System
   Modern dark-ish gradient-accent theme with sleek components
   ========================================================================== */

:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  /* Colors */
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #e0e7ff;
  --secondary: #0f172a;
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --info: #06b6d4;

  /* Theme Backgrounds */
  --bg-app: #f8fafc;
  --bg-card: #ffffff;
  --bg-sidebar: #0f172a;
  
  /* Text colors */
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-inverse: #ffffff;
  
  /* Borders & Shadows */
  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  
  --transition: all 0.2s ease-in-out;

  /* CSS Variables for Dark Mode toggling */
  --bg-input: #ffffff;
  --bg-table-header: #f1f5f9;
  --bg-chat-container: #ffffff;
  --bg-chat-feed: #f8fafc;
  --bg-chat-bubble-ai: #ffffff;
  --bg-chat-input: #ffffff;
  --bg-auth-right: #ffffff;
  --bg-auth-tab-active: #ffffff;
  --bg-auth-tabs: #f1f5f9;

  --border: var(--border-color);
  --surface: var(--bg-card);
  --text-color: var(--text-main);
}

/* Dark Mode Class Overrides */
.dark {
  --bg-app: #0f172a;       /* Slate 900 */
  --bg-card: #1e293b;      /* Slate 800 */
  --text-main: #f8fafc;    /* Slate 50 */
  --text-muted: #94a3b8;   /* Slate 400 */
  --border-color: #334155; /* Slate 700 */
  --primary-light: rgba(79, 70, 229, 0.15);
  
  --bg-input: #1e293b;
  --bg-table-header: #1e293b;
  --bg-chat-container: #1e293b;
  --bg-chat-feed: #0f172a;
  --bg-chat-bubble-ai: #1e293b;
  --bg-chat-input: #1e293b;
  --bg-auth-right: #0f172a;
  --bg-auth-tab-active: #1e293b;
  --bg-auth-tabs: #0f172a;

  --border: var(--border-color);
  --surface: var(--bg-card);
  --text-color: var(--text-main);
}

/* Global Dark Mode Overrides for embedded or page-specific styles */
.dark .card,
.dark .stat-card,
.dark .modal,
.dark .modal-v2,
.dark .settings-card,
.dark .sidebar-card {
  background-color: var(--bg-card) !important;
  background: var(--bg-card) !important;
  color: var(--text-main) !important;
  border-color: var(--border-color) !important;
}

.dark .card-header,
.dark .settings-card-header,
.dark .sidebar-card-header {
  border-bottom-color: var(--border-color) !important;
  color: var(--text-main) !important;
  background: transparent !important;
}

.dark .card-title,
.dark .assignment-title,
.dark .modal-title,
.dark .empty-state h3,
.dark .empty-state-v2 h3 {
  color: var(--text-main) !important;
}

.dark .assignment-desc,
.dark .empty-state p,
.dark .empty-state-v2 p {
  color: var(--text-muted) !important;
}

.dark .modal-body {
  background-color: var(--bg-card) !important;
  background: var(--bg-card) !important;
  color: var(--text-main) !important;
}

.dark .modal-footer {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  border-top-color: var(--border-color) !important;
}

.dark thead,
.dark thead th,
.dark th {
  background-color: var(--bg-table-header) !important;
  background: var(--bg-table-header) !important;
  color: var(--text-muted) !important;
  border-bottom-color: var(--border-color) !important;
}

.dark tbody td,
.dark td {
  border-top-color: var(--border-color) !important;
  border-bottom-color: var(--border-color) !important;
  color: var(--text-main) !important;
}

.dark tbody tr:hover,
.dark tr:hover {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
}

.dark .form-label,
.dark .field-label {
  color: var(--text-main) !important;
}

.dark .form-control,
.dark .api-key-input,
.dark .model-label {
  background-color: var(--bg-input) !important;
  border-color: var(--border-color) !important;
  color: var(--text-main) !important;
}

.dark .empty-state,
.dark .empty-state-v2 {
  background-color: var(--bg-card) !important;
  background: var(--bg-card) !important;
  border-color: var(--border-color) !important;
  color: var(--text-main) !important;
}

.dark .classroom-code-v2 {
  background-color: var(--bg-app) !important;
  border-color: var(--border-color) !important;
}

.dark .student-sidebar-class-link {
  border-bottom-color: var(--border-color) !important;
}
.dark .student-sidebar-class-link:hover {
  background-color: rgba(255, 255, 255, 0.05) !important;
}

.dark .progress {
  background-color: var(--border-color) !important;
  background: var(--border-color) !important;
}

.dark .dashboard-grid .sidebar,
.dark .progress-layout .sidebar {
  background: transparent !important;
  background-color: transparent !important;
  border: none !important;
  height: auto !important;
  position: static !important;
}

.dark .btn-secondary {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  color: var(--text-main) !important;
  border-color: var(--border-color) !important;
}
.dark .btn-secondary:hover {
  background-color: var(--border-color) !important;
  background: var(--border-color) !important;
}

.dark .empty-icon {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  color: var(--text-main) !important;
}

.dark .classroom-name {
  color: var(--text-main) !important;
}

.dark .classroom-item:hover {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  border-color: var(--border-color) !important;
}

.dark .form-group label,
.dark .form-group label span {
  color: var(--text-main) !important;
}

.dark #mcq-section {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  border-color: var(--border-color) !important;
}

.dark .upload-box {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  border-color: var(--border-color) !important;
}

.dark .image-item {
  background-color: var(--bg-app) !important;
  background: var(--bg-app) !important;
  border-color: var(--border-color) !important;
}

/* Reset & Basics */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-app);
  color: var(--text-main);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}
a:hover {
  color: var(--primary-hover);
}

/* Layout */
.layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  background-color: var(--bg-sidebar);
  color: var(--text-inverse);
  display: flex;
  flex-direction: column;
  height: 100vh;
  position: sticky;
  top: 0;
  z-index: 200;
  border-right: 1px solid rgba(255, 255, 255, 0.05);
}

.sidebar-logo {
  padding: 24px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--text-inverse);
}
.brand-icon {
  font-size: 28px;
  background: linear-gradient(135deg, #6366f1, #4f46e5);
  padding: 6px;
  border-radius: var(--radius-md);
}
.brand-name {
  font-weight: 800;
  font-size: 18px;
  line-height: 1.2;
}
.brand-name span {
  display: block;
  font-size: 11px;
  font-weight: 400;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.sidebar-nav {
  flex: 1;
  padding: 20px 16px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-section-label {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  color: #475569;
  letter-spacing: 0.1em;
  padding: 12px 12px 6px;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  color: #94a3b8;
  font-weight: 500;
  border-radius: var(--radius-sm);
  font-size: 14px;
}
.nav-item:hover, .nav-item.active {
  color: var(--text-inverse);
  background-color: rgba(255, 255, 255, 0.08);
}
.nav-icon {
  font-size: 16px;
}

.sidebar-footer {
  padding: 16px;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.user-card {
  display: flex;
  align-items: center;
  gap: 12px;
  background-color: rgba(255, 255, 255, 0.03);
  padding: 12px;
  border-radius: var(--radius-md);
}
.user-avatar {
  width: 36px;
  height: 36px;
  background-color: var(--primary);
  color: var(--text-inverse);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
}
.user-info {
  flex: 1;
  min-width: 0;
}
.user-info .name {
  font-weight: 600;
  font-size: 13px;
  color: var(--text-inverse);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.user-info .role {
  font-size: 11px;
  color: var(--text-muted);
  text-transform: capitalize;
}

/* Main Content Area */
.main-content {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  overflow-x: hidden;
}

.topbar {
  background-color: var(--bg-card);
  height: 70px;
  padding: 0 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 90;
}
.topbar-title {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-main);
}
.topbar-subtitle {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 2px;
}

.page-content {
  flex: 1;
  padding: 32px;
}

/* UI Elements & Components */
.card {
  background-color: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  padding: 24px;
  margin-bottom: 24px;
}
.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}
.card-title {
  font-size: 18px;
  font-weight: 700;
}

/* Grids & Layout Containers */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  margin-bottom: 24px;
}
.stat-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  display: flex;
  align-items: center;
  gap: 16px;
  box-shadow: var(--shadow-sm);
}
.stat-icon {
  font-size: 24px;
  width: 48px;
  height: 48px;
  background-color: var(--primary-light);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}
.stat-value {
  font-size: 24px;
  font-weight: 800;
  line-height: 1;
}
.stat-label {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 4px;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}
.btn-primary {
  background-color: var(--primary);
  color: var(--text-inverse);
}
.btn-primary:hover {
  background-color: var(--primary-hover);
  color: var(--text-inverse);
}
.btn-secondary {
  background-color: var(--bg-app);
  color: var(--text-main);
  border-color: var(--border-color);
}
.btn-secondary:hover {
  background-color: var(--border-color);
}
.btn-lg {
  padding: 12px 24px;
  font-size: 16px;
}

/* Forms */
.form-group {
  margin-bottom: 16px;
}
.form-label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-main);
}
.form-control {
  width: 100%;
  padding: 10px 14px;
  font-size: 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  outline: none;
  background-color: var(--bg-input);
  color: var(--text-main);
  transition: var(--transition);
}
.form-control:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 8px;
  font-size: 11px;
  font-weight: 700;
  border-radius: 50px;
  text-transform: uppercase;
}
.badge-easy { background-color: #d1fae5; color: #065f46; }
.badge-medium { background-color: #fef3c7; color: #92400e; }
.badge-hard { background-color: #fee2e2; color: #991b1b; }

/* Tables */
.table-responsive {
  overflow-x: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}
.table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 14px;
}
.table th {
  background-color: var(--bg-table-header);
  padding: 12px 16px;
  font-weight: 600;
  color: var(--text-muted);
}
.table td {
  padding: 16px;
  border-top: 1px solid var(--border-color);
}

/* Alert Boxes */
.alert {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
  font-size: 14px;
  font-weight: 500;
}
.alert-danger {
  background-color: #fee2e2;
  color: #991b1b;
  border: 1px solid #fecaca;
}
.alert-success {
  background-color: #d1fae5;
  color: #065f46;
  border: 1px solid #a7f3d0;
}

/* Authentication Page Spec */
.auth-page {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  min-height: 100vh;
}
.auth-left {
  background: linear-gradient(135deg, #1e1b4b 0%, #0f172a 100%);
  color: var(--text-inverse);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 60px 80px;
}
.hero-text h1 {
  font-size: 42px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
}
.hero-text p {
  font-size: 18px;
  color: #94a3b8;
  margin-bottom: 48px;
}
.auth-features {
  display: flex;
  flex-direction: column;
  gap: 24px;
}
.auth-feature {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}
.feat-icon {
  font-size: 20px;
  padding: 8px;
  background-color: rgba(255, 255, 255, 0.05);
  border-radius: var(--radius-sm);
}
.feat-text strong {
  display: block;
  font-size: 16px;
  margin-bottom: 4px;
}
.feat-text span {
  font-size: 13px;
  color: #94a3b8;
}

.auth-right {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 40px;
  background-color: var(--bg-auth-right);
}
.auth-box {
  width: 100%;
  max-width: 420px;
}
.auth-logo {
  text-align: center;
  margin-bottom: 32px;
}
.logo-icon {
  font-size: 48px;
  margin-bottom: 12px;
}
.auth-logo h2 {
  font-size: 24px;
  font-weight: 800;
  color: var(--text-main);
}
.auth-logo p {
  font-size: 14px;
  color: var(--text-muted);
  margin-top: 4px;
}

.auth-tabs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  background-color: var(--bg-auth-tabs);
  padding: 4px;
  border-radius: var(--radius-md);
  margin-bottom: 24px;
}
.auth-tab {
  padding: 10px;
  border: none;
  background: none;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: var(--radius-sm);
  font-size: 14px;
  transition: var(--transition);
}
.auth-tab.active {
  background-color: var(--bg-auth-tab-active);
  color: var(--text-main);
  box-shadow: var(--shadow-sm);
}

.role-selector {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}
.role-card {
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 16px;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
}
.role-card:hover {
  border-color: var(--primary);
  background-color: var(--primary-light);
}
.role-card.selected {
  border-color: var(--primary);
  background-color: var(--primary-light);
}
.role-icon {
  font-size: 32px;
  margin-bottom: 8px;
}
.role-name {
  font-weight: 700;
  font-size: 14px;
}

/* Chat Assistant Panel */
.chat-container {
  display: flex;
  flex-direction: column;
  height: 600px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background-color: var(--bg-chat-container);
}
.chat-feed {
  flex: 1;
  padding: 24px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
  background-color: var(--bg-chat-feed);
}
.chat-msg {
  display: flex;
  gap: 12px;
  max-width: 80%;
}
.chat-msg.user {
  align-self: flex-end;
  flex-direction: row-reverse;
}
.chat-msg.ai {
  align-self: flex-start;
}
.chat-avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}
.chat-avatar.user {
  background-color: var(--primary-light);
}
.chat-avatar.ai {
  background-color: #1e1b4b;
}
.chat-bubble {
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-size: 14px;
}
.chat-msg.user .chat-bubble {
  background-color: var(--primary);
  color: var(--text-inverse);
  border-bottom-right-radius: 2px;
}
.chat-msg.ai .chat-bubble {
  background-color: var(--bg-chat-bubble-ai);
  border: 1px solid var(--border-color);
  border-bottom-left-radius: 2px;
  color: var(--text-main);
}
.chat-input-area {
  padding: 16px;
  border-top: 1px solid var(--border-color);
  background-color: var(--bg-chat-input);
  display: flex;
  gap: 12px;
}

/* ============================================================
   Responsive Overrides — Mobile First
   ============================================================ */

[x-cloak] {
  display: none !important;
}

/* ── Tablet (≤ 1024px) ── */
@media (max-width: 1024px) {
  .auth-page {
    grid-template-columns: 1fr;
  }
  .auth-left {
    display: none;
  }
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
  }
}

/* ── Mobile (≤ 768px) ── */
@media (max-width: 768px) {

  /* Layout: collapse sidebar */
  .layout {
    grid-template-columns: 1fr;
  }
  .sidebar {
    position: fixed;
    left: -290px;
    top: 0;
    height: 100vh;
    z-index: 200;
    transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: none;
  }
  .sidebar.open {
    left: 0;
    box-shadow: 0 0 60px rgba(0, 0, 0, 0.4);
  }

  /* Topbar mobile */
  .topbar {
    padding: 0 16px;
    height: 60px;
  }
  .topbar-title {
    font-size: 16px;
  }
  .topbar-subtitle {
    display: none;
  }
  .topbar-actions {
    gap: 8px;
  }
  .topbar-actions .btn {
    padding: 7px 12px;
    font-size: 12px;
  }

  /* Page content */
  .page-content {
    padding: 16px 12px;
  }

  /* Cards */
  .card {
    padding: 16px;
    border-radius: var(--radius-md);
    margin-bottom: 16px;
  }
  .card-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    padding: 14px 16px;
  }

  /* Grids — all collapse to single column */
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
    margin-bottom: 16px;
  }
  .dashboard-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }
  .settings-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }
  .progress-layout {
    grid-template-columns: 1fr;
    gap: 16px;
  }
  .classroom-grid-v2 {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  /* Stat cards */
  .stat-card {
    padding: 14px 16px;
    gap: 12px;
  }
  .stat-icon {
    width: 40px;
    height: 40px;
    font-size: 18px;
  }
  .stat-value {
    font-size: 20px;
  }
  .stat-label {
    font-size: 12px;
  }

  /* Tables — make horizontally scrollable */
  .table-wrap,
  .table-responsive {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    border-radius: var(--radius-md);
  }
  table {
    min-width: 600px;
  }
  .table th,
  .table td,
  thead th,
  tbody td {
    padding: 10px 12px;
    font-size: 13px;
    white-space: nowrap;
  }

  /* Buttons */
  .btn {
    padding: 9px 14px;
    font-size: 13px;
  }
  .btn-lg {
    padding: 12px 20px;
    font-size: 15px;
  }

  /* Forms */
  .form-control {
    padding: 10px 12px;
    font-size: 14px;
  }

  /* Auth page */
  .auth-right {
    padding: 24px 20px;
  }
  .auth-box {
    max-width: 100%;
  }

  /* Chat */
  .chat-container {
    height: calc(100vh - 140px);
    border-radius: var(--radius-md);
  }
  .chat-feed {
    padding: 16px 12px;
  }
  .chat-msg {
    max-width: 90%;
  }
  .chat-input-area {
    padding: 12px;
  }

  /* Question form */
  #mcq-section {
    padding: 14px;
  }
  .model-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Hide long page subtitles on mobile */
  .page-subtitle-hidden-mobile {
    display: none;
  }
}

/* ── Small Mobile (≤ 480px) ── */
@media (max-width: 480px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }
  .role-selector {
    grid-template-columns: 1fr;
  }
  .auth-tabs {
    grid-template-columns: 1fr 1fr;
  }
  .topbar-title {
    font-size: 14px;
    max-width: 140px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }
  .model-grid {
    grid-template-columns: 1fr;
  }
  .action-buttons {
    flex-direction: column;
    gap: 6px;
  }
  .action-buttons .btn {
    width: 100%;
    justify-content: center;
  }
  .classroom-card-v2-content {
    padding: 16px;
  }
}