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

:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --secondary: #ec4899;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --border-color: #e5e7eb;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
  --bg-primary: #1f2937;
  --bg-secondary: #111827;
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --border-color: #374151;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* ========================
   HEADER & NAVIGATION
   ======================== */

.header {
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  max-width: 1400px;
  margin: 0 auto;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  white-space: nowrap;
}

.nav-links {
  display: none;
  flex-direction: column;
  gap: 0.5rem;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  padding: 1rem;
  box-shadow: var(--shadow-md);
}

.nav-links.active {
  display: flex;
}

.nav-link {
  padding: 0.75rem 1rem;
  cursor: pointer;
  border-radius: 0.5rem;
  transition: background-color 0.2s ease;
  text-decoration: none;
  color: var(--text-primary);
  display: block;
}

.nav-link:hover,
.nav-link.active {
  background-color: var(--bg-secondary);
  color: var(--primary);
}

.mobile-menu-toggle {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  cursor: pointer;
  background: none;
  border: none;
  padding: 0.5rem;
}

.mobile-menu-toggle span {
  width: 1.5rem;
  height: 0.2rem;
  background-color: var(--text-primary);
  border-radius: 0.1rem;
  transition: all 0.3s ease;
}

/* Notification Bell */
.notification-bell {
  font-size: 1.25rem;
  cursor: pointer;
  padding: 0.5rem;
  border-radius: 0.5rem;
  transition: background-color 0.2s ease;
  white-space: nowrap;
  margin-left: auto;
}

.notification-bell:hover {
  background-color: var(--bg-secondary);
}

/* ========================
   CONTAINER & LAYOUT
   ======================== */

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1rem;
}

.page {
  display: none;
}

.page.active {
  display: block;
}

/* ========================
   WELCOME SECTION
   ======================== */

.welcome-section {
  margin-bottom: 2rem;
  padding: 1.5rem;
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  border-radius: 1rem;
  color: white;
}

.welcome-content h1 {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
}

.welcome-content p {
  font-size: 0.95rem;
  opacity: 0.9;
}

/* ========================
   STATS GRID
   ======================== */

.stats-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin-bottom: 2rem;
}

@media (min-width: 640px) {
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .stats-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.stat-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: all 0.3s ease;
}

.stat-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.stat-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 1rem;
}

.stat-label {
  font-size: 0.875rem;
  color: var(--text-secondary);
  font-weight: 500;
  margin-bottom: 0.5rem;
}

.stat-value {
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary);
}

.stat-icon {
  font-size: 2rem;
}

.stat-change {
  font-size: 0.875rem;
  color: var(--success);
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

/* ========================
   SECTIONS
   ======================== */

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* ========================
   QUICK ACCESS
   ======================== */

.quick-access-section {
  margin-bottom: 2rem;
}

.quick-access-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 640px) {
  .quick-access-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .quick-access-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.quick-card,
.quick-access-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  padding: 1.5rem;
  text-decoration: none;
  color: var(--text-primary);
  transition: all 0.3s ease;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.quick-card:hover,
.quick-access-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--primary);
}

.qa-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.qa-icon {
  font-size: 2rem;
}

.qa-badge {
  background-color: var(--primary);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 600;
}

.qa-title {
  font-weight: 600;
  font-size: 1rem;
}

.qa-description {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.qa-meta {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

/* ========================
   ACTIVITY FEED
   ======================== */

.activity-section {
  margin-bottom: 2rem;
}

.activity-feed {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.activity-item {
  display: flex;
  gap: 1rem;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  padding: 1rem;
}

.activity-icon {
  font-size: 1.5rem;
  flex-shrink: 0;
}

.activity-content {
  flex: 1;
  min-width: 0;
}

.activity-title {
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.25rem;
}

.activity-description {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.25rem;
}

.activity-time {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

.activity-empty {
  text-align: center;
  padding: 2rem;
  color: var(--text-secondary);
}

/* ========================
   COURSE GRID
   ======================== */

.course-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin-bottom: 2rem;
}

@media (min-width: 640px) {
  .course-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .course-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.course-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  overflow: hidden;
  transition: all 0.3s ease;
}

.course-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.course-thumbnail {
  width: 100%;
  height: 150px;
  background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
}

.course-info {
  padding: 1rem;
}

.course-info h3 {
  font-size: 1rem;
  margin-bottom: 0.75rem;
  color: var(--text-primary);
}

.btn {
  display: inline-block;
  background-color: var(--primary);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: 0.5rem;
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 600;
  transition: background-color 0.2s ease;
  border: none;
  cursor: pointer;
}

.btn:hover {
  background-color: var(--primary-dark);
}

.no-courses {
  text-align: center;
  padding: 2rem;
  color: var(--text-secondary);
  grid-column: 1 / -1;
}

/* ========================
   ONBOARDING OVERLAY
   ======================== */

.onboarding-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.onboarding-overlay.active {
  display: flex;
}

.onboarding-card {
  background-color: var(--bg-primary);
  border-radius: 1rem;
  padding: 2rem;
  max-width: 500px;
  width: 100%;
  box-shadow: var(--shadow-lg);
}

.onboarding-icon {
  font-size: 3rem;
  text-align: center;
  margin-bottom: 1rem;
}

.onboarding-title {
  font-size: 1.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.onboarding-content {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  line-height: 1.6;
}

.onboarding-content ul {
  list-style: none;
  padding-left: 1rem;
}

.onboarding-content li {
  margin-bottom: 0.5rem;
  padding-left: 1.5rem;
  position: relative;
}

.onboarding-content li:before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--success);
  font-weight: bold;
}

.onboarding-progress {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.onboarding-dot {
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 50%;
  background-color: var(--border-color);
  transition: background-color 0.3s ease;
}

.onboarding-dot.active {
  background-color: var(--primary);
}

.onboarding-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

.onboarding-btn {
  padding: 0.75rem 1.5rem;
  border-radius: 0.5rem;
  border: none;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  font-size: 0.95rem;
}

.onboarding-btn-primary {
  background-color: var(--primary);
  color: white;
}

.onboarding-btn-primary:hover {
  background-color: var(--primary-dark);
}

.onboarding-btn-secondary {
  background-color: var(--border-color);
  color: var(--text-primary);
}

.onboarding-btn-secondary:hover {
  background-color: var(--bg-secondary);
}

/* ========================
   HELP BUTTON
   ======================== */

.help-button {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 3rem;
  height: 3rem;
  border-radius: 50%;
  background-color: var(--primary);
  color: white;
  border: none;
  font-size: 1.5rem;
  font-weight: bold;
  cursor: pointer;
  box-shadow: var(--shadow-lg);
  transition: all 0.3s ease;
  z-index: 50;
}

.help-button:hover {
  background-color: var(--primary-dark);
  transform: scale(1.1);
}

/* ========================
   COURSE FILTERS
   ======================== */

.course-filters {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.5rem 1rem;
  border: 1px solid var(--border-color);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  border-radius: 0.5rem;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all 0.2s ease;
}

.filter-btn:hover,
.filter-btn.active {
  background-color: var(--primary);
  color: white;
  border-color: var(--primary);
}

/* ========================
   RESPONSIVE ADJUSTMENTS
   ======================== */

@media (min-width: 768px) {
  .nav-links {
    display: flex;
    position: static;
    flex-direction: row;
    gap: 0;
    background-color: transparent;
    border: none;
    padding: 0;
    box-shadow: none;
  }

  .mobile-menu-toggle {
    display: none;
  }

  .nav-link {
    padding: 0.5rem 1rem;
  }

  .welcome-content h1 {
    font-size: 2.25rem;
  }

  .welcome-content p {
    font-size: 1rem;
  }

  .onboarding-card {
    padding: 2.5rem;
  }
}

@media (max-width: 640px) {
  .section-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .stat-value {
    font-size: 1.5rem;
  }

  .help-button {
    width: 2.5rem;
    height: 2.5rem;
    font-size: 1.25rem;
    bottom: 1.5rem;
    right: 1.5rem;
  }
}