/* AI Academy - Modern Learning Platform */
/* ====================================== */

@import url('https://fonts.googleapis.com/css2?family=Prompt:wght@300;400;500;600;700&display=swap');

:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --accent: #8b5cf6;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --bg-dark: #0f172a;
  --bg-card: #1e293b;
  --bg-card-hover: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #334155;
  --gradient-1: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  --gradient-2: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
  --gradient-3: linear-gradient(135deg, #10b981 0%, #059669 100%);
}

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

body {
  font-family: 'Prompt', 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg-dark);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Header ===== */
.header {
  background: rgba(15, 23, 42, 0.95);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  padding: 1rem 2rem;
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--gradient-1);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.logo-icon {
  font-size: 1.8rem;
  -webkit-text-fill-color: initial;
}

.tagline {
  color: var(--text-secondary);
  font-size: 0.875rem;
  display: none;
}

@media (min-width: 768px) {
  .tagline { display: block; }
}

.header-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.progress-badge {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background: var(--bg-card);
  padding: 0.5rem 1rem;
  border-radius: 50px;
  border: 1px solid var(--border);
}

.progress-ring {
  position: relative;
  width: 36px;
  height: 36px;
}

.progress-ring svg {
  transform: rotate(-90deg);
  width: 100%;
  height: 100%;
}

.progress-bg {
  fill: none;
  stroke: var(--border);
  stroke-width: 3;
}

.progress-fill {
  fill: none;
  stroke: var(--success);
  stroke-width: 3;
  stroke-linecap: round;
  transition: stroke-dasharray 0.5s ease;
}

.progress-text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 0.65rem;
  font-weight: 600;
  color: var(--success);
}

.progress-label {
  font-size: 0.75rem;
  color: var(--text-secondary);
  display: none;
}

@media (min-width: 640px) {
  .progress-label { display: block; }
}

.lang-toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  padding: 0.5rem 0.75rem;
  border-radius: 8px;
  cursor: pointer;
  color: var(--text-primary);
  font-size: 0.875rem;
  transition: all 0.2s;
}

.lang-toggle:hover {
  background: var(--bg-card-hover);
  border-color: var(--primary);
}

/* ===== Main Content ===== */
.main-content {
  max-width: 1400px;
  margin: 0 auto;
  padding: 2rem;
}

.view {
  display: none;
}

.view.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== Hero Section ===== */
.hero {
  text-align: center;
  padding: 3rem 1rem 2rem;
  margin-bottom: 2rem;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, rgba(139, 92, 246, 0.1) 100%);
  border-radius: 24px;
  border: 1px solid var(--border);
}

.hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 1rem;
  background: var(--gradient-1);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  color: var(--text-secondary);
  font-size: 1.125rem;
  max-width: 600px;
  margin: 0 auto 2rem;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 3rem;
  flex-wrap: wrap;
}

.stat-item {
  text-align: center;
}

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

.stat-label {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* ===== Category Tabs ===== */
.category-tabs {
  display: flex;
  gap: 0.5rem;
  overflow-x: auto;
  padding-bottom: 1rem;
  margin-bottom: 2rem;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.category-tabs::-webkit-scrollbar {
  display: none;
}

.category-tab {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.2s;
}

.category-tab:hover {
  background: var(--bg-card-hover);
  color: var(--text-primary);
}

.category-tab.active {
  background: var(--gradient-1);
  border-color: transparent;
  color: white;
}

.category-tab .icon {
  font-size: 1.25rem;
}

.category-tab .count {
  background: rgba(255,255,255,0.2);
  padding: 0.125rem 0.5rem;
  border-radius: 50px;
  font-size: 0.75rem;
}

.category-tab:not(.active) .count {
  background: var(--bg-dark);
}

/* ===== Category Section ===== */
.category-section {
  margin-bottom: 3rem;
}

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

.category-title {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.category-title .icon {
  font-size: 2rem;
}

.category-title h2 {
  font-size: 1.5rem;
  font-weight: 600;
}

.category-title p {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.category-progress {
  display: flex;
  align-items: center;
  gap: 1rem;
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.category-progress-bar {
  width: 120px;
  height: 8px;
  background: var(--bg-dark);
  border-radius: 4px;
  overflow: hidden;
}

.category-progress-fill {
  height: 100%;
  background: var(--gradient-3);
  border-radius: 4px;
  transition: width 0.3s ease;
}

/* ===== Lessons Grid ===== */
.lessons-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
}

/* ===== Lesson Card ===== */
.lesson-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  overflow: hidden;
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
}

.lesson-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 20px 40px rgba(0,0,0,0.3);
  border-color: var(--primary);
}

.lesson-card.completed {
  border-color: var(--success);
}

.lesson-card.locked {
  opacity: 0.6;
  cursor: not-allowed;
}

.lesson-card.locked:hover {
  transform: none;
  box-shadow: none;
}

.card-banner {
  height: 120px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.card-banner::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

/* Card banner gradients based on category */
.card-banner.foundation { background: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%); }
.card-banner.core-concepts { background: linear-gradient(135deg, #8b5cf6 0%, #6d28d9 100%); }
.card-banner.ai-models { background: linear-gradient(135deg, #ec4899 0%, #be185d 100%); }
.card-banner.practical { background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%); }
.card-banner.advanced { background: linear-gradient(135deg, #10b981 0%, #059669 100%); }

.card-banner .lesson-icon {
  font-size: 3rem;
  z-index: 1;
}

.card-banner .lesson-number {
  position: absolute;
  top: 0.75rem;
  left: 0.75rem;
  background: rgba(0,0,0,0.3);
  padding: 0.25rem 0.75rem;
  border-radius: 50px;
  font-size: 0.75rem;
  font-weight: 600;
}

.card-banner .status-icon {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
}

.lesson-card.completed .status-icon {
  background: var(--success);
}

.lesson-card.locked .status-icon {
  background: var(--bg-dark);
}

.lesson-card:not(.completed):not(.locked) .status-icon {
  background: rgba(255,255,255,0.2);
}

.card-body {
  padding: 1.25rem;
}

.card-body h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.card-body p {
  color: var(--text-secondary);
  font-size: 0.875rem;
  margin-bottom: 1rem;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.meta-item {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  color: var(--text-muted);
  font-size: 0.8rem;
}

.difficulty-badge {
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
}

.difficulty-badge.beginner {
  background: rgba(16, 185, 129, 0.2);
  color: #10b981;
}

.difficulty-badge.intermediate {
  background: rgba(245, 158, 11, 0.2);
  color: #f59e0b;
}

.difficulty-badge.advanced {
  background: rgba(239, 68, 68, 0.2);
  color: #ef4444;
}

/* ===== Lesson View ===== */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  padding: 0.75rem 1.25rem;
  border-radius: 8px;
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.875rem;
  margin-bottom: 2rem;
  transition: all 0.2s;
}

.back-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--primary);
}

.lesson-content {
  max-width: 800px;
  margin: 0 auto;
}

.lesson-header {
  margin-bottom: 2rem;
}

.lesson-header h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.lesson-header .meta {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.lesson-body {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2rem;
}

.lesson-body h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 1.5rem 0 1rem;
  color: var(--primary);
}

.lesson-body h3:first-of-type {
  margin-top: 1rem;
}

.lesson-body p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.topics-list {
  list-style: none;
  padding: 0;
}

.topics-list li {
  padding: 0.75rem 0;
  padding-left: 2rem;
  position: relative;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border);
}

.topics-list li:last-child {
  border-bottom: none;
}

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

.start-quiz-btn {
  display: block;
  width: 100%;
  padding: 1rem 2rem;
  margin-top: 2rem;
  background: var(--gradient-1);
  border: none;
  border-radius: 12px;
  color: white;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
}

.start-quiz-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 30px rgba(99, 102, 241, 0.3);
}

/* ===== Quiz View ===== */
.quiz-container {
  max-width: 700px;
  margin: 0 auto;
}

.quiz-header {
  text-align: center;
  margin-bottom: 2rem;
}

.quiz-header h2 {
  font-size: 1.5rem;
  margin-bottom: 1rem;
}

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

.quiz-progress-bar {
  width: 100%;
  height: 6px;
  background: var(--bg-dark);
  border-radius: 3px;
  margin-top: 0.75rem;
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  background: var(--gradient-1);
  border-radius: 3px;
  transition: width 0.3s ease;
}

.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2rem;
}

.question-text {
  font-size: 1.25rem;
  font-weight: 500;
  margin-bottom: 2rem;
  line-height: 1.5;
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.option-btn {
  display: block;
  width: 100%;
  padding: 1rem 1.5rem;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 12px;
  color: var(--text-primary);
  font-size: 1rem;
  text-align: left;
  cursor: pointer;
  transition: all 0.2s;
}

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

.option-btn.correct {
  background: rgba(16, 185, 129, 0.2);
  border-color: var(--success);
}

.option-btn.incorrect {
  background: rgba(239, 68, 68, 0.2);
  border-color: var(--danger);
}

.option-btn:disabled {
  cursor: not-allowed;
}

/* Quiz Result */
.quiz-result {
  text-align: center;
  padding: 2rem;
}

.result-icon {
  font-size: 5rem;
  margin-bottom: 1rem;
}

.result-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.result-score {
  color: var(--text-secondary);
  font-size: 1.125rem;
  margin-bottom: 2rem;
}

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

.result-btn {
  padding: 1rem 2rem;
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
}

.result-btn.primary {
  background: var(--gradient-1);
  color: white;
}

.result-btn.secondary {
  background: var(--bg-dark);
  border: 1px solid var(--border);
  color: var(--text-primary);
}

.result-btn:hover {
  transform: translateY(-2px);
}

/* ===== Toast ===== */
.toast {
  position: fixed;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%) translateY(100px);
  background: var(--gradient-3);
  color: white;
  padding: 1rem 2rem;
  border-radius: 12px;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  box-shadow: 0 10px 40px rgba(0,0,0,0.3);
  opacity: 0;
  transition: all 0.3s ease;
  z-index: 1000;
}

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

.toast-icon {
  font-size: 1.5rem;
}

.toast-text {
  font-weight: 500;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .header {
    padding: 1rem;
  }

  .main-content {
    padding: 1rem;
  }

  .hero {
    padding: 2rem 1rem;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .hero p {
    font-size: 1rem;
  }

  .hero-stats {
    gap: 2rem;
  }

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

  .card-banner {
    height: 100px;
  }

  .lesson-body {
    padding: 1.5rem;
  }

  .question-card {
    padding: 1.5rem;
  }

  .category-header {
    flex-direction: column;
    align-items: flex-start;
  }
}