@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
  --bg-dark: #0a0e1a;
  --surface: rgba(255, 255, 255, 0.03);
  --surface-hover: rgba(255, 255, 255, 0.08);
  --primary: #0078D4;
  --primary-glow: rgba(0, 120, 212, 0.4);
  --primary-gradient: linear-gradient(135deg, #0078D4, #7B2BFC);
  --accent: #50E6FF;
  --success: #10b981;
  --success-glow: rgba(16, 185, 129, 0.3);
  --warning: #f59e0b;
  --danger: #ef4444;
  --danger-glow: rgba(239, 68, 68, 0.3);
  --text-primary: #e2e8f0;
  --text-secondary: #94a3b8;
  --border: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(255, 255, 255, 0.15);
  
  --font-family: 'Inter', sans-serif;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;
  
  --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-family);
  background-color: var(--bg-dark);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

::selection {
  background: var(--primary);
  color: #fff;
}

/* Animations */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes pulse {
  0% { box-shadow: 0 0 0 0 var(--primary-glow); }
  70% { box-shadow: 0 0 0 10px rgba(0,0,0,0); }
  100% { box-shadow: 0 0 0 0 rgba(0,0,0,0); }
}
@keyframes float {
  0% { transform: translateY(0px); }
  50% { transform: translateY(-10px); }
  100% { transform: translateY(0px); }
}
@keyframes bgShift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}
.animate-in {
  animation: fadeInUp 0.6s ease forwards;
  opacity: 0;
}
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }

/* Layout */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
  width: 100%;
}
.main-content {
  flex: 1;
  padding: 6rem 0 4rem;
}

/* Navigation */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: rgba(10, 14, 26, 0.7);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: var(--transition);
}
.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 4.5rem;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}
.nav-logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: #fff;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.nav-logo span {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.nav-links {
  display: flex;
  gap: 2rem;
  align-items: center;
}
.nav-links a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.95rem;
  text-decoration: none;
  position: relative;
  padding: 0.5rem 0;
}
.nav-links a:hover, .nav-links a.active {
  color: #fff;
}
.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0;
  width: 0; height: 2px;
  background: var(--primary-gradient);
  transition: var(--transition);
  border-radius: var(--radius-full);
}
.nav-links a:hover::after, .nav-links a.active::after {
  width: 100%;
}
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: #fff;
  font-size: 1.5rem;
  cursor: pointer;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-full);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  text-decoration: none;
}
.btn-primary {
  background: var(--primary-gradient);
  color: #fff;
  box-shadow: 0 4px 15px var(--primary-glow);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(123, 43, 252, 0.5);
}
.btn-secondary {
  background: var(--surface);
  color: #fff;
  border: 1px solid var(--border);
}
.btn-secondary:hover {
  background: var(--surface-hover);
  border-color: var(--border-glow);
  transform: translateY(-2px);
}
.btn-success { background: var(--success); color: #fff; box-shadow: 0 4px 15px var(--success-glow); }
.btn-danger { background: var(--danger); color: #fff; box-shadow: 0 4px 15px var(--danger-glow); }

/* Cards */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  backdrop-filter: blur(10px);
  transition: var(--transition);
}
.card:hover {
  transform: translateY(-5px);
  border-color: var(--border-glow);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5), 0 0 20px var(--primary-glow);
}

/* Badges */
.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.badge-blue { background: rgba(0, 120, 212, 0.1); color: var(--accent); border: 1px solid rgba(0,120,212,0.3); }
.badge-green { background: rgba(16, 185, 129, 0.1); color: var(--success); border: 1px solid rgba(16,185,129,0.3); }

/* Progress */
.progress-container {
  width: 100%;
  height: 8px;
  background: rgba(255,255,255,0.1);
  border-radius: var(--radius-full);
  overflow: hidden;
}
.progress-bar {
  height: 100%;
  background: var(--primary-gradient);
  border-radius: var(--radius-full);
  transition: width 0.5s ease;
}

/* Hero */
.hero {
  text-align: center;
  padding: 6rem 0 4rem;
  position: relative;
}
.hero::before {
  content: '';
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 60vw; height: 60vw;
  background: radial-gradient(circle, rgba(0,120,212,0.15) 0%, rgba(0,0,0,0) 70%);
  z-index: -1;
  pointer-events: none;
}
.hero h1 {
  font-size: 4rem;
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: 1.5rem;
  background: linear-gradient(to right, #fff, #94a3b8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero p {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2.5rem;
}
.hero-btns {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

/* Module Grid */
.module-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}
.module-card {
  display: flex;
  flex-direction: column;
  height: 100%;
  text-decoration: none;
  color: var(--text-primary);
}
.module-icon {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  background: rgba(255,255,255,0.05);
  width: 60px; height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
}
.module-card h3 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}
.module-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
  flex: 1;
}
.module-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-top: 1px solid var(--border);
  padding-top: 1rem;
  margin-top: auto;
}

/* Features */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-top: 3rem;
}
.feature-card {
  text-align: center;
  padding: 2rem;
}
.feature-card .icon {
  font-size: 2rem;
  margin-bottom: 1rem;
  color: var(--primary);
}

/* Quiz Specific */
.quiz-header {
  margin-bottom: 2rem;
}
.quiz-question {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 2rem;
}
.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.quiz-option {
  padding: 1.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 1rem;
}
.quiz-option:hover {
  background: var(--surface-hover);
  border-color: var(--border-glow);
}
.quiz-option.selected {
  background: rgba(0, 120, 212, 0.1);
  border-color: var(--primary);
  box-shadow: 0 0 15px var(--primary-glow);
}
.quiz-option.correct {
  border-color: var(--success);
  background: rgba(16, 185, 129, 0.1);
  box-shadow: 0 0 15px var(--success-glow);
}
.quiz-option.incorrect {
  border-color: var(--danger);
  background: rgba(239, 68, 68, 0.1);
  box-shadow: 0 0 15px var(--danger-glow);
}
.quiz-option-letter {
  width: 30px; height: 30px;
  background: rgba(255,255,255,0.1);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-weight: 600; font-size: 0.9rem;
}
.quiz-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 2rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}
.quiz-explanation {
  margin-top: 1.5rem;
  padding: 1.5rem;
  background: rgba(16, 185, 129, 0.05);
  border-left: 4px solid var(--success);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  display: none;
}

/* Flashcards */
.flashcard-container {
  perspective: 1000px;
  width: 100%;
  max-width: 600px;
  margin: 0 auto;
  height: 400px;
}
.flashcard {
  width: 100%;
  height: 100%;
  position: relative;
  transition: transform 0.8s;
  transform-style: preserve-3d;
  cursor: pointer;
}
.flashcard.flipped {
  transform: rotateY(180deg);
}
.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 2rem;
  text-align: center;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}
.flashcard-front {
  background: linear-gradient(135deg, rgba(255,255,255,0.05), rgba(255,255,255,0.01));
}
.flashcard-back {
  transform: rotateY(180deg);
  border-color: var(--primary);
}
.flashcard-controls {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-top: 2rem;
  opacity: 0;
  transition: opacity 0.3s;
  pointer-events: none;
}
.flashcard-controls.visible {
  opacity: 1;
  pointer-events: auto;
}

/* Dashboard */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.5rem;
  margin-bottom: 3rem;
}
.stat-card {
  text-align: center;
  padding: 1.5rem;
}
.stat-value {
  font-size: 3rem;
  font-weight: 800;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 0.5rem;
}
.stat-label {
  color: var(--text-secondary);
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
}
th, td {
  padding: 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}
th {
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  font-size: 0.85rem;
  letter-spacing: 1px;
}

/* Alerts */
.alert {
  padding: 1rem 1.5rem;
  border-radius: var(--radius-md);
  margin-bottom: 1.5rem;
  font-weight: 500;
}
.alert-info { background: rgba(0,120,212,0.1); color: var(--accent); border: 1px solid rgba(0,120,212,0.3); }

/* Footer */
.footer {
  text-align: center;
  padding: 2rem 0;
  border-top: 1px solid var(--border);
  color: var(--text-secondary);
  margin-top: auto;
}

/* Responsive */
@media (max-width: 768px) {
  .hero h1 { font-size: 2.5rem; }
  .nav-links {
    display: none;
    position: absolute;
    top: 100%; left: 0; right: 0;
    background: var(--bg-dark);
    flex-direction: column;
    padding: 1rem;
    border-bottom: 1px solid var(--border);
  }
  .nav-links.active { display: flex; }
  .mobile-menu-btn { display: block; }
  .quiz-nav { flex-direction: column; gap: 1rem; }
  .quiz-nav .btn { width: 100%; }
}