/* ==========================================
   Studiverse - Main Stylesheet
   AI-Powered E-Library & Learning Platform
   Color Scheme: Purple (#7C3AED) & Orange (#F59E0B)
   ========================================== */

:root {
  --primary: #7C3AED;
  --primary-dark: #5B21B6;
  --primary-light: #8B5CF6;
  --primary-50: #F5F3FF;
  --primary-100: #EDE9FE;

  --secondary: #F59E0B;
  --secondary-dark: #D97706;
  --secondary-light: #FBBF24;
  --secondary-50: #FFFBEB;

  --accent: #EC4899;
  --accent-light: #F472B6;

  --dark: #1E1B4B;
  --dark-800: #312E81;
  --dark-700: #3730A3;
  --dark-600: #4F46E5;
  --dark-500: #6D28D9;
  --dark-400: #8B5CF6;
  --dark-300: #A78BFA;
  --dark-200: #C4B5FD;
  --dark-100: #DDD6FE;

  --white: #FFFFFF;
  --light: #FAFAFA;
  --gray-50: #F9FAFB;
  --gray-100: #F3F4F6;
  --gray-200: #E5E7EB;
  --gray-300: #D1D5DB;
  --gray-400: #9CA3AF;
  --gray-500: #6B7280;
  --gray-600: #4B5563;
  --gray-700: #374151;
  --gray-800: #1F2937;

  --success: #10B981;
  --warning: #F59E0B;
  --danger: #EF4444;
  --info: #3B82F6;

  --border-color: var(--gray-200);
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.1), 0 4px 6px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);

  --radius-sm: 4px;
  --radius: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  --transition: all 0.2s ease;
  --transition-slow: all 0.3s ease;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --sidebar-width: 260px;
  --header-height: 80px;
}

/* ========== RESET & BASE ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  color: var(--gray-800);
  background: var(--light);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--primary); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--primary-dark); }
img { max-width: 100%; height: auto; }
ul, ol { list-style: none; }
input, button, textarea, select { font-family: inherit; font-size: inherit; outline: none; }

/* ========== TYPOGRAPHY ========== */
h1, h2, h3, h4, h5, h6 { font-weight: 700; line-height: 1.3; color: var(--dark); }
h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }
p { margin-bottom: 1rem; }
.text-gradient {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.text-primary { color: var(--primary); }
.text-secondary { color: var(--secondary); }
.text-accent { color: var(--accent); }
.text-success { color: var(--success); }
.text-danger { color: var(--danger); }
.text-center { text-align: center; }
.text-muted { color: var(--gray-500); }

/* ========== LAYOUT ========== */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.container-sm { max-width: 900px; }
.container-lg { max-width: 1400px; }
.d-flex { display: flex; }
.align-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: 4px; }
.gap-2 { gap: 8px; }
.gap-3 { gap: 12px; }
.gap-4 { gap: 16px; }
.gap-5 { gap: 20px; }
.flex-wrap { flex-wrap: wrap; }
.flex-1 { flex: 1; }

/* ========== HEADER ========== */
.site-header {
  background: var(--white);
  border-bottom: 1px solid var(--border-color);
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  height: var(--header-height);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
  gap: 16px;
}
.logo a {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.2rem;
  color: var(--dark);
}
.logo img { height: 80px; width: auto; }

.main-nav ul {
  display: flex;
  gap: 4px;
}
.main-nav ul li a {
  color: var(--gray-600);
  padding: 8px 12px;
  border-radius: var(--radius);
  font-size: 0.88rem;
  font-weight: 500;
  transition: var(--transition);
  white-space: nowrap;
}
.main-nav ul li a:hover,
.main-nav ul li a.active {
  color: var(--primary);
  background: var(--primary-50);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

/* ========== BUTTONS ========== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.9rem;
  border: none;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
  line-height: 1.4;
  white-space: nowrap;
}
.btn-sm { padding: 6px 14px; font-size: 0.85rem; }
.btn-lg { padding: 14px 28px; font-size: 1rem; }
.btn-primary {
  background: var(--primary);
  color: var(--white);
}
.btn-primary:hover {
  background: var(--primary-dark);
  color: var(--white);
}
.btn-secondary {
  background: var(--secondary);
  color: var(--white);
}
.btn-secondary:hover {
  background: var(--secondary-dark);
  color: var(--white);
}
.btn-outline {
  background: transparent;
  border: 2px solid var(--primary);
  color: var(--primary);
}
.btn-outline:hover {
  background: var(--primary);
  color: var(--white);
}
.btn-light {
  background: var(--gray-100);
  color: var(--gray-700);
  border: 1px solid var(--border-color);
}
.btn-light:hover { background: var(--gray-200); }
.btn-icon { padding: 6px 10px; font-size: 1.1rem; }
.btn-block { width: 100%; justify-content: center; }

/* ========== HAMBURGER ========== */
.hamburger {
  display: none;
  flex-direction: column;
  cursor: pointer;
  gap: 4px;
  padding: 6px;
  background: none;
  border: none;
  z-index: 1001;
}
.hamburger span {
  width: 24px;
  height: 2.5px;
  background: var(--gray-700);
  border-radius: 3px;
  transition: var(--transition);
}

/* ========== HERO ========== */
.hero {
  background: linear-gradient(135deg, var(--dark) 0%, var(--primary-dark) 50%, var(--primary) 100%);
  color: var(--white);
  padding: 100px 0 90px;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url('https://images.unsplash.com/photo-1523050854058-8df90110c7f1?w=1920&q=80') center/cover;
  opacity: 0.08;
}
.hero .container { position: relative; z-index: 1; }
.hero h1 { font-size: 3rem; margin-bottom: 20px; line-height: 1.2; color: var(--white); letter-spacing: -0.5px; }
.hero h1 span { color: var(--secondary); }
.hero p { font-size: 1.15rem; max-width: 700px; margin: 0 auto 30px; opacity: 0.92; line-height: 1.6; }
.hero .btn-group { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.hero .btn-outline-light {
  background: transparent;
  border: 2px solid var(--white);
  color: var(--white);
}
.hero .btn-outline-light:hover { background: rgba(255,255,255,0.1); }

/* ========== SECTIONS ========== */
section { padding: 80px 0; }
.section-header {
  text-align: center;
  margin-bottom: 50px;
}
.section-header h2 {
  font-size: 2.2rem;
  margin-bottom: 12px;
  color: var(--dark);
}
.section-header p {
  font-size: 1.05rem;
  color: var(--gray-500);
  max-width: 600px;
  margin: 0 auto;
}
.section-bg-light { background: var(--gray-50); }
.section-bg-primary { background: var(--primary-50); }

/* ========== CARDS GRID ========== */
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 24px; }

.feature-card, .value-card {
  padding: 36px 28px;
  border-radius: var(--radius-lg);
  background: var(--white);
  border: 1px solid var(--border-color);
  text-align: center;
  transition: var(--transition-slow);
}
.feature-card:hover, .value-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}
.feature-card .icon, .value-card .icon {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 18px;
  font-size: 1.6rem;
}
.feature-card h3, .value-card h3 {
  font-size: 1.15rem;
  margin-bottom: 10px;
  color: var(--dark);
}
.feature-card p, .value-card p {
  font-size: 0.92rem;
  color: var(--gray-500);
  line-height: 1.6;
}

/* ========== STATS ========== */
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
.stat-card {
  text-align: center;
  padding: 32px 20px;
}
.stat-card .number {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
  margin-bottom: 8px;
}
.stat-card .label {
  font-size: 0.95rem;
  color: var(--gray-500);
}

/* ========== PRICING ========== */
.pricing-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.pricing-card {
  background: var(--white);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  overflow: hidden;
  transition: var(--transition-slow);
  position: relative;
}
.pricing-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.pricing-card.featured {
  border-color: var(--primary);
  box-shadow: 0 0 0 2px var(--primary-100);
}
.pricing-card.featured::before {
  content: 'Popular';
  position: absolute;
  top: 16px;
  right: -32px;
  background: var(--primary);
  color: var(--white);
  padding: 4px 40px;
  font-size: 0.75rem;
  font-weight: 700;
  transform: rotate(45deg);
}
.pricing-card .header {
  padding: 28px 24px 20px;
  text-align: center;
  border-bottom: 1px solid var(--border-color);
}
.pricing-card .header h3 { font-size: 1.2rem; margin-bottom: 4px; }
.pricing-card .header .price { font-size: 2.2rem; font-weight: 800; color: var(--primary); }
.pricing-card .header .price span { font-size: 1rem; font-weight: 400; color: var(--gray-500); }
.pricing-card .body { padding: 20px 24px; }
.pricing-card .body ul li { padding: 8px 0; font-size: 0.88rem; color: var(--gray-600); border-bottom: 1px solid var(--gray-100); display: flex; align-items: center; gap: 8px; }
.pricing-card .body ul li::before { content: '✓'; color: var(--success); font-weight: 700; }
.pricing-card .footer { padding: 16px 24px 24px; text-align: center; }

/* ========== FORMS ========== */
.form-group { margin-bottom: 16px; }
.form-group label {
  display: block;
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 6px;
  color: var(--gray-700);
}
.form-control {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 0.95rem;
  transition: var(--transition);
  background: var(--white);
}
.form-control:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-50);
}
select.form-control { appearance: auto; }
textarea.form-control { resize: vertical; min-height: 100px; }

/* ========== AUTH PAGES ========== */
.auth-page {
  min-height: calc(100vh - var(--header-height));
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
  background: linear-gradient(135deg, var(--primary-50), var(--secondary-50));
}
.auth-box {
  background: var(--white);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  padding: 40px;
  width: 100%;
  max-width: 440px;
}
.auth-box h2 { text-align: center; margin-bottom: 8px; }
.auth-box .subtitle { text-align: center; color: var(--gray-500); margin-bottom: 28px; font-size: 0.95rem; }
.auth-box .form-footer { text-align: center; margin-top: 20px; font-size: 0.9rem; color: var(--gray-500); }
.auth-box .form-footer a { font-weight: 600; }

/* ========== DASHBOARD LAYOUT ========== */
.dashboard-layout {
  display: flex;
  min-height: calc(100vh - 52px);
}
.sidebar {
  width: var(--sidebar-width);
  background: var(--white);
  border-right: 1px solid var(--border-color);
  position: fixed;
  top: 52px;
  left: 0;
  bottom: 0;
  z-index: 100;
  overflow-y: auto;
  transition: var(--transition);
}
.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  border-bottom: 1px solid var(--border-color);
}
.sidebar-logo { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--dark); }
.sidebar-close { display: none; background: none; border: none; font-size: 1.2rem; cursor: pointer; color: var(--gray-500); }
.sidebar-nav { padding: 12px; }
.nav-section { margin-bottom: 20px; }
.nav-section-title {
  display: block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--gray-400);
  padding: 0 12px;
  margin-bottom: 6px;
}
.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  border-radius: var(--radius);
  color: var(--gray-600);
  font-size: 0.88rem;
  font-weight: 500;
  transition: var(--transition);
}
.nav-item:hover { background: var(--gray-50); color: var(--primary); }
.nav-item.active { background: var(--primary-50); color: var(--primary); font-weight: 600; }

.dashboard-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  padding: 28px 32px;
  min-height: calc(100vh - 52px);
}

/* ========== FOOTER ========== */
.site-footer {
  background: var(--dark);
  color: var(--white);
  padding: 60px 0 25px;
}
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 35px; }
.footer-col h4 { margin-bottom: 18px; font-size: 1rem; color: var(--white); }
.footer-col p { font-size: 0.88rem; line-height: 1.6; opacity: 0.8; }
.footer-col ul li { margin-bottom: 8px; }
.footer-col ul li a { color: rgba(255,255,255,0.7); text-decoration: none; font-size: 0.88rem; transition: color .3s; }
.footer-col ul li a:hover { color: var(--white); }
.footer-bottom { border-top: 1px solid rgba(255,255,255,0.1); padding-top: 20px; text-align: center; font-size: 0.85rem; opacity: 0.7; }
.social-links { display: flex; gap: 10px; margin-top: 16px; }
.social-links a {
  width: 36px; height: 36px; border-radius: 50%;
  background: rgba(255,255,255,0.08);
  display: flex; align-items: center; justify-content: center;
  color: var(--white); text-decoration: none;
  transition: background .3s; font-weight: 700; font-size: 0.85rem;
}
.social-links a:hover { background: var(--primary); }

/* ========== MISC ========== */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 2px 10px;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
}
.badge-primary { background: var(--primary-100); color: var(--primary); }
.badge-secondary { background: var(--secondary-50); color: var(--secondary-dark); }
.badge-success { background: #D1FAE5; color: #065F46; }
.badge-danger { background: #FEE2E2; color: #991B1B; }

.alert {
  padding: 14px 18px;
  border-radius: var(--radius);
  margin-bottom: 16px;
  font-size: 0.9rem;
}
.alert-success { background: #D1FAE5; color: #065F46; border: 1px solid #A7F3D0; }
.alert-danger { background: #FEE2E2; color: #991B1B; border: 1px solid #FECACA; }
.alert-info { background: #DBEAFE; color: #1E40AF; border: 1px solid #BFDBFE; }

.page-hero {
  background: linear-gradient(135deg, var(--dark), var(--primary-dark));
  color: var(--white);
  padding: 48px 0;
  text-align: center;
}
.page-hero h1 { color: var(--white); font-size: 2rem; margin-bottom: 6px; }
.page-hero p { opacity: 0.85; font-size: 1rem; }

.content-section {
  background: var(--white);
  border-radius: var(--radius-lg);
  padding: 32px;
  margin-bottom: 24px;
  border: 1px solid var(--border-color);
}

/* ========== SEARCH ========== */
.search-box {
  display: flex;
  gap: 0;
  max-width: 600px;
  margin: 0 auto 32px;
}
.search-box input {
  flex: 1;
  padding: 14px 18px;
  border: 2px solid var(--border-color);
  border-right: none;
  border-radius: var(--radius) 0 0 var(--radius);
  font-size: 1rem;
}
.search-box input:focus { border-color: var(--primary); outline: none; }
.search-box button {
  padding: 14px 24px;
  background: var(--primary);
  color: var(--white);
  border: none;
  border-radius: 0 var(--radius) var(--radius) 0;
  cursor: pointer;
  font-weight: 600;
  transition: var(--transition);
}
.search-box button:hover { background: var(--primary-dark); }

/* ========== USER DROPDOWN ========== */
.user-dropdown { position: relative; }
.dropdown-toggle { cursor: pointer; }
.dropdown-menu {
  display: none;
  position: absolute;
  right: 0;
  top: 100%;
  background: var(--white);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  min-width: 200px;
  z-index: 1000;
  padding: 6px;
  margin-top: 4px;
}
.dropdown-menu.show { display: block; }
.dropdown-menu a {
  display: block;
  padding: 8px 14px;
  color: var(--gray-700);
  font-size: 0.88rem;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}
.dropdown-menu a:hover { background: var(--gray-50); color: var(--primary); }
.dropdown-menu hr { margin: 6px 0; border: none; border-top: 1px solid var(--border-color); }

/* ========== RESPONSIVE: TABLET ========== */
@media(max-width: 992px) {
  .hero h1 { font-size: 2.4rem; }
  .grid-3, .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .pricing-grid { grid-template-columns: repeat(2, 1fr); }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }

  .main-nav {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--white);
    z-index: 1000;
    overflow-y: auto;
    padding: 80px 24px 24px;
  }
  .main-nav.open { display: block; }
  .main-nav ul { flex-direction: column; gap: 2px; }
  .main-nav ul li a {
    display: block;
    padding: 14px 16px;
    font-size: 1rem;
    border-radius: var(--radius);
  }
  .hamburger { display: flex; }
  .hamburger.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
  .hamburger.active span:nth-child(2) { opacity: 0; }
  .hamburger.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

  .sidebar {
    transform: translateX(-100%);
    top: 0;
    z-index: 1100;
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-close { display: block; }
  .dashboard-content { margin-left: 0; padding: 20px; }
}

/* ========== RESPONSIVE: MOBILE ========== */
@media(max-width: 576px) {
  .hero { padding: 70px 0 60px; }
  .hero h1 { font-size: 1.8rem; }
  .hero p { font-size: 0.95rem; }
  .hero .btn { display: block; width: 100%; text-align: center; }
  section { padding: 50px 0; }
  .section-header h2 { font-size: 1.6rem; }
  .grid-3, .grid-4, .grid-2, .pricing-grid, .stats-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .auth-box { padding: 28px 20px; }
  .content-section { padding: 20px; }
  .logo span { font-size: 1rem; }
  .search-box { flex-direction: column; }
  .search-box input { border-radius: var(--radius) var(--radius) 0 0; border-right: 2px solid var(--border-color); }
  .search-box button { border-radius: 0 0 var(--radius) var(--radius); }
  .dashboard-content { padding: 16px; }
}