/* ==========================================================================
   Docker & Kubernetes Production Mastery Portal
   Master Stylesheet (Modern Glassmorphic Dark/Light Design System)
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Outfit:wght@500;600;700;800&family=Fira+Code:wght@400;500;600&display=swap');

:root {
  /* Color Palette - Dark Mode Default */
  --bg-primary: #0A0F1D;
  --bg-secondary: #0F172A;
  --bg-tertiary: #1E293B;
  --bg-card: rgba(19, 29, 51, 0.78);
  --bg-card-hover: rgba(30, 45, 78, 0.90);
  --bg-glass: rgba(15, 23, 42, 0.85);
  --bg-elevated: #162036;

  /* Docker & Kubernetes Accent Colors */
  --k8s-blue: #326CE5;
  --k8s-blue-glow: rgba(50, 108, 229, 0.4);
  --docker-blue: #0DB7ED;
  --docker-blue-glow: rgba(13, 183, 237, 0.4);
  --accent-cyan: #38BDF8;
  --accent-indigo: #6366F1;
  --accent-purple: #8B5CF6;
  --accent-emerald: #10B981;
  --accent-amber: #F59E0B;
  --accent-rose: #F43F5E;

  /* Dynamic Active Brand Accent (switches between Docker & K8s) */
  --brand-color: #326CE5;
  --brand-glow: rgba(50, 108, 229, 0.35);

  /* Text Colors */
  --text-primary: #F8FAFC;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  --text-accent: #38BDF8;

  /* Borders & Shadows */
  --border-subtle: rgba(255, 255, 255, 0.08);
  --border-card: rgba(255, 255, 255, 0.12);
  --border-accent: rgba(50, 108, 229, 0.45);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 8px 24px -4px rgba(0, 0, 0, 0.45);
  --shadow-lg: 0 16px 40px -8px rgba(0, 0, 0, 0.6);
  --shadow-glow: 0 0 25px rgba(50, 108, 229, 0.3);

  /* Dimensions & Spacing */
  --header-height: 72px;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --transition-fast: 0.15s ease;
  --transition-base: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Light Theme Variables */
[data-theme="light"] {
  --bg-primary: #F8FAFC;
  --bg-secondary: #EEF2F6;
  --bg-tertiary: #E2E8F0;
  --bg-card: rgba(255, 255, 255, 0.92);
  --bg-card-hover: #FFFFFF;
  --bg-glass: rgba(255, 255, 255, 0.88);
  --bg-elevated: #F1F5F9;

  --text-primary: #0F172A;
  --text-secondary: #475569;
  --text-muted: #64748B;
  --text-accent: #2563EB;

  --border-subtle: rgba(0, 0, 0, 0.08);
  --border-card: rgba(0, 0, 0, 0.12);
  --border-accent: rgba(50, 108, 229, 0.4);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 8px 20px -4px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 16px 36px -6px rgba(0, 0, 0, 0.15);
  --shadow-glow: 0 0 25px rgba(50, 108, 229, 0.15);
}

/* Base Styles */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color var(--transition-base), color var(--transition-base);
}

.container {
  width: 100%;
  max-width: 1380px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Site Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  height: var(--header-height);
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
  transition: background var(--transition-base), border var(--transition-base);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: 1.5rem;
}

/* Logo */
.logo-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--text-primary);
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
}

.logo-badge {
  background: linear-gradient(135deg, var(--docker-blue), var(--k8s-blue));
  color: #FFFFFF;
  font-size: 0.8rem;
  font-weight: 800;
  padding: 0.3rem 0.65rem;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  gap: 0.35rem;
  box-shadow: 0 0 12px var(--brand-glow);
}

.logo-text span {
  color: var(--accent-cyan);
}

/* Course Switcher Tabs */
.course-switcher {
  display: flex;
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  padding: 0.3rem;
  border-radius: var(--radius-md);
  gap: 0.25rem;
}

.course-switch-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.85rem;
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.course-switch-btn:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.04);
}

.course-switch-btn.active {
  background: var(--brand-color);
  color: #FFFFFF;
  box-shadow: 0 2px 10px var(--brand-glow);
}

/* Navigation Links */
.header-nav {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.nav-link {
  text-decoration: none;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.88rem;
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  gap: 0.45rem;
  transition: all var(--transition-fast);
  cursor: pointer;
}

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

.nav-link.active {
  color: var(--text-accent);
  background: var(--bg-elevated);
}

.nav-link.terminal-nav {
  background: rgba(16, 185, 129, 0.15);
  color: #10B981;
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.nav-link.terminal-nav:hover {
  background: rgba(16, 185, 129, 0.25);
  box-shadow: 0 0 12px rgba(16, 185, 129, 0.35);
}

/* Header Actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

/* Language Switcher in Header */
.lang-switcher {
  display: flex;
  align-items: center;
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-full);
  padding: 3px;
  gap: 2px;
}

.lang-switch-btn {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.65rem;
  border-radius: var(--radius-full);
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.lang-switch-btn:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.05);
}

.lang-switch-btn.active {
  background: var(--bg-elevated);
  color: var(--text-accent);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
}

.theme-toggle-btn {
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  color: var(--text-primary);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  border-color: var(--brand-color);
  box-shadow: 0 0 10px var(--brand-glow);
}

/* Hero Section */
.hero-section {
  padding: 3.5rem 0 2.5rem;
  text-align: center;
  position: relative;
  background: radial-gradient(circle at 50% 10%, rgba(50, 108, 229, 0.12) 0%, transparent 60%);
}

.hero-badge-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(50, 108, 229, 0.15);
  border: 1px solid var(--border-accent);
  color: var(--accent-cyan);
  padding: 0.4rem 1rem;
  border-radius: 9999px;
  font-size: 0.82rem;
  font-weight: 600;
  margin-bottom: 1.25rem;
  box-shadow: 0 0 15px rgba(50, 108, 229, 0.2);
}

.hero-title {
  font-family: 'Outfit', sans-serif;
  font-size: 3rem;
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
}

.gradient-text {
  background: linear-gradient(135deg, var(--docker-blue) 0%, var(--k8s-blue) 50%, var(--accent-purple) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
  max-width: 840px;
  margin: 0 auto 2.5rem;
  line-height: 1.65;
}

/* Hero Language Preference Box */
.hero-lang-box {
  max-width: 880px;
  margin: 0 auto 2.5rem;
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-accent);
  border-radius: var(--radius-lg);
  padding: 1.25rem 1.5rem;
  box-shadow: 0 4px 20px rgba(50, 108, 229, 0.15);
  text-align: center;
}

.hero-lang-title {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
}

.hero-lang-chips {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.hero-lang-chip {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding: 0.85rem 1.15rem;
  background: var(--bg-secondary);
  border: 2px solid var(--border-card);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  cursor: pointer;
  text-align: left;
  transition: all var(--transition-fast);
}

.hero-lang-chip .chip-flag {
  font-size: 1.75rem;
  line-height: 1;
}

.hero-lang-chip .chip-info {
  display: flex;
  flex-direction: column;
}

.hero-lang-chip .chip-title {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--text-primary);
}

.hero-lang-chip .chip-sub {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.hero-lang-chip:hover {
  border-color: var(--border-accent);
  transform: translateY(-2px);
}

.hero-lang-chip.active {
  border-color: var(--brand-color);
  background: rgba(50, 108, 229, 0.12);
  box-shadow: 0 0 15px rgba(50, 108, 229, 0.25);
}

.hero-lang-chip.active .chip-title {
  color: var(--accent-cyan);
}

.hero-lang-status-msg {
  margin-top: 1rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
  padding-top: 0.75rem;
  border-top: 1px solid var(--border-subtle);
}

@media (max-width: 768px) {
  .hero-lang-chips {
    grid-template-columns: 1fr;
  }
}

/* Hero Stats Grid */
.hero-stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.25rem;
  max-width: 980px;
  margin: 0 auto 2.5rem;
}

.stat-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  text-align: left;
  transition: transform var(--transition-fast), border-color var(--transition-fast);
}

.stat-card:hover {
  transform: translateY(-3px);
  border-color: var(--brand-color);
  box-shadow: var(--shadow-md);
}

.stat-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: rgba(50, 108, 229, 0.15);
  color: var(--accent-cyan);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
}

.stat-value {
  font-family: 'Outfit', sans-serif;
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.1;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* Filter & Search Bar */
.filter-search-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-lg);
  margin-bottom: 2rem;
}

.search-input-wrap {
  flex: 1;
  position: relative;
  display: flex;
  align-items: center;
}

.search-input-wrap i {
  position: absolute;
  left: 1rem;
  color: var(--text-muted);
  font-size: 1rem;
}

.search-input {
  width: 100%;
  padding: 0.65rem 1rem 0.65rem 2.75rem;
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: 'Inter', sans-serif;
  font-size: 0.95rem;
  outline: none;
  transition: border-color var(--transition-fast);
}

.search-input:focus {
  border-color: var(--brand-color);
  box-shadow: 0 0 10px var(--brand-glow);
}

.filter-chips {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.filter-chip {
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.4rem 0.85rem;
  border-radius: 9999px;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.filter-chip:hover {
  color: var(--text-primary);
  border-color: var(--border-card);
}

.filter-chip.active {
  background: var(--brand-color);
  color: #FFFFFF;
  border-color: var(--brand-color);
}

/* Course Modules Section */
.modules-container {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
  margin-bottom: 4rem;
}

.module-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-xl);
  overflow: hidden;
  transition: border-color var(--transition-base);
}

.module-header {
  padding: 1.5rem 1.75rem;
  background: linear-gradient(90deg, rgba(50, 108, 229, 0.08) 0%, transparent 100%);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.module-title-wrap {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.module-icon-box {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--bg-primary);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  color: var(--accent-cyan);
}

.module-badge {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: rgba(50, 108, 229, 0.15);
  color: var(--accent-cyan);
  border: 1px solid rgba(50, 108, 229, 0.3);
}

.module-title {
  font-family: 'Outfit', sans-serif;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
}

.module-desc {
  font-size: 0.88rem;
  color: var(--text-secondary);
  margin-top: 0.2rem;
}

.module-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.module-count {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-primary);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
}

/* Lectures Grid */
.lectures-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 1.25rem;
  padding: 1.75rem;
}

.lecture-card {
  background: var(--bg-card);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg);
  padding: 1.35rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  cursor: pointer;
  position: relative;
  transition: transform var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.lecture-card:hover {
  transform: translateY(-4px);
  border-color: var(--brand-color);
  box-shadow: var(--shadow-md), 0 0 20px var(--brand-glow);
}

.lecture-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}

.lecture-day-tag {
  font-size: 0.75rem;
  font-weight: 800;
  font-family: 'Fira Code', monospace;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent-cyan);
  border: 1px solid rgba(56, 189, 248, 0.3);
}

.lecture-completion-status {
  color: var(--text-muted);
  font-size: 1.1rem;
  transition: color var(--transition-fast);
}

.lecture-completion-status.completed {
  color: var(--accent-emerald);
}

.lecture-title {
  font-family: 'Outfit', sans-serif;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.35;
  margin-bottom: 0.5rem;
}

.lecture-preview-text {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.5;
  margin-bottom: 1rem;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.lecture-card-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.75rem;
  margin-top: auto;
}

.lecture-features-badges {
  display: flex;
  gap: 0.4rem;
}

.feature-badge {
  font-size: 0.72rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.open-lecture-btn {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent-cyan);
  display: flex;
  align-items: center;
  gap: 0.35rem;
  transition: gap var(--transition-fast);
}

.lecture-card:hover .open-lecture-btn {
  gap: 0.6rem;
}

/* Site Footer */
.site-footer {
  margin-top: auto;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-subtle);
  padding: 3rem 0 2rem;
  text-align: center;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.footer-brand {
  font-family: 'Outfit', sans-serif;
  font-size: 1.2rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.footer-text {
  max-width: 680px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Media Queries */
@media (max-width: 1024px) {
  .hero-stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding: 0.75rem 1rem;
  }
  .course-switcher {
    order: 3;
    width: 100%;
    justify-content: center;
  }
  .hero-title {
    font-size: 2.1rem;
  }
  .hero-stats-grid {
    grid-template-columns: 1fr;
  }
  .filter-search-container {
    flex-direction: column;
    align-items: stretch;
  }
  .lectures-grid {
    grid-template-columns: 1fr;
    padding: 1rem;
  }
}