/* ═══════════════════════════════════════════════════════════════
   Guitar Learning Guide - Premium Glassmorphism Design 2026
   Advanced Frosted Glass | Dynamic Gradients | Fluid Animations
   ═══════════════════════════════════════════════════════════════ */

/* ─── CSS Variables ─── */
:root {
  /* Core Colors - Deep Base (lightened for glass contrast) */
  --bg-primary: #0c0c18;
  --bg-secondary: #12121f;
  --bg-tertiary: #1a1a28;
  
  /* Premium Glass Effect */
  --glass-bg: rgba(255, 255, 255, 0.06);
  --glass-bg-light: rgba(255, 255, 255, 0.09);
  --glass-bg-hover: rgba(255, 255, 255, 0.14);
  --glass-border: rgba(255, 255, 255, 0.08);
  --glass-border-light: rgba(255, 255, 255, 0.15);
  --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  --glass-shadow-lg: 0 25px 50px rgba(0, 0, 0, 0.4);
  
  /* Premium Accent Gradients */
  --accent-primary: #ff7a45;
  --accent-secondary: #ffb347;
  --accent-tertiary: #ffd89b;
  --gradient-primary: linear-gradient(135deg, #ff7a45 0%, #ffb347 50%, #ffd89b 100%);
  --gradient-glow: linear-gradient(135deg, rgba(255,122,69,0.5) 0%, rgba(255,179,71,0.3) 100%);
  --gradient-frost: linear-gradient(180deg, rgba(255,255,255,0.1) 0%, rgba(255,255,255,0.02) 100%);
  
  /* Text Colors */
  --text-primary: rgba(255, 255, 255, 0.95);
  --text-secondary: rgba(255, 255, 255, 0.75);
  --text-muted: rgba(255, 255, 255, 0.45);
  --text-accent: #ffb347;
  
  /* Spacing */
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  
  /* Border Radius */
  --radius-sm: 12px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-xl: 32px;
  
  /* Transitions */
  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
}

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

/* Animated Aurora Background */
body::before {
  content: '';
  position: fixed;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: 
    radial-gradient(ellipse at 20% 30%, rgba(255,122,69,0.20) 0%, transparent 40%),
    radial-gradient(ellipse at 80% 70%, rgba(255,179,71,0.15) 0%, transparent 40%),
    radial-gradient(ellipse at 50% 50%, rgba(100,149,237,0.08) 0%, transparent 50%);
  pointer-events: none;
  z-index: -1;
  animation: auroraMove 20s ease-in-out infinite;
}

@keyframes auroraMove {
  0%, 100% { transform: translate(0, 0) rotate(0deg); }
  25% { transform: translate(2%, 2%) rotate(2deg); }
  50% { transform: translate(-1%, 3%) rotate(-1deg); }
  75% { transform: translate(3%, -2%) rotate(1deg); }
}

/* ─── Navigation - Premium Glass ─── */
.main-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: 0.75rem 1.5rem;
  background: rgba(5, 5, 8, 0.8);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.nav-container {
  max-width: 1600px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

.nav-brand {
  font-size: 1.3rem;
  font-weight: 800;
  background: linear-gradient(135deg, #ff7a45 0%, #ffb347 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  text-decoration: none;
  white-space: nowrap;
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  gap: 0.25rem;
  list-style: none;
  align-items: center;
  margin: 0;
  padding: 0;
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  padding: 0.5rem 0.875rem;
  border-radius: 10px;
  font-weight: 500;
  font-size: 0.9rem;
  transition: var(--transition-normal);
  position: relative;
  background: transparent;
  border: 1px solid transparent;
}

.nav-link:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.05);
}

.nav-link.active {
  color: var(--text-accent);
  background: rgba(255, 179, 71, 0.1);
  border-color: rgba(255, 179, 71, 0.2);
}

/* ─── Page Content ─── */
.page-content {
  max-width: 1600px;
  margin: 0 auto;
  padding: calc(80px + var(--space-xl)) 0 var(--space-xl);
}

/* ─── Page Header ─── */
.page-header {
  text-align: center;
  margin-bottom: 2rem;
  padding: 2rem 2rem 0.5rem;
  max-width: 1600px;
  margin-left: auto;
  margin-right: auto;
}

.section-tag {
  display: inline-block;
  padding: var(--space-xs) var(--space-md);
  background: var(--gradient-glow);
  border: 1px solid rgba(255, 179, 71, 0.3);
  border-radius: var(--radius-lg);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-accent);
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: var(--space-md);
}

.page-title {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 800;
  margin-bottom: var(--space-md);
  letter-spacing: -2px;
  line-height: 1.1;
}

.page-title span {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-desc {
  font-size: 1.2rem;
  color: var(--text-secondary);
  max-width: 700px;
  margin: 0 auto;
  line-height: 1.8;
}

/* ─── Glass Cards ─── */
.glass-card {
  background: var(--glass-bg);
  backdrop-filter: blur(20px) saturate(150%);
  -webkit-backdrop-filter: blur(20px) saturate(150%);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  transition: var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.glass-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--gradient-frost);
}

.glass-card:hover {
  background: var(--glass-bg-light);
  border-color: var(--glass-border-light);
  transform: translateY(-4px);
  box-shadow: var(--glass-shadow-lg);
}

/* ─── Buttons - Glass Style ─── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-md);
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition-normal);
  border: 1px solid var(--glass-border);
  background: var(--glass-bg);
  color: var(--text-secondary);
  position: relative;
  overflow: hidden;
}

.btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 50%;
  background: var(--gradient-frost);
  pointer-events: none;
}

.btn:hover {
  background: var(--glass-bg-hover);
  border-color: var(--glass-border-light);
  color: var(--text-primary);
  transform: translateY(-2px);
}

.btn-primary {
  background: var(--gradient-primary);
  border-color: transparent;
  color: #000;
}

.btn-primary:hover {
  box-shadow: 0 8px 25px rgba(255, 122, 69, 0.4);
}

/* ─── Filter Tabs - Glass Pills ─── */
.filter-tabs {
  display: flex;
  gap: var(--space-xs);
  flex-wrap: wrap;
  margin-bottom: var(--space-lg);
  padding: var(--space-sm);
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  justify-content: center;
}

.filter-tab {
  padding: var(--space-xs) var(--space-md);
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-lg);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition-normal);
}

.filter-tab:hover {
  background: var(--glass-bg-light);
  color: var(--text-primary);
}

.filter-tab.active {
  background: var(--gradient-primary);
  border-color: transparent;
  color: #000;
}

/* ─── Grids ─── */
.chord-grid,
.scales-grid,
.songs-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-md);
  align-items: start;
}

/* ─── Cards ─── */
.card {
  background: var(--glass-bg);
  backdrop-filter: blur(16px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--space-md);
  cursor: pointer;
  transition: var(--transition-normal);
}

.card:hover {
  background: var(--glass-bg-light);
  border-color: var(--glass-border-light);
}

.card-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}

.card-icon {
  width: 48px;
  height: 48px;
  background: var(--gradient-glow);
  border: 1px solid rgba(255, 179, 71, 0.3);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.card-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.card-subtitle {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* ─── Fretboard Container - Glass ─── */
.fretboard-container {
  background: rgba(0, 0, 0, 0.3);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin: var(--space-md) 0;
  overflow-x: auto;
}

/* ─── Info Blocks ─── */
.info-block {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-bottom: var(--space-sm);
}

.info-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: var(--space-xs);
}

.info-value {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-accent);
}

/* ─── Formula Display ─── */
.chord-formula {
  display: flex;
  gap: var(--space-xs);
  align-items: center;
  flex-wrap: wrap;
}

.formula-note {
  padding: var(--space-xs) var(--space-sm);
  background: var(--glass-bg-light);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  font-family: 'Fira Code', monospace;
  font-size: 0.9rem;
}

.formula-note.root {
  background: rgba(255, 122, 69, 0.2);
  border-color: rgba(255, 122, 69, 0.4);
  color: var(--text-accent);
}

.formula-arrow {
  color: var(--text-muted);
}

/* ─── Controls ─── */
.control-group {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: var(--space-md);
}

.control-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: var(--space-sm);
  display: block;
}

.control-options {
  display: flex;
  gap: var(--space-xs);
  flex-wrap: wrap;
}

.option-btn {
  padding: var(--space-xs) var(--space-md);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.9rem;
  cursor: pointer;
  transition: var(--transition-normal);
}

.option-btn:hover {
  background: var(--glass-bg-light);
  border-color: var(--glass-border-light);
  color: var(--text-primary);
  transform: translateY(-1px);
}

.option-btn.active {
  background: var(--gradient-primary);
  border-color: transparent;
  color: #000;
  box-shadow: 0 4px 15px rgba(255, 122, 69, 0.3);
}

/* ─── Concept Cards (CAGED) ─── */
.concept-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: var(--space-md);
  margin: var(--space-lg) 0;
}

.concept-card {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--space-md);
  text-align: center;
  cursor: pointer;
  transition: var(--transition-normal);
}

.concept-card:hover,
.concept-card.active {
  background: var(--glass-bg-light);
  border-color: var(--glass-border-light);
  transform: translateY(-4px);
  box-shadow: var(--glass-shadow);
}

.concept-letter {
  width: 56px;
  height: 56px;
  background: var(--gradient-primary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 800;
  margin: 0 auto var(--space-sm);
  color: #000;
}

.concept-name {
  font-weight: 700;
  margin-bottom: var(--space-xs);
  color: var(--text-primary);
}

.concept-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ─── Method Cards ─── */
.method-card {
  background: var(--glass-bg);
  backdrop-filter: blur(20px) saturate(150%);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  margin-bottom: var(--space-lg);
  overflow: hidden;
}

.method-header {
  padding: var(--space-lg);
  background: linear-gradient(135deg, rgba(255,122,69,0.1) 0%, rgba(255,179,71,0.05) 100%);
  border-bottom: 1px solid var(--glass-border);
}

.method-title {
  font-size: 1.6rem;
  font-weight: 800;
  margin-bottom: var(--space-xs);
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.method-subtitle {
  color: var(--text-muted);
  font-size: 1rem;
}

.method-content {
  padding: var(--space-lg);
}

/* ─── Shape Info ─── */
.shape-info {
  background: rgba(255, 179, 71, 0.08);
  border-left: 3px solid var(--accent-primary);
  padding: var(--space-md);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin-top: var(--space-md);
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--text-secondary);
}

/* ─── Footer ─── */
.footer {
  text-align: center;
  padding: var(--space-xl) var(--space-md);
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border-top: 1px solid var(--glass-border);
  color: var(--text-muted);
  margin-top: var(--space-xl);
}

/* ─── Responsive ─── */
@media (max-width: 768px) {
  .nav-links {
    overflow-x: auto;
    flex-wrap: nowrap;
    max-width: calc(100vw - 140px);
    scrollbar-width: none;
    -ms-overflow-style: none;
    gap: calc(var(--space-xs) / 2);
  }
  
  .nav-links::-webkit-scrollbar {
    display: none;
  }
  
  .nav-link {
    white-space: nowrap;
    padding: calc(var(--space-xs) / 2) var(--space-sm);
    font-size: 0.85rem;
  }
  
  .page-content {
    padding: calc(70px + var(--space-lg)) var(--space-sm) var(--space-lg);
  }
  
  .page-header {
    padding: 1.5rem 1rem 0.25rem;
  }
  
  .chord-grid,
  .scales-grid,
  .songs-grid {
    grid-template-columns: 1fr;
  }
  
  .concept-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  
  .filter-tabs {
    overflow-x: auto;
    flex-wrap: nowrap;
    justify-content: flex-start;
  }
}

/* ─── Animations ─── */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-in {
  animation: fadeInUp 0.6s ease forwards;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.pulse {
  animation: pulse 2s ease-in-out infinite;
}

/* ─── Utility Classes ─── */
.text-gradient {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.glass {
  background: var(--glass-bg);
  backdrop-filter: blur(16px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
}

/* ─── Scrollbar ─── */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--glass-border-light);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--glass-border);
}

/* ─── Selection ─── */
::selection {
  background: rgba(255, 122, 69, 0.3);
  color: var(--text-primary);
}