/* ==========================================================================
   中国传统文化探索 (Discover Chinese Culture)
   Designed & Built by: 陆氏清银 (Lục Thị Thanh Ngân)
   Mobile & iPad First Optimized CSS Design System with Video & Music
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Be+Vietnam+Pro:ital,wght@0,300;0,400;0,500;0,600;0,700;1,400&family=Ma+Shan+Zheng&family=Noto+Serif+SC:wght@300;400;600;700;900&display=swap');

:root {
  /* Default Accent Theme Color: 中国红 (Imperial Red) */
  --c-primary: #b93236;
  --c-primary-light: #e04a4f;
  --c-primary-glow: rgba(185, 50, 54, 0.3);
  --c-primary-bg: rgba(185, 50, 54, 0.12);

  --c-gold: #d4af37;
  --c-gold-light: #f3d57e;
  --c-gold-dark: #aa8524;
  --c-gold-glow: rgba(212, 175, 55, 0.25);

  /* Dark Theme Palette (水墨玄夜) */
  --bg-primary: #0d0f12;
  --bg-secondary: #14171e;
  --bg-tertiary: #1b212b;
  --card-bg: rgba(20, 24, 32, 0.85);
  --card-border: rgba(212, 175, 55, 0.2);
  --card-hover-border: var(--c-primary);
  
  --text-primary: #f5f4ef;
  --text-secondary: #b0b8c4;
  --text-muted: #747d8b;

  --glass-nav: rgba(13, 15, 18, 0.9);
  --glass-blur: blur(16px);
  --shadow-subtle: 0 8px 24px rgba(0, 0, 0, 0.4);
  --shadow-glow: 0 10px 30px var(--c-primary-glow);

  --font-serif: 'Noto Serif SC', 'Be Vietnam Pro', serif;
  --font-calligraphy: 'Ma Shan Zheng', 'Noto Serif SC', cursive;
  --font-sans: 'Be Vietnam Pro', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --radius-full: 9999px;

  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Light Theme Palette (宣纸素雅) */
[data-theme="light"] {
  --bg-primary: #f8f6f0;
  --bg-secondary: #f0ebe0;
  --bg-tertiary: #e6dfd0;
  --card-bg: rgba(255, 255, 255, 0.92);
  --card-border: rgba(180, 150, 80, 0.22);
  --card-hover-border: var(--c-primary);

  --text-primary: #1c1f24;
  --text-secondary: #4a5360;
  --text-muted: #788290;

  --glass-nav: rgba(248, 246, 240, 0.94);
  --shadow-subtle: 0 8px 24px rgba(60, 45, 25, 0.08);
  --shadow-glow: 0 10px 30px rgba(185, 50, 54, 0.1);
}

/* Accent Palette Overrides */
[data-accent="blue"] {
  --c-primary: #1e5f96;
  --c-primary-light: #3482c5;
  --c-primary-glow: rgba(30, 95, 150, 0.3);
  --c-primary-bg: rgba(30, 95, 150, 0.12);
}

[data-accent="green"] {
  --c-primary: #247a5c;
  --c-primary-light: #39a37e;
  --c-primary-glow: rgba(36, 122, 92, 0.3);
  --c-primary-bg: rgba(36, 122, 92, 0.12);
}

[data-accent="gold"] {
  --c-primary: #b5891e;
  --c-primary-light: #dcad3e;
  --c-primary-glow: rgba(181, 137, 30, 0.3);
  --c-primary-bg: rgba(181, 137, 30, 0.12);
}

/* Base Reset & Smooth Scroll */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

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

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: 1.7;
  overflow-x: hidden;
  position: relative;
  transition: background-color var(--transition-normal), color var(--transition-normal);
  -webkit-font-smoothing: antialiased;
}

/* Particles Canvas */
#particles-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 0;
  pointer-events: none;
}

.ambient-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  background-image: 
    radial-gradient(circle at 10% 20%, var(--c-primary-bg) 0%, transparent 40%),
    radial-gradient(circle at 90% 80%, rgba(212, 175, 55, 0.06) 0%, transparent 50%);
  pointer-events: none;
}

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

.container {
  width: 100%;
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 1.25rem;
  position: relative;
  z-index: 1;
}

/* Header & Navbar */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  background: var(--glass-nav);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-bottom: 1px solid var(--card-border);
  transition: background-color var(--transition-normal);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: inherit;
  min-width: 0;
}

.brand-seal {
  width: 38px;
  height: 38px;
  background: var(--c-primary);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-family: var(--font-calligraphy);
  font-size: 1.35rem;
  box-shadow: 0 4px 12px var(--c-primary-glow);
  flex-shrink: 0;
  transition: background-color var(--transition-normal);
}

.brand-text {
  min-width: 0;
}

.brand-text h1 {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
  white-space: nowrap;
}

.brand-text span {
  font-size: 0.72rem;
  color: var(--c-gold);
  font-weight: 500;
  display: block;
  white-space: nowrap;
}

.mobile-palette-row {
  display: none;
}

/* Navigation Links */
.nav-menu {
  display: flex;
  align-items: center;
  list-style: none;
  gap: 1.4rem;
}

.nav-link {
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 6px 0;
  position: relative;
  transition: color var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
  color: var(--c-primary-light);
}

.nav-link::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--c-primary);
  transition: width var(--transition-normal);
  border-radius: 2px;
}

.nav-link:hover::after,
.nav-link.active::after {
  width: 100%;
}

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

.icon-btn, .lang-select {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-primary);
  height: 36px;
  padding: 0 10px;
  border-radius: var(--radius-full);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  cursor: pointer;
  font-size: 0.82rem;
  transition: all var(--transition-fast);
  font-family: inherit;
}

.icon-btn:hover, .lang-select:hover {
  border-color: var(--c-primary);
  color: var(--c-primary-light);
}

.lang-select {
  font-weight: 600;
  outline: none;
}

/* Color Palette Dots */
.palette-picker {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 4px 8px;
  border-radius: var(--radius-full);
  height: 36px;
}

.color-dot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  cursor: pointer;
  border: 2px solid transparent;
  transition: transform var(--transition-fast);
}

.color-dot:hover {
  transform: scale(1.2);
}

.color-dot.active {
  border-color: #fff;
  transform: scale(1.15);
  box-shadow: 0 0 6px rgba(0,0,0,0.4);
}

.dot-red { background: #b93236; }
.dot-blue { background: #1e5f96; }
.dot-green { background: #247a5c; }
.dot-gold { background: #b5891e; }

.mobile-toggle {
  display: none;
  font-size: 1.25rem;
  width: 36px;
  height: 36px;
  padding: 0;
}

/* Hero Section */
.hero-section {
  min-height: 86vh;
  display: flex;
  align-items: center;
  padding-top: 92px;
  padding-bottom: 44px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 2.8rem;
  align-items: center;
}

.hero-badge-wrap {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--c-primary-bg);
  border: 1px solid var(--c-primary);
  padding: 5px 14px;
  border-radius: var(--radius-full);
  color: var(--c-primary-light);
  font-size: 0.82rem;
  font-weight: 600;
  margin-bottom: 1.2rem;
}

.badge-dot {
  width: 7px;
  height: 7px;
  background: var(--c-primary);
  border-radius: 50%;
  animation: pulseDot 2s infinite;
}

@keyframes pulseDot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.3; transform: scale(0.8); }
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4.2vw, 3.4rem);
  line-height: 1.22;
  font-weight: 800;
  margin-bottom: 1.2rem;
}

.hero-title .gradient-text {
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--c-gold-light) 60%, var(--c-gold) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

[data-theme="light"] .hero-title .gradient-text {
  background: linear-gradient(135deg, #1c1f24 0%, var(--c-primary) 65%, var(--c-gold-dark) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-desc {
  font-size: clamp(0.95rem, 1.6vw, 1.08rem);
  color: var(--text-secondary);
  line-height: 1.75;
  margin-bottom: 2rem;
  max-width: 600px;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  margin-bottom: 2.5rem;
  flex-wrap: wrap;
}

.btn-primary {
  background: linear-gradient(135deg, var(--c-primary-light), var(--c-primary));
  color: #fff;
  border: none;
  padding: 12px 26px;
  border-radius: var(--radius-full);
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  box-shadow: 0 6px 20px var(--c-primary-glow);
  transition: all var(--transition-fast);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 26px var(--c-primary-glow);
}

.btn-secondary {
  background: var(--card-bg);
  color: var(--text-primary);
  border: 1px solid var(--card-border);
  padding: 12px 22px;
  border-radius: var(--radius-full);
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all var(--transition-fast);
}

.btn-secondary:hover {
  border-color: var(--c-primary);
  color: var(--c-primary-light);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.2rem;
  border-top: 1px solid var(--card-border);
  padding-top: 1.5rem;
}

.stat-item h3 {
  font-family: var(--font-serif);
  font-size: clamp(1.2rem, 2vw, 1.45rem);
  color: var(--c-primary-light);
  font-weight: 700;
}

.stat-item p {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.hero-card {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-subtle), var(--shadow-glow);
  border: 1px solid var(--card-border);
  background: var(--card-bg);
}

.hero-card-img {
  width: 100%;
  height: clamp(280px, 42vw, 440px);
  object-fit: cover;
  display: block;
}

.hero-card-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(0, 0, 0, 0.05) 0%, rgba(0, 0, 0, 0.85) 100%);
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  padding: 1.8rem;
}

.author-seal-badge {
  display: flex;
  align-items: center;
  gap: 10px;
  background: rgba(0, 0, 0, 0.65);
  backdrop-filter: blur(8px);
  border: 1px solid var(--c-gold);
  padding: 8px 14px;
  border-radius: var(--radius-md);
  margin-bottom: 0.8rem;
  width: fit-content;
}

.seal-icon-red {
  width: 32px;
  height: 32px;
  background: var(--c-primary);
  color: #fff;
  border-radius: 4px;
  font-family: var(--font-calligraphy);
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.seal-text-title {
  font-size: 0.68rem;
  color: var(--c-gold-light);
  letter-spacing: 0.05em;
}

.seal-text-name {
  font-family: var(--font-serif);
  font-size: 0.95rem;
  color: #fff;
  font-weight: 700;
}

.hero-card-quote {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 0.92rem;
  color: #f1f5f9;
}

/* Sections */
.section {
  padding: clamp(48px, 7vw, 80px) 0;
  position: relative;
  z-index: 1;
}

.section-head {
  text-align: center;
  max-width: 720px;
  margin: 0 auto 2.4rem auto;
}

.section-tag {
  display: inline-block;
  color: var(--c-primary-light);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
}

.section-tag::before, .section-tag::after {
  content: "—";
  margin: 0 6px;
  opacity: 0.5;
}

.section-title {
  font-family: var(--font-serif);
  font-size: clamp(1.6rem, 3.2vw, 2.3rem);
  font-weight: 800;
  margin-bottom: 0.8rem;
  line-height: 1.25;
}

.section-subtitle {
  font-size: 0.95rem;
  color: var(--text-secondary);
}

/* ==========================================================================
   Video Showcase Section
   ========================================================================== */
.videos-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2rem;
}

.video-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-subtle);
  transition: transform var(--transition-normal), border-color var(--transition-normal);
}

.video-card:hover {
  transform: translateY(-4px);
  border-color: var(--c-primary);
  box-shadow: var(--shadow-subtle), var(--shadow-glow);
}

.video-player-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #000;
  overflow: hidden;
}

.video-player {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
  outline: none;
}

.video-info {
  padding: 1.6rem;
}

.video-badge {
  display: inline-block;
  background: var(--c-primary-bg);
  border: 1px solid var(--c-primary);
  color: var(--c-primary-light);
  font-size: 0.74rem;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  margin-bottom: 0.7rem;
}

.video-title {
  font-family: var(--font-serif);
  font-size: clamp(1.15rem, 2vw, 1.35rem);
  font-weight: 700;
  margin-bottom: 0.6rem;
  color: var(--text-primary);
}

.video-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* Filter & Search Bar */
.filter-wrapper {
  margin-bottom: 2.2rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.search-box {
  max-width: 440px;
  margin: 0 auto;
  position: relative;
  width: 100%;
}

.search-input {
  width: 100%;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 12px 18px 12px 42px;
  border-radius: var(--radius-full);
  color: var(--text-primary);
  font-size: 0.92rem;
  font-family: inherit;
  outline: none;
  transition: all var(--transition-fast);
}

.search-input:focus {
  border-color: var(--c-primary);
  box-shadow: 0 0 0 3px var(--c-primary-glow);
}

.search-icon {
  position: absolute;
  left: 15px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
}

.filter-pills-scroll {
  overflow-x: auto;
  padding: 6px 2px;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}

.filter-pills-scroll::-webkit-scrollbar {
  display: none;
}

.filter-pills {
  display: flex;
  justify-content: center;
  gap: 8px;
  width: max-content;
  margin: 0 auto;
}

.filter-btn {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-secondary);
  padding: 7px 16px;
  border-radius: var(--radius-full);
  font-size: 0.84rem;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  transition: all var(--transition-fast);
  font-family: inherit;
}

.filter-btn:hover {
  border-color: var(--c-primary);
  color: var(--text-primary);
}

.filter-btn.active {
  background: var(--c-primary);
  border-color: var(--c-primary);
  color: #fff;
  box-shadow: 0 3px 10px var(--c-primary-glow);
}

/* Cultural Cards Grid */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1.6rem;
}

.culture-card {
  background: var(--card-bg);
  backdrop-filter: var(--glass-blur);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: transform var(--transition-normal), border-color var(--transition-normal), box-shadow var(--transition-normal);
  display: flex;
  flex-direction: column;
  cursor: pointer;
}

.culture-card:hover {
  transform: translateY(-5px);
  border-color: var(--c-primary);
  box-shadow: var(--shadow-subtle), var(--shadow-glow);
}

.card-img-wrap {
  position: relative;
  height: 210px;
  overflow: hidden;
}

.card-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.culture-card:hover .card-img {
  transform: scale(1.06);
}

.card-badge {
  position: absolute;
  top: 10px;
  right: 10px;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(6px);
  border: 1px solid var(--c-gold);
  color: var(--c-gold-light);
  font-size: 0.7rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: var(--radius-full);
}

.card-body {
  padding: 1.4rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.card-tags {
  display: flex;
  gap: 6px;
  margin-bottom: 0.6rem;
  flex-wrap: wrap;
}

.card-tag {
  font-size: 0.72rem;
  color: var(--c-primary-light);
  background: var(--c-primary-bg);
  padding: 2px 7px;
  border-radius: var(--radius-sm);
  font-weight: 500;
}

.card-title {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
  line-height: 1.35;
  color: var(--text-primary);
}

.culture-card:hover .card-title {
  color: var(--c-primary-light);
}

.card-excerpt {
  color: var(--text-secondary);
  font-size: 0.88rem;
  line-height: 1.65;
  margin-bottom: 1.2rem;
  flex-grow: 1;
}

.card-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--card-border);
  padding-top: 0.9rem;
}

.btn-text {
  color: var(--c-primary-light);
  font-size: 0.84rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

/* Architecture Spotlight */
.architecture-feature {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: clamp(1.8rem, 4vw, 2.8rem);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.2rem;
  align-items: center;
  box-shadow: var(--shadow-subtle);
}

.arch-media-wrap {
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--card-border);
}

.arch-media-img {
  width: 100%;
  height: clamp(240px, 32vw, 360px);
  object-fit: cover;
  display: block;
}

.arch-content h3 {
  font-family: var(--font-serif);
  font-size: clamp(1.4rem, 2.4vw, 1.85rem);
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.arch-quote {
  border-left: 3px solid var(--c-primary);
  padding-left: 1rem;
  font-style: italic;
  color: var(--c-primary-light);
  margin-bottom: 1rem;
  font-size: 0.95rem;
}

.arch-desc {
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.75;
  margin-bottom: 1.4rem;
}

.arch-highlights-list {
  list-style: none;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.arch-highlights-list li {
  font-size: 0.86rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 6px;
}

.arch-highlights-list li::before {
  content: "✦";
  color: var(--c-primary);
}

/* Quiz Section */
.quiz-container {
  max-width: 700px;
  margin: 0 auto;
  background: var(--card-bg);
  backdrop-filter: var(--glass-blur);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: clamp(1.5rem, 4vw, 2.4rem);
  box-shadow: var(--shadow-subtle);
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.4rem;
  border-bottom: 1px solid var(--card-border);
  padding-bottom: 0.9rem;
}

.quiz-progress-text {
  font-weight: 700;
  color: var(--c-primary-light);
  font-size: 0.88rem;
}

.quiz-question-title {
  font-family: var(--font-serif);
  font-size: clamp(1.15rem, 2vw, 1.3rem);
  font-weight: 700;
  margin-bottom: 1.2rem;
  line-height: 1.45;
}

.quiz-options-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.quiz-option-btn {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--card-border);
  padding: 12px 18px;
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.92rem;
  text-align: left;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: inherit;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

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

.quiz-option-btn.selected-correct {
  background: rgba(36, 122, 92, 0.35);
  border-color: #39a37e;
  color: #fff;
}

.quiz-option-btn.selected-wrong {
  background: rgba(185, 50, 54, 0.35);
  border-color: #e04a4f;
  color: #fff;
}

.quiz-explanation {
  margin-top: 1.2rem;
  padding: 1rem;
  background: var(--c-primary-bg);
  border-left: 3px solid var(--c-primary);
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  color: var(--text-secondary);
  display: none;
}

.quiz-actions {
  margin-top: 1.6rem;
  display: flex;
  justify-content: flex-end;
}

.quiz-result-view {
  text-align: center;
  padding: 1.5rem 0;
  display: none;
}

.quiz-result-score {
  font-family: var(--font-serif);
  font-size: 2.8rem;
  color: var(--c-primary-light);
  font-weight: 800;
  margin-bottom: 0.4rem;
}

/* Dedicated Author Section with Photo */
.author-section {
  padding-bottom: 70px;
}

.author-card {
  background: var(--card-bg);
  backdrop-filter: var(--glass-blur);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: clamp(1.8rem, 4vw, 3rem);
  box-shadow: var(--shadow-subtle);
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 2.5rem;
  align-items: center;
}

.author-profile-side {
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.author-avatar-container {
  position: relative;
  width: 110px;
  height: 110px;
  margin-bottom: 0.9rem;
}

.author-avatar-img {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--c-primary);
  box-shadow: 0 4px 16px var(--c-primary-glow);
  display: block;
}

.author-mini-seal {
  position: absolute;
  bottom: 0;
  right: 0;
  width: 32px;
  height: 32px;
  background: var(--c-primary);
  color: #fff;
  border: 2px solid #fff;
  border-radius: 6px;
  font-family: var(--font-calligraphy);
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 6px rgba(0,0,0,0.3);
}

.author-role-badge {
  display: inline-block;
  background: var(--c-primary-bg);
  border: 1px solid var(--c-primary);
  color: var(--c-primary-light);
  font-size: 0.78rem;
  font-weight: 600;
  padding: 3px 12px;
  border-radius: var(--radius-full);
}

.author-content h3 {
  font-family: var(--font-serif);
  font-size: clamp(1.4rem, 2.5vw, 1.85rem);
  font-weight: 800;
  margin-bottom: 0.4rem;
}

.author-names-line {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}

.author-chinese-name {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--text-primary);
}

.author-vietnamese-name {
  font-size: 1.15rem;
  color: var(--c-primary-light);
  font-weight: 600;
}

.author-bio-p {
  font-size: 0.96rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 1rem;
}

.author-notice {
  font-size: 0.84rem;
  color: var(--text-muted);
  border-top: 1px solid var(--card-border);
  padding-top: 0.9rem;
}

/* Modal Lightbox */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.82);
  backdrop-filter: blur(8px);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-normal);
}

.modal-backdrop.active {
  opacity: 1;
  pointer-events: auto;
}

.modal-box {
  background: var(--bg-secondary);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  max-width: 760px;
  width: 100%;
  max-height: 88vh;
  overflow-y: auto;
  position: relative;
  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.5);
}

.modal-close-btn {
  position: absolute;
  top: 14px;
  right: 14px;
  background: rgba(0, 0, 0, 0.65);
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.25);
  width: 34px;
  height: 34px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  z-index: 10;
}

.modal-img {
  width: 100%;
  height: clamp(200px, 30vw, 320px);
  object-fit: cover;
  display: block;
}

.modal-body {
  padding: clamp(1.4rem, 3vw, 2.2rem);
}

.modal-title {
  font-family: var(--font-serif);
  font-size: clamp(1.25rem, 2.2vw, 1.6rem);
  font-weight: 800;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.modal-text {
  font-size: 0.98rem;
  color: var(--text-secondary);
  line-height: 1.85;
}

/* Footer */
.site-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--card-border);
  padding: 35px 0;
  font-size: 0.85rem;
  color: var(--text-muted);
}

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

.footer-links {
  display: flex;
  gap: 1.2rem;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
}

.footer-links a:hover {
  color: var(--c-primary-light);
}

/* ==========================================================================
   Floating Music Disc Widget (Spinning Record Disc)
   ========================================================================== */
.floating-music-widget {
  position: fixed;
  bottom: 22px;
  left: 22px;
  z-index: 99;
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--glass-nav);
  backdrop-filter: var(--glass-blur);
  border: 1px solid var(--card-border);
  padding: 6px 14px 6px 6px;
  border-radius: var(--radius-full);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.35);
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
}

.floating-music-widget:hover {
  border-color: var(--c-primary);
  transform: translateY(-2px);
}

.disc-icon {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--c-primary) 28%, #111 30%, #222 70%, #111 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 0.85rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.4);
  position: relative;
  flex-shrink: 0;
}

.disc-icon::after {
  content: "";
  position: absolute;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #fff;
}

.floating-music-widget.playing .disc-icon {
  animation: spinDisc 4s linear infinite;
}

@keyframes spinDisc {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

.music-label {
  display: flex;
  flex-direction: column;
}

.music-title-text {
  font-size: 0.76rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
}

.music-status-text {
  font-size: 0.68rem;
  color: var(--c-primary-light);
}

/* Floating Tools (Back to top) */
.floating-tools {
  position: fixed;
  bottom: 22px;
  right: 22px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  z-index: 99;
}

.tool-circle-btn {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 4px 14px rgba(0,0,0,0.25);
  font-size: 1rem;
  transition: all var(--transition-fast);
}

.tool-circle-btn:hover {
  border-color: var(--c-primary);
  color: var(--c-primary-light);
  transform: translateY(-2px);
}

/* ==========================================================================
   Responsive Adaptations for iPad & Mobile Phones
   ========================================================================== */

/* iPad & Tablet */
@media (max-width: 1024px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 2.2rem;
  }
  .hero-desc {
    max-width: 100%;
  }
  .videos-grid {
    grid-template-columns: 1fr;
    gap: 1.8rem;
  }
  .architecture-feature {
    grid-template-columns: 1fr;
    gap: 1.8rem;
  }
  .author-card {
    grid-template-columns: 1fr;
    text-align: center;
    gap: 1.8rem;
  }
  .author-profile-side {
    margin: 0 auto;
  }
  .author-names-line {
    justify-content: center;
  }
}

/* Mobile Phones (iPhone & Android) */
@media (max-width: 768px) {
  .header-inner {
    height: 58px;
    gap: 8px;
  }
  .brand {
    gap: 8px;
    min-width: 0;
    flex: 1 1 auto;
  }
  .brand-seal {
    width: 34px;
    height: 34px;
    font-size: 1.2rem;
  }
  .brand-text {
    min-width: 0;
    overflow: hidden;
  }
  /* Crucial: Hide long subtitle in header on mobile */
  .brand-text span {
    display: none !important;
  }
  .brand-text h1 {
    font-size: 0.92rem !important;
    white-space: nowrap !important;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 150px;
    line-height: 1.2;
  }
  /* Hide desktop palette picker and desktop sound button on mobile */
  .desktop-palette-picker,
  .desktop-sound-btn {
    display: none !important;
  }
  .header-controls {
    display: flex;
    align-items: center;
    gap: 5px;
    flex-shrink: 0;
  }
  .lang-select {
    height: 32px;
    padding: 0 6px;
    font-size: 0.78rem;
    font-weight: 600;
    border-radius: var(--radius-sm);
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    flex-shrink: 0;
  }
  .icon-btn {
    width: 32px;
    height: 32px;
    padding: 0;
    flex-shrink: 0;
  }
  .mobile-palette-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 0 4px 0;
    border-top: 1px solid var(--card-border);
    margin-top: 8px;
  }
  .mobile-palette-label {
    font-size: 0.88rem;
    color: var(--text-secondary);
    font-weight: 500;
  }
  .mobile-palette-picker {
    display: inline-flex !important;
  }
  .nav-menu {
    position: fixed;
    top: 58px;
    left: 0;
    width: 100%;
    background: var(--bg-secondary);
    flex-direction: column;
    padding: 1.5rem 1.25rem;
    gap: 1rem;
    border-bottom: 1px solid var(--card-border);
    transform: translateY(-120%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition-normal);
    box-shadow: 0 10px 30px rgba(0,0,0,0.3);
  }
  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .mobile-toggle {
    display: inline-flex;
  }
  .videos-grid {
    grid-template-columns: 1fr;
  }
  .cards-grid {
    grid-template-columns: 1fr;
  }
  .hero-stats {
    grid-template-columns: 1fr 1fr 1fr;
    gap: 0.6rem;
  }
  .stat-item h3 {
    font-size: 1.05rem;
  }
  .stat-item p {
    font-size: 0.7rem;
  }
  .filter-pills {
    justify-content: flex-start;
  }
  .floating-music-widget {
    bottom: 14px;
    left: 14px;
    padding: 5px 10px 5px 5px;
  }
  .disc-icon {
    width: 32px;
    height: 32px;
  }
  .music-title-text {
    font-size: 0.72rem;
  }
  .music-status-text {
    font-size: 0.64rem;
  }
  .floating-tools {
    bottom: 14px;
    right: 14px;
  }
  .tool-circle-btn {
    width: 38px;
    height: 38px;
  }
  .footer-content {
    flex-direction: column;
    text-align: center;
    gap: 0.8rem;
  }
}

@media (max-width: 480px) {
  .hero-stats {
    grid-template-columns: 1fr;
    gap: 0.8rem;
  }
  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }
  .btn-primary, .btn-secondary {
    justify-content: center;
  }
}

@media (max-width: 420px) {
  .brand-text h1 {
    font-size: 0.86rem !important;
    max-width: 120px;
  }
  .brand-seal {
    width: 30px;
    height: 30px;
    font-size: 1.05rem;
  }
  .lang-select {
    font-size: 0.74rem;
    padding: 0 4px;
  }
}