:root {
  --bbtv-primary: #6C5CE7;
  --bbtv-primary-light: #a29bfe;
  --bbtv-primary-dark: #4834d4;
  --bbtv-accent: #fd79a8;
  --bbtv-accent-light: #ffeaa7;
  --bbtv-cyan: #00cec9;
  --bbtv-bg: #f5f3ff;
  --bbtv-bg-alt: #ffffff;
  --bbtv-surface: #ffffff;
  --bbtv-surface-glass: rgba(255, 255, 255, 0.72);
  --bbtv-text: #1a1a2e;
  --bbtv-text-secondary: #5a5a7a;
  --bbtv-text-muted: #8888a8;
  --bbtv-border: rgba(108, 92, 231, 0.12);
  --bbtv-border-strong: rgba(108, 92, 231, 0.24);
  --bbtv-shadow-sm: 0 2px 8px rgba(108, 92, 231, 0.08);
  --bbtv-shadow-md: 0 8px 24px rgba(108, 92, 231, 0.12);
  --bbtv-shadow-lg: 0 16px 48px rgba(108, 92, 231, 0.16);
  --bbtv-shadow-glow: 0 0 32px rgba(108, 92, 231, 0.24);
  --bbtv-radius-sm: 10px;
  --bbtv-radius-md: 16px;
  --bbtv-radius-lg: 24px;
  --bbtv-radius-xl: 32px;
  --bbtv-radius-pill: 999px;
  --bbtv-transition: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  --bbtv-transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --bbtv-font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --bbtv-max-width: 1200px;
  --bbtv-header-height: 68px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bbtv-bg: #0f0e1a;
    --bbtv-bg-alt: #16152a;
    --bbtv-surface: #1c1b33;
    --bbtv-surface-glass: rgba(28, 27, 51, 0.72);
    --bbtv-text: #eaeaf5;
    --bbtv-text-secondary: #b0b0cc;
    --bbtv-text-muted: #7a7a9a;
    --bbtv-border: rgba(162, 155, 254, 0.14);
    --bbtv-border-strong: rgba(162, 155, 254, 0.28);
    --bbtv-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --bbtv-shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
    --bbtv-shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.5);
    --bbtv-shadow-glow: 0 0 32px rgba(108, 92, 231, 0.35);
  }
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--bbtv-header-height) + 20px);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--bbtv-font);
  font-size: 16px;
  line-height: 1.75;
  color: var(--bbtv-text);
  background-color: var(--bbtv-bg);
  background-image:
    radial-gradient(ellipse 80% 60% at 10% 0%, rgba(108, 92, 231, 0.08), transparent 60%),
    radial-gradient(ellipse 60% 50% at 90% 20%, rgba(253, 121, 168, 0.06), transparent 60%),
    radial-gradient(ellipse 70% 60% at 50% 100%, rgba(0, 206, 201, 0.05), transparent 60%);
  background-attachment: fixed;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

@media (prefers-color-scheme: dark) {
  body {
    background-image:
      radial-gradient(ellipse 80% 60% at 10% 0%, rgba(108, 92, 231, 0.15), transparent 60%),
      radial-gradient(ellipse 60% 50% at 90% 20%, rgba(253, 121, 168, 0.1), transparent 60%),
      radial-gradient(ellipse 70% 60% at 50% 100%, rgba(0, 206, 201, 0.08), transparent 60%);
  }
}

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

::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

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

::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--bbtv-primary-light), var(--bbtv-primary));
  border-radius: var(--bbtv-radius-pill);
  border: 2px solid var(--bbtv-bg);
}

::-webkit-scrollbar-thumb:hover {
  background: linear-gradient(180deg, var(--bbtv-primary), var(--bbtv-primary-dark));
}

a {
  color: var(--bbtv-primary);
  text-decoration: none;
  transition: color var(--bbtv-transition-fast), opacity var(--bbtv-transition-fast);
}

a:hover {
  color: var(--bbtv-primary-dark);
}

a:focus-visible {
  outline: 2px solid var(--bbtv-primary);
  outline-offset: 3px;
  border-radius: 4px;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol {
  list-style: none;
}

/* ========== Header / Navigation ========== */
header[role="banner"] {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--bbtv-surface-glass);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--bbtv-border);
  transition: box-shadow var(--bbtv-transition), background var(--bbtv-transition);
}

header[role="banner"]:hover {
  box-shadow: var(--bbtv-shadow-md);
}

header nav[aria-label="主导航"] {
  max-width: var(--bbtv-max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: var(--bbtv-header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

header nav > div {
  flex-shrink: 0;
}

header nav > div > a {
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--bbtv-primary), var(--bbtv-accent), var(--bbtv-cyan));
  background-size: 200% 200%;
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: gradientShift 6s ease infinite;
  transition: transform var(--bbtv-transition-fast);
  display: inline-block;
}

header nav > div > a:hover {
  transform: scale(1.06);
}

@keyframes gradientShift {
  0%, 100% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
}

header nav ul {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: nowrap;
  overflow-x: auto;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

header nav ul::-webkit-scrollbar {
  display: none;
}

header nav ul li {
  flex-shrink: 0;
}

header nav ul li a {
  display: inline-block;
  padding: 8px 14px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--bbtv-text-secondary);
  border-radius: var(--bbtv-radius-pill);
  white-space: nowrap;
  position: relative;
  transition: color var(--bbtv-transition-fast), background var(--bbtv-transition-fast), transform var(--bbtv-transition-fast);
}

header nav ul li a::after {
  content: '';
  position: absolute;
  bottom: 2px;
  left: 50%;
  transform: translateX(-50%) scaleX(0);
  width: 60%;
  height: 2px;
  background: linear-gradient(90deg, var(--bbtv-primary), var(--bbtv-accent));
  border-radius: var(--bbtv-radius-pill);
  transition: transform var(--bbtv-transition);
}

header nav ul li a:hover {
  color: var(--bbtv-primary);
  background: rgba(108, 92, 231, 0.08);
  transform: translateY(-1px);
}

header nav ul li a:hover::after {
  transform: translateX(-50%) scaleX(1);
}

/* ========== Main ========== */
main {
  max-width: var(--bbtv-max-width);
  margin: 0 auto;
  padding: 0 24px 80px;
}

/* ========== Hero Section ========== */
#hero {
  position: relative;
  margin: 32px 0 48px;
  padding: 72px 48px;
  border-radius: var(--bbtv-radius-xl);
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.92), rgba(253, 121, 168, 0.85), rgba(0, 206, 201, 0.8));
  background-size: 200% 200%;
  animation: heroGradient 12s ease infinite;
  color: #fff;
  overflow: hidden;
  box-shadow: var(--bbtv-shadow-lg), var(--bbtv-shadow-glow);
  isolation: isolate;
}

@keyframes heroGradient {
  0%, 100% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
}

#hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 20% 30%, rgba(255, 255, 255, 0.25), transparent 40%),
    radial-gradient(circle at 80% 70%, rgba(255, 234, 167, 0.2), transparent 45%);
  pointer-events: none;
  z-index: -1;
}

#hero::after {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.15), transparent 70%);
  border-radius: 50%;
  animation: floatBlob 15s ease-in-out infinite;
  pointer-events: none;
  z-index: -1;
}

@keyframes floatBlob {
  0%, 100% { transform: translate(0, 0) scale(1); }
  33% { transform: translate(-30px, 20px) scale(1.1); }
  66% { transform: translate(20px, -30px) scale(0.95); }
}

#hero h1 {
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  font-weight: 800;
  line-height: 1.3;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
  text-shadow: 0 2px 16px rgba(0, 0, 0, 0.15);
  animation: fadeInUp 0.8s ease both;
}

#hero p {
  font-size: clamp(0.95rem, 1.6vw, 1.1rem);
  line-height: 1.85;
  max-width: 800px;
  opacity: 0.95;
  margin-bottom: 12px;
  animation: fadeInUp 0.8s ease 0.15s both;
}

#hero p:last-child {
  font-size: 0.9rem;
  opacity: 0.85;
  animation-delay: 0.3s;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ========== Sections ========== */
main > section {
  margin-bottom: 56px;
  animation: sectionReveal 0.7s ease both;
}

@keyframes sectionReveal {
  from {
    opacity: 0;
    transform: translateY(32px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

main > section > h2 {
  font-size: clamp(1.4rem, 2.8vw, 1.9rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 28px;
  padding-bottom: 16px;
  position: relative;
  color: var(--bbtv-text);
}

main > section > h2::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 64px;
  height: 4px;
  border-radius: var(--bbtv-radius-pill);
  background: linear-gradient(90deg, var(--bbtv-primary), var(--bbtv-accent));
  transition: width var(--bbtv-transition);
}

main > section:hover > h2::after {
  width: 120px;
}

main > section > h3 {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  font-weight: 700;
  color: var(--bbtv-text);
  margin: 28px 0 12px;
  padding-left: 16px;
  position: relative;
  line-height: 1.5;
}

main > section > h3::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 4px;
  height: 1em;
  border-radius: var(--bbtv-radius-pill);
  background: linear-gradient(180deg, var(--bbtv-primary), var(--bbtv-accent));
}

main > section > h4 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--bbtv-primary);
  margin: 20px 0 8px;
}

main > section > p {
  color: var(--bbtv-text-secondary);
  margin-bottom: 12px;
  line-height: 1.85;
}

/* ========== Cards ========== */
#brand-intro,
#products,
#solutions,
#cases,
#news,
#articles,
#faq,
#howto,
#contact {
  background: var(--bbtv-surface);
  border-radius: var(--bbtv-radius-lg);
  padding: 40px 36px;
  border: 1px solid var(--bbtv-border);
  box-shadow: var(--bbtv-shadow-sm);
  transition: box-shadow var(--bbtv-transition), transform var(--bbtv-transition), border-color var(--bbtv-transition);
}

#brand-intro:hover,
#products:hover,
#solutions:hover,
#cases:hover,
#news:hover,
#articles:hover,
#faq:hover,
#howto:hover,
#contact:hover {
  box-shadow: var(--bbtv-shadow-md);
  border-color: var(--bbtv-border-strong);
}

/* ========== Products List ========== */
#products ul {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin-top: 20px;
}

#products ul li {
  padding: 20px 22px;
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.06), rgba(253, 121, 168, 0.04));
  border-radius: var(--bbtv-radius-md);
  border: 1px solid var(--bbtv-border);
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--bbtv-text);
  position: relative;
  padding-left: 48px;
  transition: transform var(--bbtv-transition), box-shadow var(--bbtv-transition), border-color var(--bbtv-transition);
}

#products ul li::before {
  content: '✦';
  position: absolute;
  left: 18px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.1rem;
  color: var(--bbtv-primary);
  transition: transform var(--bbtv-transition);
}

#products ul li:hover {
  transform: translateY(-4px);
  box-shadow: var(--bbtv-shadow-md);
  border-color: var(--bbtv-primary-light);
}

#products ul li:hover::before {
  transform: translateY(-50%) rotate(180deg) scale(1.2);
}

/* ========== Solutions List ========== */
#solutions ul {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 14px;
  margin-top: 20px;
}

#solutions ul li {
  padding: 16px 20px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-sm);
  border-left: 4px solid var(--bbtv-primary);
  font-size: 0.925rem;
  color: var(--bbtv-text-secondary);
  transition: transform var(--bbtv-transition-fast), background var(--bbtv-transition-fast), border-color var(--bbtv-transition-fast);
}

#solutions ul li:hover {
  transform: translateX(6px);
  background: rgba(108, 92, 231, 0.06);
  border-left-color: var(--bbtv-accent);
}

/* ========== Cases / Blockquotes ========== */
#cases blockquote {
  margin: 16px 0;
  padding: 24px 28px;
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.06), rgba(0, 206, 201, 0.04));
  border-radius: var(--bbtv-radius-md);
  border-left: 4px solid var(--bbtv-accent);
  position: relative;
  transition: transform var(--bbtv-transition), box-shadow var(--bbtv-transition);
}

#cases blockquote::before {
  content: '"';
  position: absolute;
  top: 8px;
  left: 16px;
  font-size: 3rem;
  font-family: Georgia, serif;
  color: var(--bbtv-accent);
  opacity: 0.25;
  line-height: 1;
}

#cases blockquote p {
  font-style: italic;
  color: var(--bbtv-text-secondary);
  font-size: 0.95rem;
  margin: 0;
  padding-left: 8px;
}

#cases blockquote:hover {
  transform: translateY(-3px) scale(1.01);
  box-shadow: var(--bbtv-shadow-md);
}

/* ========== News Articles ========== */
#news article {
  padding: 24px 26px;
  margin-bottom: 18px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-md);
  border: 1px solid var(--bbtv-border);
  transition: transform var(--bbtv-transition), box-shadow var(--bbtv-transition), border-color var(--bbtv-transition);
  position: relative;
  overflow: hidden;
}

#news article::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 4px;
  background: linear-gradient(180deg, var(--bbtv-primary), var(--bbtv-accent));
  transform: scaleY(0);
  transform-origin: top;
  transition: transform var(--bbtv-transition);
}

#news article:hover {
  transform: translateY(-4px);
  box-shadow: var(--bbtv-shadow-md);
  border-color: var(--bbtv-border-strong);
}

#news article:hover::before {
  transform: scaleY(1);
}

#news article h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--bbtv-text);
  margin-bottom: 8px;
  padding-left: 0;
  transition: color var(--bbtv-transition-fast);
}

#news article h3::before {
  display: none;
}

#news article:hover h3 {
  color: var(--bbtv-primary);
}

#news article p:first-of-type {
  font-size: 0.8rem;
  color: var(--bbtv-text-muted);
  margin-bottom: 8px;
  font-weight: 500;
}

#news article p:last-of-type {
  color: var(--bbtv-text-secondary);
  font-size: 0.925rem;
}

/* ========== Articles Section ========== */
#articles article {
  padding: 22px 26px;
  margin-bottom: 16px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-md);
  border: 1px solid var(--bbtv-border);
  transition: transform var(--bbtv-transition), box-shadow var(--bbtv-transition), border-color var(--bbtv-transition);
}

#articles article:hover {
  transform: translateY(-3px);
  box-shadow: var(--bbtv-shadow-md);
  border-color: var(--bbtv-primary-light);
}

#articles article h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--bbtv-text);
  margin-bottom: 8px;
  padding-left: 0;
  transition: color var(--bbtv-transition-fast);
}

#articles article h3::before {
  display: none;
}

#articles article:hover h3 {
  color: var(--bbtv-primary);
}

#articles article p:first-of-type {
  font-size: 0.8rem;
  color: var(--bbtv-text-muted);
  margin-bottom: 8px;
  font-weight: 500;
}

#articles article p:nth-of-type(2) {
  color: var(--bbtv-text-secondary);
  font-size: 0.925rem;
  margin-bottom: 12px;
}

#articles article a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--bbtv-primary);
  padding: 6px 16px;
  border-radius: var(--bbtv-radius-pill);
  background: rgba(108, 92, 231, 0.08);
  transition: background var(--bbtv-transition-fast), transform var(--bbtv-transition-fast), box-shadow var(--bbtv-transition-fast);
}

#articles article a::after {
  content: '→';
  transition: transform var(--bbtv-transition-fast);
}

#articles article a:hover {
  background: var(--bbtv-primary);
  color: #fff;
  transform: translateX(4px);
  box-shadow: var(--bbtv-shadow-sm);
}

#articles article a:hover::after {
  transform: translateX(4px);
}

/* ========== FAQ ========== */
#faq > h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--bbtv-text);
  margin: 24px 0 8px;
  padding: 16px 20px 16px 48px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-sm);
  border: 1px solid var(--bbtv-border);
  position: relative;
  cursor: default;
  transition: background var(--bbtv-transition-fast), border-color var(--bbtv-transition-fast), transform var(--bbtv-transition-fast);
}

#faq > h3::before {
  content: 'Q';
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  width: 24px;
  height: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 800;
  color: #fff;
  background: linear-gradient(135deg, var(--bbtv-primary), var(--bbtv-primary-light));
  border-radius: 50%;
  height: 1em;
  width: 1em;
  padding: 4px;
}

#faq > h3:hover {
  background: rgba(108, 92, 231, 0.06);
  border-color: var(--bbtv-primary-light);
  transform: translateX(4px);
}

#faq > h3 + p {
  padding: 0 20px 16px 48px;
  color: var(--bbtv-text-secondary);
  font-size: 0.925rem;
  line-height: 1.8;
  margin-bottom: 4px;
}

/* ========== HowTo ========== */
#howto ul {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
  margin: 16px 0;
}

#howto ul li {
  padding: 14px 18px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-sm);
  border: 1px solid var(--bbtv-border);
  font-size: 0.9rem;
  color: var(--bbtv-text-secondary);
  position: relative;
  padding-left: 40px;
  transition: transform var(--bbtv-transition-fast), background var(--bbtv-transition-fast), border-color var(--bbtv-transition-fast);
}

#howto ul li::before {
  content: '✓';
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  width: 18px;
  height: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.65rem;
  font-weight: 800;
  color: #fff;
  background: linear-gradient(135deg, var(--bbtv-cyan), var(--bbtv-primary));
  border-radius: 50%;
}

#howto ul li:hover {
  transform: translateX(4px);
  background: rgba(0, 206, 201, 0.06);
  border-color: var(--bbtv-cyan);
}

#howto h4 {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 20px;
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.08), rgba(0, 206, 201, 0.05));
  border-radius: var(--bbtv-radius-sm);
  margin: 20px 0 10px;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--bbtv-primary);
  border-left: 3px solid var(--bbtv-primary);
  transition: transform var(--bbtv-transition-fast), box-shadow var(--bbtv-transition-fast);
}

#howto h4:hover {
  transform: translateX(6px);
  box-shadow: var(--bbtv-shadow-sm);
}

#howto h4::before {
  content: '▶';
  font-size: 0.65rem;
  color: var(--bbtv-accent);
}

/* ========== Contact ========== */
#contact p {
  padding: 8px 0;
  color: var(--bbtv-text-secondary);
  font-size: 0.925rem;
  border-bottom: 1px dashed var(--bbtv-border);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: padding-left var(--bbtv-transition-fast), color var(--bbtv-transition-fast);
}

#contact p:hover {
  padding-left: 8px;
  color: var(--bbtv-primary);
}

#contact ul {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 10px;
  margin-top: 12px;
}

#contact ul li a {
  display: block;
  padding: 10px 16px;
  background: var(--bbtv-bg-alt);
  border-radius: var(--bbtv-radius-sm);
  border: 1px solid var(--bbtv-border);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--bbtv-text-secondary);
  text-align: center;
  transition: all var(--bbtv-transition-fast);
}

#contact ul li a:hover {
  background: linear-gradient(135deg, var(--bbtv-primary), var(--bbtv-primary-light));
  color: #fff;
  border-color: transparent;
  transform: translateY(-3px);
  box-shadow: var(--bbtv-shadow-md);
}

/* ========== Footer ========== */
footer[role="contentinfo"] {
  background: var(--bbtv-surface);
  border-top: 1px solid var(--bbtv-border);
  padding: 40px 24px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

footer[role="contentinfo"]::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--bbtv-primary), var(--bbtv-accent), var(--bbtv-cyan), var(--bbtv-primary));
  background-size: 300% 100%;
  animation: footerGradient 8s linear infinite;
}

@keyframes footerGradient {
  0% { background-position: 0% 50%; }
  100% { background-position: 300% 50%; }
}

footer[role="contentinfo"] p {
  color: var(--bbtv-text-muted);
  font-size: 0.85rem;
  margin-bottom: 6px;
  line-height: 1.7;
}

footer[role="contentinfo"] p:first-child {
  color: var(--bbtv-text-secondary);
  font-weight: 600;
  font-size: 0.9rem;
}

/* ========== Responsive ========== */
@media (max-width: 1024px) {
  :root {
    --bbtv-max-width: 100%;
  }

  #hero {
    padding: 56px 36px;
  }

  #brand-intro,
  #products,
  #solutions,
  #cases,
  #news,
  #articles,
  #faq,
  #howto,
  #contact {
    padding: 32px 28px;
  }
}

@media (max-width: 768px) {
  :root {
    --bbtv-header-height: 60px;
  }

  header nav[aria-label="主导航"] {
    padding: 0 16px;
    flex-direction: column;
    height: auto;
    padding-top: 12px;
    padding-bottom: 12px;
    gap: 10px;
  }

  header nav > div > a {
    font-size: 1.3rem;
  }

  header nav ul {
    width: 100%;
    justify-content: flex-start;
    padding-bottom: 4px;
  }

  header nav ul li a {
    padding: 6px 12px;
    font-size: 0.8rem;
  }

  main {
    padding: 0 16px 60px;
  }

  #hero {
    margin: 20px 0 32px;
    padding: 40px 24px;
    border-radius: var(--bbtv-radius-lg);
  }

  #hero h1 {
    font-size: 1.45rem;
  }

  #hero p {
    font-size: 0.9rem;
  }

  main > section {
    margin-bottom: 36px;
  }

  main > section > h2 {
    font-size: 1.25rem;
    margin-bottom: 20px;
  }

  main > section > h3 {
    font-size: 1rem;
    margin: 22px 0 10px;
  }

  #brand-intro,
  #products,
  #solutions,
  #cases,
  #news,
  #articles,
  #faq,
  #howto,
  #contact {
    padding: 24px 18px;
    border-radius: var(--bbtv-radius-md);
  }

  #products ul {
    grid-template-columns: 1fr;
  }

  #solutions ul {
    grid-template-columns: 1fr;
  }

  #howto ul {
    grid-template-columns: 1fr;
  }

  #contact ul {
    grid-template-columns: repeat(2, 1fr);
  }

  #faq > h3 {
    padding: 14px 16px 14px 42px;
    font-size: 0.925rem;
  }

  #faq > h3 + p {
    padding: 0 16px 14px 42px;
    font-size: 0.875rem;
  }

  #cases blockquote {
    padding: 18px 20px;
  }

  #cases blockquote::before {
    font-size: 2rem;
    top: 4px;
    left: 10px;
  }

  footer[role="contentinfo"] {
    padding: 28px 16px;
  }

  footer[role="contentinfo"] p {
    font-size: 0.78rem;
  }
}

@media (max-width: 480px) {
  #hero {
    padding: 32px 18px;
    border-radius: var(--bbtv-radius-md);
  }

  #hero h1 {
    font-size: 1.25rem;
    margin-bottom: 16px;
  }

  #hero p {
    font-size: 0.85rem;
    line-height: 1.75;
  }

  #contact ul {
    grid-template-columns: 1fr;
  }

  #news article,
  #articles article {
    padding: 18px 16px;
  }

  #articles article a {
    font-size: 0.8rem;
    padding: 5px 12px;
  }
}

/* ========== Reduced Motion ========== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ========== Print ========== */
@media print {
  header[role="banner"],
  footer[role="contentinfo"] {
    display: none;
  }

  body {
    background: #fff;
    color: #000;
  }

  main > section {
    box-shadow: none;
    border: 1px solid #ddd;
    break-inside: avoid;
  }

  #hero {
    background: #f0f0f0;
    color: #000;
    box-shadow: none;
  }
}