/* ===================================================================
   云图高速 (yuntugaosu.homes) - 全息霓光与多光谱棱镜设计系统 (Holographic Prism)
   视觉基调：深邃全息黑曜底色 + 霓虹青紫粉高饱和渐变 + 晶体半透玻璃质感 + 流光线条
   =================================================================== */

:root {
  --bg-canvas: #090d16;
  --bg-surface: #101626;
  --bg-panel: #161e33;
  --bg-panel-hover: #1f2a47;
  --bg-glass: rgba(16, 22, 38, 0.88);

  --brand-cyan: #06b6d4;
  --brand-magenta: #ec4899;
  --brand-violet: #8b5cf6;
  --brand-amber: #f59e0b;
  --brand-emerald: #10b981;

  --grad-holo: linear-gradient(135deg, #06b6d4 0%, #8b5cf6 50%, #ec4899 100%);
  --grad-accent: linear-gradient(135deg, #06b6d4 0%, #3b82f6 100%);

  --text-main: #f8fafc;
  --text-muted: #cbd5e1;
  --text-dim: #94a3b8;
  --text-dark: #090d16;

  --border-glass: rgba(6, 182, 212, 0.25);
  --border-neon: rgba(236, 72, 153, 0.4);
  --border-subtle: #232d45;

  --font-system: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;

  --radius-xs: 4px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;

  --shadow-holo: 0 4px 25px rgba(6, 182, 212, 0.2), 0 0 1px rgba(236, 72, 153, 0.3);
  --shadow-glow: 0 0 30px rgba(139, 92, 246, 0.25);
  --shadow-card: 0 4px 20px rgba(0, 0, 0, 0.4);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-system);
  background-color: var(--bg-canvas);
  color: var(--text-main);
  line-height: 1.75;
  overflow-x: hidden;
  background-image: 
    radial-gradient(circle at 15% 15%, rgba(6, 182, 212, 0.08) 0%, transparent 45%),
    radial-gradient(circle at 85% 75%, rgba(236, 72, 153, 0.08) 0%, transparent 45%),
    radial-gradient(circle at 50% 50%, rgba(139, 92, 246, 0.04) 0%, transparent 60%);
}

a {
  color: var(--brand-cyan);
  text-decoration: none;
  transition: all 0.2s ease;
}

a:hover {
  color: var(--brand-magenta);
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-glass);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border-glass);
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

.logo-img {
  display: block;
  border-radius: 10px;
  box-shadow: 0 0 15px rgba(6, 182, 212, 0.4);
}

.brand-text-wrap {
  display: flex;
  flex-direction: column;
}

.brand-name {
  font-size: 1.38rem;
  font-weight: 800;
  background: var(--grad-holo);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.01em;
}

.brand-sub {
  font-size: 0.72rem;
  color: var(--text-dim);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 1.3rem;
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-muted);
  padding: 0.35rem 0.65rem;
  border-radius: var(--radius-xs);
  transition: all 0.2s ease;
}

.nav-link:hover, .nav-link.active {
  color: #fff;
  background: var(--bg-panel);
  box-shadow: inset 0 0 0 1px var(--border-glass);
}

.btn-header-cta {
  background: var(--grad-holo);
  color: #fff !important;
  font-weight: 700;
  font-size: 0.88rem;
  padding: 0.45rem 1.15rem;
  border-radius: 30px;
  box-shadow: 0 2px 14px rgba(6, 182, 212, 0.35);
  transition: all 0.2s ease;
}

.btn-header-cta:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 20px rgba(236, 72, 153, 0.45);
}

/* Page Layout */
.page-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
}

/* Hero Section */
.hero-section {
  text-align: center;
  padding: 3.5rem 1rem 3rem;
}

.hero-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 1.2rem;
  background: rgba(16, 22, 38, 0.9);
  border: 1px solid var(--border-glass);
  border-radius: 30px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--brand-cyan);
  margin-bottom: 1.5rem;
  box-shadow: 0 0 20px rgba(6, 182, 212, 0.15);
}

.hero-pill-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--brand-magenta);
  box-shadow: 0 0 8px #ec4899;
}

.hero-title {
  font-size: clamp(2.1rem, 4.2vw, 3.2rem);
  font-weight: 900;
  line-height: 1.25;
  color: var(--text-main);
  margin-bottom: 1.25rem;
  letter-spacing: -0.02em;
}

.hero-title-highlight {
  background: var(--grad-holo);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 780px;
  margin: 0 auto 2.25rem;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.25rem;
  flex-wrap: wrap;
  margin-bottom: 2.5rem;
}

.btn-primary-action {
  background: var(--grad-holo);
  color: #fff !important;
  font-size: 1.05rem;
  font-weight: 700;
  padding: 0.85rem 2.2rem;
  border-radius: 30px;
  box-shadow: var(--shadow-holo);
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  transition: all 0.25s ease;
}

.btn-primary-action:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 30px rgba(236, 72, 153, 0.45);
}

.btn-secondary-action {
  background: var(--bg-surface);
  color: var(--text-muted) !important;
  border: 1px solid var(--border-glass);
  font-size: 1.05rem;
  font-weight: 600;
  padding: 0.85rem 1.8rem;
  border-radius: 30px;
  transition: all 0.2s ease;
}

.btn-secondary-action:hover {
  border-color: var(--brand-magenta);
  color: #fff !important;
  box-shadow: 0 0 15px rgba(236, 72, 153, 0.25);
}

/* Metrics Badges */
.metrics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
  margin-top: 1rem;
}

.metric-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 1.4rem;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  transition: all 0.25s ease;
  position: relative;
  overflow: hidden;
}

.metric-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--grad-holo);
  opacity: 0.8;
}

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

.metric-value {
  font-size: 1.85rem;
  font-weight: 800;
  background: var(--grad-holo);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-family: var(--font-mono);
  margin-bottom: 0.35rem;
}

.metric-label {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 0.25rem;
}

.metric-note {
  font-size: 0.82rem;
  color: var(--text-dim);
}

/* Section Header */
.section-header {
  text-align: center;
  margin-bottom: 2.5rem;
}

.section-tag {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--brand-cyan);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 0.5rem;
}

.section-title {
  font-size: 1.95rem;
  font-weight: 800;
  color: var(--text-main);
  letter-spacing: -0.02em;
}

.section-desc {
  font-size: 1.05rem;
  color: var(--text-muted);
  max-width: 680px;
  margin: 0.5rem auto 0;
}

/* Interactive Tool: Streaming Bitrate Simulator */
.simulator-tool-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
  padding: 2.2rem;
  box-shadow: var(--shadow-card);
  margin-bottom: 3.5rem;
}

.sim-controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.2rem;
  margin-bottom: 1.8rem;
}

.control-item label {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 0.45rem;
}

.control-item select {
  width: 100%;
  padding: 0.65rem 0.9rem;
  background: var(--bg-canvas);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  color: var(--text-main);
  outline: none;
  transition: border-color 0.2s;
}

.control-item select:focus {
  border-color: var(--brand-cyan);
  box-shadow: 0 0 0 3px rgba(6, 182, 212, 0.18);
}

.btn-run-sim {
  width: 100%;
  padding: 0.72rem;
  background: var(--grad-holo);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s ease;
  margin-top: 1.45rem;
}

.btn-run-sim:hover {
  box-shadow: 0 0 20px rgba(6, 182, 212, 0.4);
}

.sim-display-panel {
  background: #090c14;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
}

.sim-stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1.2rem;
  margin-bottom: 1.2rem;
  padding-bottom: 1.2rem;
  border-bottom: 1px solid var(--border-subtle);
}

.sim-stat-label {
  font-size: 0.75rem;
  color: var(--text-dim);
  text-transform: uppercase;
}

.sim-stat-val {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--brand-cyan);
}

.progress-track {
  width: 100%;
  height: 8px;
  background: #161e33;
  border-radius: 4px;
  overflow: hidden;
  margin: 0.5rem 0 1rem;
}

.progress-bar-fill {
  height: 100%;
  width: 15%;
  background: var(--grad-holo);
  border-radius: 4px;
  transition: width 0.4s ease;
}

/* Feature Grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
  margin-bottom: 3.5rem;
}

.feature-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 1.8rem;
  box-shadow: var(--shadow-card);
  transition: all 0.25s ease;
  position: relative;
  overflow: hidden;
}

.feature-card:hover {
  border-color: var(--brand-cyan);
  transform: translateY(-4px);
  box-shadow: var(--shadow-holo);
}

.feature-icon-box {
  width: 50px;
  height: 50px;
  border-radius: var(--radius-sm);
  background: var(--bg-panel);
  border: 1px solid var(--border-glass);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 1.25rem;
}

.feature-heading {
  font-size: 1.22rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.6rem;
}

.feature-body {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.7;
}

/* Articles Grid */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 1.5rem;
  margin-bottom: 3.5rem;
}

.article-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 1.6rem;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: all 0.25s ease;
}

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

.article-tag {
  display: inline-block;
  align-self: flex-start;
  padding: 0.2rem 0.6rem;
  background: rgba(6, 182, 212, 0.12);
  border: 1px solid var(--border-glass);
  border-radius: 4px;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--brand-cyan);
  margin-bottom: 0.8rem;
}

.article-title-link {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.45;
  margin-bottom: 0.6rem;
  display: block;
}

.article-title-link:hover {
  color: var(--brand-cyan);
}

.article-summary {
  font-size: 0.92rem;
  color: var(--text-muted);
  line-height: 1.65;
  margin-bottom: 1.25rem;
  flex-grow: 1;
}

.article-footer-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.82rem;
  color: var(--text-dim);
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.85rem;
}

/* FAQ Accordion */
.faq-container {
  max-width: 860px;
  margin: 0 auto 3.5rem;
}

.faq-item {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  margin-bottom: 0.85rem;
  overflow: hidden;
  transition: border-color 0.2s;
}

.faq-item.active {
  border-color: var(--brand-cyan);
  box-shadow: 0 0 15px rgba(6, 182, 212, 0.15);
}

.faq-question {
  width: 100%;
  padding: 1.1rem 1.4rem;
  background: none;
  border: none;
  text-align: left;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.faq-question:hover {
  color: var(--brand-cyan);
}

.faq-icon {
  font-size: 1.1rem;
  color: var(--brand-cyan);
  transition: transform 0.25s ease;
}

.faq-item.active .faq-icon {
  transform: rotate(180deg);
  color: var(--brand-magenta);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
  padding: 0 1.4rem;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

.faq-item.active .faq-answer {
  max-height: 400px;
  padding: 0 1.4rem 1.25rem;
}

/* Legal Pages & In-depth Content */
.legal-card, .article-content-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
  padding: 2.8rem 2.2rem;
  box-shadow: var(--shadow-card);
  margin-bottom: 2.5rem;
}

.page-title {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--text-main);
  line-height: 1.3;
  margin-bottom: 0.8rem;
  letter-spacing: -0.02em;
}

.update-time {
  font-size: 0.88rem;
  color: var(--text-dim);
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-subtle);
}

.content-body h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-main);
  margin: 2rem 0 1rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--border-glass);
}

.content-body h3 {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--brand-cyan);
  margin: 1.5rem 0 0.75rem;
}

.content-body p {
  font-size: 1.02rem;
  color: var(--text-muted);
  line-height: 1.8;
  margin-bottom: 1.2rem;
}

.content-body ul, .content-body ol {
  margin: 0.8rem 0 1.4rem 1.6rem;
  color: var(--text-muted);
  line-height: 1.75;
}

.content-body li {
  margin-bottom: 0.45rem;
}

.content-body blockquote {
  border-left: 4px solid var(--brand-cyan);
  background: var(--bg-panel);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 1.5rem 0;
  font-size: 0.98rem;
  color: var(--text-muted);
}

.data-table-wrapper {
  overflow-x: auto;
  margin: 1.6rem 0;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.92rem;
}

.data-table th {
  background: var(--bg-panel);
  color: var(--text-main);
  padding: 0.85rem 1rem;
  font-weight: 700;
  border-bottom: 1px solid var(--border-subtle);
}

.data-table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text-muted);
}

.data-table tr:last-child td {
  border-bottom: none;
}

.data-table tr:hover td {
  background: var(--bg-panel-hover);
}

.code-box {
  background: #090c14;
  border: 1px solid var(--border-subtle);
  color: #38bdf8;
  padding: 1.25rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
  overflow-x: auto;
  margin: 1.4rem 0;
}

/* Callout Box */
.holo-callout {
  background: linear-gradient(135deg, rgba(6, 182, 212, 0.08) 0%, rgba(236, 72, 153, 0.08) 100%);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 1.8rem;
  margin: 2.5rem 0;
  text-align: center;
  box-shadow: 0 0 25px rgba(6, 182, 212, 0.12);
}

.holo-callout h3 {
  font-size: 1.35rem;
  font-weight: 800;
  background: var(--grad-holo);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 0.5rem;
}

.holo-callout p {
  font-size: 0.98rem;
  color: var(--text-muted);
  max-width: 600px;
  margin: 0 auto 1.2rem;
}

/* Footer */
.site-footer {
  background: #0b0f19;
  border-top: 1px solid var(--border-subtle);
  padding: 3.5rem 1.5rem 2rem;
  margin-top: 4rem;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
}

.footer-top {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 2.5rem;
  margin-bottom: 2.5rem;
}

.footer-brand p {
  font-size: 0.92rem;
  color: var(--text-dim);
  margin-top: 0.8rem;
  line-height: 1.6;
  max-width: 320px;
}

.footer-col h4 {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 1rem;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 0.5rem;
}

.footer-links a {
  font-size: 0.88rem;
  color: var(--text-dim);
  transition: color 0.2s;
}

.footer-links a:hover {
  color: var(--brand-cyan);
}

.footer-bottom {
  border-top: 1px solid var(--border-subtle);
  padding-top: 1.8rem;
  font-size: 0.82rem;
  color: var(--text-dim);
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
}

.footer-disclosure {
  line-height: 1.6;
  color: var(--text-dim);
}

/* Responsive */
@media (max-width: 900px) {
  .footer-top {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 640px) {
  .header-container {
    padding: 0.75rem 1rem;
  }
  .main-nav .nav-link {
    display: none;
  }
  .page-container {
    padding: 1.8rem 1rem 3rem;
  }
  .hero-section {
    padding: 2.5rem 0.5rem 2rem;
  }
  .footer-top {
    grid-template-columns: 1fr;
    gap: 1.8rem;
  }
  .legal-card, .article-content-card {
    padding: 1.8rem 1.2rem;
  }
}