/* 小牛云 (xiaoniuyun.club) 全局设计系统 CSS */
:root {
  --primary-color: #1664ff;
  --primary-hover: #0e4ed6;
  --primary-light: #e8f3ff;
  --accent-orange: #ff7d00;
  --accent-orange-bg: #fff7e8;
  --dark-text: #1d2129;
  --muted-text: #4e5969;
  --light-text: #86909c;
  --border-color: #e5e6eb;
  --bg-light: #f7f8fa;
  --bg-white: #ffffff;
  --card-shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
  --card-shadow-hover: 0 10px 30px rgba(22, 100, 255, 0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --container-width: 1200px;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
}

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

body {
  font-family: var(--font-family);
  color: var(--dark-text);
  background-color: var(--bg-white);
  line-height: 1.6;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
}

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

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

.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* Header & Navigation */
.header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  height: 70px;
  display: flex;
  align-items: center;
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 20px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.brand-logo {
  width: 38px;
  height: 38px;
  object-fit: contain;
  border-radius: var(--radius-sm);
}

.brand-name {
  font-size: 22px;
  font-weight: 700;
  color: var(--primary-color);
  letter-spacing: -0.5px;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 24px;
  list-style: none;
}

.nav-link {
  color: var(--dark-text);
  font-weight: 500;
  font-size: 15px;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
}

.nav-link:hover {
  color: var(--primary-color);
  background-color: var(--primary-light);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 14px;
}

/* Header Recommend Button */
.btn-recommend {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background-color: var(--accent-orange-bg);
  color: var(--accent-orange);
  border: 1px solid rgba(255, 125, 0, 0.3);
  padding: 8px 16px;
  border-radius: 20px;
  font-weight: 600;
  font-size: 14px;
  transition: all 0.25s ease;
}

.btn-recommend:hover {
  background-color: var(--accent-orange);
  color: #ffffff;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(255, 125, 0, 0.25);
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 9px 20px;
  border-radius: 20px;
  font-weight: 600;
  font-size: 14px;
  border: none;
  cursor: pointer;
  transition: all 0.25s ease;
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  color: #ffffff;
  transform: translateY(-2px);
  box-shadow: 0 4px 14px rgba(22, 100, 255, 0.3);
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, #f0f6ff 0%, #ffffff 50%, #eef4ff 100%);
  padding: 80px 0 60px;
  position: relative;
  overflow: hidden;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: center;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: #ffffff;
  border: 1px solid #d9e6ff;
  border-radius: 20px;
  padding: 4px 14px;
  font-size: 13px;
  color: var(--muted-text);
  margin-bottom: 20px;
}

.badge-orange {
  background: var(--accent-orange);
  color: #fff;
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 12px;
  font-weight: 600;
}

.hero-title {
  font-size: 40px;
  line-height: 1.25;
  font-weight: 800;
  color: var(--dark-text);
  margin-bottom: 20px;
  letter-spacing: -1px;
}

.hero-subtitle {
  font-size: 16px;
  color: var(--muted-text);
  margin-bottom: 36px;
  line-height: 1.6;
}

.hero-buttons {
  display: flex;
  gap: 16px;
  align-items: center;
}

.hero-btn-lg {
  padding: 14px 32px;
  font-size: 16px;
  border-radius: 30px;
}

.hero-card-visual {
  background: rgba(255, 255, 255, 0.95);
  border: 1px solid rgba(22, 100, 255, 0.15);
  border-radius: var(--radius-lg);
  padding: 30px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.08);
  backdrop-filter: blur(10px);
  position: relative;
}

.node-status-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.node-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-light);
  padding: 12px 18px;
  border-radius: var(--radius-md);
}

.node-info {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
}

.ping-tag {
  color: #00b42a;
  background: #e8ffea;
  padding: 3px 8px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 600;
}

/* Feature Cards Grid (5 features) */
.features-promo {
  padding: 50px 0;
  background: var(--bg-white);
  border-bottom: 1px solid var(--border-color);
}

.promo-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 20px;
}

.promo-card {
  background: var(--bg-light);
  border: 1px solid var(--border-color);
  padding: 22px 18px;
  border-radius: var(--radius-md);
  transition: all 0.3s ease;
}

.promo-card:hover {
  transform: translateY(-4px);
  border-color: var(--primary-color);
  box-shadow: var(--card-shadow);
  background: #ffffff;
}

.promo-icon {
  font-size: 28px;
  margin-bottom: 12px;
}

.promo-title {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 6px;
  color: var(--dark-text);
}

.promo-desc {
  font-size: 13px;
  color: var(--muted-text);
  line-height: 1.5;
}

/* Section Common Header */
.section-header {
  text-align: center;
  margin-bottom: 50px;
}

.section-title {
  font-size: 32px;
  font-weight: 800;
  color: var(--dark-text);
  margin-bottom: 12px;
  letter-spacing: -0.5px;
}

.section-subtitle {
  font-size: 16px;
  color: var(--muted-text);
  max-width: 680px;
  margin: 0 auto;
}

/* Pricing Tiers Section */
.pricing-section {
  padding: 80px 0;
  background: var(--bg-light);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.pricing-card {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 36px 28px;
  position: relative;
  display: flex;
  flex-direction: column;
  transition: all 0.3s ease;
}

.pricing-card.featured {
  border: 2px solid var(--primary-color);
  box-shadow: var(--card-shadow-hover);
  transform: translateY(-6px);
}

.pricing-badge {
  position: absolute;
  top: -14px;
  right: 24px;
  background: var(--primary-color);
  color: #ffffff;
  padding: 4px 12px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 700;
}

.pricing-name {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}

.pricing-price {
  font-size: 36px;
  font-weight: 800;
  color: var(--primary-color);
  margin-bottom: 16px;
}

.pricing-price span {
  font-size: 15px;
  font-weight: 400;
  color: var(--muted-text);
}

.pricing-features {
  list-style: none;
  margin-bottom: 30px;
  flex: 1;
}

.pricing-features li {
  padding: 8px 0;
  color: var(--muted-text);
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 8px;
  border-bottom: 1px dashed #f0f0f0;
}

.pricing-features li::before {
  content: "✓";
  color: var(--primary-color);
  font-weight: bold;
}

.pricing-btn {
  width: 100%;
  padding: 12px;
  border-radius: 25px;
}

/* Node Advantage Grid */
.advantages-section {
  padding: 80px 0;
  background: #ffffff;
}

.adv-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 30px;
}

.adv-card {
  background: var(--bg-light);
  border-radius: var(--radius-md);
  padding: 30px;
  border: 1px solid var(--border-color);
}

.adv-icon {
  width: 50px;
  height: 50px;
  background: var(--primary-light);
  color: var(--primary-color);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  font-weight: bold;
  margin-bottom: 16px;
}

/* Articles Section */
.articles-section {
  padding: 80px 0;
  background: var(--bg-light);
}

.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 24px;
}

.article-card {
  background: #ffffff;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-color);
  transition: all 0.3s ease;
  display: flex;
  flex-direction: column;
}

.article-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--card-shadow);
  border-color: #c9ddff;
}

.article-body {
  padding: 24px;
  display: flex;
  flex-direction: column;
  flex: 1;
}

.article-tag {
  display: inline-block;
  background: var(--primary-light);
  color: var(--primary-color);
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 600;
  margin-bottom: 12px;
  width: fit-content;
}

.article-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 10px;
  line-height: 1.4;
}

.article-excerpt {
  font-size: 14px;
  color: var(--muted-text);
  margin-bottom: 16px;
  line-height: 1.6;
  flex: 1;
}

.article-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  color: var(--light-text);
  border-top: 1px solid #f0f0f0;
  padding-top: 12px;
}

/* Article Detail Page Layout */
.article-detail-page {
  padding: 60px 0;
  background: #ffffff;
}

.article-container {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px;
}

.breadcrumb {
  display: flex;
  gap: 8px;
  font-size: 14px;
  color: var(--muted-text);
  margin-bottom: 24px;
}

.article-header-detail {
  margin-bottom: 30px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 24px;
}

.article-header-detail h1 {
  font-size: 32px;
  font-weight: 800;
  line-height: 1.3;
  margin-bottom: 16px;
}

.article-meta {
  display: flex;
  gap: 20px;
  font-size: 14px;
  color: var(--light-text);
}

.article-content {
  font-size: 16px;
  line-height: 1.8;
  color: #2d3748;
}

.article-content h2 {
  font-size: 22px;
  font-weight: 700;
  margin: 36px 0 16px;
  color: var(--dark-text);
  border-left: 4px solid var(--primary-color);
  padding-left: 12px;
}

.article-content h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 24px 0 12px;
  color: var(--dark-text);
}

.article-content p {
  margin-bottom: 18px;
}

.article-content ul, .article-content ol {
  margin-bottom: 20px;
  padding-left: 24px;
}

.article-content li {
  margin-bottom: 8px;
}

.article-cta-box {
  background: linear-gradient(135deg, #e8f3ff 0%, #f0f6ff 100%);
  border: 1px solid #c9ddff;
  border-radius: var(--radius-md);
  padding: 28px;
  margin: 40px 0;
  text-align: center;
}

.article-cta-title {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--dark-text);
}

.article-cta-desc {
  font-size: 14px;
  color: var(--muted-text);
  margin-bottom: 20px;
}

/* Reviews Section */
.reviews-section {
  padding: 80px 0;
  background: #ffffff;
}

.reviews-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
  gap: 24px;
}

.review-card {
  background: var(--bg-light);
  border: 1px solid var(--border-color);
  padding: 24px;
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
}

.review-stars {
  color: #ffb400;
  font-size: 16px;
  margin-bottom: 12px;
}

.review-content {
  font-size: 14px;
  color: var(--dark-text);
  line-height: 1.6;
  margin-bottom: 16px;
  font-style: italic;
}

.review-author {
  display: flex;
  align-items: center;
  gap: 12px;
}

.author-avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--primary-light);
  color: var(--primary-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
}

.author-info {
  display: flex;
  flex-direction: column;
}

.author-name {
  font-weight: 700;
  font-size: 14px;
}

.author-role {
  font-size: 12px;
  color: var(--muted-text);
}

/* FAQ Section */
.faq-section {
  padding: 80px 0;
  background: var(--bg-light);
}

.faq-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.faq-item {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px 24px;
  transition: all 0.2s ease;
}

.faq-question {
  font-size: 17px;
  font-weight: 700;
  color: var(--dark-text);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.faq-answer {
  margin-top: 12px;
  color: var(--muted-text);
  font-size: 14px;
  line-height: 1.6;
}

/* Footer Section - Semantic HTML5 <footer> */
.site-footer {
  background: #0f141d;
  color: #94a3b8;
  padding: 60px 0 30px;
  font-size: 14px;
  border-top: 1px solid #1e293b;
}

.footer-top {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.footer-brand-title {
  font-size: 22px;
  font-weight: 700;
  color: #ffffff;
  display: flex;
  align-items: center;
  gap: 10px;
}

.footer-brand-title img {
  width: 32px;
  height: 32px;
}

.footer-desc {
  color: #64748b;
  font-size: 13px;
  max-width: 360px;
}

.footer-col-title {
  color: #ffffff;
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 16px;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  color: #94a3b8;
  font-size: 13px;
}

.footer-links a:hover {
  color: #ffffff;
}

/* PBN Friend Links Area (Task 2 Requirement) */
.footer-pbn-links {
  border-top: 1px solid #1e293b;
  padding-top: 24px;
  margin-top: 20px;
  text-align: center;
  font-size: 12px;
  color: #64748b;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.pbn-link-list {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

.pbn-link-item {
  color: #94a3b8;
  text-decoration: none;
  font-size: 13px;
  transition: color 0.2s ease;
}

.pbn-link-item:hover {
  color: var(--primary-color);
  text-decoration: underline;
}

.footer-copyright {
  text-align: center;
  margin-top: 16px;
  font-size: 12px;
  color: #475569;
}

/* Responsive Media Queries */
@media (max-width: 992px) {
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .hero-buttons {
    justify-content: center;
  }
  .footer-top {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 600px) {
  .nav-menu {
    display: none;
  }
  .hero-title {
    font-size: 28px;
  }
  .footer-top {
    grid-template-columns: 1fr;
  }
}