:root {
  --color-primary: #037dd6;
  --color-primary-dark: #0260a4;
  --color-secondary: #f6851b;
  --color-bg: #ffffff;
  --color-bg-alt: #f7f8fa;
  --color-text: #24292f;
  --color-text-light: #6e7681;
  --color-border: #d8dee4;
  --color-success: #2da44e;
  --color-warning: #bf8700;
  --color-error: #cf222e;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-size-base: 16px;
  --font-size-sm: 14px;
  --font-size-lg: 18px;
  --font-size-xl: 24px;
  --font-size-2xl: 32px;
  --line-height: 1.7;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --radius: 8px;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-lg: 0 4px 16px rgba(0,0,0,0.12);
  --header-height: 64px;
  --container-max: 1200px;
  --touch-target: 44px;
}

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

html {
  font-size: var(--font-size-base);
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 1rem);
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-family);
  font-size: 1rem;
  line-height: var(--line-height);
  color: var(--color-text);
  background: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

body.nav-open {
  overflow: hidden;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-primary);
  color: #fff;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius);
  z-index: 9999;
  text-decoration: none;
}

.skip-link:focus {
  top: var(--spacing-sm);
}

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
}

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

.logo-link {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  text-decoration: none;
  color: var(--color-text);
  font-weight: 600;
  font-size: var(--font-size-lg);
}

.logo-img {
  width: 40px;
  height: 40px;
  border-radius: var(--radius);
}

.logo-text {
  white-space: nowrap;
}

.header-right {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.header-cta {
  display: none;
}

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

.nav-list {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--spacing-xs);
}

.nav-item {
  margin: 0;
}

.nav-link {
  display: flex;
  align-items: center;
  padding: var(--spacing-xs) var(--spacing-sm);
  color: var(--color-text);
  text-decoration: none;
  border-radius: var(--radius);
  min-height: var(--touch-target);
  transition: background 0.2s, color 0.2s;
}

.nav-link:hover,
.nav-link:focus {
  background: var(--color-bg-alt);
  color: var(--color-primary);
}

body[data-page="index"] .nav-link[data-page="index"],
body[data-page="products"] .nav-link[data-page="products"],
body[data-page="guide"] .nav-link[data-page="guide"],
body[data-page="faq"] .nav-link[data-page="faq"],
body[data-page="safety"] .nav-link[data-page="safety"],
body[data-page="news"] .nav-link[data-page="news"],
body[data-page="about"] .nav-link[data-page="about"],
body[data-page="contact"] .nav-link[data-page="contact"],
body[data-page="compare"] .nav-link[data-page="compare"] {
  background: var(--color-primary);
  color: #fff;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: var(--touch-target);
  height: var(--touch-target);
  padding: 10px;
  background: none;
  border: none;
  cursor: pointer;
}

.nav-toggle-bar {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(2) {
  opacity: 0;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

main {
  flex: 1;
  padding-top: var(--spacing-lg);
  padding-bottom: var(--spacing-xl);
}

.hero {
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-md);
  background: linear-gradient(135deg, var(--color-bg-alt) 0%, var(--color-bg) 100%);
  border-radius: var(--radius);
  margin-bottom: var(--spacing-xl);
}

.hero-title {
  font-size: var(--font-size-2xl);
  margin: 0 0 var(--spacing-sm);
  color: var(--color-text);
}

.hero-desc {
  font-size: var(--font-size-lg);
  color: var(--color-text-light);
  margin: 0 0 var(--spacing-md);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin-top: var(--spacing-md);
}

.section-title {
  font-size: var(--font-size-xl);
  margin: 0 0 var(--spacing-sm);
  color: var(--color-text);
}

.section-desc {
  color: var(--color-text-light);
  margin: 0 0 var(--spacing-md);
}

.breadcrumb {
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-sm);
}

.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--spacing-xs);
}

.breadcrumb-item {
  display: flex;
  align-items: center;
}

.breadcrumb-item::after {
  content: "/";
  margin-left: var(--spacing-xs);
  color: var(--color-text-light);
}

.breadcrumb-item:last-child::after {
  display: none;
}

.breadcrumb-item a {
  color: var(--color-primary);
  text-decoration: none;
}

.breadcrumb-item a:hover {
  text-decoration: underline;
}

.breadcrumb-current {
  color: var(--color-text-light);
}

.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-md);
}

.card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: box-shadow 0.2s, transform 0.2s;
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.card-link {
  display: block;
  text-decoration: none;
  color: inherit;
}

.card-thumb {
  aspect-ratio: 3/2;
  overflow: hidden;
  background: var(--color-bg-alt);
}

.card-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.card-body {
  padding: var(--spacing-md);
}

.card-title {
  font-size: var(--font-size-lg);
  margin: 0 0 var(--spacing-xs);
  color: var(--color-text);
}

.card-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin: 0;
  line-height: 1.6;
}

.cta-tochat,
.cta-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: var(--touch-target);
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--color-secondary);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  text-decoration: none;
  transition: background 0.2s;
}

.cta-tochat:hover,
.cta-btn:hover {
  background: #d9740f;
}

.cta-block {
  background: var(--color-bg-alt);
  padding: var(--spacing-lg);
  border-radius: var(--radius);
  text-align: center;
  margin: var(--spacing-xl) 0;
}

.cta-text {
  margin: 0 0 var(--spacing-sm);
  font-size: var(--font-size-lg);
}

.network-cards {
  background: var(--color-bg-alt);
  padding: var(--spacing-lg);
  border-radius: var(--radius);
  margin: var(--spacing-xl) 0;
}

.network-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: var(--spacing-sm);
  margin: var(--spacing-md) 0;
}

.network-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--spacing-sm);
  background: var(--color-bg);
  border-radius: var(--radius);
  text-align: center;
}

.network-icon {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--color-primary);
  margin-bottom: var(--spacing-xs);
}

.network-name {
  font-weight: 500;
  font-size: var(--font-size-sm);
}

.network-tag {
  font-size: 12px;
  color: var(--color-text-light);
}

.network-tip {
  text-align: center;
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
}

.safety-checklist {
  background: #fffbeb;
  border: 1px solid #fbbf24;
  padding: var(--spacing-md);
  border-radius: var(--radius);
  margin: var(--spacing-lg) 0;
}

.checklist-title {
  font-size: var(--font-size-lg);
  margin: 0 0 var(--spacing-xs);
  color: var(--color-warning);
}

.checklist-desc {
  font-size: var(--font-size-sm);
  margin: 0 0 var(--spacing-sm);
}

.checklist-items {
  list-style: none;
  margin: 0;
  padding: 0;
}

.checklist-item {
  display: flex;
  gap: var(--spacing-xs);
  padding: var(--spacing-xs) 0;
  font-size: var(--font-size-sm);
}

.check-icon {
  color: var(--color-warning);
}

.checklist-link {
  margin-top: var(--spacing-sm);
  font-size: var(--font-size-sm);
}

.gas-widget {
  background: var(--color-bg-alt);
  padding: var(--spacing-md);
  border-radius: var(--radius);
}

.gas-title {
  font-size: 1rem;
  margin: 0 0 var(--spacing-xs);
}

.gas-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin: 0 0 var(--spacing-sm);
}

.gas-levels {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.gas-level {
  display: flex;
  justify-content: space-between;
  padding: var(--spacing-xs);
  border-radius: 4px;
  font-size: var(--font-size-sm);
}

.gas-fast {
  background: #dcfce7;
}

.gas-standard {
  background: #fef3c7;
}

.gas-slow {
  background: #fee2e2;
}

.gas-tip {
  font-size: 12px;
  color: var(--color-text-light);
  margin: var(--spacing-sm) 0 var(--spacing-xs);
}

.gas-link {
  font-size: var(--font-size-sm);
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.faq-item {
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}

.faq-question {
  font-size: 1rem;
  margin: 0;
  padding: var(--spacing-md);
  background: var(--color-bg-alt);
  cursor: pointer;
}

.faq-answer {
  padding: var(--spacing-md);
  font-size: var(--font-size-sm);
  line-height: 1.7;
}

.article-content {
  max-width: 800px;
  margin: 0 auto;
}

.article-content h2 {
  font-size: var(--font-size-xl);
  margin: var(--spacing-xl) 0 var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--color-border);
}

.article-content h3 {
  font-size: var(--font-size-lg);
  margin: var(--spacing-lg) 0 var(--spacing-sm);
}

.article-content p {
  margin: 0 0 var(--spacing-md);
}

.article-content ul,
.article-content ol {
  margin: 0 0 var(--spacing-md);
  padding-left: var(--spacing-lg);
}

.article-content li {
  margin-bottom: var(--spacing-xs);
}

.article-content a {
  color: var(--color-primary);
}

.article-content img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin: var(--spacing-md) 0;
}

.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-md);
  border-bottom: 1px solid var(--color-border);
}

.compare-table-wrap {
  overflow-x: auto;
  margin: var(--spacing-lg) 0;
}

.compare-table {
  width: 100%;
  min-width: 600px;
  border-collapse: collapse;
  font-size: var(--font-size-sm);
}

.compare-table th,
.compare-table td {
  padding: var(--spacing-sm);
  text-align: left;
  border: 1px solid var(--color-border);
}

.compare-table th {
  background: var(--color-bg-alt);
  font-weight: 600;
}

.compare-table tr:hover td {
  background: var(--color-bg-alt);
}

.site-footer {
  background: var(--color-text);
  color: #fff;
  padding: var(--spacing-xl) 0 var(--spacing-lg);
  margin-top: auto;
}

.footer-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.footer-main {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.footer-brand {
  max-width: 300px;
}

.footer-logo-text {
  font-size: var(--font-size-lg);
  font-weight: 600;
  display: block;
  margin-bottom: var(--spacing-sm);
}

.footer-desc {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.7);
  line-height: 1.6;
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
}

.footer-col-title {
  font-size: 1rem;
  margin: 0 0 var(--spacing-sm);
  font-weight: 600;
}

.footer-nav {
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-nav li {
  margin-bottom: var(--spacing-xs);
}

.footer-nav a {
  color: rgba(255,255,255,0.8);
  text-decoration: none;
  font-size: var(--font-size-sm);
  display: inline-block;
  padding: 4px 0;
  min-height: var(--touch-target);
  line-height: calc(var(--touch-target) - 8px);
}

.footer-nav a:hover {
  color: #fff;
  text-decoration: underline;
}

.footer-help {
  text-align: center;
  padding: var(--spacing-md) 0;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.footer-help p {
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

.footer-cta {
  background: var(--color-secondary);
}

.footer-bottom {
  padding-top: var(--spacing-md);
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: var(--spacing-md);
}

.footer-legal {
  font-size: var(--font-size-sm);
  color: rgba(255,255,255,0.6);
}

.footer-disclaimer {
  margin: 0 0 var(--spacing-xs);
  max-width: 600px;
}

.footer-copyright {
  margin: 0 0 var(--spacing-xs);
}

.footer-update {
  margin: 0;
}

.footer-extra-links {
  display: flex;
  gap: var(--spacing-md);
}

.footer-extra-links a {
  color: rgba(255,255,255,0.6);
  text-decoration: none;
  font-size: var(--font-size-sm);
}

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

.sticky-chat {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 999;
  background: var(--color-bg);
  border-top: 1px solid var(--color-border);
  box-shadow: 0 -2px 10px rgba(0,0,0,0.1);
  padding: var(--spacing-sm);
  padding-bottom: calc(var(--spacing-sm) + env(safe-area-inset-bottom, 0));
}

.sticky-chat.hidden {
  display: none !important;
}

.sticky-chat-inner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  max-width: var(--container-max);
  margin: 0 auto;
}

.sticky-chat-text {
  font-size: var(--font-size-sm);
  color: var(--color-text);
}

.sticky-chat-btn {
  flex-shrink: 0;
}

.sticky-chat-close {
  width: 32px;
  height: 32px;
  background: none;
  border: none;
  font-size: 20px;
  color: var(--color-text-light);
  cursor: pointer;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.page-list {
  padding-left: var(--spacing-lg);
}

.page-list li {
  margin-bottom: var(--spacing-xs);
}

.page-list a {
  color: var(--color-primary);
  text-decoration: none;
}

.page-list a:hover {
  text-decoration: underline;
}

@media (max-width: 768px) {
  :root {
    --font-size-base: 16px;
    --font-size-2xl: 24px;
    --font-size-xl: 20px;
    --header-height: 56px;
  }

  .logo-text {
    font-size: 1rem;
  }

  .header-right {
    order: 1;
  }

  .header-cta {
    display: inline-flex;
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: var(--font-size-sm);
  }

  .nav-toggle {
    display: flex;
  }

  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: var(--spacing-md);
    transform: translateX(100%);
    transition: transform 0.3s ease;
    overflow-y: auto;
  }

  .main-nav.open {
    transform: translateX(0);
  }

  .nav-list {
    flex-direction: column;
    width: 100%;
    gap: 0;
  }

  .nav-link {
    padding: var(--spacing-sm) var(--spacing-md);
    border-bottom: 1px solid var(--color-border);
    min-height: 48px;
  }

  .hero {
    padding: var(--spacing-lg) var(--spacing-sm);
  }

  .hero-title {
    font-size: var(--font-size-xl);
  }

  .hero-desc {
    font-size: 1rem;
  }

  .cards-grid {
    grid-template-columns: 1fr;
  }

  .footer-main {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }

  .footer-brand {
    max-width: none;
    text-align: center;
  }

  .footer-links {
    grid-template-columns: repeat(2, 1fr);
  }

  .footer-bottom {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .footer-legal {
    text-align: center;
  }

  .sticky-chat {
    display: block;
  }

  main {
    padding-bottom: calc(var(--spacing-xl) + 60px);
  }

  .site-footer {
    padding-bottom: calc(var(--spacing-lg) + 60px);
  }

  .compare-table-wrap {
    margin: var(--spacing-md) calc(-1 * var(--spacing-md));
    padding: 0 var(--spacing-md);
  }

  .article-meta {
    flex-direction: column;
    gap: var(--spacing-xs);
  }

  .network-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .footer-links {
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-sm);
  }

  .footer-col:nth-child(3) {
    grid-column: span 2;
  }

  .network-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media print {
  .site-header,
  .sticky-chat,
  .cta-block,
  .nav-toggle {
    display: none !important;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
  }

  .article-content {
    max-width: none;
  }
}