/* Mobile-first · 科技感 · 明亮极简 */
:root {
  --bg: #f8fafc;
  --bg-elevated: #ffffff;
  --text: #0f172a;
  --text-muted: #64748b;
  --accent: #0ea5e9;
  --accent-deep: #0284c7;
  --accent-soft: rgba(14, 165, 233, 0.12);
  --border: #e2e8f0;
  --radius: 16px;
  --radius-sm: 10px;
  --shadow: 0 4px 24px rgba(15, 23, 42, 0.06);
  --max: 1120px;
  --header-h: 64px;
  --font: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: var(--accent-deep);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.container {
  width: 100%;
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 20px;
}

/* Header */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-h);
}

.brand {
  font-weight: 800;
  font-size: 17px;
  letter-spacing: 0.02em;
  color: var(--text);
  text-decoration: none;
}

.brand:hover {
  text-decoration: none;
  color: var(--accent-deep);
}

.nav-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 10px;
  border: none;
  background: transparent;
  cursor: pointer;
  border-radius: var(--radius-sm);
}

.nav-toggle span {
  display: block;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.2s, opacity 0.2s;
}

.nav-toggle[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

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

.nav-toggle[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.site-nav {
  position: fixed;
  top: var(--header-h);
  left: 0;
  right: 0;
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  padding: 16px 20px 24px;
  transform: translateY(-120%);
  opacity: 0;
  pointer-events: none;
  transition: transform 0.25s ease, opacity 0.25s ease;
  box-shadow: var(--shadow);
}

.site-nav.is-open {
  transform: translateY(0);
  opacity: 1;
  pointer-events: auto;
}

.site-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.site-nav a {
  display: block;
  padding: 12px 14px;
  color: var(--text);
  font-weight: 500;
  border-radius: var(--radius-sm);
  text-decoration: none;
}

.site-nav a:hover {
  background: var(--accent-soft);
  text-decoration: none;
  color: var(--accent-deep);
}

/* Hero */
.hero {
  padding: calc(var(--header-h) + 48px) 0 56px;
  position: relative;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  opacity: 0.55;
  pointer-events: none;
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px;
  font-size: 13px;
  font-weight: 600;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border-radius: 999px;
  margin-bottom: 20px;
}

.hero h1 {
  margin: 0 0 16px;
  font-size: clamp(28px, 7vw, 44px);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.hero-lead {
  margin: 0 0 28px;
  font-size: 17px;
  color: var(--text-muted);
  max-width: 36em;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 24px;
  font-size: 15px;
  font-weight: 600;
  border-radius: 999px;
  border: none;
  cursor: pointer;
  text-decoration: none;
  transition: background 0.2s, transform 0.15s, box-shadow 0.2s;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-deep));
  color: #fff;
  box-shadow: 0 8px 24px rgba(14, 165, 233, 0.35);
}

.btn-primary:hover {
  box-shadow: 0 10px 28px rgba(14, 165, 233, 0.45);
  color: #fff;
}

.btn-ghost {
  background: var(--bg-elevated);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-ghost:hover {
  border-color: var(--accent);
  color: var(--accent-deep);
}

.hero-visual {
  margin-top: 40px;
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
}

/* Sections */
.section {
  padding: 56px 0;
}

.section-alt {
  background: var(--bg-elevated);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.section-head {
  text-align: center;
  max-width: 640px;
  margin: 0 auto 40px;
}

.section-label {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-deep);
  margin-bottom: 10px;
}

.section-head h2 {
  margin: 0 0 12px;
  font-size: clamp(24px, 5vw, 32px);
  letter-spacing: -0.02em;
}

.section-head p {
  margin: 0;
  color: var(--text-muted);
  font-size: 16px;
}

/* About — 自上而下：标题 → 引用 → 正文 + 支柱 */
.section-about {
  background: linear-gradient(180deg, #e0f2fe 0%, #f8fafc 220px, #f8fafc 100%);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.about-head {
  max-width: 720px;
  margin: 0 auto 28px;
  text-align: center;
}

.about-head h2 {
  margin: 0 0 14px;
  font-size: clamp(26px, 5vw, 36px);
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.about-tagline {
  margin: 0;
  font-size: 17px;
  font-weight: 500;
  color: var(--text);
  line-height: 1.55;
}

.about-detail {
  display: grid;
  gap: 24px;
  max-width: 880px;
  margin: 0 auto;
}

.about-copy p {
  margin: 0 0 16px;
  color: var(--text-muted);
  font-size: 15px;
  line-height: 1.7;
}

.about-copy p:last-child {
  margin-bottom: 0;
}

.about-pillars {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.about-pillars li {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  padding: 18px 20px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}

.pillar-icon {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 800;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border-radius: 10px;
}

.pillar-text {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
}

.pillar-text strong {
  font-size: 15px;
  color: var(--text);
}

.pillar-text span {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.45;
}

/* Services */
.services-grid {
  display: grid;
  gap: 20px;
}

.service-card {
  padding: 28px 24px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.section-alt .service-card {
  background: var(--bg);
}

.service-card:hover {
  border-color: rgba(14, 165, 233, 0.4);
  box-shadow: var(--shadow);
}

.service-icon {
  width: 48px;
  height: 48px;
  margin-bottom: 16px;
}

.service-card h3 {
  margin: 0 0 8px;
  font-size: 18px;
}

.service-card .subtitle {
  margin: 0 0 12px;
  font-size: 14px;
  font-weight: 600;
  color: var(--accent-deep);
}

.service-card p {
  margin: 0;
  font-size: 15px;
  color: var(--text-muted);
}

/* Why us */
.why-grid {
  display: grid;
  gap: 20px;
}

.why-item {
  display: flex;
  gap: 16px;
  padding: 24px;
  background: var(--bg-elevated);
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.why-num {
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 14px;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border-radius: 12px;
}

.why-item h3 {
  margin: 0 0 6px;
  font-size: 17px;
}

.why-item p {
  margin: 0;
  font-size: 14px;
  color: var(--text-muted);
}

/* Contact strip */
.contact-strip {
  text-align: center;
  padding: 40px 20px;
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.08), rgba(255, 255, 255, 0));
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.contact-strip h2 {
  margin: 0 0 8px;
  font-size: 22px;
}

.contact-strip p {
  margin: 0 0 20px;
  color: var(--text-muted);
  font-size: 15px;
}

/* Footer */
.site-footer {
  padding: 40px 0 32px;
  background: #0f172a;
  color: #94a3b8;
  font-size: 14px;
}

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

.footer-top {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
  margin-bottom: 28px;
  padding-bottom: 28px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.2);
}

.footer-brand {
  color: #f1f5f9;
  font-weight: 700;
  font-size: 16px;
}

.footer-brand p {
  margin: 10px auto 0;
  max-width: 420px;
  font-weight: 400;
  color: #94a3b8;
  font-size: 13px;
  line-height: 1.6;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 12px 20px;
}

.footer-links a {
  color: #cbd5e1;
  text-decoration: none;
}

.footer-links a:hover {
  color: #38bdf8;
  text-decoration: none;
}

.footer-icp {
  text-align: center;
  padding: 16px 0 0;
}

.footer-icp a {
  color: #94a3b8;
  font-size: 13px;
  text-decoration: none;
}

.footer-icp a:hover {
  color: #38bdf8;
}

.footer-copy {
  text-align: center;
  margin-top: 12px;
  font-size: 12px;
  color: #64748b;
}

/* Tablet+ */
@media (min-width: 640px) {
  .services-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .why-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .why-item {
    flex-direction: column;
  }

  .about-pillars {
    grid-template-columns: repeat(3, 1fr);
  }

  .about-pillars li {
    flex-direction: column;
    height: 100%;
  }
}

@media (min-width: 768px) {
  .nav-toggle {
    display: none;
  }

  .site-nav {
    position: static;
    transform: none;
    opacity: 1;
    pointer-events: auto;
    padding: 0;
    background: transparent;
    border: none;
    box-shadow: none;
  }

  .site-nav ul {
    flex-direction: row;
    gap: 8px;
  }

  .site-nav a {
    padding: 8px 14px;
    font-size: 14px;
  }

  .hero {
    padding: calc(var(--header-h) + 72px) 0 80px;
  }

  .hero-inner {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 48px;
    align-items: center;
  }

  .hero-visual {
    margin-top: 0;
  }

  .section {
    padding: 80px 0;
  }
}

@media (min-width: 1024px) {
  .services-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}