/* Beijing Shenzhun Technology — AI for Chemistry & Materials corporate site */

:root {
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-text: #0f172a;
  --color-text-muted: #475569;
  --color-border: #e2e8f0;
  --color-primary: #1e3a5f;
  --color-primary-hover: #2c5282;
  --color-accent: #0ea5e9;
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --radius: 12px;
  --header-h: 72px;
  --max-w: 1120px;
}

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: 0.75rem 1rem;
  background: var(--color-primary);
  color: #fff;
  text-decoration: none;
}

.skip-link:focus {
  left: 0;
}

.container {
  width: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  background: rgba(248, 250, 252, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
}

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

.logo {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  text-decoration: none;
  color: var(--color-text);
}

.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.25rem;
  height: 2.25rem;
  border-radius: 8px;
  background: var(--color-primary);
  color: #fff;
  font-weight: 700;
  font-size: 0.9rem;
}

.logo-text {
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  line-height: 1.2;
  max-width: 12rem;
}

.logo-text-en {
  font-weight: 600;
  font-size: 0.88rem;
  letter-spacing: -0.02em;
}

.logo-text-zh {
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--color-text-muted);
  letter-spacing: 0.02em;
}

@media (min-width: 480px) {
  .logo-text {
    max-width: none;
  }

  .logo-text-en {
    font-size: 0.95rem;
  }

  .logo-text-zh {
    font-size: 0.72rem;
  }
}

@media (min-width: 900px) {
  .logo-text-en {
    font-size: 1rem;
  }
}

@media (max-width: 380px) {
  .logo-text-zh {
    display: none;
  }
}

.nav-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 0;
  border: none;
  background: transparent;
  cursor: pointer;
}

.nav-toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  margin: 0 auto;
  transition: transform 0.2s, opacity 0.2s;
}

.site-header.is-nav-open .nav-toggle-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.site-header.is-nav-open .nav-toggle-bar:nth-child(2) {
  opacity: 0;
}

.site-header.is-nav-open .nav-toggle-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

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

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

@media (max-width: 767px) {
  .site-nav {
    position: fixed;
    inset: var(--header-h) 0 0 0;
    background: var(--color-surface);
    padding: 1rem 1.25rem 2rem;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: transform 0.25s ease, opacity 0.25s ease, visibility 0.25s;
  }

  .site-nav.is-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .site-nav .nav-list a {
    display: block;
    padding: 0.85rem 0;
    border-bottom: 1px solid var(--color-border);
    font-size: 1.05rem;
  }
}

@media (min-width: 768px) {
  .site-nav .nav-list {
    flex-direction: row;
    gap: 2rem;
  }

  .site-nav .nav-list a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color 0.15s;
  }

  .site-nav .nav-list a:hover {
    color: var(--color-primary);
  }
}

.site-nav .nav-list a {
  color: inherit;
  text-decoration: none;
}

/* Hero */
.hero {
  position: relative;
  padding: 3.5rem 0 4.5rem;
  overflow: hidden;
}

@media (min-width: 768px) {
  .hero {
    padding: 5rem 0 6rem;
  }
}

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

.hero-eyebrow {
  margin: 0 0 0.5rem;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-accent);
}

.hero-title {
  margin: 0 0 1rem;
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.2;
  color: var(--color-primary);
}

.hero-lead {
  margin: 0 0 1.75rem;
  max-width: 36rem;
  font-size: 1.1rem;
  color: var(--color-text-muted);
}

.hero-lead-wide {
  max-width: 48rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.65rem 1.35rem;
  font-size: 0.95rem;
  font-weight: 600;
  font-family: inherit;
  border-radius: 999px;
  text-decoration: none;
  border: 2px solid transparent;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-primary-hover);
}

.btn-ghost {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-border);
}

.btn-ghost:hover {
  border-color: var(--color-primary);
  background: rgba(30, 58, 95, 0.06);
}

.hero-gradient {
  position: absolute;
  top: -20%;
  right: -15%;
  width: min(55vw, 480px);
  height: min(55vw, 480px);
  border-radius: 50%;
  background: radial-gradient(circle, rgba(14, 165, 233, 0.18) 0%, transparent 70%);
  pointer-events: none;
}

.hero-strip {
  margin: 2rem 0 0;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem;
}

.hero-strip-dot {
  opacity: 0.45;
  user-select: none;
}

/* Sections */
.section {
  padding: 3.5rem 0;
}

@media (min-width: 768px) {
  .section {
    padding: 4.5rem 0;
  }
}

.section-eyebrow {
  margin: 0 0 0.35rem;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-accent);
}

.section-title {
  margin: 0 0 0.75rem;
  font-size: clamp(1.35rem, 2.5vw, 1.65rem);
  font-weight: 700;
  color: var(--color-primary);
}

.section-intro {
  margin: 0 0 2rem;
  max-width: 42rem;
  color: var(--color-text-muted);
}

.section-intro-wide {
  max-width: 48rem;
}

.section-capabilities {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

.legal-name {
  margin: -0.5rem 0 1.75rem;
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

.about-quote {
  margin: 0;
  padding: 1.25rem 1.5rem;
  border-left: 4px solid var(--color-accent);
  background: var(--color-bg);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.about-quote p {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 500;
  font-style: italic;
  color: var(--color-primary);
  line-height: 1.5;
}

.section-about {
  background: var(--color-bg);
}

.section-verticals {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

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

@media (min-width: 768px) {
  .verticals-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1100px) {
  .verticals-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.about-grid {
  display: grid;
  gap: 1.25rem;
}

@media (min-width: 768px) {
  .about-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
  }
}

.about-card {
  margin: 0;
  padding: 1.35rem 1.5rem;
  background: var(--color-bg);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.about-card h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
}

.about-card p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

.service-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1rem;
}

@media (min-width: 768px) {
  .service-list {
    grid-template-columns: repeat(3, 1fr);
    gap: 1.25rem;
  }

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

@media (min-width: 1024px) {
  .platform-modules {
    grid-template-columns: repeat(3, 1fr);
  }
}

.service-item {
  margin: 0;
  padding: 1.5rem;
  background: var(--color-surface);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
}

.service-item h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
}

.service-item p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

.section-contact .contact-card {
  max-width: 40rem;
  padding: 1.75rem 1.5rem;
  background: var(--color-surface);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
}

.contact-dl {
  margin: 0;
}

.contact-row {
  display: grid;
  gap: 0.25rem;
  padding: 0.85rem 0;
  border-bottom: 1px solid var(--color-border);
}

.contact-row:first-child {
  padding-top: 0;
}

.contact-row:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.contact-row dt {
  margin: 0;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.contact-row dd {
  margin: 0;
  font-size: 1rem;
}

.contact-dd-sub {
  display: block;
  margin-top: 0.25rem;
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

.placeholder-note {
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.contact-row a {
  color: var(--color-accent);
  word-break: break-all;
}

.contact-row a:hover {
  text-decoration: underline;
}

/* Footer */
.site-footer {
  padding: 2rem 0;
  background: var(--color-primary);
  color: rgba(255, 255, 255, 0.88);
}

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

.footer-brand {
  margin: 0 0 0.35rem;
  font-size: 0.9rem;
}

.footer-legal-cn {
  margin: 0;
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.78);
}