/* ============================================================
   LAIKUN ToB Site — Minimal, High-Conversion, Enterprise
   Inspired by OpenAI + Stripe + Palantir
   ============================================================ */

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #fafafa;
  --surface: #fff;
  --text: #171717;
  --text-secondary: #525252;
  --text-tertiary: #8a8a8a;
  --accent: #0066ff;
  --accent-hover: #0052cc;
  --accent-soft: rgba(0,102,255,0.06);
  --border: #e5e5e5;
  --radius: 12px;
  --radius-lg: 20px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.04);
  --shadow: 0 4px 24px rgba(0,0,0,0.06);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.08);
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", "PingFang SC", "Microsoft YaHei", sans-serif;
  --max-width: 1200px;
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

html { scroll-behavior: smooth; font-size: 16px; }

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

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 40px;
}

/* --- Header --- */
.header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: rgba(255,255,255,0.82);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition);
}
.header.scrolled { border-bottom-color: var(--border); }

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 40px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.02em;
}
.logo-dot { color: var(--accent); font-size: 1.5rem; }

.nav { display: flex; gap: 36px; }
.nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}
.nav a:hover { color: var(--text); }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none; border: none;
  cursor: pointer; padding: 4px;
}
.nav-toggle span {
  display: block;
  width: 22px; height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: var(--transition);
}

/* --- Hero --- */
.hero {
  position: relative;
  padding: 180px 0 120px;
  text-align: center;
  overflow: hidden;
}
.hero-bg {
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(0,102,255,0.06), transparent 60%),
              radial-gradient(ellipse 60% 40% at 80% 80%, rgba(0,102,255,0.03), transparent 60%);
  pointer-events: none;
}
.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  border: 1px solid var(--border);
  border-radius: 100px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 32px;
  background: var(--surface);
}
.hero-title {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 24px;
}
.gradient-text {
  background: linear-gradient(135deg, var(--accent) 0%, #6366f1 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-sub {
  max-width: 640px;
  margin: 0 auto 40px;
  font-size: 1.125rem;
  color: var(--text-secondary);
  line-height: 1.7;
}
.hero-actions { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; margin-bottom: 64px; }
.hero-stats {
  display: flex;
  justify-content: center;
  gap: 72px;
}
.stat { text-align: center; }
.stat strong {
  display: block;
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}
.stat span {
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  margin-top: 4px;
  display: block;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  border-radius: 100px;
  font-size: 0.9375rem;
  font-weight: 600;
  text-decoration: none;
  transition: all var(--transition);
  cursor: pointer;
  border: none;
  font-family: inherit;
}
.btn-primary {
  background: var(--text);
  color: #fff;
}
.btn-primary:hover { background: #333; transform: translateY(-1px); box-shadow: var(--shadow); }
.btn-outline {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
}
.btn-outline:hover { border-color: #ccc; background: #f9f9f9; }

/* --- Section Common --- */
section { padding: 100px 0; }

.section-header { text-align: center; margin-bottom: 64px; }
.section-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin-bottom: 16px;
}
.section-title {
  font-size: clamp(1.8rem, 3vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}
.section-desc {
  max-width: 540px;
  margin: 0 auto;
  color: var(--text-secondary);
  font-size: 1rem;
}

/* --- Trust --- */
.trust { padding: 60px 0; background: var(--surface); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.trust-label { text-align: center; font-size: 0.8125rem; font-weight: 500; color: var(--text-tertiary); margin-bottom: 32px; text-transform: uppercase; letter-spacing: 0.06em; }
.trust-row { display: flex; justify-content: center; gap: 48px; flex-wrap: wrap; }
.trust-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
}
.trust-icon { color: var(--accent); opacity: 0.8; }

/* --- Services --- */
.services { background: var(--bg); }
.service-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 24px;
}
.service-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px;
  transition: all var(--transition);
}
.service-card:hover { box-shadow: var(--shadow-lg); border-color: transparent; transform: translateY(-2px); }
.service-card h3 {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: 8px;
}
.service-card > p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 20px;
  line-height: 1.6;
}
.service-card ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.service-card ul li {
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  padding-left: 16px;
  position: relative;
}
.service-card ul li::before {
  content: '';
  position: absolute;
  left: 0; top: 7px;
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--accent);
  opacity: 0.4;
}

/* --- Solutions --- */
.solutions { background: var(--surface); }
.solution-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}
.solution-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px;
  transition: all var(--transition);
}
.solution-card:hover { border-color: var(--accent); background: var(--accent-soft); }
.solution-num {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--accent);
  display: block;
  margin-bottom: 12px;
  opacity: 0.6;
}
.solution-card h3 { font-size: 1.125rem; font-weight: 600; margin-bottom: 8px; }
.solution-card p { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.6; }

/* --- Why Us --- */
.why { background: var(--bg); }
.why-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}
.why-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px;
  transition: all var(--transition);
}
.why-card:hover { box-shadow: var(--shadow); }
.why-card h4 { font-size: 1.0625rem; font-weight: 600; margin-bottom: 8px; }
.why-card p { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.6; }

/* --- Products (Integration bridge) --- */
.products { background: var(--surface); }
.products-card {
  display: flex;
  align-items: center;
  gap: 64px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 64px;
}
.products-content { flex: 1; }
.products-content h2 { font-size: 2rem; font-weight: 700; margin: 16px 0 12px; letter-spacing: -0.02em; }
.products-content p { color: var(--text-secondary); margin-bottom: 24px; font-size: 1rem; line-height: 1.6; }
.products-visual { flex: 1; display: flex; justify-content: center; }
.app-preview-stack {
  position: relative;
  width: 200px; height: 280px;
}
.app-preview {
  position: absolute;
  width: 140px; height: 200px;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  transition: all var(--transition);
}
.app-preview.p1 { top: 0; left: 30px; z-index: 3; transform: rotate(-3deg); }
.app-preview.p2 { top: 20px; left: 0; z-index: 2; transform: rotate(2deg); background: #f0f0f0; }
.app-preview.p3 { top: 40px; left: 50px; z-index: 1; transform: rotate(-2deg); background: #e8e8e8; }

/* --- CTA --- */
.cta {
  text-align: center;
  background: var(--text);
  color: #fff;
  padding: 120px 0;
}
.cta h2 {
  font-size: clamp(1.8rem, 3vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}
.cta p { color: rgba(255,255,255,0.65); margin-bottom: 32px; font-size: 1rem; }
.cta .btn-primary { background: #fff; color: var(--text); }
.cta .btn-primary:hover { background: #eee; }

/* --- Contact --- */
.contact { background: var(--bg); }
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: 64px;
  max-width: 900px;
  margin: 0 auto;
}
.contact-info { display: flex; flex-direction: column; gap: 24px; }
.contact-item strong { display: block; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--text-tertiary); margin-bottom: 4px; }
.contact-item span { font-size: 0.9375rem; color: var(--text); }
.contact-form { display: flex; flex-direction: column; gap: 16px; }
.contact-form input,
.contact-form textarea {
  width: 100%;
  padding: 14px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.9375rem;
  font-family: inherit;
  background: var(--surface);
  color: var(--text);
  transition: border-color var(--transition);
  outline: none;
}
.contact-form input:focus,
.contact-form textarea:focus { border-color: var(--accent); }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.contact-form .btn-primary { align-self: flex-start; }

/* --- Footer --- */
.footer {
  padding: 32px 0;
  text-align: center;
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  border-top: 1px solid var(--border);
  background: var(--surface);
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .container { padding: 0 24px; }
  .header-inner { padding: 0 24px; }
  .nav { display: none; }
  .nav.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 64px; left: 0; right: 0;
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(20px);
    padding: 24px;
    gap: 20px;
    border-bottom: 1px solid var(--border);
  }
  .nav-toggle { display: flex; }
  .hero { padding: 140px 0 80px; }
  .hero-stats { gap: 36px; }
  .service-grid { grid-template-columns: 1fr; }
  .solution-grid { grid-template-columns: 1fr 1fr; }
  .why-grid { grid-template-columns: 1fr 1fr; }
  .products-card { flex-direction: column; padding: 40px 24px; }
  .contact-grid { grid-template-columns: 1fr; }
  .form-row { grid-template-columns: 1fr; }
}