/* === renxuai.com Shared Design System === */
/* Minimalism & Swiss Style — clean, professional, research-oriented */

@import url('https://fonts.googleapis.com/css2?family=Atkinson+Hyperlegible:wght@400;700&family=Crimson+Pro:wght@400;500;600;700&display=swap');

/* Prefer shared primitives from /design-tokens.css when adding new tokens. */

:root {
  /* Color tokens */
  --primary: #2563EB;
  --primary-hover: #1D4ED8;
  --primary-soft: #EFF6FF;
  --secondary: #3B82F6;
  --cta: #F97316;
  --cta-hover: #EA580C;
  --bg: #F8FAFC;
  --surface: #FFFFFF;
  --text: #1E293B;
  --muted: #64748B;
  --muted-light: #94A3B8;
  --border: #E2E8F0;
  --border-light: #F1F5F9;
  --shadow-sm: 0 1px 2px rgba(0,0,0,.05);
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,.06), 0 1px 3px rgba(0,0,0,.04);
  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 16px;

  /* Typography */
  --font-heading: 'Crimson Pro', Georgia, 'Times New Roman', serif;
  --font-body: 'Atkinson Hyperlegible', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;

  /* Spacing scale */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 96px;

  /* Layout */
  --max-width: 1200px;
  --nav-height: 56px;
}

/* === Reset & Base === */
html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

a { color: var(--primary); text-decoration: none; transition: color .2s ease; }
a:hover { color: var(--primary-hover); }

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  line-height: 1.2;
  margin: 0;
  color: var(--text);
}

p { margin: 0 0 var(--space-md); color: var(--muted); }

/* === Site Navigation (unified) === */
.site-nav {
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
}

.site-nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
}

.site-nav-logo {
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text) !important;
  text-decoration: none;
  letter-spacing: -0.01em;
}

.site-nav-links {
  display: flex;
  gap: var(--space-sm);
  align-items: center;
}

.site-nav-links a {
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  color: var(--muted);
  font-size: .92rem;
  font-weight: 500;
  text-decoration: none;
  transition: color .2s, background .2s;
}

.site-nav-links a:hover {
  color: var(--primary);
  background: var(--primary-soft);
}

.site-nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text);
  cursor: pointer;
  padding: 8px;
  border-radius: var(--radius-sm);
  line-height: 1;
}

/* === Layout === */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* === Hero Section (gradient, no image) === */
.hero {
  padding: var(--space-4xl) 0 var(--space-3xl);
  text-align: center;
  background: linear-gradient(135deg, #F8FAFC 0%, #EFF6FF 50%, #F0F9FF 100%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 0%, rgba(37,99,235,.06), transparent),
    radial-gradient(ellipse 50% 50% at 80% 100%, rgba(59,130,246,.04), transparent);
  pointer-events: none;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-md);
  position: relative;
}

.hero .subtitle {
  font-size: 1.15rem;
  max-width: 640px;
  margin: 0 auto var(--space-xl);
  color: var(--muted);
  line-height: 1.65;
  position: relative;
}

.hero-actions {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  flex-wrap: wrap;
  position: relative;
}

/* === Buttons === */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 22px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: .95rem;
  font-family: var(--font-body);
  text-decoration: none;
  cursor: pointer;
  transition: color .2s ease, background-color .2s ease, border-color .2s ease, transform .2s ease, box-shadow .2s ease;
  border: none;
  line-height: 1.4;
}

.btn-primary {
  background: var(--primary);
  color: #fff !important;
  box-shadow: 0 1px 3px rgba(37,99,235,.25);
}
.btn-primary:hover {
  background: var(--primary-hover);
  box-shadow: 0 2px 6px rgba(37,99,235,.35);
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
}
.btn-secondary:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-soft);
}

.btn-cta {
  background: var(--cta);
  color: #fff !important;
  box-shadow: 0 1px 3px rgba(249,115,22,.25);
}
.btn-cta:hover {
  background: var(--cta-hover);
  box-shadow: 0 2px 6px rgba(249,115,22,.35);
}

/* === Cards === */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow);
  transition: box-shadow .25s ease, transform .25s ease;
}

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

.card h3 {
  font-size: 1.2rem;
  margin-bottom: var(--space-sm);
  line-height: 1.35;
}

.card p { font-size: .95rem; margin-bottom: var(--space-md); }

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-lg);
}

/* === Sections === */
.section {
  padding: var(--space-3xl) 0;
}

.section-title {
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  font-weight: 700;
  margin-bottom: var(--space-sm);
}

.section-desc {
  color: var(--muted);
  max-width: 680px;
}

/* === Footer === */
.site-footer {
  border-top: 1px solid var(--border);
  padding: var(--space-xl) 0;
  text-align: center;
  color: var(--muted);
  font-size: .88rem;
}

/* === Responsive === */
@media (max-width: 768px) {
  .site-nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: rgba(255,255,255,.98);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: var(--space-md);
    gap: 4px;
  }

  .site-nav-links.open { display: flex; }

  .site-nav-toggle { display: block; }

  .hero { padding: var(--space-3xl) 0 var(--space-2xl); }

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

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .01ms !important;
    transition-duration: .01ms !important;
  }
}


:focus-visible {
  outline: 2px solid #4F46E5;
  outline-offset: 2px;
}
button:focus-visible, a:focus-visible {
  outline-offset: 4px;
}