/* =============================================
   Yu Wei Nets — Design System
   Computer Systems Design | Zunyi, Guizhou
   ============================================= */

/* --- CSS Custom Properties --- */
:root {
  /* Palette — no rgba(), hex only */
  --color-bg:          #FAFBFC;
  --color-bg-alt:      #F1F5F9;
  --color-surface:     #FFFFFF;
  --color-border:      #E2E8F0;
  --color-border-strong: #CBD5E1;

  --color-text:        #0F172A;
  --color-text-muted:  #475569;
  --color-text-soft:   #64748B;
  --color-text-inverse:#F8FAFC;

  --color-primary:     #0284C7;
  --color-primary-hover: #0369A1;
  --color-primary-soft:  #E0F2FE;
  --color-accent:      #38BDF8;
  --color-accent-2:    #0EA5E9;

  --color-slate-900:   #0F172A;
  --color-slate-800:   #1E293B;
  --color-slate-700:   #334155;
  --color-slate-600:   #475569;
  --color-slate-500:   #64748B;
  --color-slate-200:   #E2E8F0;
  --color-slate-100:   #F1F5F9;
  --color-slate-50:    #F8FAFC;

  --color-success:     #059669;
  --color-error:       #DC2626;

  /* Typography */
  --font-sans:  'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-mono:  'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  /* Spacing scale */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Radii */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  /* Shadows — using colored shadows, not rgba */
  --shadow-sm: 0 1px 2px 0 #0F172A08;
  --shadow-md: 0 4px 12px -2px #0F172A0D, 0 2px 4px -2px #0F172A06;
  --shadow-lg: 0 10px 30px -5px #0F172A0F, 0 4px 8px -4px #0F172A08;
  --shadow-xl: 0 20px 50px -10px #0F172A14, 0 8px 16px -8px #0F172A0A;

  /* Layout */
  --max-width: 1200px;
  --header-height: 72px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

img, svg {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

address {
  font-style: normal;
}

/* --- Container --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

/* --- Site Header --- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  z-index: 100;
  transition: box-shadow var(--transition-base);
}

.site-header.scrolled {
  box-shadow: var(--shadow-md);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-slate-900);
  letter-spacing: -0.01em;
}

.logo-mark {
  flex-shrink: 0;
}

.logo-accent {
  color: var(--color-primary);
}

/* Navigation */
.main-nav .nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav-link {
  display: inline-flex;
  align-items: center;
  padding: var(--space-2) var(--space-4);
  font-size: 0.925rem;
  font-weight: 500;
  color: var(--color-slate-600);
  border-radius: var(--radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-slate-900);
  background: var(--color-slate-100);
}

/* Mobile menu button */
.mobile-menu-btn {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: background var(--transition-fast);
}

.mobile-menu-btn:hover {
  background: var(--color-slate-100);
}

.hamburger,
.hamburger::before,
.hamburger::after {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-slate-700);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.hamburger::before,
.hamburger::after {
  content: '';
  position: absolute;
}

.hamburger {
  position: relative;
}

.hamburger::before {
  transform: translateY(-7px);
}

.hamburger::after {
  transform: translateY(7px);
}

.mobile-menu-btn.active .hamburger {
  background: transparent;
}

.mobile-menu-btn.active .hamburger::before {
  transform: rotate(45deg);
}

.mobile-menu-btn.active .hamburger::after {
  transform: rotate(-45deg);
}

/* =============================================
   Hero Section
   ============================================= */
.hero {
  position: relative;
  padding: calc(var(--header-height) + var(--space-20)) 0 var(--space-24);
  overflow: hidden;
  background: var(--color-slate-900);
  color: var(--color-text-inverse);
}

.hero-pattern {
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle at 20% 30%, #0284C718 0%, transparent 50%),
    radial-gradient(circle at 80% 60%, #38BDF810 0%, transparent 50%),
    radial-gradient(circle at 50% 80%, #0EA5E90D 0%, transparent 40%);
  pointer-events: none;
}

.hero-visual {
  position: absolute;
  right: -10%;
  top: 15%;
  width: 55%;
  height: 70%;
  pointer-events: none;
  opacity: 0.12;
}

.topo-grid {
  width: 100%;
  height: 100%;
  background-image:
    linear-gradient(#38BDF8 1px, transparent 1px),
    linear-gradient(90deg, #38BDF8 1px, transparent 1px);
  background-size: 40px 40px;
  mask-image: radial-gradient(ellipse 70% 70% at 50% 50%, black 30%, transparent 70%);
  -webkit-mask-image: radial-gradient(ellipse 70% 70% at 50% 50%, black 30%, transparent 70%);
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: 720px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  margin-bottom: var(--space-8);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-accent);
  background: #38BDF814;
  border: 1px solid #38BDF820;
  border-radius: 9999px;
}

.badge-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-accent);
  box-shadow: 0 0 8px #38BDF860;
}

.hero-title {
  font-size: clamp(2.5rem, 5.5vw, 4rem);
  font-weight: 800;
  line-height: 1.08;
  letter-spacing: -0.025em;
  margin-bottom: var(--space-6);
}

.hero-highlight {
  background: linear-gradient(135deg, var(--color-accent) 0%, var(--color-accent-2) 50%, var(--color-primary) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

.hero-subtitle {
  font-size: 1.15rem;
  line-height: 1.7;
  color: #94A3B8;
  margin-bottom: var(--space-10);
  max-width: 580px;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  flex-wrap: wrap;
}

/* =============================================
   Buttons
   ============================================= */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-primary);
  color: #FFFFFF;
  box-shadow: 0 1px 3px #0284C740;
}

.btn-primary:hover {
  background: var(--color-primary-hover);
  box-shadow: 0 4px 14px #0284C750;
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  color: var(--color-text-inverse);
  border: 1px solid #FFFFFF20;
}

.btn-outline:hover {
  background: #FFFFFF0D;
  border-color: #FFFFFF35;
}

.btn-full {
  width: 100%;
  justify-content: center;
  padding: var(--space-4) var(--space-6);
}

/* =============================================
   Section Shared Styles
   ============================================= */
section {
  padding: var(--space-24) 0;
}

.section-header {
  text-align: center;
  max-width: 640px;
  margin: 0 auto var(--space-16);
}

.section-tag {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}

.section-title {
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--color-slate-900);
  margin-bottom: var(--space-4);
}

.section-desc {
  font-size: 1.1rem;
  color: var(--color-slate-500);
  line-height: 1.65;
}

/* =============================================
   Services Grid
   ============================================= */
.services {
  background: var(--color-surface);
}

.services-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
}

.service-card {
  position: relative;
  padding: var(--space-8);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: border-color var(--transition-base), box-shadow var(--transition-base), transform var(--transition-base);
}

.service-card:hover {
  border-color: #38BDF840;
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.service-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  margin-bottom: var(--space-5);
  background: var(--color-primary-soft);
  border-radius: var(--radius-md);
}

.service-name {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-slate-900);
  margin-bottom: var(--space-3);
}

.service-desc {
  font-size: 0.925rem;
  color: var(--color-slate-500);
  line-height: 1.6;
  margin-bottom: var(--space-5);
}

.service-features {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.service-features li {
  position: relative;
  padding-left: var(--space-5);
  font-size: 0.875rem;
  color: var(--color-slate-600);
}

.service-features li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 9px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
}

/* =============================================
   About Section
   ============================================= */
.about {
  background: var(--color-slate-900);
  color: var(--color-text-inverse);
}

.about .section-title {
  color: var(--color-text-inverse);
}

.about .section-desc {
  color: #94A3B8;
}

.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-16);
  align-items: center;
}

.about-content .section-tag {
  margin-bottom: var(--space-4);
}

.about-content .section-title {
  margin-bottom: var(--space-6);
}

.about-text {
  font-size: 1.025rem;
  line-height: 1.7;
  color: #CBD5E1;
  margin-bottom: var(--space-5);
}

.about-stats {
  display: flex;
  gap: var(--space-10);
  margin-top: var(--space-8);
  padding-top: var(--space-8);
  border-top: 1px solid #FFFFFF10;
}

.stat-number {
  display: block;
  font-size: 2rem;
  font-weight: 800;
  color: var(--color-accent);
  letter-spacing: -0.02em;
  line-height: 1.1;
}

.stat-label {
  display: block;
  font-size: 0.85rem;
  color: #94A3B8;
  margin-top: var(--space-1);
}

/* About Card (visual) */
.about-visual {
  display: flex;
  justify-content: center;
}

.about-card {
  width: 100%;
  max-width: 420px;
  background: var(--color-slate-800);
  border: 1px solid #FFFFFF0D;
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.about-card-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-6);
  background: var(--color-slate-700);
  border-bottom: 1px solid #FFFFFF08;
}

.about-card-dots {
  display: flex;
  gap: 6px;
}

.about-card-dots span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--color-slate-500);
}

.about-card-dots span:first-child { background: #EF4444; }
.about-card-dots span:nth-child(2) { background: #F59E0B; }
.about-card-dots span:nth-child(3) { background: #22C55E; }

.about-card-title {
  font-size: 0.8rem;
  font-family: var(--font-mono);
  color: #94A3B8;
}

.about-card-body {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

.about-card-row {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.about-card-row .label {
  font-size: 0.725rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #64748B;
}

.about-card-row .value {
  font-size: 0.925rem;
  color: #E2E8F0;
  line-height: 1.5;
}

/* =============================================
   Contact Section
   ============================================= */
.contact {
  background: var(--color-bg);
}

.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1.2fr;
  gap: var(--space-12);
  align-items: start;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
}

.contact-item {
  display: flex;
  gap: var(--space-4);
}

.contact-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  flex-shrink: 0;
  background: var(--color-primary-soft);
  border-radius: var(--radius-md);
}

.contact-label {
  display: block;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-slate-400);
  margin-bottom: var(--space-1);
}

.contact-value {
  display: block;
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-slate-900);
  transition: color var(--transition-fast);
}

a.contact-value:hover {
  color: var(--color-primary);
}

.contact-value.address {
  line-height: 1.6;
}

/* Contact Form */
.contact-form {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.form-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-slate-700);
}

.form-input {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
}

.form-input::placeholder {
  color: #94A3B8;
}

.form-input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px #38BDF825;
}

textarea.form-input {
  resize: vertical;
  min-height: 110px;
}

.form-note {
  font-size: 0.825rem;
  color: var(--color-slate-400);
  text-align: center;
}

/* =============================================
   Footer
   ============================================= */
.site-footer {
  background: var(--color-slate-900);
  color: #CBD5E1;
  padding: var(--space-16) 0 var(--space-8);
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--space-12);
  margin-bottom: var(--space-12);
}

.footer-logo {
  margin-bottom: var(--space-4);
}

.footer-desc {
  font-size: 0.925rem;
  line-height: 1.65;
  color: #94A3B8;
  max-width: 360px;
}

.footer-heading {
  font-size: 0.825rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--color-accent);
  margin-bottom: var(--space-5);
}

.footer-links ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer-links a {
  font-size: 0.925rem;
  color: #94A3B8;
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-text-inverse);
}

.footer-bottom {
  padding-top: var(--space-8);
  border-top: 1px solid #FFFFFF0D;
  font-size: 0.85rem;
  color: #64748B;
}

/* =============================================
   Legal Pages (Privacy & Terms)
   ============================================= */
.page-legal {
  background: var(--color-surface);
}

.legal-main {
  padding: calc(var(--header-height) + var(--space-16)) 0 var(--space-20);
}

.legal-header {
  text-align: center;
  margin-bottom: var(--space-16);
  padding-bottom: var(--space-10);
  border-bottom: 1px solid var(--color-border);
}

.legal-header h1 {
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 800;
  color: var(--color-slate-900);
  letter-spacing: -0.02em;
  margin: var(--space-4) 0 var(--space-3);
}

.legal-date {
  font-size: 0.9rem;
  color: var(--color-slate-400);
}

.legal-content {
  max-width: 780px;
  margin: 0 auto;
}

.legal-section {
  margin-bottom: var(--space-12);
}

.legal-section h2 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-slate-900);
  margin-bottom: var(--space-5);
  padding-bottom: var(--space-3);
  border-bottom: 2px solid var(--color-primary-soft);
}

.legal-section h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-slate-700);
  margin: var(--space-6) 0 var(--space-3);
}

.legal-section p {
  font-size: 0.975rem;
  color: var(--color-slate-600);
  line-height: 1.75;
  margin-bottom: var(--space-4);
}

.legal-section ul {
  list-style: none;
  margin-bottom: var(--space-4);
  padding-left: var(--space-6);
}

.legal-section ul li {
  position: relative;
  font-size: 0.975rem;
  color: var(--color-slate-600);
  line-height: 1.65;
  margin-bottom: var(--space-2);
  padding-left: var(--space-4);
}

.legal-section ul li::before {
  content: '';
  position: absolute;
  left: -1.5rem;
  top: 0.65rem;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
}

.legal-contact {
  margin-top: var(--space-4);
  padding: var(--space-6);
  background: var(--color-bg-alt);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
}

.legal-contact p {
  font-size: 0.925rem;
  color: var(--color-slate-600);
  margin-bottom: var(--space-1);
}

.legal-contact p:first-child {
  margin-bottom: var(--space-4);
}

/* =============================================
   Animations
   ============================================= */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-in {
  animation: fadeInUp 0.6s ease forwards;
}

/* =============================================
   Responsive
   ============================================= */
@media (max-width: 1024px) {
  .services-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: var(--space-12);
  }

  .about-card {
    max-width: 100%;
  }

  .contact-grid {
    grid-template-columns: 1fr;
    gap: var(--space-10);
  }
}

@media (max-width: 768px) {
  :root {
    --header-height: 64px;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--color-surface);
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding-top: var(--space-16);
    transform: translateX(100%);
    transition: transform var(--transition-base);
  }

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

  .main-nav .nav-list {
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
  }

  .nav-link {
    font-size: 1.125rem;
    padding: var(--space-3) var(--space-6);
  }

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

  .hero-title {
    font-size: 2rem;
  }

  .hero-actions {
    flex-direction: column;
    align-items: flex-start;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }

  section {
    padding: var(--space-16) 0;
  }

  .about-stats {
    gap: var(--space-6);
    flex-wrap: wrap;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-4);
  }

  .hero {
    padding: calc(var(--header-height) + var(--space-12)) 0 var(--space-16);
  }

  .hero-title {
    font-size: 1.75rem;
  }

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

  .section-title {
    font-size: 1.6rem;
  }

  .legal-content {
    padding: 0;
  }
}