/* === Variables === */
:root {
  --primary: #1677ff;
  --primary-dark: #0958d9;
  --primary-light: #e6f4ff;
  --text: #1a1a2e;
  --text-secondary: #555;
  --text-muted: #888;
  --bg: #ffffff;
  --bg-alt: #f7f8fc;
  --bg-dark: #0f1629;
  --border: #e8e8e8;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 2px 16px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.1);
  --transition: 0.3s ease;
  --max-width: 1140px;
}

/* === Language Toggle === */
.lang-en .zh { display: none !important; }
.lang-zh .en { display: none !important; }
.lang-en .chat-demo-zh { display: none !important; }
.lang-zh .chat-demo-en { display: none !important; }

.btn-lang {
  padding: 6px 14px;
  font-size: 0.85rem;
  font-weight: 600;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--text-secondary);
  cursor: pointer;
  transition: var(--transition);
}
.btn-lang:hover {
  border-color: var(--primary);
  color: var(--primary);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }
ul { list-style: none; }
img { max-width: 100%; display: block; }

/* === Layout === */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* === Buttons === */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 24px;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  transition: var(--transition);
  border: 2px solid transparent;
  cursor: pointer;
  white-space: nowrap;
}

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

.btn-outline {
  border-color: var(--primary);
  color: var(--primary);
  background: transparent;
}
.btn-outline:hover { background: var(--primary); color: #fff; }

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

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

.btn-lg { padding: 14px 36px; font-size: 1.05rem; }
.btn-block { width: 100%; }

/* === Header === */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: 32px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 1.25rem;
}

.logo-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: var(--primary);
  color: #fff;
  border-radius: 10px;
  font-size: 1.1rem;
  font-weight: 800;
}

.nav-links {
  display: flex;
  gap: 28px;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: var(--transition);
}
.nav-links a:hover { color: var(--primary); }

.nav-actions {
  display: flex;
  gap: 12px;
  align-items: center;
}

.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.mobile-menu-btn span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  transition: var(--transition);
}
.mobile-menu-btn.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.mobile-menu-btn.active span:nth-child(2) { opacity: 0; }
.mobile-menu-btn.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* === Hero === */
.hero {
  padding: 120px 0 80px;
  background: linear-gradient(135deg, #f0f5ff 0%, #e6f4ff 50%, #f7f8fc 100%);
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.hero-title {
  font-size: 3rem;
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.highlight { color: var(--primary); }

.hero-subtitle {
  margin-top: 20px;
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 520px;
  line-height: 1.7;
}

.hero-cta {
  margin-top: 32px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.hero-note {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.hero-stats {
  margin-top: 48px;
  display: flex;
  gap: 40px;
}

.stat { text-align: center; }
.stat-number {
  display: block;
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary);
}
.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Phone mockup */
.phone-mockup {
  background: var(--bg-dark);
  border-radius: 28px;
  padding: 16px;
  box-shadow: var(--shadow-lg);
  max-width: 360px;
  margin: 0 auto;
}

.phone-screen {
  background: #fff;
  border-radius: 16px;
  padding: 24px 16px;
  min-height: 300px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.chat-bubble {
  padding: 12px 16px;
  border-radius: 16px;
  font-size: 0.9rem;
  line-height: 1.5;
  max-width: 85%;
}

.chat-bubble.bot {
  background: var(--primary-light);
  color: var(--text);
  align-self: flex-start;
  border-bottom-left-radius: 4px;
}

.chat-bubble.user {
  background: var(--primary);
  color: #fff;
  align-self: flex-end;
  border-bottom-right-radius: 4px;
}

.chat-name {
  display: block;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 4px;
}

/* === Section Shared === */
.section-title {
  font-size: 2.2rem;
  font-weight: 800;
  text-align: center;
  letter-spacing: -0.01em;
}

.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  margin-top: 12px;
  font-size: 1.05rem;
}

/* === Features === */
.features {
  padding: 100px 0;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
  margin-top: 56px;
}

.feature-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 28px;
  transition: var(--transition);
}
.feature-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.feature-icon {
  font-size: 2.2rem;
  margin-bottom: 16px;
}

.feature-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.65;
}

/* === How It Works === */
.how-it-works {
  padding: 100px 0;
  background: var(--bg-alt);
}

.steps {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  gap: 0;
  margin-top: 56px;
}

.step {
  flex: 1;
  text-align: center;
  max-width: 280px;
  padding: 0 20px;
}

.step-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  font-size: 1.4rem;
  font-weight: 800;
  margin-bottom: 20px;
}

.step h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.step p {
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.65;
}

.step-connector {
  width: 60px;
  height: 2px;
  background: var(--border);
  margin-top: 28px;
  flex-shrink: 0;
}

/* === Languages === */
.languages {
  padding: 80px 0;
}

.lang-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 12px;
  margin-top: 40px;
}

.lang-badge {
  padding: 10px 20px;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition);
}
.lang-badge:hover {
  border-color: var(--primary);
  color: var(--primary);
}

/* === Pricing === */
.pricing {
  padding: 100px 0;
  background: var(--bg-alt);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
  margin-top: 56px;
  align-items: start;
}

.price-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px 28px;
  text-align: center;
  position: relative;
  transition: var(--transition);
}
.price-card:hover {
  box-shadow: var(--shadow-lg);
}

.price-card.featured {
  border-color: var(--primary);
  box-shadow: 0 0 0 1px var(--primary), var(--shadow);
  transform: scale(1.04);
}

.featured-badge {
  position: absolute;
  top: -14px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--primary);
  color: #fff;
  padding: 4px 20px;
  border-radius: 100px;
  font-size: 0.8rem;
  font-weight: 700;
}

.plan-name {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.plan-price {
  margin-bottom: 28px;
}

.price-amount {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.price-period {
  font-size: 1rem;
  color: var(--text-muted);
}

.plan-features {
  text-align: left;
  margin-bottom: 28px;
}

.plan-features li {
  padding: 8px 0;
  font-size: 0.92rem;
  color: var(--text-secondary);
  border-bottom: 1px solid #f0f0f0;
}
.plan-features li:last-child { border-bottom: none; }

.plan-features li::before {
  content: "\2713";
  color: var(--primary);
  font-weight: 700;
  margin-right: 10px;
}

.pricing-note {
  text-align: center;
  margin-top: 36px;
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* === FAQ === */
.faq {
  padding: 100px 0;
}

.faq-list {
  max-width: 720px;
  margin: 48px auto 0;
}

.faq-item {
  border-bottom: 1px solid var(--border);
}

.faq-item summary {
  padding: 20px 0;
  font-size: 1.05rem;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: var(--transition);
}
.faq-item summary:hover { color: var(--primary); }

.faq-item summary::after {
  content: "+";
  font-size: 1.4rem;
  font-weight: 300;
  color: var(--text-muted);
  transition: var(--transition);
}

.faq-item[open] summary::after {
  content: "\2212";
}

.faq-item p {
  padding: 0 0 20px;
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* === CTA === */
.cta {
  padding: 80px 0;
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
  color: #fff;
  text-align: center;
}

.cta h2 {
  font-size: 2.2rem;
  font-weight: 800;
}

.cta p {
  margin: 16px 0 32px;
  font-size: 1.1rem;
  opacity: 0.9;
}

/* === Footer === */
.footer {
  padding: 60px 0 0;
  background: var(--bg-dark);
  color: #ccc;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 40px;
}

.footer-brand .logo-icon {
  background: rgba(255, 255, 255, 0.15);
}

.footer-brand .logo-text {
  color: #fff;
  font-size: 1.25rem;
  font-weight: 700;
}

.footer-tagline {
  margin-top: 8px;
  font-size: 0.88rem;
  color: #888;
}

.footer-links {
  display: flex;
  gap: 60px;
}

.footer-col h4 {
  color: #fff;
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.footer-col a {
  display: block;
  font-size: 0.88rem;
  color: #999;
  padding: 4px 0;
  transition: var(--transition);
}
.footer-col a:hover { color: #fff; }

.footer-bottom {
  margin-top: 40px;
  padding: 20px 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  font-size: 0.82rem;
  color: #666;
}

/* === Animations === */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* === Responsive === */
@media (max-width: 1024px) {
  .hero-title { font-size: 2.4rem; }
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .pricing-grid { grid-template-columns: repeat(2, 1fr); }
  .price-card.featured { transform: scale(1); }
}

@media (max-width: 768px) {
  .nav-links, .nav-actions {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: #fff;
    border-bottom: 1px solid var(--border);
    padding: 16px 24px;
  }
  .nav-links.open, .nav-actions.open { display: flex; }
  .nav-links {
    flex-direction: column;
    gap: 12px;
  }
  .nav-actions {
    top: auto;
    border-top: 1px solid var(--border);
  }
  .mobile-menu-btn { display: flex; }

  .hero { padding: 100px 0 60px; }
  .hero-inner {
    grid-template-columns: 1fr;
    gap: 40px;
    text-align: center;
  }
  .hero-title { font-size: 2rem; }
  .hero-subtitle { margin: 16px auto 0; }
  .hero-cta { justify-content: center; flex-direction: column; }
  .hero-stats { justify-content: center; }
  .phone-mockup { max-width: 300px; }

  .section-title { font-size: 1.7rem; }

  .features-grid { grid-template-columns: 1fr; gap: 20px; }

  .steps { flex-direction: column; align-items: center; gap: 24px; }
  .step-connector { width: 2px; height: 24px; }

  .pricing-grid { grid-template-columns: 1fr; max-width: 400px; margin-left: auto; margin-right: auto; }
  .price-card.featured { transform: scale(1); }

  .footer-inner { flex-direction: column; gap: 32px; }
  .footer-links { flex-direction: column; gap: 24px; }
}