/* ===== CSS Variables ===== */
:root {
  /* Colors */
  --primary-color: #667eea;
  --primary-dark: #5a67d8;
  --secondary-color: #764ba2;
  --accent-color: #f093fb;
  --success-color: #48bb78;
  --warning-color: #ed8936;
  --error-color: #f56565;

  /* Gradients */
  --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);

  /* Text Colors */
  --text-primary: #2d3748;
  --text-secondary: #4a5568;
  --text-muted: #718096;
  --text-light: #a0aec0;
  --text-white: #ffffff;

  /* Background Colors */
  --bg-white: #ffffff;
  --bg-light: #f7fafc;
  --bg-gray: #edf2f7;
  --bg-dark: #2d3748;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.1);

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;

  /* Z-index */
  --z-loading: 9999;
  --z-navbar: 1000;
  --z-dropdown: 999;
  --z-modal: 998;
  --z-tooltip: 997;
}

/* ===== Reset & Base Styles ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Noto Sans SC', 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-white);
  overflow-x: hidden;
}

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-sm);
}

h1 { font-size: clamp(2rem, 5vw, 4rem); }
h2 { font-size: clamp(1.75rem, 4vw, 3rem); }
h3 { font-size: clamp(1.5rem, 3vw, 2rem); }
h4 { font-size: clamp(1.25rem, 2.5vw, 1.5rem); }

p {
  margin-bottom: var(--spacing-sm);
  color: var(--text-secondary);
}

a {
  text-decoration: none;
  color: inherit;
  transition: var(--transition-normal);
}

/* ===== Utility Classes ===== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.gradient-text {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

.section-title {
  font-size: clamp(2rem, 4vw, 3rem);
  margin-bottom: var(--spacing-sm);
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-muted);
  max-width: 600px;
  margin: 0 auto;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--radius-lg);
  font-weight: 500;
  font-size: 1rem;
  text-decoration: none;
  transition: var(--transition-normal);
  cursor: pointer;
  border: none;
  outline: none;
}

.btn-primary {
  background: var(--gradient-primary);
  color: var(--text-white);
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-outline {
  background: transparent;
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
}

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

/* ===== Loading Screen ===== */
#loading-screen {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg-white);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: var(--z-loading);
  opacity: 1;
  transition: opacity var(--transition-slow);
}

#loading-screen.hidden {
  opacity: 0;
  pointer-events: none;
}

.loading-spinner {
  text-align: center;
}

.spinner {
  width: 50px;
  height: 50px;
  border: 4px solid var(--bg-gray);
  border-top: 4px solid var(--primary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin: 0 auto var(--spacing-md);
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* ===== Navigation ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  z-index: var(--z-navbar);
  transition: var(--transition-normal);
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.navbar.scrolled {
  background: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow-sm);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.nav-logo {
  font-size: 2rem;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--spacing-lg);
}

.nav-link {
  font-weight: 500;
  color: var(--text-secondary);
  transition: var(--transition-normal);
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary-color);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--gradient-primary);
  border-radius: 1px;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-xs);
}

.nav-toggle span {
  width: 25px;
  height: 3px;
  background: var(--text-primary);
  transition: var(--transition-normal);
  border-radius: 2px;
}

/* ===== Hero Section ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
}

.hero-background {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: -1;
}

.hero-gradient {
  width: 100%;
  height: 100%;
  background: var(--gradient-hero);
  opacity: 0.1;
}

.hero-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  align-items: center;
  padding: var(--spacing-2xl) var(--spacing-md);
}

.hero-text {
  z-index: 1;
}

.hero-title {
  margin-bottom: var(--spacing-md);
  line-height: 1.1;
}

.hero-subtitle {
  font-size: 1.2rem;
  color: var(--text-muted);
  margin-bottom: var(--spacing-xl);
  line-height: 1.6;
}

.hero-actions {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
}

.hero-qr {
  display: flex;
  justify-content: center;
  align-items: center;
}

.qr-container {
  text-align: center;
  padding: var(--spacing-xl);
  background: var(--bg-white);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  border: 2px solid var(--bg-gray);
}

.qr-image {
  width: 200px;
  height: 200px;
  border-radius: var(--radius-lg);
  margin-bottom: var(--spacing-md);
  box-shadow: var(--shadow-md);
}

.qr-text {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--primary-color);
  margin: 0;
}

/* ===== Features Section ===== */
.features {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-light);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-xl);
}

.feature-card {
  background: var(--bg-white);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: var(--transition-normal);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.feature-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto var(--spacing-md);
  background: var(--gradient-primary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  color: var(--text-white);
}

.feature-card h3 {
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.feature-card p {
  color: var(--text-muted);
  line-height: 1.6;
}

/* ===== Statistics Section ===== */
.stats {
  padding: var(--spacing-2xl) 0;
  background: var(--gradient-primary);
  color: var(--text-white);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-xl);
}

.stat-item {
  text-align: center;
}

.stat-number {
  font-size: 3rem;
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
}

.stat-label {
  font-size: 1.1rem;
  opacity: 0.9;
}

/* ===== Download Section ===== */
.download {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-white);
}

.download-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  align-items: center;
}

.download-text h2 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.download-text p {
  font-size: 1.2rem;
  color: var(--text-muted);
  margin-bottom: var(--spacing-xl);
}

.download-features {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.download-feature {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.download-feature i {
  color: var(--success-color);
  font-size: 1.2rem;
}

.download-options {
  text-align: center;
}

.qr-section {
  margin-bottom: var(--spacing-xl);
}

.qr-code {
  width: 200px;
  height: 200px;
  background: var(--bg-light);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--spacing-md);
  border: 2px dashed var(--text-light);
}

.qr-placeholder {
  font-size: 4rem;
  opacity: 0.5;
}

.download-buttons {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.download-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-white);
  border: 2px solid var(--bg-gray);
  border-radius: var(--radius-lg);
  transition: var(--transition-normal);
}

.download-btn:hover {
  border-color: var(--primary-color);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.download-btn i {
  font-size: 2rem;
}

.download-btn.wechat i { color: #07c160; }
.download-btn.app-store i { color: #000; }

.download-btn div {
  text-align: left;
}

.btn-title {
  display: block;
  font-weight: 600;
  color: var(--text-primary);
}

.btn-subtitle {
  display: block;
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* ===== About Section ===== */
.about {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-light);
}

.about-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  align-items: center;
}

.about-text h2 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.about-intro {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xl);
  line-height: 1.7;
}

.about-features {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.about-feature h4 {
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
}

.about-feature p {
  color: var(--text-muted);
}

.about-illustration {
  position: relative;
  width: 400px;
  height: 400px;
  margin: 0 auto;
}

.illustration-bg {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--gradient-primary);
  border-radius: 50%;
  opacity: 0.1;
  animation: float 3s ease-in-out infinite;
}

.illustration-content {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 8rem;
  color: var(--primary-color);
  opacity: 0.7;
}

@keyframes float {
  0%, 100% { transform: translateY(0px); }
  50% { transform: translateY(-20px); }
}

/* ===== Footer ===== */
.footer {
  background: var(--bg-dark);
  color: var(--text-white);
  padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

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

.footer-brand {
  max-width: 300px;
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-md);
}

.logo-icon {
  font-size: 2rem;
}

.footer-brand p {
  color: var(--text-light);
  margin-bottom: var(--spacing-md);
}

.social-links {
  display: flex;
  gap: var(--spacing-sm);
}

.social-link {
  width: 40px;
  height: 40px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition-normal);
}

.social-link:hover {
  background: var(--primary-color);
  transform: translateY(-2px);
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-xl);
}

.footer-column h4 {
  margin-bottom: var(--spacing-md);
  color: var(--text-white);
}

.footer-column a,
.footer-column p {
  color: var(--text-light);
  display: block;
  margin-bottom: var(--spacing-xs);
  transition: var(--transition-normal);
}

.footer-column a:hover {
  color: var(--text-white);
}

.footer-bottom {
  text-align: center;
  padding-top: var(--spacing-lg);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  color: var(--text-light);
}

.footer-bottom p {
  margin-bottom: var(--spacing-xs);
}

/* ===== Back to Top Button ===== */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: var(--gradient-primary);
  color: var(--text-white);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  transition: var(--transition-normal);
  opacity: 0;
  visibility: hidden;
  z-index: var(--z-tooltip);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    background: var(--bg-white);
    flex-direction: column;
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition-normal);
  }

  .nav-menu.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }

  .nav-toggle.active span:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
  }

  .hero-content {
    grid-template-columns: 1fr;
    text-align: center;
    gap: var(--spacing-xl);
  }

  .qr-container {
    padding: var(--spacing-lg);
  }

  .qr-image {
    width: 150px;
    height: 150px;
  }

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

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

  .download-content,
  .about-content {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .footer-content {
    grid-template-columns: 1fr;
  }

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

  .hero-actions {
    justify-content: center;
  }

  .download-buttons {
    max-width: 300px;
    margin: 0 auto;
  }
}

@media (max-width: 480px) {
  :root {
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
  }

  .container {
    padding: 0 var(--spacing-sm);
  }

  .hero-title {
    font-size: 2.5rem;
  }

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

  .btn {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.9rem;
  }

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

  .stat-number {
    font-size: 2.5rem;
  }

  .footer-links {
    grid-template-columns: 1fr;
  }

  .qr-container {
    padding: var(--spacing-md);
  }

  .qr-image {
    width: 120px;
    height: 120px;
  }

  .qr-text {
    font-size: 1rem;
  }

  .about-illustration {
    width: 300px;
    height: 300px;
  }

  .illustration-content {
    font-size: 6rem;
  }
}

/* ===== Accessibility ===== */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Focus styles for accessibility */
.btn:focus,
.nav-link:focus,
.nav-toggle:focus,
.back-to-top:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --text-primary: #000000;
    --text-secondary: #000000;
    --bg-white: #ffffff;
    --bg-light: #f0f0f0;
  }
}