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

:root {
  --primary-color: #4A90A4;
  --primary-dark: #2C5F6B;
  --primary-light: #6BA8B8;
  --text-color: #2C3E50;
  --text-light: #5A6C7D;
  --bg-color: #ffffff;
  --bg-light: #F5F8F9;
  --border-color: #D4E4E8;
  --error-color: #dc2626;
  --success-color: #16a34a;
  --spacing-unit: 1rem;
  --max-width: 1200px;
  --transition: all 0.3s ease;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--bg-color);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Skip to main content link for accessibility */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--primary-color);
  color: white;
  padding: 8px;
  text-decoration: none;
  z-index: 100;
}

.skip-link:focus {
  top: 0;
}

/* Header and Navigation */
header {
  background-color: var(--bg-color);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-unit);
  display: flex;
  justify-content: space-between;
  align-items: center;
  min-height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  transition: var(--transition);
}

.logo img,
.logo svg {
  height: 50px;
  width: auto;
  max-width: 250px;
  object-fit: contain;
}

.logo-text {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
  font-family: Arial, 'Microsoft YaHei', '微软雅黑', sans-serif;
}

.logo:hover,
.logo:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

.logo:hover .logo-text,
.logo:focus .logo-text {
  color: var(--primary-dark);
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-unit);
}

.nav-menu a {
  color: var(--text-color);
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  transition: var(--transition);
  display: block;
}

.nav-menu a:hover,
.nav-menu a:focus {
  background-color: var(--bg-light);
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

.nav-menu a.active {
  color: var(--primary-color);
  font-weight: 600;
}

.language-switcher {
  padding: 0.5rem 1rem;
  border: 2px solid var(--border-color);
  border-radius: 4px;
  background-color: var(--bg-color);
  color: var(--text-color);
  font-size: 0.9rem;
  font-family: inherit;
  cursor: pointer;
  transition: var(--transition);
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%234A90A4' d='M6 9L1 4h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.5rem center;
  padding-right: 2rem;
}

.language-switcher:hover,
.language-switcher:focus {
  border-color: var(--primary-color);
  outline: none;
  box-shadow: 0 0 0 3px rgba(74, 144, 164, 0.1);
}

.menu-toggle {
  display: none;
  flex-direction: column;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  gap: 4px;
}

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

.menu-toggle:hover span,
.menu-toggle:focus span {
  background-color: var(--primary-color);
}

.menu-toggle:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* Main Content */
main {
  flex: 1;
}

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

/* Hero Section */
.hero {
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
  color: white;
  padding: 4rem var(--spacing-unit);
  text-align: center;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  font-weight: 700;
}

.hero-subtitle {
  font-size: 1.25rem;
  margin-bottom: 2rem;
  opacity: 0.9;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.75rem 2rem;
  text-decoration: none;
  border-radius: 6px;
  font-weight: 600;
  transition: var(--transition);
  border: none;
  cursor: pointer;
  font-size: 1rem;
  font-family: inherit;
}

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

.btn-primary:hover,
.btn-primary:focus {
  background-color: var(--bg-light);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
  outline: 2px solid white;
  outline-offset: 2px;
}

.btn-primary:active {
  transform: translateY(0);
}

/* Features Section */
.features {
  padding: 4rem var(--spacing-unit);
  background-color: var(--bg-light);
}

.features h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 3rem;
  color: var(--text-color);
}

.features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

.feature-card {
  background: white;
  padding: 2rem;
  border-radius: 8px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.feature-card h3 {
  color: var(--primary-color);
  margin-bottom: 1rem;
  font-size: 1.5rem;
}

.feature-card p {
  color: var(--text-light);
}

/* Page Header */
.page-header {
  background-color: var(--bg-light);
  padding: 3rem var(--spacing-unit);
  text-align: center;
}

.page-header h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  color: var(--text-color);
}

.page-header p {
  font-size: 1.125rem;
  color: var(--text-light);
}

/* Content Sections */
.content-section {
  padding: 3rem var(--spacing-unit);
}

.content-section h2 {
  font-size: 2rem;
  margin-bottom: 1.5rem;
  color: var(--text-color);
}

.content-section p {
  margin-bottom: 1rem;
  color: var(--text-light);
  max-width: 800px;
}

.values-list {
  list-style: none;
  max-width: 800px;
}

.values-list li {
  padding: 1rem 0;
  border-bottom: 1px solid var(--border-color);
}

.values-list li:last-child {
  border-bottom: none;
}

.values-list strong {
  color: var(--primary-color);
  display: block;
  margin-bottom: 0.5rem;
}

/* Contact Form */
.contact-form {
  max-width: 600px;
  margin: 0 auto;
  background: white;
  padding: 2rem;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.form-group {
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: var(--text-color);
}

.required {
  color: var(--error-color);
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.75rem;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-size: 1rem;
  font-family: inherit;
  transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group input:invalid:not(:focus):not(:placeholder-shown),
.form-group textarea:invalid:not(:focus):not(:placeholder-shown) {
  border-color: var(--error-color);
}

.error-message {
  display: block;
  color: var(--error-color);
  font-size: 0.875rem;
  margin-top: 0.5rem;
  min-height: 1.25rem;
}

.success-message {
  background-color: #d1fae5;
  color: var(--success-color);
  padding: 1rem;
  border-radius: 6px;
  margin-bottom: 1rem;
  border: 1px solid var(--success-color);
}

/* Footer */
footer {
  background-color: var(--text-color);
  color: white;
  padding: 1.5rem var(--spacing-unit);
  margin-top: auto;
}

footer .footer-content {
  max-width: var(--max-width);
  margin: 0 auto;
}

footer .footer-main {
  text-align: center;
  margin-bottom: 1rem;
}

footer .footer-copyright {
  font-size: 0.85rem;
  margin-bottom: 0.75rem;
  opacity: 0.9;
}

footer .footer-company {
  font-size: 0.85rem;
  line-height: 1.6;
}

footer .company-name {
  display: block;
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  opacity: 1;
}

footer .company-details {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 0.5rem;
  opacity: 0.85;
}

footer .company-details span:not(.separator) {
  white-space: nowrap;
}

footer .separator {
  color: rgba(255, 255, 255, 0.4);
  margin: 0 0.25rem;
  user-select: none;
}

footer .footer-bottom {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.8rem;
  opacity: 0.8;
  padding-top: 0.75rem;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}

footer .footer-bottom .sitemap-link {
  color: rgba(255, 255, 255, 0.8);
  text-decoration: none;
  transition: opacity 0.3s ease;
}

footer .footer-bottom .sitemap-link:hover {
  opacity: 1;
  text-decoration: underline;
}

/* Breadcrumb Navigation (hidden but available for SEO) */
.breadcrumb {
  display: none;
}

.breadcrumb ol {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap;
}

.breadcrumb li {
  display: inline;
}

.breadcrumb li:not(:last-child)::after {
  content: " / ";
  margin: 0 0.5rem;
  color: var(--text-light);
}

.breadcrumb a {
  color: var(--primary-color);
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

/* Screen Reader Only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Responsive Design - Tablet */
@media (min-width: 768px) {
  :root {
    --spacing-unit: 2rem;
  }

  .hero h1 {
    font-size: 3rem;
  }

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

  .nav-menu {
    gap: 1.5rem;
  }
}

/* Responsive Design - Desktop */
@media (min-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .hero {
    padding: 6rem var(--spacing-unit);
  }

  .content-section {
    padding: 4rem var(--spacing-unit);
  }
}

/* Mobile Navigation */
@media (max-width: 767px) {
  .menu-toggle {
    display: flex;
  }

  .logo img,
  .logo svg {
    height: 40px;
    max-width: 200px;
    object-fit: contain;
  }

  .nav-menu {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background-color: var(--bg-color);
    flex-direction: column;
    padding: var(--spacing-unit);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transform: translateX(-100%);
    transition: transform 0.3s ease;
    z-index: 999;
  }

  .nav-menu.active {
    transform: translateX(0);
  }

  .nav-menu a {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
  }

  .nav-menu a:last-child {
    border-bottom: none;
  }

  .language-switcher {
    width: 100%;
    margin-top: 0.5rem;
    padding: 0.75rem;
  }

  .hero h1 {
    font-size: 2rem;
  }

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

  .page-header h1 {
    font-size: 2rem;
  }

  .contact-form {
    padding: 1.5rem;
  }

  /* Footer mobile styles */
  footer {
    padding: 1.25rem var(--spacing-unit);
  }

  footer .footer-copyright {
    font-size: 0.8rem;
    margin-bottom: 0.5rem;
  }

  footer .footer-company {
    font-size: 0.75rem;
  }

  footer .company-name {
    font-size: 0.85rem;
    margin-bottom: 0.4rem;
  }

  footer .company-details {
    flex-direction: column;
    gap: 0.3rem;
    align-items: flex-start;
    text-align: left;
  }

  footer .company-details .separator {
    display: none;
  }

  footer .footer-bottom {
    flex-direction: column;
    gap: 0.3rem;
    font-size: 0.75rem;
    padding-top: 0.5rem;
  }

  footer .footer-bottom .separator {
    display: none;
  }
}