/* 
 * 谷歌浏览器仿制页面 - 现代化UI样式
 * 设计风格：现代化、简洁、Material Design风格
 */

/* ===== 变量定义 ===== */
:root {
  /* 品牌颜色 */
  --primary-blue: #4285F4;
  --primary-green: #34A853;
  --primary-yellow: #FBBC04;
  --primary-red: #EA4335;
  --primary-dark: #1A1A1A;
  
  /* 辅助颜色 */
  --secondary-blue: #8AB4F8;
  --secondary-green: #81C995;
  --secondary-yellow: #FDD663;
  --secondary-red: #F28B82;
  
  /* 中性色 */
  --neutral-50: #F8F9FA;
  --neutral-100: #F1F3F4;
  --neutral-200: #E8EAED;
  --neutral-300: #DADCE0;
  --neutral-400: #BDC1C6;
  --neutral-500: #9AA0A6;
  --neutral-600: #80868B;
  --neutral-700: #5F6368;
  --neutral-800: #3C4043;
  --neutral-900: #202124;
  
  /* 阴影 */
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.12);
  --shadow-xl: 0 20px 50px rgba(0, 0, 0, 0.15);
  
  /* 过渡效果 */
  --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  
  /* 圆角 */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;
  
  /* 间距 */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 80px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', 'SF Pro Display', -apple-system, BlinkMacSystemFont, sans-serif;
  color: var(--neutral-900);
  background-color: #FFFFFF;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

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

h1 {
  font-size: 3.5rem;
  letter-spacing: -0.02em;
}

h2 {
  font-size: 2.5rem;
  letter-spacing: -0.01em;
}

h3 {
  font-size: 1.75rem;
}

p {
  margin-bottom: var(--space-md);
  color: var(--neutral-700);
  font-size: 1.125rem;
  line-height: 1.7;
}

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

ul {
  list-style-position: inside;
  margin-bottom: var(--space-md);
}

li {
  margin-bottom: var(--space-sm);
  color: var(--neutral-700);
}

/* ===== 按钮样式 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-xl);
  border-radius: var(--radius-lg);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  border: none;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.btn::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 5px;
  height: 5px;
  background: rgba(255, 255, 255, 0.5);
  opacity: 0;
  border-radius: 100%;
  transform: scale(1, 1) translate(-50%);
  transform-origin: 50% 50%;
}

.btn:focus:not(:active)::after {
  animation: ripple 1s ease-out;
}

@keyframes ripple {
  0% {
    transform: scale(0, 0);
    opacity: 0.5;
  }
  20% {
    transform: scale(25, 25);
    opacity: 0.3;
  }
  100% {
    opacity: 0;
    transform: scale(40, 40);
  }
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-blue) 0%, #3367D6 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #3367D6 0%, var(--primary-blue) 100%);
}

.btn-primary:active {
  transform: translateY(-1px);
}

.btn-secondary {
  background: transparent;
  color: var(--primary-blue);
  border: 1px solid var(--neutral-200);
}

.btn-secondary:hover {
  border-color: var(--primary-blue);
  background: rgba(66, 133, 244, 0.1);
}

.btn-large {
  padding: var(--space-lg) var(--space-2xl);
  font-size: 1.125rem;
}

.btn-xl {
  padding: var(--space-xl) var(--space-3xl);
  font-size: 1.25rem;
  border-radius: var(--radius-xl);
}

/* ===== 操作系统特定按钮颜色 ===== */
.btn-windows {
  background: linear-gradient(135deg, #4285F4 0%, #3367D6 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-windows:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #3367D6 0%, #4285F4 100%);
}

.btn-macos {
  background: linear-gradient(135deg, #1D1D1F 0%, #000000 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-macos:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #000000 0%, #1D1D1F 100%);
}

.btn-linux {
  background: linear-gradient(135deg, #F1502F 0%, #E95420 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-linux:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #E95420 0%, #F1502F 100%);
}

.btn-android {
  background: linear-gradient(135deg, #3DDC84 0%, #34A853 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-android:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #34A853 0%, #3DDC84 100%);
}

.btn-ios {
  background: linear-gradient(135deg, #007AFF 0%, #0056CC 100%);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-ios:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  background: linear-gradient(135deg, #0056CC 0%, #007AFF 100%);
}

/* ===== 下载卡片网格样式 ===== */
.download-grid-section {
  padding: var(--space-4xl) 0;
  background: white;
}

.download-grid-section .section-header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-xl);
  margin: var(--space-2xl) 0;
}

.download-card {
  background: white;
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-md);
  border: 2px solid var(--neutral-200);
  transition: all var(--transition-normal);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

.download-card:hover {
  transform: translateY(-10px);
  box-shadow: var(--shadow-xl);
  border-color: var(--primary-blue);
}

.os-icon {
  font-size: 3rem;
  margin-bottom: var(--space-lg);
  color: var(--primary-blue);
}

.download-card h3 {
  color: var(--neutral-900);
  margin-bottom: var(--space-sm);
}

.download-card p {
  color: var(--neutral-700);
  margin-bottom: var(--space-sm);
  font-size: 0.95rem;
}

.file-size {
  background: var(--neutral-100);
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  color: var(--neutral-600);
  margin: var(--space-sm) 0;
}

.download-card .btn {
  margin-top: var(--space-md);
  width: 100%;
  justify-content: center;
}

.download-note {
  text-align: center;
  margin-top: var(--space-2xl);
  color: var(--neutral-600);
  font-size: 0.95rem;
}

.download-note i {
  color: var(--primary-blue);
  margin-right: var(--space-xs);
}

/* ===== 导航栏 ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(0, 0, 0, 0.05);
  z-index: 1000;
  padding: var(--space-md) 0;
  transition: all var(--transition-normal);
}

.navbar.scrolled {
  padding: var(--space-sm) 0;
  box-shadow: var(--shadow-sm);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

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

.chrome-logo {
  width: 40px;
  height: 40px;
  position: relative;
}

.chrome-logo.small {
  width: 32px;
  height: 32px;
}

.chrome-gradient {
  width: 100%;
  height: 100%;
  background: conic-gradient(
    from 0deg,
    var(--primary-red) 0deg,
    var(--primary-yellow) 90deg,
    var(--primary-green) 180deg,
    var(--primary-blue) 270deg,
    var(--primary-red) 360deg
  );
  border-radius: 50%;
  position: relative;
}

.chrome-gradient::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 16px;
  height: 16px;
  background: white;
  border-radius: 50%;
}

.brand-text {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--neutral-900);
}

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

.nav-link {
  color: var(--neutral-700);
  font-weight: 500;
  padding: var(--space-xs) 0;
  position: relative;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary-blue);
  transition: width var(--transition-normal);
}

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

.nav-link:hover::after {
  width: 100%;
}

.nav-btn {
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--radius-md);
  background: var(--primary-blue);
  color: white;
  font-weight: 500;
  transition: all var(--transition-normal);
}

.nav-btn:hover {
  background: #3367D6;
  transform: translateY(-2px);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--neutral-700);
  cursor: pointer;
  padding: var(--space-sm);
}

/* ===== 英雄区域 ===== */
.hero {
  padding-top: 120px;
  padding-bottom: var(--space-4xl);
  background: linear-gradient(135deg, #F8F9FA 0%, #FFFFFF 100%);
  overflow: hidden;
}

.hero .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-2xl);
  align-items: center;
}

.hero-title {
  font-size: 3rem;
  color: var(--neutral-900);
  margin-bottom: var(--space-md);
  line-height: 1.1;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--neutral-700);
  margin-bottom: var(--space-xl);
  max-width: 600px;
}

.hero-actions {
  display: flex;
  gap: var(--space-md);
  margin-bottom: var(--space-2xl);
}

.hero-stats {
  display: flex;
  gap: var(--space-2xl);
}

.stat {
  display: flex;
  flex-direction: column;
}

.stat-number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary-blue);
  line-height: 1;
}

.stat-label {
  font-size: 0.875rem;
  color: var(--neutral-600);
  margin-top: var(--space-xs);
}

.hero-visual {
  position: relative;
}

.browser-mockup {
  background: white;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  overflow: hidden;
  transform: perspective(1000px) rotateY(-5deg) rotateX(5deg);
  transition: transform var(--transition-normal);
}

.browser-mockup:hover {
  transform: perspective(1000px) rotateY(0) rotateX(0);
}

.browser-header {
  background: var(--neutral-100);
  padding: var(--space-md);
  display: flex;
  align-items: center;
}

.browser-dots {
  display: flex;
  gap: var(--space-xs);
}

.dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

.dot.red { background: var(--primary-red); }
.dot.yellow { background: var(--primary-yellow); }
.dot.green { background: var(--primary-green); }

.browser-content {
  padding: var(--space-xl);
}

.url-bar {
  background: var(--neutral-50);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  font-family: 'SF Mono', 'Roboto Mono', monospace;
  font-size: 0.875rem;
  color: var(--neutral-600);
  margin-bottom: var(--space-xl);
}

.page-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.content-line {
  height: 12px;
  background: var(--neutral-100);
  border-radius: var(--radius-sm);
}

.content-line.short { width: 60%; }
.content-line.medium { width: 80%; }

/* ===== 特性区域 ===== */
.features {
  padding: var(--space-4xl) 0;
  background: var(--neutral-50);
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.section-header h2 {
  color: var(--neutral-900);
  margin-bottom: var(--space-md);
}

.section-header p {
  color: var(--neutral-600);
  max-width: 600px;
  margin: 0 auto;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
}

.feature-card {
  background: white;
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
  border: 1px solid transparent;
}

.feature-card:hover {
  transform: translateY(-10px);
  box-shadow: var(--shadow-xl);
  border-color: var(--neutral-200);
}

.feature-icon {
  width: 64px;
  height: 64px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
  font-size: 1.75rem;
  color: white;
}

.feature-icon.speed {
  background: linear-gradient(135deg, var(--primary-blue) 0%, var(--secondary-blue) 100%);
}

.feature-icon.security {
  background: linear-gradient(135deg, var(--primary-green) 0%, var(--secondary-green) 100%);
}

.feature-icon.sync {
  background: linear-gradient(135deg, var(--primary-yellow) 0%, var(--secondary-yellow) 100%);
}

.feature-icon.extensions {
  background: linear-gradient(135deg, var(--primary-red) 0%, var(--secondary-red) 100%);
}

.feature-card h3 {
  margin-bottom: var(--space-md);
  color: var(--neutral-900);
}

.feature-card p {
  font-size: 1rem;
  color: var(--neutral-700);
}

/* ===== 下载区域 ===== */
.download-section {
  padding: var(--space-4xl) 0;
  background: linear-gradient(135deg, #E8F0FE 0%, #F1F8FF 100%);
}

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

.download-info h2 {
  color: var(--neutral-900);
  margin-bottom: var(--space-md);
}

.download-desc {
  font-size: 1.25rem;
  margin-bottom: var(--space-xl);
  color: var(--neutral-700);
}

.version-card {
  background: white;
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  margin-bottom: var(--space-xl);
}

.version-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-lg);
}

.version-header h3 {
  color: var(--neutral-900);
  margin-bottom: 0;
}

.version-badge {
  background: var(--primary-green);
  color: white;
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 600;
}

.version-details {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.detail {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--neutral-700);
}

.detail i {
  color: var(--primary-blue);
  width: 20px;
}

.download-note {
  color: var(--neutral-600);
  font-size: 0.875rem;
  margin-top: var(--space-xl);
  margin-bottom: var(--space-lg);
  text-align: center;
}

.download-visual .platforms {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
}

.platform {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-lg);
  background: white;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
}

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

.platform i {
  font-size: 2rem;
  color: var(--neutral-700);
}

.platform span {
  font-weight: 500;
  color: var(--neutral-800);
}

/* ===== 系统要求 ===== */
.requirements {
  padding: var(--space-4xl) 0;
  background: white;
}

.requirements-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--space-xl);
}

.req-card {
  background: var(--neutral-50);
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  border-left: 4px solid var(--primary-blue);
  transition: all var(--transition-normal);
}

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

.req-icon {
  font-size: 2rem;
  color: var(--primary-blue);
  margin-bottom: var(--space-md);
}

.req-card h3 {
  color: var(--neutral-900);
  margin-bottom: var(--space-md);
}

.req-card ul {
  list-style: none;
  padding: 0;
}

.req-card li {
  padding: var(--space-xs) 0;
  border-bottom: 1px solid var(--neutral-200);
  color: var(--neutral-700);
}

.req-card li:last-child {
  border-bottom: none;
}

/* ===== 常见问题 ===== */
.faq {
  padding: var(--space-4xl) 0;
  background: var(--neutral-50);
}

.faq-grid {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  background: white;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
}

.faq-item.active {
  box-shadow: var(--shadow-lg);
}

.faq-question {
  padding: var(--space-xl);
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  background: white;
}

.faq-question h3 {
  color: var(--neutral-900);
  margin-bottom: 0;
  font-size: 1.125rem;
}

.faq-question i {
  color: var(--neutral-500);
  transition: transform var(--transition-normal);
}

.faq-item.active .faq-question i {
  transform: rotate(180deg);
}

.faq-answer {
  padding: 0 var(--space-xl);
  max-height: 0;
  overflow: hidden;
  transition: all var(--transition-normal);
  background: white;
  border-top: 1px solid transparent;
}

.faq-item.active .faq-answer {
  padding: var(--space-xl);
  max-height: 300px;
  border-top-color: var(--neutral-200);
}

.faq-answer p {
  margin-bottom: 0;
  color: var(--neutral-700);
}

/* ===== 页脚 ===== */
.footer {
  background: var(--neutral-900);
  color: white;
  padding: var(--space-4xl) 0 var(--space-xl);
}

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

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.brand-info h3 {
  color: white;
  font-size: 1.5rem;
  margin-bottom: var(--space-xs);
}

.brand-info p {
  color: var(--neutral-400);
  font-size: 0.875rem;
  margin-bottom: 0;
}

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

.link-group h4 {
  color: white;
  font-size: 1.125rem;
  margin-bottom: var(--space-md);
}

.link-group a {
  display: block;
  color: var(--neutral-400);
  font-size: 0.875rem;
  padding: var(--space-xs) 0;
  transition: color var(--transition-fast);
}

.link-group a:hover {
  color: white;
}

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

.footer-bottom p {
  color: var(--neutral-500);
  font-size: 0.875rem;
  margin-bottom: 0;
}

/* ===== 响应式设计 ===== */
@media (max-width: 1024px) {
  h1 { font-size: 2.75rem; }
  h2 { font-size: 2.25rem; }
  
  .hero .container,
  .download-content {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .hero-actions {
    justify-content: center;
  }
  
  .hero-stats {
    justify-content: center;
  }
  
  .browser-mockup {
    max-width: 500px;
    margin: 0 auto;
  }
}

@media (max-width: 768px) {
  h1 { font-size: 2.25rem; }
  h2 { font-size: 1.875rem; }
  h3 { font-size: 1.5rem; }
  
  .container {
    padding: 0 var(--space-md);
  }
  
  .nav-menu {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    flex-direction: column;
    padding: var(--space-xl);
    box-shadow: var(--shadow-xl);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 999;
    max-height: calc(100vh - 70px);
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }

  .nav-menu.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .nav-toggle {
    display: block;
  }
  
  .features-grid,
  .requirements-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-content {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .footer-links {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }
  
  .download-visual .platforms {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .download-note {
    margin-top: var(--space-lg);
    margin-bottom: var(--space-md);
  }
}

@media (max-width: 480px) {
  h1 { font-size: 2rem; }
  h2 { font-size: 1.625rem; }
  
  .hero {
    padding-top: 100px;
  }
  
  .hero-stats {
    flex-direction: column;
    gap: var(--space-lg);
  }
  
  .hero-actions {
    flex-direction: column;
    align-items: center;
  }
  
  .btn {
    width: 100%;
  }
  
  .download-visual .platforms {
    grid-template-columns: 1fr;
  }
  
  .download-note {
    margin-top: var(--space-md);
    margin-bottom: var(--space-md);
  }
}

/* ===== 动画效果 ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-fadeInUp {
  animation: fadeInUp 0.6s cubic-bezier(0.4, 0, 0.2, 1) both;
}

/* ===== 工具类 ===== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-1 { margin-top: var(--space-sm); }
.mt-2 { margin-top: var(--space-md); }
.mt-3 { margin-top: var(--space-lg); }
.mt-4 { margin-top: var(--space-xl); }
.mt-5 { margin-top: var(--space-2xl); }

.mb-1 { margin-bottom: var(--space-sm); }
.mb-2 { margin-bottom: var(--space-md); }
.mb-3 { margin-bottom: var(--space-lg); }
.mb-4 { margin-bottom: var(--space-xl); }
.mb-5 { margin-bottom: var(--space-2xl); }

.ml-1 { margin-left: var(--space-sm); }
.ml-2 { margin-left: var(--space-md); }
.ml-3 { margin-left: var(--space-lg); }
.ml-4 { margin-left: var(--space-xl); }

.mr-1 { margin-right: var(--space-sm); }
.mr-2 { margin-right: var(--space-md); }
.mr-3 { margin-right: var(--space-lg); }
.mr-4 { margin-right: var(--space-xl); }

.p-1 { padding: var(--space-sm); }
.p-2 { padding: var(--space-md); }
.p-3 { padding: var(--space-lg); }
.p-4 { padding: var(--space-xl); }
.p-5 { padding: var(--space-2xl); }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: var(--space-sm); }
.gap-2 { gap: var(--space-md); }
.gap-3 { gap: var(--space-lg); }

.grid { display: grid; }
.grid-cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid-cols-3 { grid-template-columns: repeat(3, 1fr); }

.w-full { width: 100%; }
.h-full { height: 100%; }

.relative { position: relative; }
.absolute { position: absolute; }

.hidden { display: none; }
.block { display: block; }

.rounded-lg { border-radius: var(--radius-lg); }
.rounded-xl { border-radius: var(--radius-xl); }

.shadow-md { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }

.transition-normal { transition: all var(--transition-normal); }

/* ===== 性能优化 ===== */
.will-change-transform { will-change: transform; }
.will-change-opacity { will-change: opacity; }
.backface-visibility-hidden { backface-visibility: hidden; }

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

.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--primary-blue);
  color: white;
  padding: 8px 16px;
  border-radius: 0 0 4px 0;
  text-decoration: none;
  font-weight: 600;
  z-index: 1001;
  transition: top 0.3s ease;
}

.skip-link:focus {
  top: 0;
  outline: 2px solid white;
  outline-offset: -2px;
}

.focus-visible:focus-visible {
  outline: 2px solid var(--primary-blue);
  outline-offset: 2px;
}

/* ===== 现代滚动条 ===== */
::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: var(--neutral-100);
  border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb {
  background: var(--neutral-300);
  border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--neutral-400);
}

/* ===== 打印样式优化 ===== */
@media print {
  .navbar,
  .footer,
  .hero-actions,
  .download-section,
  .features,
  .requirements,
  .faq {
    display: none !important;
  }
  
  .container {
    max-width: 100% !important;
    padding: 0 !important;
  }
  
  body {
    background: white !important;
    color: black !important;
    font-size: 12pt !important;
    line-height: 1.5 !important;
  }
  
  h1, h2, h3 {
    page-break-after: avoid;
    page-break-inside: avoid;
  }
  
  p {
    page-break-inside: avoid;
  }
}