/* Modern CSS Variables */
:root {
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --accent-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
  --success-gradient: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);
  --warning-gradient: linear-gradient(135deg, #fa709a 0%, #fee140 100%);
  
  --bg-primary: #0f0f23;
  --bg-secondary: #1a1a2e;
  --bg-tertiary: #16213e;
  --bg-card: rgba(255, 255, 255, 0.05);
  --bg-card-hover: rgba(255, 255, 255, 0.1);
  
  --text-primary: #ffffff;
  --text-secondary: #b8b8d1;
  --text-muted: #6c7293;
  --text-accent: #667eea;
  
  --border-primary: rgba(255, 255, 255, 0.1);
  --border-secondary: rgba(255, 255, 255, 0.2);
  --border-accent: #667eea;
  
  --shadow-sm: 0 2px 4px 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, 0.15);
  --shadow-glow: 0 0 20px rgba(102, 126, 234, 0.3);
  
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* Global reset and base styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 100vh;
}

/* Background animation */
body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: 
    radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(118, 75, 162, 0.1) 0%, transparent 50%),
    radial-gradient(circle at 40% 80%, rgba(79, 172, 254, 0.1) 0%, transparent 50%);
  z-index: -1;
  animation: backgroundShift 20s ease-in-out infinite;
}

@keyframes backgroundShift {
  0%, 100% { transform: translateX(0) translateY(0); }
  33% { transform: translateX(-20px) translateY(-10px); }
  66% { transform: translateX(20px) translateY(10px); }
}

/* Navigation bar */
.modern-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(15, 15, 35, 0.95);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-primary);
  padding: 1rem 0;
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-brand i {
  font-size: 1.75rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: all var(--transition-normal);
  font-weight: 500;
  position: relative;
  overflow: hidden;
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-card);
  transform: translateY(-2px);
}

.nav-link.active {
  color: var(--text-primary);
  background: var(--bg-card);
  box-shadow: var(--shadow-glow);
}

.nav-link.active::before {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 30px;
  height: 2px;
  background: var(--primary-gradient);
  border-radius: 1px;
}

.nav-link::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: var(--primary-gradient);
  opacity: 0.1;
  transition: left var(--transition-normal);
}

.nav-link:hover::before {
  left: 0;
}

.nav-link.external {
  background: var(--primary-gradient);
  color: white;
  box-shadow: var(--shadow-glow);
}

.nav-link.external:hover {
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 10px 25px rgba(102, 126, 234, 0.4);
}

/* Mobile navigation styles */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 30px;
  height: 30px;
  cursor: pointer;
  transition: all var(--transition-normal);
}

.hamburger-line {
  width: 25px;
  height: 3px;
  background: var(--text-primary);
  margin: 3px 0;
  transition: all var(--transition-normal);
  border-radius: 2px;
}

.mobile-menu-toggle.active .hamburger-line:nth-child(1) {
  transform: rotate(45deg) translate(6px, 6px);
}

.mobile-menu-toggle.active .hamburger-line:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.active .hamburger-line:nth-child(3) {
  transform: rotate(-45deg) translate(6px, -6px);
}

.mobile-nav {
  position: fixed;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100vh;
  background: rgba(15, 15, 35, 0.95);
  backdrop-filter: blur(20px);
  z-index: 999;
  transition: left var(--transition-normal);
  display: flex;
  align-items: center;
  justify-content: center;
}

.mobile-nav.active {
  left: 0;
}

.mobile-nav-content {
  display: flex;
  flex-direction: column;
  gap: 2rem;
  text-align: center;
  padding: 2rem;
}

.mobile-nav-link {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 2rem;
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: var(--radius-lg);
  transition: all var(--transition-normal);
  font-weight: 500;
  font-size: 1.2rem;
  position: relative;
  overflow: hidden;
  min-width: 200px;
  justify-content: center;
}

.mobile-nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-card);
  transform: translateX(10px);
}

.mobile-nav-link.active {
  color: var(--text-primary);
  background: var(--primary-gradient);
  box-shadow: var(--shadow-glow);
}

.mobile-nav-link.external {
  background: var(--secondary-gradient);
  color: white;
  box-shadow: 0 10px 25px rgba(240, 147, 251, 0.3);
}

.mobile-nav-link.external:hover {
  transform: translateX(10px) scale(1.05);
  box-shadow: 0 15px 35px rgba(240, 147, 251, 0.4);
}

/* Main container */
.main-container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 8rem 2rem 4rem;
  position: relative;
}

/* Hero section */
.hero-section {
  text-align: center;
  margin-bottom: 4rem;
  position: relative;
}

.hero-content {
  position: relative;
  z-index: 2;
}

.hero-title {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 800;
  margin-bottom: 1.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.hero-title i {
  font-size: 0.8em;
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0px); }
  50% { transform: translateY(-10px); }
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
  line-height: 1.8;
}

/* Settings panel */
.settings-panel {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-bottom: 2rem;
  backdrop-filter: blur(20px);
  box-shadow: var(--shadow-lg);
  transition: all var(--transition-normal);
}

.settings-panel:hover {
  border-color: var(--border-secondary);
  box-shadow: var(--shadow-xl);
}

.panel-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-primary);
}

.panel-header i {
  font-size: 1.25rem;
  color: var(--text-accent);
}

.panel-header h3 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
}

.settings-grid {
  display: grid;
  gap: 2rem;
}

.setting-item {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.setting-label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.setting-label i {
  color: var(--text-accent);
  font-size: 1.1rem;
}

.setting-value {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-weight: 700;
  font-size: 1.1rem;
}

.slider-container {
  position: relative;
  margin: 1rem 0;
}

.modern-slider {
  width: 100%;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 4px;
  outline: none;
  -webkit-appearance: none;
  appearance: none;
  cursor: pointer;
  position: relative;
  z-index: 2;
}

.modern-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 24px;
  height: 24px;
  background: var(--primary-gradient);
  border-radius: 50%;
  cursor: pointer;
  box-shadow: var(--shadow-md);
  transition: all var(--transition-fast);
  border: 3px solid var(--bg-primary);
}

.modern-slider::-webkit-slider-thumb:hover {
  transform: scale(1.1);
  box-shadow: var(--shadow-glow);
}

.modern-slider::-moz-range-thumb {
  width: 24px;
  height: 24px;
  background: var(--primary-gradient);
  border-radius: 50%;
  cursor: pointer;
  border: 3px solid var(--bg-primary);
  box-shadow: var(--shadow-md);
}

.slider-track {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 4px;
  overflow: hidden;
}

.slider-fill {
  height: 100%;
  background: var(--primary-gradient);
  border-radius: 4px;
  transition: width var(--transition-normal);
  width: 0%;
}

.recommended-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--success-gradient);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 600;
  align-self: flex-start;
}

.format-selector {
  margin-top: 0.5rem;
}

.modern-select {
  width: 100%;
  padding: 1rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  cursor: pointer;
  transition: all var(--transition-normal);
}

.modern-select:focus {
  outline: none;
  border-color: var(--border-accent);
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

/* Upload area */
.upload-section {
  margin-bottom: 2rem;
}

.upload-area {
  position: relative;
  width: 100%;
  min-height: 300px;
  border: 2px dashed var(--border-primary);
  border-radius: var(--radius-lg);
  background: var(--bg-card);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  margin-bottom: 2rem;
  transition: all var(--transition-normal);
  cursor: pointer;
  overflow: hidden;
}

.upload-area::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--primary-gradient);
  opacity: 0;
  transition: opacity var(--transition-normal);
  z-index: 1;
}

.upload-area:hover {
  border-color: var(--border-accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow-xl);
}

.upload-area:hover::before {
  opacity: 0.05;
}

.upload-area.drag-over {
  border-color: var(--border-accent);
  border-style: solid;
  background: rgba(102, 126, 234, 0.1);
  transform: scale(1.02);
}

.upload-area input[type="file"] {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  opacity: 0;
  cursor: pointer;
  z-index: 3;
}

.upload-content {
  position: relative;
  z-index: 2;
  text-align: center;
  pointer-events: none;
}

.upload-icon {
  font-size: 4rem;
  margin-bottom: 1.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.upload-text h3 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.upload-text p {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.upload-hint {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.upload-hint i {
  color: var(--text-accent);
}

.error-message {
  color: #ff6b6b;
  margin-top: 1rem;
  font-weight: 500;
  display: none;
}

/* 压缩按钮 */
.compress-btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1.25rem 3rem;
  background: var(--primary-gradient);
  color: white;
  border: none;
  border-radius: var(--radius-lg);
  font-size: 1.125rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition-normal);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  width: 100%;
  justify-content: center;
}

.compress-btn:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-xl), var(--shadow-glow);
}

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

.btn-shine {
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: left 0.5s;
}

.compress-btn:hover .btn-shine {
  left: 100%;
}

/* 进度条 */
.progress-section {
  margin-bottom: 2rem;
}

.progress-bar {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  backdrop-filter: blur(20px);
  display: none;
}

.progress-track {
  width: 100%;
  height: 12px;
  background: var(--bg-secondary);
  border-radius: 6px;
  overflow: hidden;
  margin-bottom: 1rem;
}

.progress-fill {
  height: 100%;
  background: var(--primary-gradient);
  border-radius: 6px;
  transition: width var(--transition-normal);
  width: 0%;
  position: relative;
}

.progress-fill::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
  animation: shimmer 2s infinite;
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

.progress-text {
  text-align: center;
  font-weight: 600;
  color: var(--text-primary);
}

/* 文件信息面板 */
.file-info-panel {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-bottom: 2rem;
  backdrop-filter: blur(20px);
  display: none;
}

.info-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-primary);
}

.info-header i {
  font-size: 1.25rem;
  color: var(--text-accent);
}

.info-header h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
}

.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.5rem;
}

.info-item {
  text-align: center;
  padding: 1.5rem;
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-primary);
  transition: all var(--transition-normal);
}

.info-item:hover {
  transform: translateY(-2px);
  border-color: var(--border-secondary);
}

.info-item.highlight {
  background: var(--primary-gradient);
  border: none;
  color: white;
}

.info-label {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  font-weight: 500;
}

.info-item.highlight .info-label {
  color: rgba(255, 255, 255, 0.8);
}

.info-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.info-item.highlight .info-value {
  color: white;
}

/* 下载区域 */
.download-section {
  margin-bottom: 2rem;
}

.download-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1.25rem 3rem;
  background: var(--success-gradient);
  color: white;
  text-decoration: none;
  border-radius: var(--radius-lg);
  font-size: 1.125rem;
  font-weight: 700;
  transition: all var(--transition-normal);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  width: 100%;
  justify-content: center;
  position: relative;
}

.download-btn:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-xl);
  color: white;
}

.download-btn .btn-shine {
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: left 0.5s;
}

.download-btn:hover .btn-shine {
  left: 100%;
}

/* 预览区域 */
.preview-section {
  margin-bottom: 2rem;
}

.preview-container {
  position: relative;
  display: inline-block;
  max-width: 100%;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--border-primary);
  transition: all var(--transition-normal);
}

.preview-container:hover {
  transform: scale(1.02);
  box-shadow: var(--shadow-xl), var(--shadow-glow);
}

.preview-image {
  max-width: 100%;
  display: block;
  transition: all var(--transition-normal);
}

.preview-overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.7);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  color: white;
  font-weight: 600;
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.preview-container:hover .preview-overlay {
  opacity: 1;
}

.preview-overlay i {
  font-size: 2rem;
  color: #4ade80;
}

.preview-overlay span {
  font-size: 1rem;
}

/* 语言切换 */
.language-switcher {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  margin-top: 3rem;
  padding: 1rem;
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-primary);
  backdrop-filter: blur(20px);
}

.lang-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  transition: all var(--transition-normal);
}

.lang-link:hover,
.lang-link.active {
  color: var(--text-primary);
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.lang-separator {
  color: var(--text-muted);
  font-weight: 300;
}

/* 响应式设计 */
@media (max-width: 768px) {
  .main-container {
    padding: 6rem 1rem 2rem;
  }
  
  .nav-container {
    padding: 0 1rem;
  }
  
  .nav-brand {
    font-size: 1.25rem;
  }
  
  /* Mobile navigation styles */
  .desktop-nav {
    display: none;
  }
  
  .mobile-menu-toggle {
    display: flex;
  }
  
  .nav-links {
    display: none;
  }
  
  .hero-title {
    font-size: 2.5rem;
    flex-direction: column;
    gap: 0.5rem;
  }
  
  .hero-subtitle {
    font-size: 1rem;
  }
  
  .settings-panel,
  .file-info-panel {
    padding: 1.5rem;
  }
  
  .settings-grid {
    gap: 1.5rem;
  }
  
  .info-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  
  .upload-area {
    min-height: 250px;
  }
  
  .upload-icon {
    font-size: 3rem;
  }
  
  .compress-btn,
  .download-btn {
    padding: 1rem 2rem;
    font-size: 1rem;
  }
}

@media (max-width: 480px) {
  .main-container {
    padding: 5rem 0.5rem 2rem;
  }
  
  .nav-container {
    padding: 0 0.5rem;
  }
  
  .hero-title {
    font-size: 2rem;
  }
  
  .settings-panel,
  .file-info-panel {
    padding: 1rem;
    margin: 0 0.5rem 1rem;
  }
  
  .upload-area {
    margin: 0 0.5rem 1rem;
  }
  
  .language-switcher {
    margin: 2rem 0.5rem 0;
  }
}

/* 动画和过渡效果 */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.settings-panel,
.upload-area,
.file-info-panel {
  animation: fadeInUp 0.6s ease-out;
}

.hero-section {
  animation: fadeIn 1s ease-out;
}

/* 滚动条样式 */
::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--primary-gradient);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--accent-gradient);
}

/* 选择文本样式 */
::selection {
  background: rgba(102, 126, 234, 0.3);
  color: var(--text-primary);
}

/* 焦点样式 */
*:focus {
  outline: 2px solid var(--border-accent);
  outline-offset: 2px;
}

/* 帮助和说明区域 */
.help-section {
  background: var(--bg-secondary);
  padding: 4rem 0;
  position: relative;
  overflow: hidden;
}

.help-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: 
    radial-gradient(circle at 10% 20%, rgba(102, 126, 234, 0.05) 0%, transparent 50%),
    radial-gradient(circle at 90% 80%, rgba(118, 75, 162, 0.05) 0%, transparent 50%);
  z-index: 1;
}

.help-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
  position: relative;
  z-index: 2;
}

/* 通用区域头部 */
.section-header {
  text-align: center;
  margin-bottom: 3rem;
}

.section-header i {
  font-size: 2.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 1rem;
  display: block;
}

.section-header h2 {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.section-header p {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* 使用教程 */
.tutorial-section {
  margin-bottom: 4rem;
}

.tutorial-steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.step-item {
  display: flex;
  align-items: flex-start;
  gap: 1.5rem;
  padding: 2rem;
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.step-item::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--primary-gradient);
  opacity: 0;
  transition: opacity var(--transition-normal);
  z-index: 1;
}

.step-item:hover {
  transform: translateY(-5px);
  border-color: var(--border-accent);
  box-shadow: var(--shadow-xl);
}

.step-item:hover::before {
  opacity: 0.05;
}

.step-number {
  width: 60px;
  height: 60px;
  background: var(--primary-gradient);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 700;
  flex-shrink: 0;
  position: relative;
  z-index: 2;
}

.step-content {
  flex: 1;
  position: relative;
  z-index: 2;
}

.step-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.step-content p {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* 功能特点 */
.features-section {
  margin-bottom: 4rem;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: 2rem;
  text-align: center;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.feature-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--primary-gradient);
  opacity: 0;
  transition: opacity var(--transition-normal);
  z-index: 1;
}

.feature-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-accent);
  box-shadow: var(--shadow-xl);
}

.feature-card:hover::before {
  opacity: 0.05;
}

.feature-icon {
  width: 80px;
  height: 80px;
  background: var(--primary-gradient);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
  position: relative;
  z-index: 2;
}

.feature-icon i {
  font-size: 2rem;
  color: white;
}

.feature-card h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 1rem;
  position: relative;
  z-index: 2;
}

.feature-card p {
  color: var(--text-secondary);
  line-height: 1.6;
  position: relative;
  z-index: 2;
}

/* 使用案例 */
.examples-section {
  margin-bottom: 4rem;
}

.examples-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.example-card {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-normal);
  position: relative;
}

.example-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-accent);
  box-shadow: var(--shadow-xl);
}

.example-header {
  background: var(--primary-gradient);
  color: white;
  padding: 1.5rem;
  display: flex;
  align-items: center;
  gap: 1rem;
}

.example-header i {
  font-size: 1.5rem;
}

.example-header h3 {
  font-size: 1.25rem;
  font-weight: 600;
}

.example-content {
  padding: 1.5rem;
}

.example-content p {
  margin-bottom: 0.75rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.example-content p:last-child {
  margin-bottom: 0;
}

.example-content strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* 常见问题 */
.faq-section {
  margin-bottom: 4rem;
}

.faq-list {
  max-width: 800px;
  margin: 2rem auto 0;
}

.faq-item {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  margin-bottom: 1rem;
  overflow: hidden;
  transition: all var(--transition-normal);
}

.faq-item:hover {
  border-color: var(--border-secondary);
  box-shadow: var(--shadow-md);
}

.faq-question {
  padding: 1.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 1rem;
  transition: all var(--transition-normal);
  position: relative;
}

.faq-question:hover {
  background: var(--bg-secondary);
}

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

.faq-question span {
  font-weight: 600;
  color: var(--text-primary);
  flex: 1;
}

.faq-answer {
  padding: 0 1.5rem 1.5rem;
  color: var(--text-secondary);
  line-height: 1.6;
  display: none;
}

.faq-item.active .faq-answer {
  display: block;
  animation: fadeIn 0.3s ease-in-out;
}

.faq-item.active .faq-question i {
  transform: rotate(90deg);
}

/* 技巧提示 */
.tips-section {
  margin-bottom: 2rem;
}

.tips-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.tip-card {
  background: var(--bg-card);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  text-align: center;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.tip-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--accent-gradient);
  opacity: 0;
  transition: opacity var(--transition-normal);
  z-index: 1;
}

.tip-card:hover {
  transform: translateY(-3px);
  border-color: var(--border-accent);
  box-shadow: var(--shadow-lg);
}

.tip-card:hover::before {
  opacity: 0.05;
}

.tip-icon {
  width: 60px;
  height: 60px;
  background: var(--accent-gradient);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1rem;
  position: relative;
  z-index: 2;
}

.tip-icon i {
  font-size: 1.5rem;
  color: white;
}

.tip-card h3 {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
  position: relative;
  z-index: 2;
}

.tip-card p {
  color: var(--text-secondary);
  line-height: 1.5;
  font-size: 0.875rem;
  position: relative;
  z-index: 2;
}

/* FAQ 交互功能 */
.faq-question {
  user-select: none;
}

/* 响应式设计 */
@media (max-width: 768px) {
  .help-container {
    padding: 0 1rem;
  }
  
  .section-header h2 {
    font-size: 2rem;
  }
  
  .tutorial-steps {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  .step-item {
    flex-direction: column;
    text-align: center;
    padding: 1.5rem;
  }
  
  .step-number {
    margin: 0 auto;
  }
  
  .features-grid,
  .examples-grid,
  .tips-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  .feature-card,
  .example-card,
  .tip-card {
    padding: 1.5rem;
  }
  
  .example-header {
    padding: 1rem;
  }
  
  .example-content {
    padding: 1rem;
  }
}

@media (max-width: 480px) {
  .help-section {
    padding: 2rem 0;
  }
  
  .section-header h2 {
    font-size: 1.75rem;
  }
  
  .section-header p {
    font-size: 1rem;
  }
  
  .step-item,
  .feature-card,
  .example-card,
  .tip-card {
    padding: 1rem;
  }
  
  .faq-question {
    padding: 1rem;
  }
  
  .faq-answer {
    padding: 0 1rem 1rem;
  }
}

/* 确保所有可点击元素有足够的点击区域 */
@media (hover: none) and (pointer: coarse) {
  .compress-btn,
  .download-btn,
  .modern-select,
  .upload-area,
  .nav-link,
  .faq-question {
    min-height: 44px;
  }
}