* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

: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%);
  --dark-bg: #0f0f23;
  --card-bg: rgba(255, 255, 255, 0.05);
  --glass-bg: rgba(255, 255, 255, 0.1);
  --text-primary: #ffffff;
  --text-secondary: rgba(255, 255, 255, 0.7);
  --border-color: rgba(255, 255, 255, 0.1);
  --shadow-color: rgba(0, 0, 0, 0.3);
}

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

body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: 
    radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.15) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(118, 75, 162, 0.15) 0%, transparent 50%),
    radial-gradient(circle at 40% 80%, rgba(79, 172, 254, 0.1) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 30px;
  position: relative;
  z-index: 1;
}

.header {
  background: rgba(15, 15, 35, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-color);
  color: white;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  transition: all 0.3s ease;
}

.header.scrolled {
  background: rgba(15, 15, 35, 0.95);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 0;
}

.logo h1 {
  font-size: 1.8rem;
  font-weight: 800;
  margin: 0;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
}

.nav-list {
  display: flex;
  list-style: none;
  gap: 2.5rem;
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: all 0.3s ease;
  padding: 0.6rem 1.2rem;
  border-radius: 8px;
  position: relative;
  font-size: 0.95rem;
}

.nav-link::before {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  width: 0;
  height: 2px;
  background: var(--primary-gradient);
  transition: all 0.3s ease;
  transform: translateX(-50%);
}

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

.nav-link:hover::before,
.nav-link.active::before {
  width: 60%;
}

.menu-toggle {
  display: none;
  background: var(--glass-bg);
  border: 1px solid var(--border-color);
  color: white;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.75rem;
  border-radius: 12px;
  transition: all 0.3s ease;
}

.menu-toggle:hover {
  background: rgba(255, 255, 255, 0.15);
  transform: scale(1.05);
}

.mobile-menu {
  display: none;
  background: rgba(15, 15, 35, 0.98);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  border-bottom: 1px solid var(--border-color);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
}

.mobile-menu.active {
  display: block;
  animation: slideDown 0.3s ease;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.mobile-nav-list {
  list-style: none;
  padding: 1.5rem 0;
}

.mobile-nav-item {
  margin: 0.5rem 0;
}

.mobile-nav-link {
  display: block;
  color: var(--text-secondary);
  text-decoration: none;
  padding: 1rem 2rem;
  font-weight: 500;
  transition: all 0.3s ease;
  border-left: 3px solid transparent;
}

.mobile-nav-link:hover,
.mobile-nav-link.active {
  color: var(--text-primary);
  background: var(--glass-bg);
  border-left-color: #667eea;
}

.hero {
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.2) 0%, rgba(118, 75, 162, 0.2) 100%);
  color: white;
  padding: 8rem 0 4rem;
  margin-top: 70px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(102, 126, 234, 0.1) 0%, transparent 50%);
  animation: rotate 20s linear infinite;
}

@keyframes rotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero h1,
.hero h2 {
  font-size: 3.5rem;
  margin-bottom: 1.5rem;
  font-weight: 800;
  background: linear-gradient(135deg, #ffffff 0%, #a0a0a0 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -1px;
  animation: fadeInUp 0.8s ease;
}

.hero p {
  font-size: 1.3rem;
  opacity: 0.8;
  margin-bottom: 2.5rem;
  animation: fadeInUp 0.8s ease 0.2s backwards;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.main {
  padding: 3rem 0;
}

.intro {
  padding: 4rem 0;
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: 24px;
  margin-bottom: 3rem;
  box-shadow: 0 8px 32px var(--shadow-color);
}

.intro h3 {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 1.5rem;
  font-size: 2rem;
  font-weight: 700;
}

.intro-content {
  max-width: 900px;
  margin: 0 auto;
}

.intro p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  margin-bottom: 1.5rem;
  line-height: 1.8;
}

.topics {
  padding: 4rem 0;
}

.topics h3 {
  text-align: center;
  color: var(--text-primary);
  margin-bottom: 3rem;
  font-size: 2.5rem;
  font-weight: 700;
}

.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.topic-card {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 2.5rem;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  box-shadow: 0 8px 32px var(--shadow-color);
  transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  position: relative;
  overflow: hidden;
}

.topic-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--primary-gradient);
  transform: scaleX(0);
  transition: transform 0.4s ease;
}

.topic-card:hover {
  transform: translateY(-10px) scale(1.02);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
  border-color: rgba(102, 126, 234, 0.3);
}

.topic-card:hover::before {
  transform: scaleX(1);
}

.topic-icon {
  font-size: 3rem;
  margin-bottom: 1.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: inline-block;
  transition: transform 0.3s ease;
}

.topic-card:hover .topic-icon {
  transform: scale(1.1) rotate(5deg);
}

.topic-card h4 {
  font-size: 1.5rem;
  margin-bottom: 1rem;
  color: var(--text-primary);
  font-weight: 600;
}

.topic-card p {
  color: var(--text-secondary);
  margin-bottom: 2rem;
  line-height: 1.7;
}

.content {
  padding: 3rem 0;
}

.content-wrapper {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 3rem;
  align-items: start;
}

.sidebar {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 2rem;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  position: sticky;
  top: 100px;
  height: fit-content;
  box-shadow: 0 8px 32px var(--shadow-color);
}

.sidebar-nav h3 {
  margin-bottom: 1.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-size: 1.2rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.sidebar-nav ul {
  list-style: none;
}

.sidebar-nav li {
  margin-bottom: 0.75rem;
}

.sidebar-nav a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: all 0.3s ease;
  display: block;
  padding: 0.75rem 1rem;
  border-radius: 10px;
  border-left: 3px solid transparent;
}

.sidebar-nav a:hover {
  color: var(--text-primary);
  background: var(--glass-bg);
  border-left-color: #667eea;
  padding-left: 1.5rem;
}

.main-content {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 3rem;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  box-shadow: 0 8px 32px var(--shadow-color);
}

.main-content h2 {
  color: var(--text-primary);
  margin-bottom: 2rem;
  font-size: 2.2rem;
  font-weight: 700;
  padding-bottom: 1rem;
  border-bottom: 2px solid;
  border-image: var(--primary-gradient) 1;
}

.main-content h3 {
  color: var(--text-primary);
  margin: 2rem 0 1.2rem;
  font-size: 1.6rem;
  font-weight: 600;
}

.main-content p {
  margin-bottom: 1.5rem;
  color: var(--text-secondary);
  line-height: 1.9;
  font-size: 1.05rem;
}

.main-content ul,
.main-content ol {
  margin-bottom: 2rem;
  padding-left: 2rem;
}

.main-content li {
  margin-bottom: 0.75rem;
  color: var(--text-secondary);
  line-height: 1.8;
}

.main-content blockquote {
  border-left: 4px solid;
  border-image: var(--primary-gradient) 1;
  padding-left: 2rem;
  margin: 2rem 0;
  font-style: italic;
  color: var(--text-secondary);
  background: var(--glass-bg);
  padding: 1.5rem 2rem;
  border-radius: 0 12px 12px 0;
}

.btn {
  display: inline-block;
  padding: 1rem 2.5rem;
  border-radius: 12px;
  text-decoration: none;
  font-weight: 600;
  transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  cursor: pointer;
  border: none;
  font-size: 1rem;
  position: relative;
  overflow: hidden;
  animation: fadeInUp 0.8s ease 0.4s backwards;
}

.btn::before {
  content: '';
  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 ease;
}

.btn:hover::before {
  left: 100%;
}

.btn-primary {
  background: var(--primary-gradient);
  color: white;
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 35px rgba(102, 126, 234, 0.5);
}

.btn-secondary {
  background: transparent;
  color: var(--text-primary);
  border: 2px solid;
  border-image: var(--primary-gradient) 1;
}

.btn-secondary:hover {
  background: var(--primary-gradient);
  color: white;
  transform: translateY(-3px);
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.tips-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin: 3rem 0;
}

.tip-card {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 2rem;
  border-radius: 16px;
  border: 1px solid var(--border-color);
  transition: all 0.4s ease;
  position: relative;
  overflow: hidden;
}

.tip-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--primary-gradient);
}

.tip-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
}

.tip-icon {
  font-size: 2.5rem;
  margin-bottom: 1.2rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tip-card h3 {
  color: var(--text-primary);
  margin-bottom: 0.8rem;
  font-size: 1.3rem;
  font-weight: 600;
}

.tip-card p {
  color: var(--text-secondary);
  margin-bottom: 0;
  line-height: 1.7;
}

.footer {
  background: rgba(15, 15, 35, 0.95);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-top: 1px solid var(--border-color);
  color: white;
  text-align: center;
  padding: 3rem 0;
  margin-top: 4rem;
}

.footer-content {
  opacity: 0.7;
  font-size: 0.95rem;
}

.beian-link {
  color: rgba(255, 255, 255, 0.5);
  text-decoration: none;
  font-size: 0.85rem;
  margin-top: 1rem;
  display: inline-block;
  transition: all 0.3s ease;
}

.beian-link:hover {
  color: white;
  text-decoration: underline;
  opacity: 1;
}

@media (max-width: 992px) {
  .content-wrapper {
    grid-template-columns: 1fr;
  }
  
  .sidebar {
    position: static;
    margin-bottom: 2rem;
  }
  
  .hero h1,
  .hero h2 {
    font-size: 2.8rem;
  }
}

@media (max-width: 768px) {
  .nav {
    display: none;
  }
  
  .menu-toggle {
    display: block;
  }
  
  .hero {
    padding: 6rem 0 3rem;
  }
  
  .hero h1,
  .hero h2 {
    font-size: 2.2rem;
  }
  
  .hero p {
    font-size: 1.1rem;
  }
  
  .topics-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  .content-wrapper {
    grid-template-columns: 1fr;
    gap: 2rem;
  }
  
  .main-content {
    padding: 2rem;
  }
  
  .main-content h2 {
    font-size: 1.8rem;
  }
  
  .main-content h3 {
    font-size: 1.4rem;
  }
  
  .sidebar {
    display: none;
  }
  
  .tips-container {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  .container {
    padding: 0 20px;
  }
  
  .intro {
    padding: 2.5rem;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 15px;
  }
  
  .header-content {
    padding: 0.75rem 0;
  }
  
  .logo h1 {
    font-size: 1.4rem;
  }
  
  .hero {
    padding: 5rem 0 2.5rem;
  }
  
  .hero h1,
  .hero h2 {
    font-size: 1.8rem;
  }
  
  .hero p {
    font-size: 1rem;
  }
  
  .intro {
    padding: 2rem;
  }
  
  .intro h3 {
    font-size: 1.5rem;
  }
  
  .topics {
    padding: 3rem 0;
  }
  
  .topics h3 {
    font-size: 2rem;
  }
  
  .topic-card {
    padding: 2rem;
  }
  
  .topic-card h4 {
    font-size: 1.3rem;
  }
  
  .topic-icon {
    font-size: 2.5rem;
  }
  
  .content {
    padding: 2rem 0;
  }
  
  .main-content {
    padding: 1.5rem;
  }
  
  .main-content h2 {
    font-size: 1.5rem;
  }
  
  .main-content h3 {
    font-size: 1.2rem;
  }
  
  .tips-container {
    margin: 2rem 0;
  }
  
  .tip-card {
    padding: 1.5rem;
  }
  
  .footer {
    padding: 2rem 0;
  }
  
  .footer-content {
    font-size: 0.85rem;
  }
  
  .btn {
    padding: 0.85rem 2rem;
    font-size: 0.95rem;
  }
}

@media (max-width: 360px) {
  .hero h1,
  .hero h2 {
    font-size: 1.6rem;
  }
  
  .mobile-nav-link {
    padding: 0.8rem 1.5rem;
    font-size: 0.9rem;
  }
  
  .btn {
    padding: 0.75rem 1.5rem;
    font-size: 0.9rem;
  }
}