:root {
  --primary: #00f0ff;
  --secondary: #7000ff;
  --accent: #ff0055;
  --bg-color: #050508;
  --surface: rgba(255, 255, 255, 0.03);
  --surface-hover: rgba(255, 255, 255, 0.08);
  --text-main: #ffffff;
  --text-muted: #8b8b9e;
  --border-light: rgba(255, 255, 255, 0.1);
  
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --transition: all 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.6;
  overflow-x: hidden;
  background-image: 
    radial-gradient(circle at 15% 50%, rgba(112, 0, 255, 0.15), transparent 25%),
    radial-gradient(circle at 85% 30%, rgba(0, 240, 255, 0.1), transparent 25%);
  background-attachment: fixed;
}

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

ul {
  list-style: none;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 1rem;
}

.gradient-text {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-title {
  text-align: center;
  font-size: 2.5rem;
  margin-bottom: 3rem;
  position: relative;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -15px;
  left: 50%;
  transform: translateX(-50%);
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 2px;
}

/* Header & Nav */
header {
  position: fixed;
  top: 0;
  width: 100%;
  padding: 1.2rem 5%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 1000;
  background: rgba(5, 5, 8, 0.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-light);
  transition: var(--transition);
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: 1px;
}

.nav-links {
  display: flex;
  gap: 2rem;
}

.nav-links li a {
  font-weight: 500;
  font-size: 0.95rem;
}

.nav-links li a:hover {
  color: var(--primary);
  text-shadow: 0 0 10px rgba(0, 240, 255, 0.5);
}

.btn-primary {
  display: inline-block;
  padding: 0.8rem 1.8rem;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  border-radius: 30px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  box-shadow: 0 4px 15px rgba(112, 0, 255, 0.3);
  transition: var(--transition);
  text-align: center;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 240, 255, 0.4);
}

/* Hero Section */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 0 5%;
  position: relative;
  overflow: hidden;
}

.hero-content {
  max-width: 800px;
  z-index: 2;
}

.hero h1 {
  font-size: 4rem;
  margin-bottom: 1.5rem;
  letter-spacing: -1px;
}

.hero p {
  font-size: 1.2rem;
  color: var(--text-muted);
  margin-bottom: 2.5rem;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-buttons {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
}

.btn-secondary {
  display: inline-block;
  padding: 0.8rem 1.8rem;
  background: transparent;
  color: var(--text-main);
  border: 1px solid var(--border-light);
  border-radius: 30px;
  font-weight: 600;
  transition: var(--transition);
}

.btn-secondary:hover {
  border-color: var(--primary);
  background: rgba(0, 240, 255, 0.05);
}

/* General Sections */
section {
  padding: 6rem 5%;
}

/* Features Section */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
  max-width: 1200px;
  margin: 0 auto;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border-light);
  border-radius: 20px;
  padding: 2.5rem 2rem;
  text-align: center;
  backdrop-filter: blur(10px);
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-10px);
  background: var(--surface-hover);
  border-color: rgba(0, 240, 255, 0.3);
  box-shadow: 0 10px 30px rgba(0, 240, 255, 0.1);
}

.feature-icon {
  font-size: 3rem;
  margin-bottom: 1.5rem;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* Pricing Section */
.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 2rem;
  max-width: 1200px;
  margin: 0 auto;
  align-items: center;
}

.pricing-card {
  background: var(--surface);
  border: 1px solid var(--border-light);
  border-radius: 20px;
  padding: 3rem 2rem;
  position: relative;
  overflow: hidden;
  transition: var(--transition);
}

.pricing-card.popular {
  border-color: var(--primary);
  background: linear-gradient(180deg, rgba(0, 240, 255, 0.05) 0%, rgba(5, 5, 8, 0) 100%);
  transform: scale(1.05);
}

.pricing-card.popular::before {
  content: '推荐';
  position: absolute;
  top: 15px;
  right: -35px;
  background: var(--primary);
  color: #000;
  padding: 5px 40px;
  transform: rotate(45deg);
  font-weight: bold;
  font-size: 0.8rem;
}

.pricing-card:hover {
  transform: translateY(-10px) scale(1.05);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
  border-color: var(--secondary);
}

.plan-name {
  font-size: 1.5rem;
  margin-bottom: 1rem;
}

.plan-price {
  font-size: 3rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.plan-price span {
  font-size: 1rem;
  color: var(--text-muted);
  font-weight: normal;
}

.plan-features {
  margin: 2rem 0;
  text-align: left;
}

.plan-features li {
  margin-bottom: 1rem;
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 0.95rem;
}

.plan-features li i {
  color: var(--primary);
  margin-top: 4px;
}

.pricing-card .btn-primary {
  width: 100%;
}

/* FAQ Section */
.faq-container {
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  background: var(--surface);
  border: 1px solid var(--border-light);
  border-radius: 10px;
  margin-bottom: 1rem;
  overflow: hidden;
}

.faq-question {
  padding: 1.5rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 600;
  transition: var(--transition);
}

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

.faq-answer {
  padding: 0 1.5rem;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
  color: var(--text-muted);
}

.faq-item.active .faq-answer {
  padding: 0 1.5rem 1.5rem 1.5rem;
  max-height: 500px; /* arbitrary max-height for animation */
}

.faq-item.active .faq-question {
  color: var(--primary);
}

/* Footer & Tags */
footer {
  background: rgba(0, 0, 0, 0.5);
  padding: 4rem 5% 2rem;
  border-top: 1px solid var(--border-light);
  text-align: center;
}

.footer-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: center;
  max-width: 1000px;
  margin: 0 auto 3rem auto;
}

.footer-tags a {
  font-size: 0.8rem;
  color: var(--text-muted);
  background: var(--surface);
  padding: 5px 12px;
  border-radius: 15px;
  border: 1px solid var(--border-light);
}

.footer-tags a:hover {
  background: var(--primary);
  color: #000;
  border-color: var(--primary);
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-bottom {
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 2.5rem;
  }
  
  .nav-links {
    display: none; /* simple mobile menu hidden for now */
  }
  
  .pricing-card.popular {
    transform: scale(1);
  }
  
  .pricing-card:hover {
    transform: translateY(-5px);
  }
}