/* ==================== Variables ==================== */
:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --text-primary: #1a1a1a;
  --text-secondary: #6b7280;
  --border-color: #e5e7eb;
  --accent-color: #1a1a1a;
  --accent-hover: #333333;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
  text-decoration: none;
}

img {
  max-width: 100%;
  height: auto;
}

/* ==================== Layout ==================== */
.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

.section-title {
  font-size: 28px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 48px;
}

/* ==================== Header ==================== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 20px;
  font-weight: 700;
}

.nav {
  display: flex;
  gap: 32px;
}

.nav a {
  font-size: 14px;
  color: var(--text-secondary);
  transition: color 0.2s;
}

.nav a:hover {
  color: var(--text-primary);
}

/* ==================== Buttons ==================== */
.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 500;
  transition: all 0.2s;
  cursor: pointer;
}

.btn-primary {
  background: var(--accent-color);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  border: 1px solid var(--border-color);
  color: var(--text-primary);
}

.btn-secondary:hover {
  border-color: var(--text-secondary);
}

.btn-disabled {
  background: #e5e7eb;
  color: #9ca3af;
  cursor: not-allowed;
}

/* ==================== Hero ==================== */
.hero {
  padding: 140px 0 80px;
  text-align: center;
}

.hero h1 {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
}

.hero-subtitle {
  font-size: 18px;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 40px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
}

/* ==================== Features ==================== */
.features {
  padding: 80px 0;
  background: var(--bg-secondary);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.feature-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 32px;
  transition: box-shadow 0.2s;
}

.feature-card:hover {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
}

.feature-icon {
  width: 56px;
  height: 56px;
  border-radius: 12px;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.feature-card h3 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 12px;
}

.feature-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ==================== How it works ==================== */
.how-it-works {
  padding: 80px 0;
}

.flow {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
}

.flow-step {
  text-align: center;
  flex: 0 0 200px;
}

.flow-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--accent-color);
  color: #fff;
  font-size: 20px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
}

.flow-step h4 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 8px;
}

.flow-step p {
  font-size: 14px;
  color: var(--text-secondary);
}

.flow-arrow {
  color: var(--text-secondary);
  flex-shrink: 0;
}

/* ==================== Channels ==================== */
.channels {
  padding: 80px 0;
  background: var(--bg-secondary);
}

.channel-list {
  display: flex;
  justify-content: center;
  gap: 48px;
  flex-wrap: wrap;
}

.channel-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.channel-item img {
  width: 48px;
  height: 48px;
  border-radius: 12px;
}

.channel-item span {
  font-size: 14px;
  color: var(--text-secondary);
}

/* ==================== Download ==================== */
.download {
  padding: 80px 0;
}

.download-subtitle {
  text-align: center;
  color: var(--text-secondary);
  margin-top: -36px;
  margin-bottom: 48px;
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 32px;
  max-width: 700px;
  margin: 0 auto;
}

.download-card {
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 40px 32px;
  text-align: center;
  transition: box-shadow 0.2s;
}

.download-card:hover {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
}

.download-card-disabled {
  opacity: 0.6;
}

.download-card-disabled:hover {
  box-shadow: none;
}

.download-icon {
  margin-bottom: 16px;
  color: var(--text-primary);
}

.download-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 8px;
}

.download-card p {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.download-btn {
  width: 100%;
  text-align: center;
}

/* ==================== Footer ==================== */
.footer {
  padding: 32px 0;
  border-top: 1px solid var(--border-color);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
}

.footer-links {
  display: flex;
  gap: 24px;
}

.footer-links a {
  font-size: 14px;
  color: var(--text-secondary);
  transition: color 0.2s;
}

.footer-links a:hover {
  color: var(--text-primary);
}

.footer-copy {
  font-size: 13px;
  color: var(--text-secondary);
}

/* ==================== Responsive ==================== */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 32px;
  }

  .hero-subtitle {
    font-size: 15px;
  }

  .hero-subtitle br {
    display: none;
  }

  .features-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .flow {
    flex-direction: column;
    gap: 16px;
  }

  .flow-arrow {
    transform: rotate(90deg);
  }

  .flow-step {
    flex: none;
  }

  .channel-list {
    gap: 32px;
  }

  .download-grid {
    grid-template-columns: 1fr;
  }

  .footer-inner {
    flex-direction: column;
    gap: 16px;
    text-align: center;
  }

  .nav {
    gap: 20px;
  }
}