:root {
  --bg-page: #080a0f;
  --bg-surface: #0e121b;
  --bg-card: #141a26;
  --bg-card-hover: #1a2232;
  --border-subtle: rgba(255, 255, 255, 0.08);
  --border-strong: rgba(255, 255, 255, 0.16);
  --border-accent: rgba(56, 189, 248, 0.35);

  --accent-primary: #38bdf8;
  --accent-primary-hover: #7dd3fc;
  --accent-glow: rgba(56, 189, 248, 0.25);
  --accent-green: #10b981;
  --accent-purple: #a855f7;

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", Menlo, monospace;

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-main);
  background-color: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(8, 10, 15, 0.9);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
}
.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.nav-left { display: flex; align-items: center; gap: 1.25rem; }
.back-root-btn {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color 0.15s;
}
.back-root-btn:hover { color: var(--text-primary); }
.brand-link {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: var(--text-primary);
}
.brand-logo { font-size: 1.5rem; }
.brand-name { font-weight: 700; font-size: 1.15rem; }
.brand-ver {
  font-size: 0.72rem;
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent-primary);
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
}

.main-nav { display: flex; align-items: center; gap: 1.25rem; }
.main-nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.15s;
}
.main-nav a:hover { color: var(--accent-primary); }

.lang-switch {
  display: flex;
  background-color: var(--bg-card);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
  overflow: hidden;
}
.lang-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 0.25rem 0.6rem;
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
}
.lang-btn.active {
  background-color: var(--accent-primary);
  color: #000;
}

.btn-github {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary) !important;
  padding: 0.4rem 0.8rem;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.btn-github:hover {
  background-color: var(--bg-card-hover);
  border-color: var(--border-accent);
}

/* Hero */
.hero-section {
  padding: 5rem 1.5rem 4rem;
  text-align: center;
  max-width: 900px;
  margin: 0 auto;
}
.badge-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.25);
  color: var(--accent-primary);
  font-size: 0.82rem;
  font-weight: 600;
  padding: 0.35rem 0.9rem;
  border-radius: 9999px;
  margin-bottom: 1.5rem;
}
.hero-title {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 1.25rem;
}
.hero-title span {
  color: var(--accent-primary);
  text-shadow: 0 0 24px var(--accent-glow);
}
.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 2.25rem;
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}
.hero-cta {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}
.btn-primary {
  background-color: var(--accent-primary);
  color: #000;
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.8rem 1.6rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: all 0.2s;
  box-shadow: 0 4px 14px var(--accent-glow);
}
.btn-primary:hover {
  background-color: var(--accent-primary-hover);
  transform: translateY(-2px);
}
.btn-secondary {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-primary);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.8rem 1.6rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: all 0.2s;
}
.btn-secondary:hover {
  background-color: var(--bg-card-hover);
  border-color: var(--border-accent);
  transform: translateY(-2px);
}

/* Sections */
.section {
  padding: 4.5rem 1.5rem;
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
}
.section-header {
  text-align: center;
  max-width: 650px;
  margin: 0 auto 3rem;
}
.section-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}
.section-desc {
  color: var(--text-secondary);
  font-size: 1rem;
}

/* Feature Grid */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
}
.card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.75rem;
  transition: all 0.2s;
}
.card:hover {
  background-color: var(--bg-card);
  border-color: var(--border-accent);
  transform: translateY(-3px);
}
.card-icon {
  font-size: 2rem;
  margin-bottom: 1rem;
  display: inline-block;
}
.card-title {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}
.card-desc {
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.5;
}

/* Architecture section */
.arch-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  margin-top: 2rem;
}
.arch-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}
.arch-item {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 1.25rem;
}
.arch-item h4 {
  color: var(--accent-primary);
  font-size: 1rem;
  margin-bottom: 0.4rem;
}
.arch-item p {
  color: var(--text-secondary);
  font-size: 0.85rem;
  line-height: 1.45;
}

/* Downloads section */
.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}
.download-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 2rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}
.download-icon { font-size: 2.5rem; }
.download-title { font-size: 1.2rem; font-weight: 700; }
.download-meta {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}
.btn-download {
  width: 100%;
  background-color: var(--bg-card);
  border: 1px solid var(--border-strong);
  color: var(--text-primary);
  padding: 0.65rem 1rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.88rem;
  transition: all 0.15s;
}
.btn-download:hover {
  background-color: var(--accent-primary);
  color: #000;
  border-color: var(--accent-primary);
}

/* About / Open Source section */
.about-box {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.about-header { display: flex; align-items: center; gap: 1rem; }
.author-avatar {
  width: 54px;
  height: 54px;
  border-radius: 50%;
  border: 2px solid var(--accent-primary);
}
.author-info h3 { font-size: 1.25rem; font-weight: 700; }
.author-info p { color: var(--text-muted); font-size: 0.85rem; }

/* Footer */
.site-footer {
  margin-top: auto;
  border-top: 1px solid var(--border-subtle);
  background-color: var(--bg-surface);
  padding: 2rem 1.5rem;
}
.footer-container {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.footer-links { display: flex; gap: 1.25rem; }
.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.15s;
}
.footer-links a:hover { color: var(--accent-primary); }

@media (max-width: 768px) {
  .hero-title { font-size: 2.2rem; }
  .main-nav { display: none; }
  .footer-container { flex-direction: column; text-align: center; }
}