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

:root {
  --color-bg: #0f1117;
  --color-surface: #1a1d2e;
  --color-surface-hover: #232740;
  --color-primary: #6366f1;
  --color-primary-light: #818cf8;
  --color-accent: #22d3ee;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-border: #2d3154;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Noto Sans SC', sans-serif;
  --max-width: 1100px;
  --radius: 12px;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--color-primary-light); text-decoration: none; transition: color .2s; }
a:hover { color: var(--color-accent); }

img { max-width: 100%; display: block; }

/* ===== Language Toggle ===== */
.lang-toggle {
  position: fixed;
  top: 18px;
  right: 24px;
  z-index: 1000;
  display: flex;
  gap: 4px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 4px;
}

.lang-toggle button {
  background: transparent;
  border: none;
  color: var(--color-text-muted);
  font-size: 13px;
  padding: 4px 12px;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: all .2s;
}

.lang-toggle button.active {
  background: var(--color-primary);
  color: #fff;
}

[lang="cn"] { display: none; }
body.zh [lang="en"] { display: none; }
body.zh [lang="cn"] { display: block; }
body.zh [lang="cn-inline"] { display: inline; }
body.zh [lang="en-inline"] { display: none; }
[lang="cn-inline"] { display: none; }

/* ===== Nav ===== */
nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(15, 17, 23, .85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
}

nav .nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

nav .logo {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: 8px;
}

nav .logo span { color: var(--color-primary-light); }

nav .nav-links { display: flex; gap: 28px; }

nav .nav-links a {
  color: var(--color-text-muted);
  font-size: 14px;
  font-weight: 500;
  transition: color .2s;
}

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

/* ===== Hero ===== */
.hero {
  text-align: center;
  padding: 100px 24px 80px;
  max-width: var(--max-width);
  margin: 0 auto;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  background: linear-gradient(135deg, var(--color-text), var(--color-primary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto 36px;
}

.hero .btn-group {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: 10px;
  font-size: 15px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: transform .15s, box-shadow .2s;
}

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

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  color: #fff;
  box-shadow: 0 4px 20px rgba(99, 102, 241, .35);
}

.btn-primary:hover { box-shadow: 0 6px 28px rgba(99, 102, 241, .5); color: #fff; }

.btn-outline {
  background: transparent;
  color: var(--color-text);
  border: 1.5px solid var(--color-border);
}

.btn-outline:hover { border-color: var(--color-primary-light); color: var(--color-primary-light); }

/* ===== Features Grid ===== */
.features {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 40px 24px 100px;
}

.features h2 {
  text-align: center;
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 48px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}

.feature-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 32px 28px;
  transition: border-color .2s, transform .2s;
}

.feature-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-3px);
}

.feature-card .icon {
  font-size: 28px;
  margin-bottom: 14px;
}

.feature-card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: .9rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ===== Legal Pages (Privacy / Terms) ===== */
.legal {
  max-width: 800px;
  margin: 0 auto;
  padding: 60px 24px 100px;
}

.legal h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.legal .updated {
  color: var(--color-text-muted);
  font-size: .9rem;
  margin-bottom: 40px;
}

.legal h2 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-top: 40px;
  margin-bottom: 12px;
  color: var(--color-primary-light);
}

.legal p, .legal li {
  font-size: .95rem;
  color: var(--color-text-muted);
  margin-bottom: 12px;
}

.legal ul {
  padding-left: 24px;
  margin-bottom: 12px;
}

.legal li { margin-bottom: 6px; }

/* ===== Footer ===== */
footer {
  margin-top: auto;
  border-top: 1px solid var(--color-border);
  padding: 28px 24px;
  text-align: center;
  font-size: .85rem;
  color: var(--color-text-muted);
}

footer .footer-links {
  display: flex;
  gap: 20px;
  justify-content: center;
  margin-bottom: 10px;
}

footer .footer-links a { color: var(--color-text-muted); font-size: .85rem; }
footer .footer-links a:hover { color: var(--color-text); }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  nav .nav-links { gap: 16px; }
  nav .nav-links a { font-size: 13px; }
  .hero { padding: 60px 20px 50px; }
  .features { padding: 20px 20px 60px; }
  .legal { padding: 40px 20px 60px; }
  .lang-toggle { top: 12px; right: 12px; }
}