:root {
  --blue-600: #0060DF;
  --blue-500: #007AFF;
  --blue-400: #0A84FF;
  --blue-50:  #EBF4FF;
  --ink:      #0B1220;
  --muted:    #5A6B7B;
  --line:     #E4E9EE;
  --bg:       #FFFFFF;
  --card:     #F7F9FC;
}

@media (prefers-color-scheme: dark) {
  :root {
    --blue-600: #4DA2FF;
    --blue-500: #0A84FF;
    --blue-400: #0A84FF;
    --blue-50:  #0F1B2E;
    --ink:      #ECF1F7;
    --muted:    #98A6B4;
    --line:     #1E2837;
    --bg:       #0A0E14;
    --card:     #131924;
  }
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", system-ui, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: var(--blue-500); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap { max-width: 960px; margin: 0 auto; padding: 0 24px; }
.wrap-narrow { max-width: 720px; margin: 0 auto; padding: 0 24px; }

/* Nav */
nav.top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 20px 24px;
  max-width: 1100px; margin: 0 auto;
  border-bottom: 1px solid var(--line);
}
nav.top .logo {
  font-weight: 700; font-size: 18px; letter-spacing: -0.01em;
  color: var(--ink);
  display: flex; align-items: center; gap: 8px;
}
nav.top .logo-dot {
  width: 20px; height: 20px; border-radius: 6px;
  background: linear-gradient(135deg, var(--blue-400), var(--blue-600));
}
nav.top .links a {
  margin-left: 22px; color: var(--muted); font-size: 14px; font-weight: 500;
}
nav.top .links a:hover { color: var(--blue-500); text-decoration: none; }
nav.top .lang {
  margin-left: 22px; color: var(--muted); font-size: 13px; font-weight: 600;
  cursor: pointer; background: none; border: 1px solid var(--line); padding: 5px 10px; border-radius: 999px;
  font-family: inherit;
}
nav.top .lang:hover { color: var(--blue-500); border-color: var(--blue-500); }

/* Hero */
.hero {
  text-align: center;
  padding: 72px 24px 56px;
}
.hero h1 {
  font-size: clamp(38px, 6vw, 60px);
  line-height: 1.05;
  letter-spacing: -0.035em;
  margin: 0 0 20px;
  color: var(--ink);
}
.hero h1 .accent {
  background: linear-gradient(135deg, var(--blue-400), var(--blue-600));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero p.lead {
  font-size: clamp(17px, 2vw, 20px);
  color: var(--muted);
  max-width: 640px; margin: 0 auto 32px;
}

.cta {
  display: inline-block;
  background: linear-gradient(135deg, var(--blue-400), var(--blue-600));
  color: #fff;
  padding: 14px 28px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 15px;
  letter-spacing: -0.005em;
  box-shadow: 0 4px 14px rgba(0, 122, 255, 0.25);
  transition: transform .15s ease, box-shadow .15s ease;
}
.cta:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(0, 122, 255, 0.35); text-decoration: none; }
.cta.secondary {
  background: none; color: var(--blue-500);
  border: 1px solid var(--line); box-shadow: none;
}
.cta.secondary:hover { border-color: var(--blue-500); }
.cta.disabled { opacity: 0.55; cursor: not-allowed; }

/* Features */
.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  padding: 32px 24px 80px;
  max-width: 1100px; margin: 0 auto;
}
.feature {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 24px;
}
.feature .icon {
  width: 40px; height: 40px; border-radius: 10px;
  background: var(--blue-50);
  color: var(--blue-500);
  display: flex; align-items: center; justify-content: center;
  font-size: 20px; font-weight: 700;
  margin-bottom: 14px;
}
.feature h3 {
  margin: 0 0 8px;
  font-size: 17px; letter-spacing: -0.01em;
}
.feature p {
  margin: 0;
  font-size: 14px; color: var(--muted); line-height: 1.55;
}

/* Content pages */
.page-body {
  padding: 48px 24px 96px;
}
.page-body h1 {
  font-size: clamp(28px, 4vw, 38px);
  letter-spacing: -0.02em;
  margin: 0 0 8px;
}
.page-body .updated {
  color: var(--muted);
  font-size: 14px;
  margin: 0 0 32px;
}
.page-body h2 {
  margin: 36px 0 12px;
  font-size: 20px;
  letter-spacing: -0.01em;
}
.page-body p, .page-body li {
  color: var(--ink);
  font-size: 16px;
  line-height: 1.7;
}
.page-body ul { padding-left: 22px; }
.page-body li { margin-bottom: 8px; }
.page-body code {
  background: var(--card);
  border: 1px solid var(--line);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 14px;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

/* FAQ */
.faq-item {
  border-bottom: 1px solid var(--line);
  padding: 20px 0;
}
.faq-item h3 {
  margin: 0 0 8px;
  font-size: 16px;
  color: var(--ink);
}
.faq-item p {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
}

/* Footer */
footer {
  border-top: 1px solid var(--line);
  padding: 32px 24px 48px;
  color: var(--muted);
  font-size: 13px;
  text-align: center;
}
footer a { color: var(--muted); margin: 0 12px; }
footer a:hover { color: var(--blue-500); }
footer .copy { margin-top: 12px; opacity: 0.7; }

/* i18n: hide the inactive language */
html[lang="en"] .zh { display: none; }
html[lang="zh-Hans"] .en { display: none; }