:root {
  --primary-500: #7878ff;
  --primary-600: #5b5bd6;
  --primary-100: #eeeeff;
  --bg: #ffffff;
  --surface: #fbfbfb;
  --text: #1a1a1a;
  --text-secondary: #5e5e5e;
  --text-muted: #a4a4a4;
  --border: #e6e6e6;
  --radius: 16px;
  --maxw: 760px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans TC",
    "PingFang TC", "Microsoft JhengHei", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--primary-600); }

/* ── Header ── */
.site-header {
  background: linear-gradient(135deg, var(--primary-500), var(--primary-600));
  color: #fff;
  padding: 28px 20px;
}
.site-header .inner {
  max-width: var(--maxw);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 14px;
}
.site-header .logo {
  width: 44px; height: 44px;
  border-radius: 12px;
  background: rgba(255,255,255,0.18);
  display: grid; place-items: center;
  font-size: 24px;
  flex-shrink: 0;
}
.site-header h1 { font-size: 19px; margin: 0; font-weight: 700; letter-spacing: .3px; }
.site-header .sub { font-size: 13px; opacity: .9; margin-top: 2px; }
.site-header a { color: #fff; text-decoration: none; }

/* ── Layout ── */
main {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 36px 20px 72px;
}
.updated {
  color: var(--text-muted);
  font-size: 13px;
  margin: 0 0 24px;
}
.intro {
  color: var(--text-secondary);
  font-size: 15px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin-bottom: 28px;
}

h2.page-title { font-size: 26px; margin: 0 0 6px; }

section.card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 22px;
  margin-bottom: 16px;
  background: var(--bg);
}
section.card h3 {
  font-size: 17px;
  margin: 0 0 10px;
  color: var(--text);
  display: flex; align-items: center; gap: 8px;
}
section.card h3::before {
  content: "";
  width: 4px; height: 18px;
  background: var(--primary-500);
  border-radius: 3px;
  flex-shrink: 0;
}
section.card p, section.card li {
  color: var(--text-secondary);
  font-size: 15px;
  margin: 0 0 10px;
}
section.card p:last-child, section.card li:last-child { margin-bottom: 0; }
section.card ul { margin: 0; padding-left: 20px; }

.highlight {
  background: var(--primary-100);
  border: 1px solid #d6d6ff;
  border-radius: var(--radius);
  padding: 18px 20px;
  margin-bottom: 16px;
}
.highlight h3 { color: var(--primary-600); }
.highlight p, .highlight li { color: #3a3a6a; }

/* ── Index hub ── */
.hub-links { display: grid; gap: 16px; margin-top: 8px; }
.hub-card {
  display: block;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  text-decoration: none;
  color: var(--text);
  transition: border-color .15s, transform .15s, box-shadow .15s;
}
.hub-card:hover {
  border-color: var(--primary-500);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(120,120,255,0.12);
}
.hub-card .t { font-size: 18px; font-weight: 700; }
.hub-card .d { color: var(--text-secondary); font-size: 14px; margin-top: 4px; }

/* ── Footer ── */
footer {
  border-top: 1px solid var(--border);
  padding: 28px 20px;
  text-align: center;
  color: var(--text-muted);
  font-size: 13px;
}
footer a { color: var(--text-muted); margin: 0 8px; }

.toc {
  font-size: 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin-bottom: 28px;
}
.toc strong { display: block; margin-bottom: 8px; color: var(--text); }
.toc a { display: inline-block; margin: 2px 12px 2px 0; }