:root {
  --brand: #ff6a2b;
  --ink: #1b2536;
  --ink-soft: #48566b;
  --muted: #8794a7;
  --line: #e6e9ef;
  --bg: #f5f7fa;
  --card: #ffffff;
  --accent: #16305b;
  --info-bg: #f0f5ff;
  --info-line: #cfe0ff;
  --max: 840px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
  font-size: 16px;
}

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

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--line);
}
.site-header .bar {
  max-width: var(--max);
  margin: 0 auto;
  padding: 14px 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 2px;
  font-weight: 800;
  font-size: 20px;
  letter-spacing: -0.02em;
  color: var(--ink);
}
.brand .dot { color: var(--brand); }
.site-header nav { display: flex; gap: 8px; flex-wrap: wrap; }
.site-header nav a {
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 14px;
  padding: 7px 12px;
  border-radius: 8px;
}
.site-header nav a:hover { background: var(--bg); text-decoration: none; }
.site-header nav a.active { color: var(--brand); background: #fff2ec; }

/* Layout */
main {
  max-width: var(--max);
  margin: 28px auto 64px;
  padding: 0 22px;
}
.doc {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 40px clamp(22px, 5vw, 56px);
  box-shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 8px 24px rgba(16, 24, 40, 0.05);
}

h1 {
  font-size: clamp(26px, 5vw, 34px);
  line-height: 1.2;
  margin: 0 0 6px;
  letter-spacing: -0.02em;
}
.meta { color: var(--muted); font-size: 14px; margin: 0 0 8px; }
.subtitle { color: var(--ink-soft); font-size: 15px; margin: 0 0 24px; }

h2 {
  font-size: 20px;
  color: var(--accent);
  margin: 40px 0 10px;
  padding-top: 8px;
  border-top: 1px solid var(--line);
  letter-spacing: -0.01em;
}
h2:first-of-type { border-top: none; padding-top: 0; }
h3 { font-size: 16px; margin: 24px 0 6px; color: var(--ink); }

p { margin: 10px 0; color: var(--ink-soft); }
ul { margin: 10px 0; padding-left: 22px; color: var(--ink-soft); }
li { margin: 5px 0; }
strong { color: var(--ink); }

.overview {
  background: linear-gradient(180deg, #fff7f3, #fff);
  border: 1px solid #ffd9c7;
  border-radius: 12px;
  padding: 18px 22px;
  margin: 8px 0 24px;
}
.overview h3 { margin-top: 0; }

.note {
  background: var(--info-bg);
  border: 1px solid var(--info-line);
  border-radius: 12px;
  padding: 14px 18px;
  margin: 18px 0;
  color: var(--ink-soft);
  font-size: 15px;
}

.tier {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px 18px;
  margin: 12px 0;
  background: #fbfcfe;
}
.tier h3 { margin-top: 0; }

/* Landing */
.hero { text-align: center; padding: 24px 0 8px; }
.hero .brand { font-size: 40px; }
.hero p { max-width: 560px; margin: 12px auto 0; }
.cards { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 28px 0 8px; }
.card-link {
  display: block;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 22px;
  color: var(--ink);
  transition: box-shadow .15s ease, transform .15s ease, border-color .15s ease;
}
.card-link:hover { text-decoration: none; box-shadow: 0 8px 24px rgba(16,24,40,.08); transform: translateY(-2px); border-color: #ffd0bd; }
.card-link h2 { border: none; padding: 0; margin: 0 0 6px; color: var(--ink); font-size: 18px; }
.card-link p { margin: 0; }
.card-link .go { color: var(--brand); font-weight: 700; margin-top: 12px; display: inline-block; }
@media (max-width: 620px) { .cards { grid-template-columns: 1fr; } }

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  background: #fff;
}
.site-footer .bar {
  max-width: var(--max);
  margin: 0 auto;
  padding: 24px 22px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 20px;
  justify-content: space-between;
  align-items: center;
  color: var(--muted);
  font-size: 14px;
}
.site-footer nav { display: flex; gap: 16px; flex-wrap: wrap; }
.site-footer a { color: var(--ink-soft); font-weight: 600; }

.back-top { margin-top: 32px; font-weight: 600; font-size: 14px; }