:root {
  --ink: #14120f;
  --ink-2: #3d3832;
  --ink-3: #6f675d;
  --paper: #faf9f6;
  --paper-2: #f3f0e9;
  --line: #e2ddd2;
  --line-2: #d2cbbb;
  --accent: #b8431d;
  --accent-soft: #f7e8e1;
  --green: #2f6b4f;
  --green-soft: #e8f1eb;
  --amber: #8a6216;
  --amber-soft: #f7efdc;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, "Songti SC", "Noto Serif SC", Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  --max: 1180px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: inherit; text-decoration: none; }
p { margin: 0 0 1em; }
ul { margin: 0; padding: 0; list-style: none; }

.wrap {
  width: min(var(--max), calc(100% - 48px));
  margin: 0 auto;
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--paper);
  padding: 10px 16px;
  z-index: 99;
}
.skip:focus { left: 12px; top: 12px; }

/* ---------- top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(250, 249, 246, .92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}

.topbar-inner {
  display: flex;
  align-items: center;
  gap: 28px;
  height: 64px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  letter-spacing: -.02em;
  font-size: 19px;
  flex: none;
}

.brand-mark {
  display: inline-grid;
  place-items: center;
  width: 30px;
  height: 30px;
  border-radius: 9px;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--serif);
  font-size: 20px;
  font-style: italic;
  line-height: 1;
  padding-bottom: 3px;
}
.brand-mark.small { width: 24px; height: 24px; font-size: 16px; border-radius: 7px; }
.brand-name span { color: var(--accent); }

.nav {
  display: flex;
  gap: 4px;
  margin-left: auto;
}

.nav a {
  padding: 7px 11px;
  border-radius: 8px;
  font-size: 14px;
  color: var(--ink-3);
  transition: color .18s ease, background .18s ease;
}
.nav a:hover { color: var(--ink); background: var(--paper-2); }
.nav a.active { color: var(--ink); background: var(--paper-2); font-weight: 600; }

.edition {
  flex: none;
  font-size: 12px;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--ink-3);
}
.edition i { font-style: normal; color: var(--line-2); margin: 0 4px; }

.progress {
  height: 2px;
  background: transparent;
}
.progress span {
  display: block;
  height: 100%;
  width: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: var(--accent);
  transition: transform .12s linear;
}

/* ---------- hero ---------- */

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(0, .9fr);
  gap: 64px;
  padding: 84px 0 56px;
  align-items: end;
}

.kicker {
  font-size: 12px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 18px;
}

.hero h1 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: clamp(38px, 4.6vw, 58px);
  line-height: 1.14;
  letter-spacing: -.03em;
  margin: 0 0 26px;
  max-width: 12em;
}

.hero-lead {
  font-size: 17px;
  color: var(--ink-2);
  max-width: 33em;
  line-height: 1.85;
}

.hero-links {
  display: flex;
  align-items: center;
  gap: 22px;
  margin-top: 30px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: var(--ink);
  color: var(--paper);
  padding: 12px 20px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 600;
  transition: transform .18s ease, background .18s ease;
}
.btn:hover { background: #2a2621; transform: translateY(-1px); }
.btn span { color: #d8a48f; }

.link {
  font-size: 14px;
  color: var(--ink-2);
  border-bottom: 1px solid var(--line-2);
  padding-bottom: 2px;
}
.link span { color: var(--accent); }
.link:hover { border-color: var(--ink-2); }

.hero-stats {
  display: grid;
  gap: 22px;
  padding-left: 36px;
  border-left: 1px solid var(--line);
}

.stat { display: grid; gap: 3px; }

.stat-num {
  font-family: var(--serif);
  font-size: clamp(34px, 3.4vw, 46px);
  line-height: 1.1;
  letter-spacing: -.03em;
}
.stat-num span { font-size: .48em; color: var(--ink-3); letter-spacing: 0; }

.stat-label { font-size: 14px; font-weight: 600; }
.stat-note { font-size: 12.5px; color: var(--ink-3); line-height: 1.5; }
.stat.muted .stat-num { color: var(--accent); }

/* ---------- caliber ---------- */

.caliber {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 40px;
  align-items: center;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 26px 0;
  margin-bottom: 24px;
}
.caliber strong { display: block; font-size: 13px; letter-spacing: .06em; margin-bottom: 6px; }
.caliber p { margin: 0; font-size: 14px; color: var(--ink-2); max-width: 60em; }
.caliber-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.caliber-tags span {
  font-size: 12px;
  color: var(--ink-3);
  background: var(--paper-2);
  border: 1px solid var(--line);
  padding: 5px 10px;
  border-radius: 999px;
  white-space: nowrap;
}

/* ---------- chapters ---------- */

.chapter { padding: 72px 0 24px; scroll-margin-top: 80px; }
.system { scroll-margin-top: 80px; }

.chapter-head {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 30px;
}
.chapter-no {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent);
  letter-spacing: .1em;
  text-transform: uppercase;
}
.chapter-sub { font-size: 12.5px; color: var(--ink-3); letter-spacing: .04em; }

.chapter h2 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: clamp(30px, 3.4vw, 44px);
  line-height: 1.2;
  letter-spacing: -.03em;
  margin: 0 0 26px;
  max-width: 22em;
}

.system-title {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, .95fr);
  gap: 48px;
  align-items: end;
  margin-bottom: 40px;
}
.system-title h2 { margin-bottom: 0; }
.system-title p { font-size: 15.5px; color: var(--ink-2); line-height: 1.85; }

/* ---------- table ---------- */

.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; background: #fff; }
table { width: 100%; border-collapse: collapse; min-width: 760px; }
th, td {
  text-align: left;
  vertical-align: top;
  padding: 18px 20px;
  border-bottom: 1px solid var(--line);
  font-size: 14px;
  line-height: 1.65;
}
th {
  font-size: 11.5px;
  letter-spacing: .09em;
  text-transform: uppercase;
  color: var(--ink-3);
  font-weight: 600;
  background: var(--paper-2);
}
tr:last-child td { border-bottom: 0; }
td b { display: block; font-size: 15px; margin-bottom: 2px; }
td:first-child { white-space: nowrap; }

.tag {
  display: inline-block;
  font-size: 10.5px;
  letter-spacing: .06em;
  color: var(--ink-3);
  border: 1px solid var(--line-2);
  border-radius: 4px;
  padding: 1px 6px;
  vertical-align: 1px;
}
.tag.accent { color: var(--accent); border-color: #e3c2b3; background: var(--accent-soft); }

.lede-quote {
  font-family: var(--serif);
  font-size: clamp(19px, 1.9vw, 24px);
  line-height: 1.6;
  color: var(--ink-2);
  border-left: 3px solid var(--accent);
  padding-left: 22px;
  margin: 34px 0 0;
  max-width: 40em;
}

/* ---------- three columns ---------- */

.three-col {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 26px;
  margin-top: 8px;
}

.col {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 26px 24px 20px;
}

.col h3 {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 15px;
  margin: 0 0 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}
.col h3 span {
  display: inline-grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--paper-2);
  color: var(--accent);
  font-size: 12px;
  font-family: var(--mono);
}

.facts { display: grid; gap: 13px; }
.facts li {
  font-size: 13.5px;
  line-height: 1.72;
  color: var(--ink-2);
  padding-left: 13px;
  position: relative;
}
.facts li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .68em;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--line-2);
}
.facts b { color: var(--ink); font-weight: 600; }

/* ---------- layers ---------- */

.layers {
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  margin-bottom: 40px;
}
.layer {
  display: grid;
  grid-template-columns: 40px 150px minmax(0, 1fr) auto;
  gap: 18px;
  align-items: center;
  background: #fff;
  padding: 15px 20px;
}
.layer > span {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--accent);
}
.layer b { font-size: 14px; }
.layer small {
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--ink-3);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.layer em {
  font-style: normal;
  font-size: 12.5px;
  color: var(--ink-3);
  text-align: right;
}

/* ---------- boundary note ---------- */

.boundary-note {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  margin-top: 26px;
  padding: 16px 20px;
  background: var(--amber-soft);
  border: 1px solid #e8d9b5;
  border-radius: 12px;
}
.boundary-label {
  flex: none;
  font-size: 11px;
  letter-spacing: .08em;
  color: var(--amber);
  border: 1px solid #dcc492;
  border-radius: 4px;
  padding: 2px 7px;
}
.boundary-note p { margin: 0; font-size: 13px; color: #5f502e; line-height: 1.7; }

/* ---------- personas ---------- */

.persona-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin-bottom: 40px;
}
.persona-grid > div {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px 16px 14px;
}
.persona-grid b { display: block; font-size: 14.5px; margin-bottom: 3px; }
.persona-grid span { font-size: 12px; color: var(--ink-3); }

/* ---------- boundary section ---------- */

.boundary { padding-bottom: 40px; }
.boundary-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
  margin-bottom: 34px;
}
.boundary-grid article {
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 26px 24px 18px;
  background: #fff;
}
.boundary-grid article:first-child { background: var(--green-soft); border-color: #cfe0d5; }
.boundary-grid article:last-child { background: var(--amber-soft); border-color: #e8d9b5; }
.boundary-grid h3 { font-size: 15px; margin: 0 0 16px; }
.boundary-grid .facts b { color: var(--ink); }

.index-list {
  border-top: 1px solid var(--line);
  padding-top: 24px;
}
.index-list p { margin-bottom: 10px; font-size: 13px; }
.index-list ul { display: grid; gap: 8px; }
.index-list li {
  font-size: 12.5px;
  color: var(--ink-3);
  font-family: var(--mono);
  line-height: 1.65;
  padding-left: 14px;
  position: relative;
}
.index-list li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--line-2);
}

/* ---------- footer ---------- */

.footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 30px;
  border-top: 1px solid var(--line);
  margin-top: 40px;
  padding: 28px 0 46px;
  font-size: 12.5px;
  color: var(--ink-3);
}
.footer > div { display: flex; align-items: center; gap: 10px; }
.footer p { margin: 0; }

/* ---------- architecture index ---------- */

.index-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin-top: 34px;
}
.index-card {
  display: grid;
  gap: 4px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 15px 16px 13px;
  transition: border-color .18s ease, transform .18s ease;
}
.index-card:hover { border-color: var(--line-2); transform: translateY(-1px); }
.index-card span { font-family: var(--mono); font-size: 10.5px; color: var(--accent); letter-spacing: .08em; }
.index-card b { font-size: 13.5px; }
.index-card small { font-size: 11.5px; color: var(--ink-3); line-height: 1.5; }

/* ---------- chips ---------- */

.chips { display: flex; flex-wrap: wrap; gap: 7px; margin-top: 16px; }
.chip {
  font-size: 12px;
  color: var(--ink-2);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 4px 10px;
}
.chip.hot { color: var(--accent); border-color: #e3c2b3; background: var(--accent-soft); }
.chip.off { color: var(--ink-3); text-decoration: line-through; }

/* ---------- flow ---------- */

.flow-steps {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  margin: 22px 0;
}
.flow-step {
  background: #fff;
  padding: 18px 16px 16px;
  display: grid;
  gap: 5px;
}
.flow-step span { font-family: var(--mono); font-size: 10.5px; color: var(--accent); }
.flow-step b { font-size: 13.5px; }
.flow-step small { font-size: 11.5px; color: var(--ink-3); line-height: 1.55; }

/* ---------- mechanism grid ---------- */

.mech-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin: 22px 0;
}
.mech {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 15px 16px 13px;
}
.mech b { display: block; font-size: 13.5px; margin-bottom: 4px; }
.mech p { margin: 0 0 5px; font-size: 12.5px; color: var(--ink-2); line-height: 1.6; }
.mech code {
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--ink-3);
  background: var(--paper-2);
  padding: 1px 5px;
  border-radius: 3px;
}

/* ---------- warn ---------- */

.warnbox {
  border: 1px solid #e8c9b9;
  background: #fdf1eb;
  border-radius: 14px;
  padding: 20px 22px;
  margin: 26px 0;
}
.warnbox h4 {
  margin: 0 0 10px;
  font-size: 14px;
  color: #8f3517;
  letter-spacing: .02em;
}
.warnbox ul { display: grid; gap: 9px; }
.warnbox li {
  font-size: 13px;
  color: #6b3a28;
  line-height: 1.7;
  padding-left: 14px;
  position: relative;
}
.warnbox li::before { content: "×"; position: absolute; left: 0; color: #b4552f; }

/* ---------- trace stats ---------- */

.trace-stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin: 24px 0;
}
.trace-stat {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
  padding: 18px 18px 15px;
}
.trace-stat strong {
  display: block;
  font-family: var(--serif);
  font-size: 28px;
  line-height: 1.15;
  letter-spacing: -.02em;
}
.trace-stat span { font-size: 12px; color: var(--ink-3); }
.trace-stat em { display: block; font-style: normal; font-size: 11.5px; color: var(--ink-3); margin-top: 4px; }

/* ---------- dense table ---------- */

.table-wrap.dense th, .table-wrap.dense td { padding: 13px 15px; font-size: 12.5px; }
.table-wrap.dense td b { font-size: 13px; }

/* ---------- section intro ---------- */

.section-note {
  font-size: 13px;
  color: var(--ink-3);
  border-left: 2px solid var(--line-2);
  padding-left: 14px;
  margin: 14px 0 22px;
  max-width: 46em;
}

/* ---------- responsive ---------- */

@media (max-width: 980px) {
  .hero { grid-template-columns: 1fr; gap: 44px; padding-top: 60px; }
  .hero-stats { grid-template-columns: repeat(3, 1fr); padding-left: 0; border-left: 0; border-top: 1px solid var(--line); padding-top: 26px; }
  .caliber { grid-template-columns: 1fr; gap: 16px; }
  .system-title { grid-template-columns: 1fr; gap: 12px; }
  .three-col { grid-template-columns: 1fr; }
  .layer { grid-template-columns: 32px 130px minmax(0, 1fr); }
  .layer em { display: none; }
  .persona-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .index-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .flow-steps { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .mech-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .trace-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .edition { display: none; }
}

@media (max-width: 700px) {
  .wrap { width: calc(100% - 32px); }
  .topbar-inner { height: 58px; gap: 12px; }
  .nav { overflow-x: auto; gap: 0; }
  .nav a { padding: 6px 8px; font-size: 13px; white-space: nowrap; }
  .hero { padding: 44px 0 40px; }
  .hero-stats { grid-template-columns: 1fr; gap: 16px; }
  .chapter { padding-top: 52px; }
  .boundary-grid { grid-template-columns: 1fr; }
  .layer { grid-template-columns: 26px minmax(0, 1fr); gap: 4px 10px; padding: 13px 14px; }
  .layer small { grid-column: 2; }
  .footer { flex-direction: column; align-items: flex-start; gap: 10px; }
  .flow-steps { grid-template-columns: 1fr; }
  .mech-grid { grid-template-columns: 1fr; }
  .index-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .trace-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  th, td { padding: 14px 14px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}