:root {
  --font-body: "Inter", "Segoe UI", system-ui, sans-serif;
  --font-display: "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --font-mono: "SFMono-Regular", Menlo, Consolas, monospace;

  --bg: #e9eef5;
  --surface: #f7fafc;
  --surface-strong: #ffffff;
  --surface-muted: #edf3f8;
  --ink: #0b1620;
  --ink-dim: #42586c;
  --line: rgba(11, 22, 32, 0.11);
  --line-strong: rgba(11, 22, 32, 0.2);

  --blue: #135d91;
  --blue-soft: rgba(19, 93, 145, 0.1);
  --sage: #476a58;
  --sage-soft: rgba(71, 106, 88, 0.1);
  --amber: #9b6a24;
  --amber-soft: rgba(155, 106, 36, 0.12);
  --rose: #8a4867;
  --rose-soft: rgba(138, 72, 103, 0.11);

  --shadow: 0 18px 38px rgba(36, 60, 85, 0.08);
  --radius: 22px;
  --max-reading: 74ch;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1118;
    --surface: #141d27;
    --surface-strong: #192330;
    --surface-muted: #101822;
    --ink: #edf4fb;
    --ink-dim: #b5c4d4;
    --line: rgba(237, 244, 251, 0.1);
    --line-strong: rgba(237, 244, 251, 0.18);

    --blue: #7bc5ff;
    --blue-soft: rgba(123, 197, 255, 0.12);
    --sage: #9cc8af;
    --sage-soft: rgba(156, 200, 175, 0.12);
    --amber: #e7c281;
    --amber-soft: rgba(231, 194, 129, 0.12);
    --rose: #e4a9c5;
    --rose-soft: rgba(228, 169, 197, 0.12);

    --shadow: 0 24px 52px rgba(0, 0, 0, 0.34);
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-body);
  color: var(--ink);
  line-height: 1.6;
  background:
    radial-gradient(circle at top left, var(--blue-soft), transparent 20%),
    radial-gradient(circle at bottom right, var(--sage-soft), transparent 18%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.24), transparent 18%),
    var(--bg);
}

a {
  color: inherit;
}

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

code {
  font-family: var(--font-mono);
  font-size: 0.95em;
  background: var(--surface-muted);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 2px 6px;
  overflow-wrap: anywhere;
}

.shell {
  max-width: 1400px;
  margin: 0 auto;
  padding: 24px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-bottom: 18px;
  color: var(--ink-dim);
  font-size: 14px;
}

.topbar .brand {
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  font-size: 11px;
}

.hero {
  position: relative;
  overflow: hidden;
  border-radius: calc(var(--radius) + 4px);
  border: 1px solid var(--line-strong);
  background: linear-gradient(180deg, var(--surface-strong), var(--surface));
  box-shadow: var(--shadow);
  padding: 32px;
  margin-bottom: 24px;
}

.hero::after {
  content: "";
  position: absolute;
  right: -72px;
  top: -90px;
  width: 280px;
  height: 280px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--blue-soft), transparent 70%);
  pointer-events: none;
}

.eyebrow {
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.18em;
  font-size: 12px;
  color: var(--blue);
  margin-bottom: 10px;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  letter-spacing: -0.03em;
  margin: 0;
}

h1 {
  font-size: clamp(2.5rem, 5vw, 4.5rem);
  line-height: 0.96;
  max-width: 12ch;
}

h2 {
  font-size: clamp(1.75rem, 3vw, 2.4rem);
  margin-bottom: 10px;
}

h3 {
  font-size: 1.2rem;
  margin-bottom: 6px;
}

.lede {
  font-size: 1.08rem;
  color: var(--ink-dim);
  max-width: var(--max-reading);
  margin: 16px 0 0;
}

.hero-summary {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin-top: 24px;
}

.summary-card,
.card,
.step,
.callout,
.mini-grid > article,
.nav-card {
  min-width: 0;
  border-radius: 18px;
  border: 1px solid var(--line);
  background: var(--surface-strong);
  padding: 16px 18px;
}

.summary-card p,
.card p,
.step p,
.callout p,
.callout li,
.mini-grid li,
.mini-grid p {
  margin: 0;
  color: var(--ink-dim);
}

.content-layout {
  display: grid;
  grid-template-columns: 200px minmax(0, 1fr);
  gap: 28px;
  align-items: start;
}

.toc {
  position: sticky;
  top: 22px;
  align-self: start;
  max-height: calc(100dvh - 44px);
  overflow-y: auto;
  padding: 8px 0;
}

.toc-title {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--ink-dim);
  border-bottom: 1px solid var(--line);
  padding-bottom: 10px;
  margin-bottom: 10px;
}

.toc a {
  display: block;
  text-decoration: none;
  font-size: 12px;
  color: var(--ink-dim);
  border-left: 2px solid transparent;
  padding: 6px 8px;
  border-radius: 6px;
  transition: 0.15s ease;
}

.toc a:hover {
  color: var(--ink);
  background: var(--surface);
}

.toc a.active {
  color: var(--ink);
  border-left-color: var(--blue);
  background: var(--surface);
}

.page {
  min-width: 0;
}

.section {
  scroll-margin-top: 32px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--surface-strong);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 22px;
}

.section-kicker {
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.18em;
  font-size: 12px;
  color: var(--amber);
  margin-bottom: 8px;
}

.section > p {
  max-width: var(--max-reading);
  color: var(--ink-dim);
}

.grid-2,
.grid-3,
.mini-grid,
.response-grid {
  display: grid;
  gap: 12px;
}

.grid-2,
.response-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.grid-3,
.mini-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 12px;
}

.chip {
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--blue-soft);
}

.chip.sage {
  background: var(--sage-soft);
}

.chip.amber {
  background: var(--amber-soft);
}

.chip.rose {
  background: var(--rose-soft);
}

.sequence {
  display: grid;
  gap: 12px;
  position: relative;
}

.sequence::before {
  content: "";
  position: absolute;
  left: 26px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(var(--blue-soft), transparent);
}

.step {
  display: grid;
  grid-template-columns: 54px minmax(0, 1fr);
  gap: 14px;
}

.step-num {
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border-radius: 18px;
  border: 1px solid var(--line-strong);
  background: var(--surface-strong);
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--blue);
  z-index: 1;
}

.principles {
  display: grid;
  gap: 12px;
}

.principle {
  border-left: 3px solid var(--blue);
  padding-left: 14px;
}

.principle strong {
  display: block;
  margin-bottom: 4px;
}

.principle span {
  color: var(--ink-dim);
  font-size: 14px;
}

.diagram {
  display: grid;
  gap: 12px;
}

.diagram-row {
  display: grid;
  grid-template-columns: 1fr 90px 1fr;
  gap: 12px;
  align-items: center;
}

.arrow {
  text-align: center;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--blue);
  text-transform: uppercase;
  letter-spacing: 0.14em;
}

dl.meta {
  display: grid;
  grid-template-columns: 170px 1fr;
  gap: 10px 14px;
  margin: 0;
}

dl.meta dt {
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 11px;
}

dl.meta dd {
  margin: 0;
  color: var(--ink-dim);
}

.table-wrap {
  overflow-x: auto;
  border-radius: 20px;
  border: 1px solid var(--line);
  background: var(--surface-strong);
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 860px;
}

.data-table th,
.data-table td {
  padding: 14px 16px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--line);
}

.data-table thead th {
  position: sticky;
  top: 0;
  z-index: 1;
  background: var(--surface-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--ink-dim);
}

.data-table tbody tr:nth-child(even) {
  background: var(--surface-muted);
}

.data-table tbody tr:hover {
  background: var(--blue-soft);
}

.data-table tbody tr:last-child td {
  border-bottom: 0;
}

.data-table td:first-child {
  min-width: 210px;
}

.template-stack {
  display: grid;
  gap: 10px;
  margin-top: 12px;
}

.template-detail {
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--surface-strong);
  overflow: hidden;
}

.template-detail summary {
  cursor: pointer;
  list-style: none;
  padding: 14px 16px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--ink);
  background: var(--surface-muted);
}

.template-detail summary::-webkit-details-marker {
  display: none;
}

.template-detail pre {
  margin: 0;
  padding: 16px;
  overflow-x: auto;
  background: var(--surface);
  border-top: 1px solid var(--line);
}

.template-detail pre code {
  display: block;
  padding: 0;
  border: 0;
  background: transparent;
  white-space: pre;
  min-width: max-content;
}

.callout {
  background: var(--surface-muted);
  border-color: var(--line-strong);
}

.callout ul {
  margin: 10px 0 0;
  padding-left: 18px;
}

.footnote {
  font-size: 13px;
  color: var(--ink-dim);
  margin-top: 14px;
}

.index-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 18px;
}

.nav-list {
  display: grid;
  gap: 12px;
}

.nav-card {
  text-decoration: none;
  display: block;
  transition: transform 0.16s ease, border-color 0.16s ease, box-shadow 0.16s ease;
}

.nav-card:hover {
  transform: translateY(-2px);
  border-color: var(--line-strong);
  box-shadow: 0 16px 30px rgba(16, 34, 53, 0.12);
}

.nav-card .label {
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  font-size: 11px;
  color: var(--blue);
  margin-bottom: 8px;
}

.nav-card p:last-child {
  margin-top: 8px;
  color: var(--ink-dim);
}

.read-order {
  display: grid;
  gap: 10px;
  padding-left: 0;
  margin: 0;
  list-style: none;
}

.read-order li {
  padding: 12px 14px;
  border-radius: 14px;
  background: var(--surface-muted);
  border: 1px solid var(--line);
  color: var(--ink-dim);
}

.read-order strong {
  display: block;
  color: var(--ink);
  margin-bottom: 4px;
}

.footer {
  margin-top: 28px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  color: var(--ink-dim);
  font-size: 13px;
}

@media (max-width: 1080px) {
  .content-layout {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .toc {
    position: sticky;
    top: 0;
    z-index: 30;
    display: flex;
    gap: 4px;
    align-items: center;
    overflow-x: auto;
    max-height: none;
    background: var(--bg);
    border-bottom: 1px solid var(--line);
    padding: 10px 0;
    margin: 0 -24px 18px;
    padding-left: 24px;
    padding-right: 24px;
  }

  .toc-title {
    display: none;
  }

  .toc a {
    white-space: nowrap;
    border-left: none;
    border-bottom: 2px solid transparent;
    border-radius: 6px 6px 0 0;
    font-size: 11px;
  }

  .toc a.active {
    border-left: none;
    border-bottom-color: var(--blue);
  }
}

@media (max-width: 900px) {
  .hero-summary,
  .grid-2,
  .grid-3,
  .mini-grid,
  .response-grid,
  .index-grid,
  .diagram-row,
  dl.meta {
    grid-template-columns: 1fr;
  }

  .arrow {
    transform: rotate(90deg);
    padding: 8px 0;
  }
}

@media (max-width: 640px) {
  .shell {
    padding: 16px;
  }

  .hero,
  .section {
    padding: 20px;
  }

  .topbar {
    flex-direction: column;
    align-items: flex-start;
  }

  .lede,
  .hero p {
    font-size: 1rem;
  }

  .step {
    grid-template-columns: 46px minmax(0, 1fr);
  }

  .step-num {
    width: 46px;
    height: 46px;
    border-radius: 14px;
    font-size: 12px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  * {
    transition: none !important;
  }
}