:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --ink: #1a2233;
  --ink-soft: #4b5567;
  --ink-faint: #8590a3;
  --line: #dde2ea;
  --accent: #3b5bdb;
  --accent-soft: #eef1fd;
  --accent-line: #c3cdf5;
  --warn-bg: #fff8e6;
  --warn-line: #f0d9a0;
  --radius: 10px;
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 1.5rem;
  padding: 0.7rem 1.5rem;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--line);
}

.brand {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--ink);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.brand span {
  color: var(--accent);
}

.site-header nav {
  display: flex;
  gap: 1.1rem;
  margin-left: auto;
  flex-wrap: wrap;
}

.site-header nav a {
  color: var(--ink-soft);
  text-decoration: none;
  font-size: 0.92rem;
  padding: 0.15rem 0;
  border-bottom: 2px solid transparent;
}

.site-header nav a:hover {
  color: var(--ink);
}

.site-header nav a[aria-current="page"] {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
}

.hero h1 {
  font-size: 1.9rem;
  letter-spacing: -0.02em;
  margin: 0 0 0.5rem;
}

.lede {
  color: var(--ink-soft);
  max-width: 46rem;
  margin: 0 0 1.25rem;
}

.legend {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  font-size: 0.85rem;
  color: var(--ink-soft);
  padding: 0.75rem 1rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  margin-bottom: 2rem;
}

.legend b {
  font-weight: 600;
  color: var(--ink);
}

.diagram {
  display: flex;
  flex-direction: column;
}

.band {
  display: flex;
  gap: 1.25rem;
  align-items: stretch;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.9rem 1.1rem;
}

.band:hover {
  border-color: var(--accent-line);
}

.band.external {
  border-style: dashed;
}

.rail {
  flex: 0 0 11.5rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  border-right: 1px solid var(--line);
  padding-right: 1.1rem;
}

.rail .num {
  font-family: var(--mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
}

.rail a {
  font-weight: 650;
  font-size: 1.02rem;
  color: var(--ink);
  text-decoration: none;
  line-height: 1.35;
}

.rail a:hover {
  color: var(--accent);
}

.rail .hint {
  font-size: 0.78rem;
  color: var(--ink-faint);
  margin-top: 0.2rem;
}

.chips {
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  align-content: center;
}

.chip {
  display: inline-block;
  padding: 0.42rem 0.75rem;
  background: var(--accent-soft);
  border: 1px solid var(--accent-line);
  border-radius: 8px;
  color: var(--ink);
  text-decoration: none;
  font-family: var(--mono);
  font-size: 0.82rem;
  line-height: 1.45;
}

.chip small {
  display: block;
  font-family: inherit;
  color: var(--ink-soft);
  font-size: 0.74rem;
}

.chip:hover {
  border-color: var(--accent);
  box-shadow: 0 2px 8px rgba(59, 91, 219, 0.14);
}

.chip.plain {
  background: var(--surface);
  cursor: default;
}

.chip.plain:hover {
  box-shadow: none;
  border-color: var(--accent-line);
}

.connector {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.18rem 0;
  color: var(--ink-faint);
  font-size: 0.72rem;
}

.connector .arrow {
  color: var(--accent);
  font-size: 0.85rem;
  line-height: 1;
}

section.block {
  margin-top: 2.75rem;
}

section.block > h2 {
  font-size: 1.25rem;
  letter-spacing: -0.01em;
  margin: 0 0 0.9rem;
}

.notes {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.25rem 1rem 2.25rem;
  margin: 0;
}

.notes li + li {
  margin-top: 0.5rem;
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 0.9rem;
}

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.95rem 1.1rem;
}

.card h3 {
  margin: 0 0 0.35rem;
  font-size: 0.98rem;
}

.card h3 code,
td code,
li code,
p code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--accent-soft);
  border-radius: 5px;
  padding: 0.08em 0.35em;
}

.card p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.doclist {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.5rem 1.25rem;
}

.doclist ul {
  list-style: none;
  padding: 0;
  margin: 0.4rem 0;
}

.doclist li {
  padding: 0.28rem 0;
  border-bottom: 1px solid var(--line);
}

.doclist li:last-child {
  border-bottom: none;
}

.doclist a {
  color: var(--accent);
  text-decoration: none;
  font-family: var(--mono);
  font-size: 0.88rem;
}

.doclist a:hover {
  text-decoration: underline;
}

.breadcrumb {
  font-size: 0.85rem;
  color: var(--ink-faint);
  margin-bottom: 1.25rem;
}

.purpose {
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 0.7rem 1.1rem;
  margin: 0 0 1.5rem;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.purpose em {
  color: var(--ink);
}

.breadcrumb a {
  color: var(--ink-soft);
  text-decoration: none;
}

.breadcrumb a:hover {
  color: var(--accent);
}

.layer-head {
  display: flex;
  align-items: baseline;
  gap: 0.9rem;
  flex-wrap: wrap;
  margin-bottom: 0.4rem;
}

.layer-head .num {
  font-family: var(--mono);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  border: 1px solid var(--accent-line);
  background: var(--accent-soft);
  border-radius: 999px;
  padding: 0.12rem 0.65rem;
}

h1 {
  font-size: 1.7rem;
  letter-spacing: -0.02em;
  margin: 0;
}

h2 {
  font-size: 1.15rem;
  margin: 2.25rem 0 0.7rem;
}

.edges {
  width: 100%;
  border-collapse: collapse;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  font-size: 0.92rem;
}

.edges th,
.edges td {
  text-align: left;
  padding: 0.55rem 0.9rem;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}

.edges th {
  background: var(--accent-soft);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}

.edges tr:last-child td {
  border-bottom: none;
}

.edges td:first-child {
  white-space: nowrap;
  font-family: var(--mono);
  font-size: 0.84rem;
}

.rules {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.25rem 1rem 2.25rem;
  margin: 0;
}

.callout {
  background: var(--warn-bg);
  border: 1px solid var(--warn-line);
  border-radius: var(--radius);
  padding: 0.8rem 1.1rem;
  font-size: 0.92rem;
  color: var(--ink-soft);
}

.pager {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 3rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--line);
}

.pager a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
}

.pager a:hover {
  text-decoration: underline;
}

.pager .spacer {
  flex: 1;
}

.viewer-status {
  color: var(--ink-faint);
  font-size: 0.9rem;
}

.markdown-body {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem 2rem;
  max-width: none;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3 {
  letter-spacing: -0.01em;
}

.markdown-body pre {
  background: #f0f2f7;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.9rem 1.1rem;
  overflow-x: auto;
}

.markdown-body code {
  font-family: var(--mono);
  font-size: 0.86em;
}

.markdown-body pre code {
  background: none;
  padding: 0;
}

.markdown-body table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.9rem;
}

.markdown-body th,
.markdown-body td {
  border: 1px solid var(--line);
  padding: 0.4rem 0.7rem;
  text-align: left;
}

.markdown-body th {
  background: var(--accent-soft);
}

.markdown-body blockquote {
  border-left: 3px solid var(--accent-line);
  margin: 0;
  padding: 0.1rem 1rem;
  color: var(--ink-soft);
}

.mermaid {
  background: var(--surface);
  display: flex;
  justify-content: center;
  overflow-x: auto;
}

footer.site-footer {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1.5rem;
  color: var(--ink-faint);
  font-size: 0.82rem;
  border-top: 1px solid var(--line);
}

@media (max-width: 720px) {
  .band {
    flex-direction: column;
    gap: 0.6rem;
  }

  .rail {
    flex: none;
    border-right: none;
    border-bottom: 1px solid var(--line);
    padding: 0 0 0.5rem;
  }
}