:root {
  --ink: #111111;
  --ink-soft: #3d3d3d;
  --ink-mute: #6b6b6b;
  --line: #d8d8d8;
  --line-soft: #e6e6e4;
  --paper: #f4f4f2;
  --card: #ffffff;
  --ink-deep: #0a0a0a;
  --container: 1120px;
  --radius: 6px;
  --shadow-soft: 0 1px 2px rgba(17, 17, 17, 0.06), 0 8px 24px rgba(17, 17, 17, 0.05);
  --serif: "Songti SC", "SimSun", "Noto Serif SC", "Source Han Serif SC", Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
}

/* ============================================================
   base
   ============================================================ */

*,
*::before,
*::after {
  box-sizing: border-box;
}

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

body.site-body {
  margin: 0;
  background-color: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--ink);
  text-decoration: none;
  transition: color 0.18s ease, border-color 0.18s ease, background-color 0.18s ease;
}

a:hover {
  color: var(--ink-deep);
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 3px;
  border-radius: 2px;
}

h1,
h2,
h3,
h4 {
  font-family: var(--serif);
  font-weight: 600;
  line-height: 1.35;
  color: var(--ink);
  margin: 0;
}

h1 {
  font-size: 32px;
}

h2 {
  font-size: 22px;
}

h3 {
  font-size: 17px;
}

p {
  margin: 0;
}

ul,
ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

dl,
dd,
dt,
figure,
figcaption {
  margin: 0;
}

table {
  border-collapse: collapse;
  width: 100%;
}

caption {
  text-align: left;
}

button {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ============================================================
   layout · shell
   ============================================================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background-color: var(--card);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
  min-height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  position: relative;
}

.brand {
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 700;
  letter-spacing: 0;
  color: var(--ink);
  white-space: nowrap;
  padding: 8px 0;
}

.brand:hover {
  color: var(--ink-deep);
}

.site-nav {
  display: flex;
  align-items: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-list li {
  list-style: none;
}

.nav-list a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0 14px;
  font-size: 15px;
  color: var(--ink-soft);
  border-bottom: 2px solid transparent;
}

.nav-list a:hover {
  color: var(--ink);
  border-bottom-color: var(--ink-mute);
}

.nav-list a.is-current {
  color: var(--ink);
  font-weight: 600;
  border-bottom-color: var(--ink);
}

.nav-toggle {
  display: none;
  width: 44px;
  height: 44px;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background-color: var(--card);
}

.nav-toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  background-color: var(--ink);
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(2) {
  opacity: 0;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.site-main {
  display: block;
}

.home-main,
.inner-main {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px 72px;
}

.clue-bar {
  background-color: var(--ink);
  color: #f0f0ee;
  font-size: 14px;
  line-height: 1.6;
  text-align: center;
  padding: 10px 24px;
}

.site-footer {
  background-color: var(--ink);
  color: #d5d5d3;
  margin-top: 0;
}

.footer-top {
  max-width: var(--container);
  margin: 0 auto;
  padding: 16px 24px 0;
  border-bottom: 1px solid #2a2a2a;
  padding-bottom: 14px;
}

.back-to-main {
  font-size: 14px;
  color: #d5d5d3;
  border-bottom: 1px solid #4a4a4a;
  padding-bottom: 2px;
}

.back-to-main:hover {
  color: #ffffff;
  border-bottom-color: #ffffff;
}

.footer-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 32px 24px 8px;
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1fr;
  gap: 32px;
}

.footer-brand-name {
  font-family: var(--serif);
  font-size: 17px;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 8px;
}

.footer-brand-text {
  font-size: 14px;
  line-height: 1.7;
  color: #a9a9a7;
  max-width: 320px;
}

.footer-title {
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 600;
  color: #ffffff;
  margin-bottom: 12px;
  letter-spacing: 0;
}

.footer-list li {
  margin-bottom: 8px;
}

.footer-list a {
  font-size: 14px;
  color: #b8b8b6;
}

.footer-list a:hover {
  color: #ffffff;
}

.footer-copy {
  max-width: var(--container);
  margin: 0 auto;
  padding: 20px 24px 28px;
  font-size: 13px;
  color: #8b8b89;
  border-top: 1px solid #2a2a2a;
}

/* ============================================================
   layout · inner pages
   ============================================================ */

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--ink-mute);
  padding: 20px 0 0;
}

.breadcrumb a {
  color: var(--ink-mute);
}

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

.breadcrumb-sep {
  color: var(--line);
}

.breadcrumb-current {
  color: var(--ink-soft);
}

.page-header {
  padding: 20px 0 28px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 40px;
}

.page-title {
  font-size: 32px;
  font-weight: 600;
  margin-bottom: 12px;
  max-width: 760px;
}

.page-description {
  font-size: 16px;
  line-height: 1.75;
  color: var(--ink-soft);
  max-width: 760px;
}

/* ============================================================
   components · section scaffolding
   ============================================================ */

.section-head {
  margin-bottom: 24px;
  max-width: 760px;
}

.section-head h2 {
  margin-bottom: 8px;
}

.section-note {
  font-size: 14px;
  color: var(--ink-mute);
  line-height: 1.7;
}

.section-foot {
  margin-top: 20px;
  font-size: 14px;
}

.text-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--ink);
  border-bottom: 1px solid var(--line);
  padding-bottom: 2px;
}

.text-link::after {
  content: "→";
  font-size: 13px;
  color: var(--ink-mute);
}

.text-link:hover {
  border-bottom-color: var(--ink);
}

.text-link:hover::after {
  color: var(--ink);
}

.section-intro {
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink-soft);
  max-width: 760px;
  margin-bottom: 24px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 22px;
  font-size: 15px;
  font-weight: 500;
  border-radius: var(--radius);
  border: 1px solid var(--ink);
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}

.btn-solid {
  background-color: var(--ink);
  color: #ffffff;
}

.btn-solid:hover {
  background-color: var(--ink-deep);
  color: #ffffff;
}

.btn-line {
  background-color: transparent;
  color: var(--ink);
}

.btn-line:hover {
  background-color: var(--ink);
  color: #ffffff;
}

/* ============================================================
   components · tables
   ============================================================ */

.table-scroll {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background-color: var(--card);
  -webkit-overflow-scrolling: touch;
}

.data-table,
.channel-table,
.field-table {
  width: 100%;
  min-width: 640px;
  font-size: 15px;
}

.channel-table caption,
.field-table caption,
.data-table caption {
  padding: 12px 16px;
  font-size: 14px;
  color: var(--ink-mute);
  text-align: left;
  border-bottom: 1px solid var(--line);
}

.channel-table thead th,
.field-table thead th,
.data-table thead th {
  background-color: #fafaf8;
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-soft);
  text-align: left;
  padding: 12px 16px;
  border-bottom: 1px solid var(--line);
  white-space: nowrap;
}

.channel-table tbody th,
.field-table tbody th,
.data-table tbody th {
  font-family: var(--serif);
  font-size: 16px;
  font-weight: 600;
  color: var(--ink);
  text-align: left;
  padding: 14px 16px;
  border-bottom: 1px solid var(--line-soft);
  white-space: nowrap;
  vertical-align: top;
}

.channel-table tbody td,
.field-table tbody td,
.data-table tbody td {
  padding: 14px 16px;
  color: var(--ink-soft);
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
  line-height: 1.7;
}

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

.channel-table tbody tr:hover,
.field-table tbody tr:hover,
.data-table tbody tr:hover {
  background-color: #fafaf8;
}

/* ============================================================
   components · figures
   ============================================================ */

figure {
  margin: 0;
}

.lead-media,
.lead-side-media,
.collection-media,
.collection-cover,
.channel-figure,
.field-figure,
.timeline-figure {
  border-radius: var(--radius);
  overflow: hidden;
  background-color: #ececea;
}

.lead-media img,
.lead-side-media img,
.collection-media img,
.collection-cover img,
.channel-figure img,
.field-figure img,
.timeline-figure img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

figcaption {
  font-size: 13px;
  color: var(--ink-mute);
  line-height: 1.6;
  padding: 10px 2px 0;
}

/* ============================================================
   pages · index
   ============================================================ */

.home-main {
  padding-top: 36px;
}

.lead-section {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr);
  gap: 32px;
  align-items: start;
  margin-bottom: 56px;
}

.lead-main {
  display: block;
}

.lead-media {
  aspect-ratio: 16 / 9;
  margin-bottom: 20px;
}

.lead-kicker {
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-mute);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 10px;
}

.lead-main h1 {
  font-size: 32px;
  margin-bottom: 14px;
}

.lead-text {
  font-size: 16px;
  line-height: 1.8;
  color: var(--ink-soft);
  max-width: 620px;
  margin-bottom: 20px;
}

.lead-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.lead-side {
  display: grid;
  grid-template-rows: 1fr 1fr;
  gap: 20px;
  border-left: 1px solid var(--line);
  padding-left: 24px;
}

.lead-side-item {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.lead-side-media {
  aspect-ratio: 16 / 9;
}

.lead-side-title {
  font-size: 17px;
}

.lead-side-text {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.lead-side-item .text-link {
  margin-top: auto;
}

.channel-overview,
.collection-entry,
.log-preview,
.page-index {
  margin-bottom: 56px;
}

.collection-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

.collection-card {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: border-color 0.18s ease, box-shadow 0.18s ease;
}

.collection-card:hover {
  border-color: var(--ink-mute);
  box-shadow: var(--shadow-soft);
}

.collection-media {
  aspect-ratio: 16 / 9;
  border-radius: 0;
}

.collection-title {
  font-size: 17px;
  margin: 16px 18px 8px;
}

.collection-text {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
  margin: 0 18px 10px;
}

.collection-meta {
  font-size: 13px;
  color: var(--ink-mute);
  margin: 0 18px 18px;
  margin-top: auto;
  padding-top: 10px;
  border-top: 1px solid var(--line-soft);
}

.log-groups {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 24px;
}

.log-group {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
}

.log-month {
  font-size: 16px;
  padding-bottom: 10px;
  margin-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.log-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.log-item {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px;
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.6;
}

.log-item time {
  font-size: 13px;
  color: var(--ink-mute);
  font-variant-numeric: tabular-nums;
  flex: 0 0 auto;
}

.log-channel {
  color: var(--ink);
  font-weight: 500;
}

.log-type {
  font-size: 12px;
  color: var(--ink-mute);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 1px 6px;
  flex: 0 0 auto;
}

.field-boundary {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 40px;
  margin-bottom: 56px;
  padding: 32px;
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.field-column,
.boundary-column {
  min-width: 0;
}

.field-column h2,
.boundary-heading {
  font-size: 22px;
  margin-bottom: 8px;
}

.field-list {
  margin-top: 20px;
  border-top: 1px solid var(--line);
}

.field-row {
  display: grid;
  grid-template-columns: 120px minmax(0, 1fr);
  gap: 16px;
  padding: 12px 0;
  border-bottom: 1px solid var(--line-soft);
}

.field-row dt {
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 600;
  color: var(--ink);
}

.field-row dd {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.boundary-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 20px;
}

.boundary-list li {
  position: relative;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.boundary-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 11px;
  width: 8px;
  height: 1px;
  background-color: var(--ink-mute);
}

.boundary-note {
  margin-top: 20px;
  font-size: 14px;
  color: var(--ink-mute);
  line-height: 1.7;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}

.page-index h2 {
  margin-bottom: 24px;
}

.index-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 20px;
}

.index-column {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  display: flex;
  flex-direction: column;
  transition: border-color 0.18s ease;
}

.index-column:hover {
  border-color: var(--ink-mute);
}

.index-title {
  font-size: 16px;
  margin-bottom: 8px;
}

.index-text {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
  margin-bottom: 16px;
}

.index-column .text-link {
  margin-top: auto;
  align-self: flex-start;
}

/* ============================================================
   pages · genre-channels
   ============================================================ */

.channel-overview {
  margin-bottom: 56px;
}

.channel-figure {
  margin-bottom: 24px;
  aspect-ratio: 21 / 9;
}

.channel-methods {
  margin-bottom: 56px;
}

.method-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

.method-column {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  min-width: 0;
}

.method-column h3 {
  margin-bottom: 10px;
}

.method-column p {
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink-soft);
  margin-bottom: 16px;
}

.method-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.method-list li {
  position: relative;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.method-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 11px;
  width: 8px;
  height: 1px;
  background-color: var(--ink-mute);
}

.channel-collection-map {
  margin-bottom: 24px;
}

.map-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.map-item {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  min-width: 0;
}

.map-item h3 {
  margin-bottom: 8px;
}

.map-item p {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.channel-collection-map .section-note {
  margin-top: 24px;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

/* ============================================================
   pages · special-collections
   ============================================================ */

.collection-list-section {
  margin-bottom: 56px;
}

.collection-grid .collection-card {
  min-width: 0;
}

.collection-cover {
  aspect-ratio: 16 / 9;
  border-radius: 0;
}

.collection-body {
  padding: 18px;
  display: flex;
  flex-direction: column;
  flex: 1;
}

.collection-name {
  font-size: 17px;
  margin-bottom: 8px;
}

.collection-name a {
  color: var(--ink);
}

.collection-name a:hover {
  color: var(--ink-deep);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.collection-desc {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
  margin-bottom: 16px;
}

.collection-meta {
  margin-top: auto;
  display: grid;
  grid-template-columns: 88px minmax(0, 1fr);
  gap: 6px 12px;
  font-size: 13px;
  padding-top: 12px;
  border-top: 1px solid var(--line-soft);
}

.collection-meta dt {
  color: var(--ink-mute);
}

.collection-meta dd {
  color: var(--ink-soft);
}

.division-section,
.principle-section {
  margin-bottom: 56px;
}

.division-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

.division-column {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  min-width: 0;
}

.division-column h3 {
  margin-bottom: 10px;
}

.division-column p {
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink-soft);
  margin-bottom: 16px;
}

.division-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.division-list li {
  position: relative;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.division-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 11px;
  width: 8px;
  height: 1px;
  background-color: var(--ink-mute);
}

.principle-list {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
  counter-reset: principle;
}

.principle-item {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  min-width: 0;
  position: relative;
}

.principle-item::before {
  counter-increment: principle;
  content: counter(principle, decimal-leading-zero);
  display: block;
  font-family: var(--serif);
  font-size: 13px;
  color: var(--ink-mute);
  margin-bottom: 10px;
}

.principle-item h3 {
  margin-bottom: 8px;
}

.principle-item p {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.principle-note {
  margin-top: 24px;
  font-size: 14px;
}

/* ============================================================
   pages · field-guide
   ============================================================ */

.content-section {
  margin-bottom: 56px;
}

.field-figure {
  margin-bottom: 24px;
  aspect-ratio: 16 / 9;
}

.step-list {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
  counter-reset: step;
}

.step-item {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  min-width: 0;
}

.step-item::before {
  counter-increment: step;
  content: counter(step, decimal-leading-zero);
  display: block;
  font-family: var(--serif);
  font-size: 13px;
  color: var(--ink-mute);
  margin-bottom: 10px;
}

.step-title {
  margin-bottom: 8px;
}

.step-item p {
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink-soft);
}

.step-item p a {
  color: var(--ink);
  border-bottom: 1px solid var(--line);
}

.step-item p a:hover {
  border-bottom-color: var(--ink);
}

.boundary-section {
  margin-bottom: 24px;
}

.boundary-section .boundary-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
  margin-top: 0;
}

.boundary-item {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  min-width: 0;
}

.boundary-item::before {
  content: none;
}

.boundary-title {
  margin-bottom: 8px;
}

.boundary-item p {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
}

.boundary-more {
  margin-top: 24px;
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 20px;
}

.boundary-more summary {
  cursor: pointer;
  font-size: 15px;
  font-weight: 600;
  color: var(--ink);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 8px;
  min-height: 32px;
}

.boundary-more summary::-webkit-details-marker {
  display: none;
}

.boundary-more summary::before {
  content: "+";
  font-family: var(--serif);
  font-size: 16px;
  color: var(--ink-mute);
  width: 14px;
}

.boundary-more[open] summary::before {
  content: "–";
}

.boundary-more p {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--line-soft);
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink-soft);
}

/* ============================================================
   pages · archive-log
   ============================================================ */

.section {
  margin-bottom: 56px;
}

.timeline-figure {
  margin-bottom: 28px;
  aspect-ratio: 21 / 9;
}

.timeline-groups {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.timeline-month {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px 24px;
}

.timeline-month-title {
  font-size: 17px;
  padding-bottom: 12px;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--line);
}

.timeline-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
  counter-reset: timeline;
}

.timeline-item {
  display: grid;
  grid-template-columns: 96px 140px 120px minmax(0, 1fr);
  gap: 16px;
  align-items: baseline;
  padding-bottom: 14px;
  border-bottom: 1px dashed var(--line-soft);
  min-width: 0;
}

.timeline-item:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.timeline-date {
  font-size: 13px;
  color: var(--ink-mute);
  font-variant-numeric: tabular-nums;
}

.timeline-channel {
  font-size: 14px;
  font-weight: 500;
  color: var(--ink);
}

.timeline-type {
  font-size: 12px;
  color: var(--ink-mute);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 2px 8px;
  justify-self: start;
  white-space: nowrap;
}

.timeline-note {
  font-size: 14px;
  line-height: 1.7;
  color: var(--ink-soft);
  min-width: 0;
}

.reason-list,
.impact-list {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.reason-item,
.impact-item {
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  min-width: 0;
}

.reason-item h3,
.impact-item h3 {
  margin-bottom: 8px;
}

.reason-item p,
.impact-item p {
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink-soft);
}

.impact-item p a {
  color: var(--ink);
  border-bottom: 1px solid var(--line);
}

.impact-item p a:hover {
  border-bottom-color: var(--ink);
}

/* ============================================================
   pages · 404
   ============================================================ */

.error-main {
  max-width: var(--container);
  margin: 0 auto;
  padding: 72px 24px 80px;
}

.error-panel {
  max-width: 640px;
  margin-bottom: 48px;
}

.error-code {
  font-family: var(--serif);
  font-size: 56px;
  font-weight: 700;
  line-height: 1;
  color: var(--line);
  margin-bottom: 16px;
}

.error-panel h1 {
  font-size: 32px;
  margin-bottom: 14px;
}

.error-text {
  font-size: 16px;
  line-height: 1.8;
  color: var(--ink-soft);
  margin-bottom: 24px;
}

.error-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.button-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 22px;
  font-size: 15px;
  font-weight: 500;
  border-radius: var(--radius);
  background-color: var(--ink);
  color: #ffffff;
  border: 1px solid var(--ink);
}

.button-primary:hover {
  background-color: var(--ink-deep);
  color: #ffffff;
}

.error-links h2 {
  font-size: 22px;
  margin-bottom: 20px;
}

.error-link-list {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
}

.error-link-list li {
  min-width: 0;
}

.error-link-list a {
  display: flex;
  align-items: center;
  min-height: 56px;
  padding: 12px 16px;
  font-size: 15px;
  background-color: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink);
  transition: border-color 0.18s ease, background-color 0.18s ease;
}

.error-link-list a:hover {
  border-color: var(--ink-mute);
  background-color: #fafaf8;
}

/* ============================================================
   responsive
   ============================================================ */

@media (max-width: 900px) {
  .header-inner {
    padding: 0 20px;
    flex-wrap: wrap;
    justify-content: space-between;
  }

  .nav-toggle {
    display: flex;
  }

  .site-nav {
    width: 100%;
    order: 3;
  }

  .nav-list {
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    width: 100%;
    padding: 8px 0 12px;
    border-top: 1px solid var(--line);
  }

  .nav-list.is-open {
    display: flex;
  }

  .nav-list a {
    min-height: 48px;
    padding: 0 4px;
    border-bottom: 1px solid var(--line-soft);
    border-left: 0;
    font-size: 16px;
  }

  .nav-list a:hover,
  .nav-list a.is-current {
    border-bottom-color: var(--ink);
    border-left: 0;
  }

  .home-main,
  .inner-main {
    padding: 0 20px 56px;
  }

  .home-main {
    padding-top: 28px;
  }

  .lead-section {
    grid-template-columns: minmax(0, 1fr);
    gap: 28px;
    margin-bottom: 44px;
  }

  .lead-side {
    grid-template-rows: none;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px;
    border-left: 0;
    padding-left: 0;
    border-top: 1px solid var(--line);
    padding-top: 24px;
  }

  .channel-overview,
  .collection-entry,
  .log-preview,
  .page-index,
  .channel-methods,
  .collection-list-section,
  .division-section,
  .principle-section,
  .content-section,
  .section {
    margin-bottom: 44px;
  }

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

  .field-boundary {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
    padding: 24px;
    margin-bottom: 44px;
  }

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

  .method-columns,
  .division-columns,
  .map-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .principle-list,
  .step-list,
  .reason-list,
  .impact-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .timeline-item {
    grid-template-columns: 96px 140px minmax(0, 1fr);
  }

  .timeline-note {
    grid-column: 1 / -1;
  }

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

  .footer-inner {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 28px;
  }

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

@media (max-width: 600px) {
  h1,
  .page-title,
  .lead-main h1,
  .error-panel h1 {
    font-size: 26px;
  }

  h2 {
    font-size: 20px;
  }

  .clue-bar {
    font-size: 13px;
    padding: 10px 16px;
    text-align: left;
  }

  .header-inner {
    padding: 0 16px;
  }

  .home-main,
  .inner-main {
    padding: 0 16px 48px;
  }

  .home-main {
    padding-top: 24px;
  }

  .page-header {
    padding: 16px 0 22px;
    margin-bottom: 32px;
  }

  .lead-section,
  .lead-side {
    grid-template-columns: minmax(0, 1fr);
  }

  .lead-side {
    grid-template-rows: none;
  }

  .lead-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .btn {
    width: 100%;
  }

  .collection-grid,
  .log-groups,
  .index-grid,
  .method-columns,
  .division-columns,
  .map-list,
  .principle-list,
  .step-list,
  .reason-list,
  .impact-list,
  .boundary-section .boundary-list,
  .error-link-list {
    grid-template-columns: minmax(0, 1fr);
  }

  .field-boundary {
    padding: 20px;
  }

  .field-row {
    grid-template-columns: minmax(0, 1fr);
    gap: 4px;
  }

  .timeline-month {
    padding: 18px 16px;
  }

  .timeline-item {
    grid-template-columns: minmax(0, 1fr);
    gap: 6px;
  }

  .timeline-type {
    justify-self: start;
  }

  .channel-table,
  .field-table,
  .data-table {
    min-width: 560px;
  }

  .footer-inner {
    grid-template-columns: minmax(0, 1fr);
    gap: 24px;
    padding: 28px 16px 8px;
  }

  .footer-top {
    padding: 14px 16px;
  }

  .footer-copy {
    padding: 18px 16px 24px;
  }

  .error-main {
    padding: 48px 16px 64px;
  }

  .error-code {
    font-size: 44px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}