:root {
  --bg: #f7f7f5;
  --ink: #1f2328;
  --ink-soft: #5b6470;
  --accent: #3f5a7a;
  --accent-deep: #33496a;
  --line: #d9dce0;
  --card: #ffffff;
  --radius: 6px;
  --wrap: 1120px;
  --gutter: 24px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: "SFMono-Regular", "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

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

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

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  letter-spacing: 0;
}

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

p {
  margin: 0;
}

ul,
ol,
dl,
dd {
  margin: 0;
  padding: 0;
}

li {
  list-style: none;
}

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

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover,
a:focus-visible {
  text-decoration: underline;
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

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

th,
td {
  text-align: left;
  vertical-align: top;
}

figure {
  margin: 0;
}

figcaption {
  margin-top: 8px;
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.6;
}

.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
   ========================================================================== */

.site-body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  background: var(--bg);
}

.site-main {
  flex: 1 1 auto;
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 0 var(--gutter) 72px;
}

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

.home-main {
  padding-top: 0;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 40;
  padding: 10px 16px;
  background: var(--ink);
  color: #fff;
  border-radius: 0 0 var(--radius) 0;
  font-size: 14px;
}

.skip-link:focus {
  left: 0;
}

/* --- header --- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  background: rgba(247, 247, 245, 0.96);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 20px;
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 14px var(--gutter);
}

.brand {
  flex: 0 0 auto;
  color: var(--ink);
  font-size: 18px;
  font-weight: 600;
  letter-spacing: 0.02em;
}

.brand:hover {
  color: var(--accent);
  text-decoration: none;
}

.site-nav {
  flex: 1 1 auto;
  display: flex;
  justify-content: flex-end;
}

.nav-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 4px 22px;
}

.nav-list a {
  display: inline-block;
  padding: 6px 0;
  color: var(--ink-soft);
  font-size: 15px;
  border-bottom: 2px solid transparent;
}

.nav-list a:hover {
  color: var(--ink);
  text-decoration: none;
}

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

.nav-toggle {
  display: none;
  flex: 0 0 auto;
  width: 44px;
  height: 44px;
  padding: 0;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink);
  font-size: 15px;
  cursor: pointer;
}

.nav-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* --- breadcrumb --- */

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  padding: 4px 0 16px;
  color: var(--ink-soft);
  font-size: 13px;
}

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

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

.breadcrumb-sep::before {
  content: "/";
  color: var(--line);
}

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

/* --- page header --- */

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

.page-title {
  font-size: 30px;
  font-weight: 600;
  line-height: 1.3;
}

.page-description {
  max-width: 780px;
  margin-top: 12px;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

/* --- footer --- */

.site-footer {
  margin-top: auto;
  background: var(--card);
  border-top: 1px solid var(--line);
}

.footer-top {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 32px;
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 40px var(--gutter) 28px;
}

.footer-heading {
  margin-bottom: 12px;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.footer-links a {
  color: var(--ink-soft);
  font-size: 14px;
}

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

.footer-bottom {
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 20px var(--gutter) 36px;
  border-top: 1px solid var(--line);
}

.footer-about,
.footer-boundary,
.footer-copy {
  max-width: 820px;
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.8;
}

.footer-boundary {
  margin-top: 8px;
}

.footer-copy {
  margin-top: 12px;
  color: #8b929b;
}

.back-to-top {
  display: inline-block;
  margin-top: 16px;
  padding: 8px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink-soft);
  font-size: 13px;
  background: var(--bg);
}

.back-to-top:hover {
  border-color: var(--accent);
  color: var(--accent);
  text-decoration: none;
}

/* ==========================================================================
   components
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 22px;
  border-radius: var(--radius);
  border: 1px solid transparent;
  font-size: 15px;
  font-weight: 500;
  transition: background-color 0.18s ease, border-color 0.18s ease, color 0.18s ease;
}

.btn:hover {
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-deep);
  border-color: var(--accent-deep);
}

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

.btn-ghost:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.section {
  padding: 48px 0;
  border-top: 1px solid var(--line);
}

.section-head {
  margin-bottom: 26px;
}

.section-head h2,
.section-title,
.section-heading {
  font-size: 22px;
  font-weight: 600;
}

.section-head p,
.section-lead,
.section-intro {
  max-width: 760px;
  margin-top: 10px;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

.section-more {
  margin-top: 22px;
  font-size: 14px;
}

.section-more a {
  color: var(--accent);
}

.section-note {
  margin-top: 20px;
  color: var(--ink-soft);
  font-size: 14px;
}

.content-section {
  padding: 40px 0;
  border-top: 1px solid var(--line);
}

.content-section:first-child {
  border-top: 0;
  padding-top: 0;
}

.content-section .section-title {
  margin-bottom: 12px;
}

.content-section .section-lead {
  margin-bottom: 22px;
}

.section-figure {
  margin-bottom: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.section-figure img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.section-figure figcaption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

.index-no,
.step-no,
.step-index,
.channel-index {
  display: inline-block;
  min-width: 2.4em;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--accent);
  letter-spacing: 0.04em;
}

/* --- tables --- */

.table-wrap,
.mapping-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--card);
}

.fields-table,
.mapping-table,
.clue-table,
.field-table {
  width: 100%;
  font-size: 14px;
}

.fields-table caption,
.mapping-caption,
.clue-caption,
.field-table-caption {
  padding: 14px 16px;
  color: var(--ink-soft);
  font-size: 13px;
  text-align: left;
  border-bottom: 1px solid var(--line);
}

.fields-table th,
.fields-table td,
.mapping-table th,
.mapping-table td,
.clue-table th,
.clue-table td,
.field-table th,
.field-table td {
  padding: 13px 16px;
  border-bottom: 1px solid var(--line);
  line-height: 1.7;
}

.fields-table thead th,
.mapping-table thead th,
.clue-table thead th,
.field-table thead th {
  background: #f1f2f0;
  color: var(--ink);
  font-size: 13px;
  font-weight: 600;
  white-space: nowrap;
}

.fields-table tbody th,
.mapping-table tbody th,
.field-table tbody th {
  color: var(--ink);
  font-weight: 600;
  white-space: nowrap;
}

.fields-table tbody tr:last-child th,
.fields-table tbody tr:last-child td,
.mapping-table tbody tr:last-child th,
.mapping-table tbody tr:last-child td,
.clue-table tbody tr:last-child td,
.field-table tbody tr:last-child th,
.field-table tbody tr:last-child td {
  border-bottom: 0;
}

.fields-table td,
.mapping-table td,
.clue-table td,
.field-table td {
  color: var(--ink-soft);
}

/* --- steps (shared base) --- */

.step-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.step-item {
  display: grid;
  grid-template-columns: 3.2em minmax(0, 1fr);
  gap: 4px 18px;
  padding: 22px 0;
  border-top: 1px solid var(--line);
}

.step-item:first-child {
  border-top: 0;
  padding-top: 0;
}

.step-title {
  font-size: 17px;
  font-weight: 600;
}

.step-desc,
.step-text {
  grid-column: 2 / -1;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

/* ==========================================================================
   pages
   ========================================================================== */

/* --- home: hero --- */

.hero-section {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
  gap: 40px;
  padding: 52px 0 44px;
}

.hero-copy {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.hero-kicker {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--accent);
  letter-spacing: 0.08em;
}

.hero-title {
  font-size: 34px;
  font-weight: 600;
  line-height: 1.32;
}

.hero-lead {
  max-width: 560px;
  margin-top: 18px;
  color: var(--ink-soft);
  font-size: 16px;
  line-height: 1.85;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}

.hero-side {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.hero-figure {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.hero-figure img {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
}

.hero-figure figcaption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

.hero-index {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.hero-index-item {
  padding: 14px 16px;
  background: var(--card);
}

.hero-index-item dt {
  font-size: 13px;
  color: var(--ink-soft);
}

.hero-index-item dd {
  margin-top: 4px;
  font-size: 15px;
  font-weight: 600;
  color: var(--ink);
}

.content-media {
  grid-column: 1 / -1;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.content-media img {
  width: 100%;
  aspect-ratio: 21 / 8;
  object-fit: cover;
}

.content-media figcaption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

/* --- home: channel rows --- */

.channel-rows {
  border-top: 1px solid var(--line);
}

.channel-row {
  display: grid;
  grid-template-columns: 160px minmax(0, 1fr) minmax(0, 1fr);
  gap: 20px;
  align-items: baseline;
  padding: 18px 4px;
  border-bottom: 1px solid var(--line);
  transition: background-color 0.18s ease;
}

.channel-row:hover {
  background: #f1f2f0;
}

.channel-name {
  font-size: 16px;
  font-weight: 600;
  color: var(--ink);
}

.channel-focus {
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.channel-types {
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

/* --- home: playlist cards --- */

.playlist-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 20px;
}

.playlist-card {
  display: flex;
  flex-direction: column;
  padding: 22px 20px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: border-color 0.18s ease, transform 0.18s ease;
}

.playlist-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.playlist-name {
  font-size: 17px;
  font-weight: 600;
}

.playlist-summary {
  margin-top: 10px;
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.playlist-scope,
.playlist-compose {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.75;
}

/* --- home: path summary --- */

.path-list {
  display: flex;
  flex-direction: column;
}

.path-step {
  display: grid;
  grid-template-columns: 3.4em minmax(0, 1fr);
  gap: 4px 16px;
  padding: 20px 0;
  border-top: 1px solid var(--line);
}

.path-step:first-child {
  border-top: 0;
  padding-top: 0;
}

.path-step .step-name {
  font-size: 17px;
  font-weight: 600;
}

.path-step .step-desc {
  grid-column: 2 / -1;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

/* --- home: feedback preview --- */

.feedback-preview .section-more a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 8px 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--card);
  font-size: 14px;
}

.feedback-preview .section-more a:hover {
  border-color: var(--accent);
  text-decoration: none;
}

/* --- channels --- */

.channel-overview-list {
  margin-top: 22px;
  border-top: 1px solid var(--line);
}

.channel-overview-row {
  display: grid;
  grid-template-columns: 3em minmax(0, 200px) minmax(0, 1fr);
  gap: 8px 18px;
  align-items: baseline;
  padding: 16px 4px;
  border-bottom: 1px solid var(--line);
}

.channel-overview-row .channel-name {
  font-size: 16px;
  font-weight: 600;
}

.channel-overview-row .channel-focus {
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.channel-detail {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.channel-block {
  display: grid;
  grid-template-columns: minmax(0, 320px) minmax(0, 1fr);
  gap: 28px;
  padding: 32px 0;
  border-top: 1px solid var(--line);
}

.channel-block:first-of-type {
  border-top: 0;
  padding-top: 0;
}

.channel-figure {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.channel-figure img {
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
}

.channel-figure .channel-caption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

.channel-body {
  min-width: 0;
}

.channel-heading {
  display: flex;
  align-items: baseline;
  gap: 10px;
  font-size: 19px;
  font-weight: 600;
}

.channel-spec {
  display: grid;
  grid-template-columns: 100px minmax(0, 1fr);
  gap: 8px 18px;
  margin-top: 16px;
}

.channel-spec dt {
  color: var(--ink);
  font-size: 14px;
  font-weight: 600;
}

.channel-spec dd {
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.channel-spec dd a {
  margin-right: 12px;
}

.channel-relation .relation-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 28px;
  margin-top: 22px;
}

.relation-col {
  padding: 22px 20px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.relation-heading {
  font-size: 16px;
  font-weight: 600;
}

.relation-col p {
  margin-top: 10px;
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.relation-list {
  margin-top: 14px;
  border-top: 1px solid var(--line);
}

.relation-list li {
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.75;
}

.relation-list li:last-child {
  border-bottom: 0;
}

/* --- playlists --- */

.playlist-intro .intro-body {
  display: grid;
  grid-template-columns: minmax(0, 360px) minmax(0, 1fr);
  gap: 28px;
  align-items: start;
  margin-top: 22px;
}

.intro-media {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.intro-media img {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
}

.intro-media figcaption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

.intro-text {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.intro-text p {
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.85;
}

.playlist-archive {
  display: flex;
  flex-direction: column;
}

.playlist-item {
  padding: 26px 0;
  border-top: 1px solid var(--line);
}

.playlist-item:first-of-type {
  border-top: 0;
  padding-top: 0;
}

.playlist-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px 14px;
}

.playlist-title {
  font-size: 18px;
  font-weight: 600;
}

.playlist-channel {
  padding: 2px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--ink-soft);
  font-size: 12px;
}

.playlist-item .playlist-summary {
  margin-top: 12px;
  color: var(--ink);
  font-size: 15px;
  line-height: 1.85;
}

.playlist-item .playlist-scope,
.playlist-item .playlist-order {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.mapping-note {
  margin-top: 18px;
  color: var(--ink-soft);
  font-size: 14px;
}

/* --- fields --- */

.page-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(240px, 300px);
  gap: 40px;
  align-items: start;
  padding-top: 32px;
}

.page-layout .content-section:first-child {
  padding-top: 0;
}

.content-aside {
  position: sticky;
  top: 88px;
  padding: 22px 20px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.aside-title {
  font-size: 16px;
  font-weight: 600;
}

.aside-text {
  margin-top: 10px;
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

.aside-links {
  margin-top: 16px;
  border-top: 1px solid var(--line);
}

.aside-link-item {
  border-bottom: 1px solid var(--line);
}

.aside-link-item a {
  display: block;
  padding: 10px 0;
  font-size: 14px;
}

.scope-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
  margin-top: 22px;
}

.scope-col {
  padding: 20px 18px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.scope-heading {
  font-size: 16px;
  font-weight: 600;
}

.scope-list {
  margin-top: 14px;
  border-top: 1px solid var(--line);
}

.scope-item {
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.75;
}

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

.rule-list {
  display: flex;
  flex-direction: column;
  margin-top: 22px;
  border-top: 1px solid var(--line);
}

.rule-item {
  display: grid;
  grid-template-columns: minmax(0, 180px) minmax(0, 1fr);
  gap: 6px 20px;
  padding: 16px 0;
  border-bottom: 1px solid var(--line);
}

.rule-name {
  font-size: 15px;
  font-weight: 600;
}

.rule-text {
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.8;
}

/* --- guide --- */

.guide-steps,
.guide-io,
.guide-faq,
.guide-feedback {
  padding: 44px 0;
  border-top: 1px solid var(--line);
}

.guide-steps {
  border-top: 0;
  padding-top: 32px;
}

.guide-steps .section-intro,
.guide-io .section-intro,
.guide-faq .section-intro,
.guide-feedback .section-intro {
  margin-top: 10px;
  margin-bottom: 24px;
}

.guide-steps .step-item {
  grid-template-columns: minmax(0, 260px) minmax(0, 1fr);
  gap: 6px 28px;
  align-items: start;
}

.guide-steps .step-media {
  grid-row: span 3;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.guide-steps .step-media img {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
}

.guide-steps .step-body {
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 0;
}

.guide-steps .step-meta {
  color: var(--ink-soft);
  font-size: 13px;
}

.guide-steps .step-link {
  align-self: flex-start;
  font-size: 14px;
}

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

.faq-item {
  border-bottom: 1px solid var(--line);
}

.faq-question {
  position: relative;
  padding: 16px 40px 16px 0;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  list-style: none;
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::after {
  content: "+";
  position: absolute;
  right: 6px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 18px;
}

.faq-item[open] .faq-question::after {
  content: "\2212";
}

.faq-answer {
  padding: 0 40px 18px 0;
}

.faq-answer p {
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.85;
}

.feedback-path {
  display: flex;
  flex-direction: column;
  border-top: 1px solid var(--line);
}

.feedback-step {
  position: relative;
  padding: 16px 0 16px 34px;
  border-bottom: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

.feedback-step::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 26px;
  width: 7px;
  height: 7px;
  background: var(--accent);
  border-radius: 50%;
}

/* --- feedback --- */

.page-figure {
  margin-top: 28px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--card);
}

.page-figure img {
  width: 100%;
  aspect-ratio: 21 / 9;
  object-fit: cover;
}

.page-figure figcaption {
  padding: 10px 14px 12px;
  margin-top: 0;
}

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

.boundary-item {
  position: relative;
  padding: 12px 0 12px 22px;
  border-bottom: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

.boundary-item::before {
  content: "";
  position: absolute;
  left: 4px;
  top: 22px;
  width: 6px;
  height: 6px;
  background: var(--line);
  border-radius: 50%;
}

.boundary-exclude .boundary-item::before {
  background: #b9bfc7;
}

.correction-path .step-item {
  grid-template-columns: 3em minmax(0, 1fr);
}

.correction-path .step-title {
  font-size: 16px;
}

.correction-path .step-desc {
  grid-column: 2 / -1;
}

.related-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1px;
  margin-top: 20px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.related-item {
  background: var(--card);
}

.related-item a {
  display: block;
  padding: 16px 18px;
  font-size: 15px;
}

/* --- 404 --- */

.error-main {
  padding-top: 56px;
}

.error-main .page-title {
  font-size: 32px;
}

.error-main .page-title p {
  margin-top: 12px;
  color: var(--ink-soft);
  font-size: 15px;
  font-weight: 400;
}

.error-reason,
.error-entry,
.error-feedback {
  padding: 36px 0;
  border-top: 1px solid var(--line);
}

.error-reason h2,
.error-entry h2,
.error-feedback h2 {
  font-size: 20px;
  font-weight: 600;
}

.error-list {
  margin-top: 18px;
  border-top: 1px solid var(--line);
}

.error-list li {
  padding: 12px 0;
  border-bottom: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

.entry-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1px;
  margin-top: 18px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.entry-list a {
  display: block;
  padding: 16px 18px;
  background: var(--card);
  font-size: 15px;
}

.error-cta {
  margin-top: 24px;
}

.btn-home {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 22px;
  background: var(--accent);
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  color: #fff;
  font-size: 15px;
}

.btn-home:hover {
  background: var(--accent-deep);
  border-color: var(--accent-deep);
  text-decoration: none;
}

.error-feedback p {
  margin-top: 12px;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.8;
}

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

@media (max-width: 960px) {
  .hero-section {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
    padding-top: 36px;
  }

  .page-layout {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
  }

  .content-aside {
    position: static;
  }

  .channel-block {
    grid-template-columns: minmax(0, 1fr);
    gap: 20px;
  }

  .playlist-intro .intro-body {
    grid-template-columns: minmax(0, 1fr);
  }

  .guide-steps .step-item {
    grid-template-columns: minmax(0, 1fr);
  }

  .guide-steps .step-media {
    grid-row: auto;
  }
}

@media (max-width: 760px) {
  :root {
    --gutter: 18px;
  }

  .site-main {
    padding-bottom: 52px;
  }

  .header-inner {
    flex-wrap: wrap;
    gap: 12px;
  }

  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-left: auto;
  }

  .site-nav {
    flex: 1 0 100%;
    justify-content: flex-start;
  }

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

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

  .nav-list li {
    border-bottom: 1px solid var(--line);
  }

  .nav-list a {
    display: flex;
    align-items: center;
    min-height: 44px;
    padding: 8px 2px;
    border-bottom: 0;
    font-size: 16px;
  }

  .nav-list a.is-current {
    border-bottom: 0;
    color: var(--accent);
  }

  .page-title {
    font-size: 24px;
  }

  .hero-title {
    font-size: 26px;
  }

  .error-main .page-title {
    font-size: 26px;
  }

  .hero-index {
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  }

  .channel-row {
    grid-template-columns: minmax(0, 1fr);
    gap: 6px;
    padding: 16px 2px;
  }

  .channel-overview-row {
    grid-template-columns: 2.6em minmax(0, 1fr);
    gap: 6px 12px;
  }

  .channel-overview-row .channel-focus {
    grid-column: 2 / -1;
  }

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

  .channel-spec dd {
    margin-bottom: 10px;
  }

  .channel-relation .relation-columns {
    grid-template-columns: minmax(0, 1fr);
    gap: 18px;
  }

  .scope-columns {
    grid-template-columns: minmax(0, 1fr);
    gap: 18px;
  }

  .rule-item {
    grid-template-columns: minmax(0, 1fr);
  }

  .path-step,
  .step-item,
  .correction-path .step-item {
    grid-template-columns: 2.6em minmax(0, 1fr);
    gap: 4px 12px;
  }

  .footer-top {
    grid-template-columns: minmax(0, 1fr);
    gap: 24px;
    padding-top: 32px;
  }

  .section {
    padding: 36px 0;
  }

  .guide-steps,
  .guide-io,
  .guide-faq,
  .guide-feedback,
  .content-section {
    padding: 32px 0;
  }

  .fields-table,
  .mapping-table,
  .clue-table,
  .field-table {
    min-width: 520px;
  }
}

@media (max-width: 420px) {
  .hero-actions {
    flex-direction: column;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .playlist-cards {
    grid-template-columns: minmax(0, 1fr);
  }

  .related-list,
  .entry-list {
    grid-template-columns: minmax(0, 1fr);
  }
}