:root {
  --ink: #18181B;
  --ink-2: #3f3f46;
  --ink-3: #71717a;
  --line: #e4e4e7;
  --line-2: #f4f4f5;
  --bg: #fafaf9;
  --paper: #ffffff;
  --accent: #4a6b52;
  --accent-2: #7ba286;
  --accent-soft: #eaf0ec;
  --accent-softer: #f3f7f4;
  --tag: #f5f2ec;
  --tag-ink: #6b5d3f;
  --quote: #3a4a3d;
  --quote-bg: #f5f8f5;
  --quote-border: #4a6b52;
  --case-bg: #faf7ee;
  --case-ink: #6b5d3f;
  --case-border: #c9b789;
  --work-bg: #f6f2ff;
  --work-ink: #4b3f6b;
  --work-border: #9d8bc7;
  --check-bg: #f4f8f5;
  --check-border: #cbe0d0;
  --code-bg: #f4f4f5;
  --code-ink: #18181B;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink: #f4f4f5;
    --ink-2: #d4d4d8;
    --ink-3: #a1a1aa;
    --line: #3f3f46;
    --line-2: #27272a;
    --bg: #11110f;
    --paper: #18181b;
    --accent: #9fc5a8;
    --accent-2: #7fa58a;
    --accent-soft: #26362b;
    --accent-softer: #1e2a22;
    --tag: #312e26;
    --tag-ink: #dccb9e;
    --quote: #d7eadb;
    --quote-bg: #17251b;
    --quote-border: #9fc5a8;
    --case-bg: #272316;
    --case-ink: #ead7aa;
    --case-border: #b7a06a;
    --work-bg: #241f32;
    --work-ink: #d6c7ff;
    --work-border: #a995d7;
    --check-bg: #17251b;
    --check-border: #31543a;
    --code-bg: #27272a;
    --code-ink: #f4f4f5;
  }
}
:root[data-theme="dark"] {
  --ink: #f4f4f5;
  --ink-2: #d4d4d8;
  --ink-3: #a1a1aa;
  --line: #3f3f46;
  --line-2: #27272a;
  --bg: #11110f;
  --paper: #18181b;
  --accent: #9fc5a8;
  --accent-2: #7fa58a;
  --accent-soft: #26362b;
  --accent-softer: #1e2a22;
  --tag: #312e26;
  --tag-ink: #dccb9e;
  --quote: #d7eadb;
  --quote-bg: #17251b;
  --quote-border: #9fc5a8;
  --case-bg: #272316;
  --case-ink: #ead7aa;
  --case-border: #b7a06a;
  --work-bg: #241f32;
  --work-ink: #d6c7ff;
  --work-border: #a995d7;
  --check-bg: #17251b;
  --check-border: #31543a;
  --code-bg: #27272a;
  --code-ink: #f4f4f5;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100dvh;
  background: var(--bg);
  color: var(--ink);
  font-family: "Noto Sans JP", system-ui, -apple-system, "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;
  font-size: 17px;
  line-height: 1.95;
  font-feature-settings: "palt" 1;
  text-rendering: optimizeLegibility;
}
.en, .num { font-family: "Outfit", "Noto Sans JP", sans-serif; font-feature-settings: "tnum" 1; }
.budoux { word-break: keep-all; overflow-wrap: anywhere; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
.wrap { max-width: 780px; margin: 0 auto; padding: 0 1.4rem; }
.wrap-narrow { max-width: 720px; margin: 0 auto; padding: 0 1.4rem; }

/* Header nav */
.site-nav {
  border-bottom: 1px solid var(--line);
  background: var(--paper);
  padding: 0.9rem 0;
  font-size: 0.85rem;
  color: var(--ink-3);
}
.site-nav .wrap { display: flex; justify-content: space-between; align-items: center; gap: 1rem; flex-wrap: wrap; }
.site-nav .brand { font-weight: 700; color: var(--ink); letter-spacing: 0.02em; }
.site-nav .brand a { color: var(--ink); }
.site-nav .crumbs { color: var(--ink-3); }
.site-nav .crumbs a { color: var(--ink-3); }
.site-nav .crumbs a:hover { color: var(--accent); }

/* Sticky chapter bar */
.textbook-topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  min-height: 44px;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}
.textbook-topbar-inner {
  width: 100%;
  max-width: 780px;
  min-height: 44px;
  margin: 0 auto;
  padding: 0 1.4rem;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  align-items: center;
  gap: 0.75rem;
  font-size: 0.82rem;
  line-height: 1.35;
}
.textbook-topbar-brand {
  min-width: 0;
  overflow: hidden;
  color: var(--ink);
  font-weight: 700;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.textbook-topbar-current {
  color: var(--ink-3);
  font-family: "Outfit", "Noto Sans JP", sans-serif;
  font-weight: 600;
  white-space: nowrap;
}
.textbook-topbar-links {
  min-width: 0;
  display: flex;
  justify-content: flex-end;
  gap: 0.55rem;
}
.textbook-topbar-links a {
  min-width: 0;
  overflow: hidden;
  color: var(--accent);
  font-weight: 700;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.textbook-theme-toggle {
  border: 1px solid var(--line);
  background: var(--accent-softer);
  color: var(--accent);
  border-radius: 999px;
  padding: 0.12rem 0.48rem;
  font: inherit;
  font-weight: 700;
  line-height: 1.35;
  cursor: pointer;
  white-space: nowrap;
}
.textbook-theme-toggle:hover { border-color: var(--accent); }
.textbook-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 3px;
  overflow: hidden;
  background: var(--accent-soft);
}
.textbook-progress-fill {
  width: 100%;
  height: 100%;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left center;
}

/* Hero */
.hero { padding: 3.5rem 0 2.75rem; background: var(--paper); border-bottom: 1px solid var(--line); }
.hero .kicker {
  font-family: "Outfit", sans-serif;
  color: var(--accent);
  font-size: 0.8rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: 1rem;
}
.hero h1 {
  font-size: clamp(1.65rem, 4.5vw, 2.4rem);
  line-height: 1.4;
  letter-spacing: -0.01em;
  margin: 0 0 1rem;
  font-weight: 700;
}
.hero .subtitle { color: var(--ink-3); font-size: 1rem; margin: 0 0 1.5rem; }
.hero .lead { font-size: 1.02rem; color: var(--ink-2); line-height: 1.95; margin: 0; max-width: 40em; }

/* Article body */
.body { padding: 3.25rem 0 4rem; }
.body h1 {
  font-size: clamp(1.55rem, 3.6vw, 2.05rem);
  line-height: 1.45;
  margin: 0 0 2rem;
  font-weight: 700;
  letter-spacing: -0.005em;
  padding-bottom: 1rem;
  border-bottom: 2px solid var(--ink);
}
.body h2 {
  font-size: clamp(1.25rem, 2.9vw, 1.45rem);
  line-height: 1.55;
  margin: 3.75rem 0 1.5rem;
  padding-bottom: 0.65rem;
  border-bottom: 1px solid var(--line);
  font-weight: 700;
  letter-spacing: -0.005em;
  scroll-margin-top: 1.5rem;
}
.body h2 .sec-num {
  font-family: "Outfit", sans-serif;
  color: var(--accent);
  font-weight: 600;
  font-size: 0.7em;
  letter-spacing: 0.05em;
  background: var(--accent-soft);
  padding: 0.18rem 0.55rem;
  border-radius: 3px;
  margin-right: 0.55rem;
  vertical-align: 0.15em;
  white-space: nowrap;
}
.body h3 {
  font-size: 1.1rem;
  line-height: 1.6;
  margin: 2.75rem 0 1rem;
  font-weight: 700;
  color: var(--ink);
  scroll-margin-top: 1.5rem;
  padding-left: 0.85rem;
  border-left: 3px solid var(--accent);
}
.body h4 {
  font-size: 1rem;
  line-height: 1.55;
  margin: 1.9rem 0 0.7rem;
  font-weight: 700;
  color: var(--ink-2);
}
.body .anchor {
  color: transparent;
  margin-right: 0.4rem;
  font-weight: 400;
  text-decoration: none;
  transition: color 0.2s;
  font-size: 0.7em;
  vertical-align: middle;
}
.body h2:hover .anchor, .body h3:hover .anchor { color: var(--ink-3); }
.body .anchor:hover { color: var(--accent) !important; }

.body p {
  margin: 0 0 1.55rem;
  color: var(--ink-2);
  max-width: 42em;
}
.body strong { color: var(--ink); font-weight: 700; }
.body em { font-style: normal; color: var(--ink); font-weight: 500; }

.body ul, .body ol {
  margin: 0.4rem 0 1.75rem;
  padding-left: 1.5rem;
  max-width: 42em;
  color: var(--ink-2);
}
.body li { margin-bottom: 0.55rem; line-height: 1.9; }
.body li > p { margin-bottom: 0.6rem; }

.body hr {
  border: none;
  border-top: 1px solid var(--line);
  margin: 3rem 0;
}

/* Keyphrase */
.body blockquote.keyphrase {
  margin: 2.5rem 0;
  padding: 1.5rem 1.75rem 1.5rem 2.5rem;
  background: var(--quote-bg);
  border-left: 4px solid var(--quote-border);
  color: var(--quote);
  border-radius: 2px;
  position: relative;
}
.body blockquote.keyphrase::before {
  content: "\201C";
  position: absolute;
  left: 0.75rem;
  top: 0.2rem;
  font-size: 2.6rem;
  color: var(--quote-border);
  opacity: 0.3;
  line-height: 1;
  font-family: Georgia, serif;
}
.body blockquote.keyphrase p {
  margin: 0;
  color: var(--quote);
  font-size: 1.12rem;
  font-weight: 500;
  line-height: 1.8;
  max-width: none;
}

/* CASE card */
.body .case {
  margin: 2rem 0;
  padding: 1.35rem 1.55rem 0.5rem;
  background: var(--case-bg);
  border-left: 3px solid var(--case-border);
  border-radius: 3px;
}
.body .case-tag {
  display: inline-block;
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--case-ink);
  background: color-mix(in srgb, var(--paper) 70%, transparent);
  padding: 0.25rem 0.6rem;
  border-radius: 2px;
  margin-bottom: 0.65rem;
}
.body .case-title {
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--case-ink);
  margin: 0 0 0.75rem;
}
.body .case-body p {
  color: var(--case-ink);
  margin-bottom: 1.1rem;
  max-width: none;
}
.body .case-body blockquote.keyphrase {
  background: color-mix(in srgb, var(--paper) 55%, transparent);
  border-left-color: var(--case-border);
  margin: 1.1rem 0;
}
.body .case-body blockquote.keyphrase p { color: var(--case-ink); font-size: 1.02rem; }
.body .case-body blockquote.keyphrase::before { color: var(--case-border); }

/* WORK box */
.body .work {
  margin: 2rem 0;
  padding: 1.35rem 1.55rem 0.5rem;
  background: var(--work-bg);
  border: 1px solid var(--work-border);
  border-radius: 4px;
}
.body .work-tag {
  display: inline-block;
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--work-ink);
  background: color-mix(in srgb, var(--paper) 75%, transparent);
  padding: 0.25rem 0.6rem;
  border-radius: 2px;
  margin-bottom: 0.65rem;
}
.body .work-title {
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--work-ink);
  margin: 0 0 0.75rem;
}
.body .work-body p { color: var(--work-ink); margin-bottom: 1.1rem; max-width: none; }
.body .work-body ul, .body .work-body ol {
  color: var(--work-ink);
  padding-left: 1.3rem;
  max-width: none;
}
.body .work-body li { margin-bottom: 0.4rem; }
.body .work h3.work-title { font-size: 1rem; margin: 0 0 0.7rem; }
.term-note { font-size: .85rem; color: var(--ink-3); border-left: 2px solid var(--line); padding-left: .7rem; margin: .6rem 0 1.2rem; }

/* TOOL NOW box (ツールの現在地) — 腐りやすい固有名詞をここに隔離する */
.body .tool-now {
  margin: 2rem 0;
  padding: 1.3rem 1.5rem 1.1rem;
  background: var(--accent-softer);
  border: 1px dashed var(--accent-2);
  border-radius: 4px;
}
.body .tool-now-head {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: .55rem;
  margin-bottom: .8rem;
}
.body .tool-now-tag {
  display: inline-block;
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--accent);
  background: color-mix(in srgb, var(--paper) 75%, transparent);
  padding: 0.25rem 0.6rem;
  border-radius: 2px;
}
.body .tool-now-title {
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--accent);
}
.body .tool-now-note {
  font-size: .85rem;
  color: var(--ink-3);
  margin: 0 0 1rem;
  max-width: none;
  line-height: 1.8;
}
.body .tool-now-body dl { margin: 0; }
.body .tool-now-body dt {
  font-size: .82rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: .02em;
  margin-top: .95rem;
}
.body .tool-now-body dt:first-of-type { margin-top: 0; }
.body .tool-now-body dd {
  margin: .3rem 0 0;
  color: var(--ink-2);
  font-size: .93rem;
  line-height: 1.85;
}
@media (max-width: 640px) {
  .body .tool-now { padding: 1.1rem 1.15rem 1rem; }
}
.section-lead {
  font-weight: 600;
  color: var(--ink);
  border-left: 3px solid var(--accent);
  background: var(--accent-softer);
  padding: .7rem .9rem;
  margin: 1rem 0 1.6rem;
  border-radius: 0 4px 4px 0;
  line-height: 1.8;
}
.section-links {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem;
  font-size: .8rem;
  margin: 1.4rem 0 2.2rem;
}
.section-links a {
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: .2rem .7rem;
  color: var(--ink-3);
  text-decoration: none;
  white-space: nowrap;
}
.section-links a:hover { border-color: var(--accent); color: var(--accent); }

/* Checklist */
.body .checklist {
  margin: 3.5rem 0 1rem;
  padding: 1.75rem 1.75rem 1.25rem;
  background: var(--check-bg);
  border: 1px solid var(--check-border);
  border-radius: 6px;
}
.body .checklist-head { margin-bottom: 1.15rem; }
.body .checklist-tag {
  display: inline-block;
  font-family: "Outfit", sans-serif;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--accent);
  background: color-mix(in srgb, var(--paper) 75%, transparent);
  padding: 0.25rem 0.6rem;
  border-radius: 2px;
  margin-bottom: 0.7rem;
}
.body .checklist-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--ink);
  margin: 0 0 0.35rem;
}
.body .checklist-desc { font-size: 0.85rem; color: var(--ink-3); margin: 0; }
.body .checklist-body ul {
  list-style: none;
  padding-left: 0;
  margin: 0;
  max-width: none;
}
.body .checklist-body li {
  padding: 0.65rem 0.25rem 0.65rem 0;
  border-bottom: 1px solid var(--check-border);
  color: var(--ink-2);
  line-height: 1.8;
  font-size: 0.96rem;
}
.body .checklist-body li:last-child { border-bottom: none; }
.cl-check {
  accent-color: var(--accent);
  width: 1rem;
  height: 1rem;
  margin-right: 0.5rem;
  vertical-align: -1px;
}
.body .checklist-body label { cursor: pointer; }
.body .checklist-body .cl-mark {
  display: inline-block;
  color: var(--accent);
  font-family: "Outfit", sans-serif;
  font-weight: 500;
  margin-right: 0.55rem;
  font-size: 1.05rem;
  line-height: 1;
  vertical-align: 0.05em;
}
.work-memo {
  width: 100%;
  border: 1px solid var(--work-border);
  background: var(--paper);
  border-radius: 6px;
  padding: 0.6rem;
  font: inherit;
  font-size: 0.92rem;
  color: var(--ink);
  resize: vertical;
  margin-top: 0.8rem;
  box-sizing: border-box;
}
.work-recap {
  border: 1px dashed var(--line);
  border-radius: 8px;
  padding: 1rem 1.1rem;
  margin: 2rem 0;
  font-size: 0.92rem;
  color: var(--ink-2);
}
.work-recap[hidden] { display: none; }
.work-recap h4 {
  margin: 0 0 0.6rem;
  font-size: 0.85rem;
  color: var(--ink-3);
}
.work-recap-item { margin-top: 0.8rem; }
.work-recap-item:first-of-type { margin-top: 0; }
.work-recap-item strong { color: var(--ink); font-size: 0.9rem; }
.work-recap-item p {
  margin: 0.25rem 0 0;
  white-space: pre-wrap;
  max-width: none;
  color: var(--ink-2);
}
.ch-progress,
.ch-last {
  margin-top: 0.7rem;
  font-size: 0.82rem;
  color: var(--ink-3);
}
.ch-last { color: var(--accent); }

/* Code */
.body code {
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 0.1rem 0.4rem;
  border-radius: 3px;
  font-size: 0.87em;
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, monospace;
}
.body pre {
  background: var(--code-bg);
  padding: 1rem 1.15rem;
  border-radius: 4px;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-size: 0.9rem;
  line-height: 1.7;
  max-width: 100%;
}
.body pre code { background: transparent; padding: 0; font-size: 0.9rem; }

/* Tables */
.body table {
  border-collapse: collapse;
  margin: 1.75rem 0;
  width: 100%;
  font-size: 0.94rem;
  max-width: 100%;
}
.table-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 1.75rem 0;
}
.table-scroll > table {
  min-width: 560px;
  margin: 0;
}
.body th, .body td {
  border: 1px solid var(--line);
  padding: 0.6rem 0.85rem;
  text-align: left;
  vertical-align: top;
}
.body th { background: var(--line-2); font-weight: 700; color: var(--ink); }
.body td { color: var(--ink-2); }

/* On-page TOC */
.page-toc {
  margin: 0 0 3rem;
  padding: 1.35rem 1.5rem;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 5px;
}
.page-toc .label {
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin: 0 0 0.75rem;
  font-weight: 600;
}
.page-toc ol { list-style: none; margin: 0; padding: 0; }
.page-toc li {
  margin: 0.35rem 0;
  font-size: 0.94rem;
  line-height: 1.65;
  padding-left: 1.5rem;
  position: relative;
}
.page-toc li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.75rem;
  width: 0.75rem;
  height: 1px;
  background: var(--line);
}
.page-toc li a { color: var(--ink-2); }
.page-toc li a:hover { color: var(--accent); }

/* Diagram */
.body .diagram {
  margin: 2.5rem 0 2.75rem;
  padding: 1.75rem 1.5rem 1.5rem;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 6px;
}
.body .diagram-title {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--ink);
  margin: 0 0 1.35rem;
  letter-spacing: -0.005em;
}
.body .diagram-caption {
  margin: 1.35rem 0 0;
  font-size: 0.83rem;
  color: var(--ink-3);
  line-height: 1.7;
  text-align: center;
  max-width: none;
}

/* dg-stack */
.dg-stack { display: flex; flex-direction: column; gap: 0.55rem; max-width: 520px; margin: 0 auto; }
.dg-stack-row {
  display: flex; align-items: center; gap: 0.9rem;
  padding: 0.85rem 1rem; border-radius: 4px;
  background: var(--accent-softer);
  border-left: 3px solid var(--accent);
}
.dg-stack-1 { background: color-mix(in srgb, var(--accent-soft) 45%, var(--paper)); }
.dg-stack-2 { background: color-mix(in srgb, var(--accent-soft) 65%, var(--paper)); }
.dg-stack-3 { background: color-mix(in srgb, var(--accent-soft) 82%, var(--paper)); }
.dg-stack-4 { background: var(--accent-soft); }
.dg-stack-num {
  font-family: "Outfit", sans-serif;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--accent);
  min-width: 1.6rem;
  text-align: center;
}
.dg-stack-body { flex: 1; }
.dg-stack-title { font-weight: 700; color: var(--ink); font-size: 0.98rem; line-height: 1.5; }
.dg-stack-desc { color: var(--ink-3); font-size: 0.85rem; line-height: 1.6; margin-top: 0.1rem; }

/* dg-pyramid */
.dg-pyramid { display: flex; flex-direction: column; gap: 0.5rem; max-width: 560px; margin: 0 auto; align-items: center; }
.dg-p-row {
  padding: 1rem 1.25rem;
  border-radius: 4px;
  display: flex;
  align-items: center;
  gap: 1rem;
  border-left: 3px solid var(--accent);
  width: 100%;
}
.dg-p-top { width: 60%; background: color-mix(in srgb, var(--accent-soft) 50%, var(--paper)); }
.dg-p-mid { width: 80%; background: color-mix(in srgb, var(--accent-soft) 72%, var(--paper)); }
.dg-p-base { width: 100%; background: var(--accent-soft); }
.dg-p-label {
  font-family: "Outfit", sans-serif;
  font-weight: 700;
  color: var(--accent);
  font-size: 0.92rem;
  min-width: 6.5rem;
}
.dg-p-desc { color: var(--ink-2); font-size: 0.9rem; line-height: 1.5; }

/* dg-flow */
.dg-flow { display: flex; align-items: stretch; gap: 0.5rem; flex-wrap: wrap; justify-content: center; }
.dg-flow-vert { flex-direction: column; align-items: center; max-width: 380px; margin: 0 auto; }
.dg-flow-step {
  flex: 1 1 140px;
  min-width: 140px;
  max-width: 220px;
  padding: 0.85rem 0.85rem;
  background: var(--accent-softer);
  border: 1px solid var(--accent-soft);
  border-radius: 5px;
  text-align: center;
}
.dg-flow-vert .dg-flow-step { width: 100%; max-width: 320px; }
.dg-flow-num {
  font-family: "Outfit", sans-serif;
  font-weight: 700;
  color: var(--accent);
  font-size: 0.85rem;
  letter-spacing: 0.04em;
  margin-bottom: 0.35rem;
}
.dg-flow-title { font-weight: 700; color: var(--ink); font-size: 0.95rem; line-height: 1.5; margin-bottom: 0.2rem; }
.dg-flow-desc { color: var(--ink-3); font-size: 0.82rem; line-height: 1.55; }
.dg-flow-body { min-width: 0; }
.dg-flow-note {
  font-size: 0.75rem;
  color: var(--accent);
  background: var(--accent-softer);
  border-radius: 4px;
  padding: 0.15rem 0.5rem;
  margin-top: 0.35rem;
  display: inline-block;
  line-height: 1.5;
}
.dg-flow-arrow {
  align-self: center;
  color: var(--accent);
  font-size: 1.3rem;
  font-weight: 700;
  padding: 0 0.15rem;
  font-family: "Outfit", sans-serif;
}
.dg-flow-arrow-vert { padding: 0.15rem 0; }
.dg-tone-1 { background: color-mix(in srgb, var(--accent-soft) 45%, var(--paper)); }
.dg-tone-2 { background: color-mix(in srgb, var(--accent-soft) 65%, var(--paper)); }
.dg-tone-3 { background: color-mix(in srgb, var(--accent-soft) 82%, var(--paper)); }
.dg-tone-4 { background: var(--accent-soft); }

/* dg-two-col */
.dg-two-col {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  gap: 1rem;
  align-items: stretch;
}
.dg-two-col-vs .dg-col-left { border-color: #c9b789; background: #faf7ee; }
.dg-two-col-vs .dg-col-right { border-color: #9d8bc7; background: #f6f2ff; }
.dg-col {
  padding: 1.1rem 1.2rem;
  background: var(--accent-softer);
  border: 1px solid var(--accent-soft);
  border-radius: 5px;
}
.dg-col-tag {
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--accent);
  margin-bottom: 0.4rem;
}
.dg-two-col-vs .dg-col-left .dg-col-tag { color: #6b5d3f; }
.dg-two-col-vs .dg-col-right .dg-col-tag { color: #4b3f6b; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .dg-two-col-vs .dg-col-left {
    border-color: #3a3325;
    background: #2a2519;
  }
  :root:not([data-theme="light"]) .dg-two-col-vs .dg-col-right {
    border-color: #3a3350;
    background: #241f32;
  }
  :root:not([data-theme="light"]) .dg-two-col-vs .dg-col-left .dg-col-tag { color: var(--case-ink); }
  :root:not([data-theme="light"]) .dg-two-col-vs .dg-col-right .dg-col-tag { color: var(--work-ink); }
}
:root[data-theme="dark"] .dg-two-col-vs .dg-col-left {
  border-color: #3a3325;
  background: #2a2519;
}
:root[data-theme="dark"] .dg-two-col-vs .dg-col-right {
  border-color: #3a3350;
  background: #241f32;
}
:root[data-theme="dark"] .dg-two-col-vs .dg-col-left .dg-col-tag { color: var(--case-ink); }
:root[data-theme="dark"] .dg-two-col-vs .dg-col-right .dg-col-tag { color: var(--work-ink); }
.dg-col-title { font-weight: 700; color: var(--ink); font-size: 1rem; margin-bottom: 0.7rem; line-height: 1.5; }
.dg-col-list { list-style: none; padding: 0; margin: 0; max-width: none; }
.dg-col-list li {
  padding: 0.3rem 0 0.3rem 1rem;
  color: var(--ink-2);
  font-size: 0.9rem;
  line-height: 1.65;
  position: relative;
  margin: 0;
}
.dg-col-list li::before {
  content: "\2022";
  position: absolute;
  left: 0;
  top: 0.3rem;
  color: var(--accent);
}
.dg-two-col-vs .dg-col-left .dg-col-list li::before { color: #c9b789; }
.dg-two-col-vs .dg-col-right .dg-col-list li::before { color: #9d8bc7; }
.dg-col-arrow {
  align-self: center;
  color: var(--accent);
  font-size: 1.5rem;
  font-weight: 700;
  padding: 0 0.35rem;
}
.dg-col-divider {
  align-self: stretch;
  width: 1px;
  background: var(--line);
  margin: 0.5rem 0.35rem;
}

/* dg-grid-4 */
.dg-grid-4 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.7rem;
}
@media (min-width: 720px) { .dg-grid-4 { grid-template-columns: repeat(4, 1fr); } }
.dg-card {
  padding: 1rem;
  background: var(--accent-softer);
  border: 1px solid var(--accent-soft);
  border-radius: 5px;
}
.dg-card-tag {
  font-family: "Outfit", sans-serif;
  font-size: 0.66rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--accent);
  margin-bottom: 0.35rem;
}
.dg-card-title { font-weight: 700; color: var(--ink); font-size: 0.95rem; margin-bottom: 0.35rem; line-height: 1.45; }
.dg-card-desc { color: var(--ink-3); font-size: 0.82rem; line-height: 1.6; }

/* Chapter cards on index */
.chapter-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin: 0 0 3rem;
}
@media (min-width: 720px) { .chapter-cards { grid-template-columns: 1fr 1fr; gap: 1.15rem; } }
.ch-card {
  display: block;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 1.35rem 1.4rem 1.4rem;
  color: var(--ink);
  transition: border-color 0.2s, transform 0.2s;
}
.ch-card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-1px); }
.ch-card .ch-num {
  font-family: "Outfit", sans-serif;
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  color: var(--accent);
  text-transform: uppercase;
  margin-bottom: 0.5rem;
  font-weight: 600;
}
.ch-card h3 { font-size: 1.02rem; line-height: 1.55; margin: 0 0 0.7rem; font-weight: 700; color: var(--ink); }
.ch-card p { margin: 0; font-size: 0.88rem; color: var(--ink-3); line-height: 1.8; }
.exam-card {
  margin-top: 0.5rem;
  border-color: var(--accent);
  background: var(--accent-softer);
}
.exam-card .ch-num { color: var(--accent); }
.exam-card p { color: var(--ink-2); }
.quest-launch-card {
  position: relative;
  overflow: hidden;
  margin: 2.25rem 0 3rem;
  border-color: var(--accent);
  background: var(--accent-softer);
}
.quest-launch-card::after {
  position: absolute;
  width: 9rem;
  height: 9rem;
  border: 1.25rem solid var(--accent-soft);
  border-radius: 50%;
  content: "";
  right: -3rem;
  top: -3rem;
  pointer-events: none;
}
.quest-launch-card h3,
.quest-launch-card p,
.quest-launch-card .ch-num,
.quest-launch-cta {
  position: relative;
  z-index: 1;
}
.quest-launch-card h3 { font-size: 1.3rem; }
.quest-launch-cta {
  display: inline-block;
  margin-top: 1rem;
  color: var(--accent);
  font-size: 0.88rem;
  font-weight: 700;
}

.part-label {
  font-family: "Outfit", sans-serif;
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 2.5rem 0 0.75rem;
  font-weight: 600;
}
.part-label:first-child { margin-top: 0; }
.part-title { font-size: 1.15rem; line-height: 1.5; margin: 0 0 1.5rem; font-weight: 700; color: var(--ink); }

/* Chapter nav */
.ch-nav {
  margin: 3.5rem 0 0;
  padding: 1.5rem 0 0;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}
.ch-nav a {
  display: inline-block;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0.8rem 1.15rem;
  font-size: 0.9rem;
  color: var(--ink-2);
  min-width: 45%;
  transition: border-color 0.2s;
}
.ch-nav a:hover { border-color: var(--accent); text-decoration: none; color: var(--accent); }
.ch-nav a.prev::before { content: "\2190\00a0"; color: var(--ink-3); }
.ch-nav a.next { text-align: right; margin-left: auto; }
.ch-nav a.next::after { content: "\00a0\2192"; color: var(--ink-3); }
.ch-nav .ch-nav-label {
  display: block;
  font-family: "Outfit", sans-serif;
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  color: var(--ink-3);
  text-transform: uppercase;
  margin-bottom: 0.2rem;
  font-weight: 500;
}
.ch-nav a strong { color: var(--ink); font-weight: 700; font-size: 0.94rem; }

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  padding: 2rem 0 3rem;
  color: var(--ink-3);
  font-size: 0.82rem;
  background: var(--paper);
  margin-top: 3rem;
}
.site-footer .wrap { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; }

@media (max-width: 640px) {
  body { font-size: 15.5px; line-height: 1.9; }
  .wrap, .wrap-narrow { padding: 0 1.15rem; }
  .textbook-topbar-inner {
    padding: 0 0.75rem;
    grid-template-columns: minmax(0, 0.9fr) auto minmax(0, 1fr);
    gap: 0.45rem;
    font-size: 0.74rem;
  }
  .textbook-topbar-links { gap: 0.4rem; }
  .hero { padding: 2.5rem 0 2rem; }
  .body { padding: 2.25rem 0 3rem; }
  .body h2 { margin: 2.75rem 0 1.2rem; font-size: 1.2rem; }
  .body h2 .sec-num { font-size: 0.7em; }
  .body h3 { margin: 2rem 0 0.85rem; font-size: 1.02rem; }
  .body blockquote.keyphrase { padding: 1.15rem 1.25rem 1.15rem 2rem; margin: 2rem 0; }
  .body blockquote.keyphrase p { font-size: 1.02rem; }
  .body .case, .body .work { padding: 1.1rem 1.15rem 0.4rem; }
  .body .checklist { padding: 1.35rem 1.35rem 1rem; }
  .table-scroll table { font-size: 0.88rem; }
  .ch-nav a { min-width: 100%; }
  .dg-two-col { grid-template-columns: 1fr; }
  .dg-col-arrow, .dg-col-divider { display: none; }
  .dg-flow-step { flex-basis: 100%; max-width: 100%; }
  .dg-flow-arrow:not(.dg-flow-arrow-vert) { transform: rotate(90deg); align-self: center; }
  .dg-p-top, .dg-p-mid { width: 100%; }
}

/* チップからのアンカー着地時にスティッキーヘッダーで隠れないための余白 */
.work, .checklist, figure.diagram, .body h2, .body h3 { scroll-margin-top: 72px; }

/* トップのリード折りたたみ */
.lead-more { margin-top: 0.9rem; font-size: 0.92rem; color: var(--ink-3); }
.lead-more summary { cursor: pointer; color: var(--accent); font-weight: 500; }
.lead-more p { margin: 0.6rem 0 0; line-height: 1.9; }