:root {
  --bg-page: #edf2f8;
  --bg-surface: #ffffff;
  --bg-soft: #f5f7fb;
  --bg-dark: #0f172a;
  --bg-dark-soft: #162033;
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-light: #d8e2f0;
  --border: #d7dfeb;
  --border-strong: #b8c5da;
  --blue: #2563eb;
  --teal: #0f766e;
  --amber: #d97706;
  --rose: #be185d;
  --shadow: 0 20px 48px rgba(15, 23, 42, 0.08);
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;
  --content-width: 1200px;
  --transition: 180ms ease;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Inter", "PingFang SC", "Noto Sans CJK SC", "Microsoft YaHei", sans-serif;
  background: var(--bg-page);
  color: var(--text-main);
  line-height: 1.65;
}

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

a {
  color: inherit;
  text-decoration: none;
}

button,
input,
textarea,
select {
  font: inherit;
}

.page-home {
  background: var(--bg-page);
}

.page-chapter {
  background: linear-gradient(180deg, #f8fbff 0, var(--bg-page) 280px, var(--bg-page) 100%);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(18px);
  border-bottom: 1px solid rgba(215, 223, 235, 0.3);
}

.page-home .site-header {
  background: rgba(15, 23, 42, 0.84);
  color: #f7fbff;
}

.page-chapter .site-header {
  background: rgba(248, 251, 255, 0.9);
  color: var(--text-main);
}

.header-inner,
.section-inner,
.chapter-header-inner,
.chapter-layout,
.site-footer-inner {
  width: min(calc(100% - 32px), var(--content-width));
  margin: 0 auto;
}

.header-inner {
  min-height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  font-size: 0.98rem;
}

.brand-mark {
  width: 38px;
  height: 38px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--blue), var(--teal));
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 700;
  flex-shrink: 0;
}

.header-nav {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.header-link {
  padding: 8px 12px;
  border-radius: 999px;
  font-size: 0.9rem;
  color: inherit;
  transition: background var(--transition), color var(--transition);
}

.page-home .header-link:hover,
.page-home .header-link.is-active {
  background: rgba(255, 255, 255, 0.1);
}

.page-chapter .header-link:hover,
.page-chapter .header-link.is-active {
  background: rgba(37, 99, 235, 0.12);
}

/* Keep the dark landing treatment attached to the hero so it grows with the first-screen content. */
.hero {
  padding: 56px 0 30px;
  background: linear-gradient(180deg, rgba(15, 23, 42, 0.98) 0%, rgba(15, 23, 42, 0.96) 100%);
}

.hero-panel {
  display: grid;
  grid-template-columns: minmax(0, 1.02fr) minmax(340px, 0.98fr);
  gap: 24px;
  align-items: stretch;
}

.hero-copy,
.hero-visual {
  min-width: 0;
}

.hero-copy {
  padding: 28px 0 16px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 18px;
  color: rgba(216, 226, 240, 0.92);
  font-size: 0.85rem;
}

.eyebrow::before {
  content: "";
  width: 28px;
  height: 2px;
  background: linear-gradient(90deg, var(--blue), var(--teal));
  border-radius: 999px;
}

.hero h1 {
  margin: 0;
  font-size: clamp(2rem, 2.9vw, 3.55rem);
  line-height: 1.08;
  color: #f7fbff;
}

.hero-lead {
  margin: 18px 0 0;
  max-width: 62ch;
  color: rgba(216, 226, 240, 0.84);
  font-size: 1rem;
}

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

.button,
.button-subtle,
.back-to-top {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border-radius: 999px;
  border: 1px solid transparent;
  transition: transform var(--transition), background var(--transition), border-color var(--transition);
  cursor: pointer;
}

.button {
  background: linear-gradient(135deg, var(--blue), var(--teal));
  color: #fff;
  padding: 12px 18px;
  font-weight: 600;
}

.button-subtle {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(255, 255, 255, 0.14);
  color: #f7fbff;
  padding: 12px 18px;
}

.page-chapter .button-subtle {
  background: var(--bg-soft);
  border-color: rgba(37, 99, 235, 0.18);
  color: var(--text-main);
}

.button:hover,
.button-subtle:hover,
.back-to-top:hover {
  transform: translateY(-1px);
}

.hero-stats {
  margin-top: 26px;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
}

.hero-stat {
  padding: 16px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.hero-stat strong {
  display: block;
  font-size: 1.35rem;
  color: #f7fbff;
}

.hero-stat span {
  font-size: 0.88rem;
  color: rgba(216, 226, 240, 0.78);
}

.hero-visual {
  display: grid;
}

.visual-card {
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: 0 22px 54px rgba(0, 0, 0, 0.22);
  overflow: hidden;
}

.visual-card img {
  width: 100%;
  aspect-ratio: 5 / 4;
  object-fit: cover;
}

.visual-caption {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  padding: 18px;
}

.visual-chip {
  padding: 12px 14px;
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.06);
  color: rgba(216, 226, 240, 0.86);
  font-size: 0.9rem;
}

.section {
  padding: 28px 0;
}

.section-anchor {
  scroll-margin-top: 94px;
}

.section-heading {
  margin-bottom: 18px;
}

.section-heading h2 {
  margin: 8px 0 0;
  font-size: clamp(1.5rem, 2vw, 2.2rem);
  line-height: 1.2;
}

.section-heading p {
  margin: 10px 0 0;
  max-width: 60ch;
  color: var(--text-muted);
}

.section-label {
  display: inline-block;
  color: var(--blue);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.card-grid {
  display: grid;
  gap: 16px;
}

.stage-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.card,
.chapter-card,
.overview-card,
.advice-card,
.content-card,
.chapter-section,
.milestone-card,
.pitfall-card,
.chapter-summary,
.toc-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}

.page-home .card,
.page-home .chapter-card,
.page-home .overview-card,
.page-home .advice-card {
  box-shadow: 0 24px 60px rgba(15, 23, 42, 0.06);
}

.card {
  padding: 22px;
}

.stage-card {
  display: flex;
  flex-direction: column;
  gap: 16px;
  min-height: 240px;
}

.stage-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  font-weight: 700;
  color: #fff;
}

.stage-card.blue .stage-number { background: var(--blue); }
.stage-card.amber .stage-number { background: var(--amber); }
.stage-card.teal .stage-number { background: var(--teal); }
.stage-card.rose .stage-number { background: var(--rose); }

.stage-meta {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 30px;
  padding: 0 10px;
  border-radius: 999px;
  background: var(--bg-soft);
  color: var(--text-muted);
  border: 1px solid var(--border);
  font-size: 0.82rem;
}

.stage-card h3,
.chapter-card h3,
.advice-card h3,
.chapter-section h2,
.chapter-section h3,
.chapter-summary h1,
.toc-card h2 {
  margin: 0;
}

.stage-card p,
.chapter-card p,
.advice-card p,
.chapter-intro,
.chapter-section > p,
.topic-group p,
.pitfall-card p {
  color: var(--text-muted);
}

.check-list,
.topic-list,
.task-list,
.milestone-list,
.pitfall-list,
.toc-list,
.chapter-nav-links {
  list-style: none;
  padding: 0;
  margin: 0;
}

.check-list li,
.task-list li,
.milestone-list li,
.pitfall-list li {
  position: relative;
  padding-left: 24px;
}

.check-list li::before,
.task-list li::before,
.milestone-list li::before,
.pitfall-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.62em;
  width: 10px;
  height: 10px;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--blue), var(--teal));
}

.roadmap-shell {
  display: grid;
  gap: 20px;
  padding: 26px;
  border-radius: 28px;
  background: linear-gradient(180deg, #fff 0, #f7f9fd 100%);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.roadmap-line {
  position: relative;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.roadmap-line::before {
  content: "";
  position: absolute;
  left: 12%;
  right: 12%;
  top: 26px;
  height: 4px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--blue), var(--amber), var(--teal), var(--rose));
}

.roadmap-step {
  position: relative;
  padding-top: 44px;
}

.roadmap-dot {
  position: absolute;
  top: 16px;
  left: 0;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 3px solid #fff;
  box-shadow: 0 0 0 1px rgba(15, 23, 42, 0.08);
}

.roadmap-step.blue .roadmap-dot { background: var(--blue); }
.roadmap-step.amber .roadmap-dot { background: var(--amber); }
.roadmap-step.teal .roadmap-dot { background: var(--teal); }
.roadmap-step.rose .roadmap-dot { background: var(--rose); }

.roadmap-step h3 {
  margin: 0 0 8px;
  font-size: 1rem;
}

.roadmap-step p {
  margin: 0 0 12px;
  color: var(--text-muted);
}

.roadmap-step ul {
  margin: 0;
  padding-left: 18px;
  color: var(--text-muted);
}

.chapter-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.overview-shell {
  display: grid;
  gap: 18px;
}

.overview-phase-band {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}

.phase-pill-card {
  padding: 18px;
  border-radius: var(--radius-md);
  background: linear-gradient(180deg, #fff 0, #f8fbff 100%);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.phase-pill-card strong,
.phase-pill-card span {
  display: block;
}

.phase-pill-card strong {
  font-size: 0.96rem;
}

.phase-pill-card span {
  margin-top: 4px;
  color: var(--text-muted);
  font-size: 0.88rem;
}

.phase-pill-card p {
  margin: 10px 0 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.phase-pill-card.blue { border-top: 4px solid var(--blue); }
.phase-pill-card.amber { border-top: 4px solid var(--amber); }
.phase-pill-card.teal { border-top: 4px solid var(--teal); }
.phase-pill-card.rose { border-top: 4px solid var(--rose); }

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

.overview-card {
  position: relative;
  display: grid;
  gap: 16px;
  min-height: 332px;
  padding: 20px;
  transition: transform var(--transition), border-color var(--transition);
  overflow: hidden;
}

.overview-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-strong);
}

.overview-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
}

.overview-card.blue::before { background: var(--blue); }
.overview-card.amber::before { background: var(--amber); }
.overview-card.teal::before { background: var(--teal); }
.overview-card.rose::before { background: var(--rose); }

.overview-card-top,
.overview-output {
  display: grid;
  gap: 10px;
}

.overview-card-top p,
.overview-output span {
  margin: 0;
  color: var(--text-muted);
}

.overview-card h3 {
  font-size: 1.02rem;
  line-height: 1.35;
}

.overview-card-title {
  color: var(--text-main);
  transition: color var(--transition);
}

.overview-card-title:hover {
  color: var(--blue);
}

.learning-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.chapter-learning-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin-top: 20px;
}

.learning-nav-item {
  display: grid;
  gap: 6px;
  min-height: 88px;
  padding: 12px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: linear-gradient(180deg, #fff 0, #f8fbff 100%);
}

.page-chapter .chapter-learning-nav .learning-nav-item {
  min-height: 100%;
  background: var(--bg-soft);
  border-color: rgba(37, 99, 235, 0.12);
}

.learning-nav-label {
  color: var(--text-muted);
  font-size: 0.78rem;
  font-weight: 700;
}

.learning-nav-item strong {
  display: block;
  font-size: 0.9rem;
}

.prereq-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.page-chapter .chapter-learning-nav .prereq-links {
  margin-top: 2px;
}

.prereq-chip {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.16);
  background: rgba(37, 99, 235, 0.08);
  color: var(--blue);
  font-size: 0.78rem;
  font-weight: 700;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}

.prereq-chip:hover {
  background: rgba(37, 99, 235, 0.14);
  border-color: rgba(37, 99, 235, 0.24);
}

.prereq-chip.is-static {
  border-color: rgba(15, 118, 110, 0.18);
  background: rgba(15, 118, 110, 0.1);
  color: var(--teal);
}

.overview-entry {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 0 12px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.16);
  background: rgba(37, 99, 235, 0.08);
  color: var(--blue);
  font-size: 0.85rem;
  font-weight: 700;
  transition: transform var(--transition), background var(--transition), border-color var(--transition);
}

.overview-entry:hover {
  transform: translateY(-1px);
  background: rgba(37, 99, 235, 0.14);
  border-color: rgba(37, 99, 235, 0.24);
}

.mini-map {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  padding: 14px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: linear-gradient(180deg, #fff 0, #f8fbff 100%);
}

.mini-node {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 34px;
  padding: 0 10px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.14);
  background: rgba(255, 255, 255, 0.94);
  color: var(--text-main);
  font-size: 0.8rem;
  font-weight: 700;
}

.mini-connector {
  width: 18px;
  height: 2px;
  border-radius: 999px;
  background: rgba(37, 99, 235, 0.26);
  flex-shrink: 0;
}

.overview-card.amber .mini-node {
  border-color: rgba(217, 119, 6, 0.18);
}

.overview-card.amber .mini-connector {
  background: rgba(217, 119, 6, 0.26);
}

.overview-card.teal .mini-node {
  border-color: rgba(15, 118, 110, 0.18);
}

.overview-card.teal .mini-connector {
  background: rgba(15, 118, 110, 0.28);
}

.overview-card.rose .mini-node {
  border-color: rgba(190, 24, 93, 0.18);
}

.overview-card.rose .mini-connector {
  background: rgba(190, 24, 93, 0.24);
}

.overview-output {
  margin-top: auto;
  padding: 14px;
  border-radius: 12px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
}

.overview-output strong {
  display: block;
  font-size: 0.92rem;
}

.overview-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--blue);
  font-size: 0.88rem;
  font-weight: 600;
}

.overview-card.amber .overview-card-footer {
  color: var(--amber);
}

.overview-card.teal .overview-card-footer {
  color: var(--teal);
}

.overview-card.rose .overview-card-footer {
  color: var(--rose);
}

.chapter-card {
  display: flex;
  flex-direction: column;
  min-height: 260px;
  overflow: hidden;
  transition: transform var(--transition), border-color var(--transition);
}

.chapter-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-strong);
}

.chapter-card-top {
  padding: 22px 22px 18px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.06), rgba(37, 99, 235, 0.01));
}

.chapter-card-body {
  padding: 18px 22px 22px;
  display: flex;
  flex: 1;
  flex-direction: column;
  gap: 14px;
}

.chapter-card-footer {
  margin-top: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--blue);
  font-size: 0.9rem;
  font-weight: 600;
}

.topic-list {
  display: grid;
  gap: 8px;
}

.topic-list li {
  display: flex;
  gap: 10px;
  color: var(--text-muted);
}

.topic-list li::before {
  content: "•";
  color: var(--teal);
  font-weight: 700;
}

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

.advice-card {
  padding: 22px;
}

.advice-card ol,
.advice-card ul {
  margin: 0;
  padding-left: 20px;
  color: var(--text-muted);
}

.site-footer {
  padding: 34px 0 56px;
}

.site-footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 16px;
  color: var(--text-muted);
  font-size: 0.92rem;
}

.footer-links {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}

.chapter-header {
  padding: 36px 0 18px;
}

.chapter-header-inner {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 18px;
  align-items: start;
}

.chapter-summary {
  padding: 28px;
}

.chapter-summary h1 {
  margin: 12px 0 8px;
  font-size: clamp(1.8rem, 2.6vw, 3rem);
  line-height: 1.12;
}

.chapter-breadcrumb {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.chapter-layout {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
  padding-bottom: 52px;
}

.chapter-nav {
  position: sticky;
  top: 96px;
}

.toc-card {
  padding: 18px;
}

.toc-card h2 {
  font-size: 1rem;
  margin-bottom: 14px;
}

.toc-list {
  display: grid;
  gap: 8px;
}

.toc-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 12px;
  color: var(--text-muted);
  background: var(--bg-soft);
  border: 1px solid transparent;
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}

.toc-link:hover,
.toc-link.is-active {
  background: rgba(37, 99, 235, 0.08);
  border-color: rgba(37, 99, 235, 0.18);
  color: var(--blue);
}

.toc-link small {
  color: inherit;
}

.chapter-main {
  display: grid;
  gap: 18px;
}

.chapter-section {
  padding: 24px;
  scroll-margin-top: 96px;
}

.section-grid {
  display: grid;
  gap: 16px;
}

.guide-grid,
.insight-grid,
.resource-grid,
.details-grid,
.decision-grid,
.scenario-grid {
  display: grid;
  gap: 16px;
}

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

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

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

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

.guide-card,
.insight-card,
.resource-card,
.detail-card,
.self-check-item,
.decision-card,
.scenario-card {
  padding: 18px;
  border-radius: var(--radius-md);
  background: linear-gradient(180deg, #fff 0, #f7fbff 100%);
  border: 1px solid var(--border);
}

.guide-card h3,
.insight-card h3,
.resource-card h3,
.detail-card h3,
.self-check-item h3,
.decision-card h3,
.scenario-card h3 {
  margin-bottom: 8px;
}

.guide-card p,
.insight-card p,
.resource-card p,
.detail-card p,
.self-check-item p,
.decision-card p,
.scenario-card p,
.resource-card li,
.detail-card li {
  margin: 0;
  color: var(--text-muted);
}

.guide-card ul,
.detail-card ul,
.resource-card ul {
  margin: 12px 0 0;
  padding-left: 18px;
  color: var(--text-muted);
}

.chapter-section > .section-intro {
  margin: 12px 0 0;
}

.topic-group {
  padding: 18px;
  border-radius: var(--radius-md);
  background: var(--bg-soft);
  border: 1px solid var(--border);
}

.topic-group h3 {
  margin-bottom: 8px;
}

.topic-group h4 {
  margin: 14px 0 6px;
  font-size: 0.96rem;
}

.topic-group ul {
  margin: 12px 0 0;
  padding-left: 18px;
  color: var(--text-muted);
}

.topic-group > *:last-child {
  margin-bottom: 0;
}

.comparison-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 640px;
  background: #fff;
}

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

.comparison-table th {
  background: #eff5ff;
  color: var(--text-main);
  font-size: 0.92rem;
}

.comparison-table td {
  color: var(--text-muted);
}

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

.task-list {
  display: grid;
  gap: 14px;
}

.task-card {
  padding: 16px 18px;
  border-radius: var(--radius-md);
  background: linear-gradient(180deg, #fff 0, #f8fbff 100%);
  border: 1px solid rgba(37, 99, 235, 0.16);
}

.task-card h3 {
  margin: 0 0 6px;
  font-size: 1rem;
}

.task-card p {
  margin: 0;
  color: var(--text-muted);
}

.milestones-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.milestone-card {
  padding: 18px;
}

.self-check-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.self-check-item {
  border-left: 4px solid rgba(37, 99, 235, 0.35);
}

.resource-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.resource-list li {
  display: grid;
  gap: 4px;
}

.resource-link {
  color: var(--blue);
  font-weight: 600;
}

.decision-card ul,
.scenario-card ul {
  margin: 12px 0 0;
  padding-left: 18px;
  color: var(--text-muted);
}

.scenario-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 10px;
}

.scenario-meta span {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  background: rgba(15, 118, 110, 0.08);
  color: var(--teal);
  font-size: 0.78rem;
  font-weight: 700;
}

.resource-type {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border-radius: 999px;
  background: rgba(37, 99, 235, 0.08);
  color: var(--blue);
  font-size: 0.78rem;
  font-weight: 700;
}

.diagram-lab-intro {
  margin: 10px 0 0;
  color: var(--text-muted);
}

.diagram-board {
  display: grid;
  gap: 20px;
  padding: 22px;
  border-radius: var(--radius-md);
  background: linear-gradient(180deg, #fff 0, #f7fbff 100%);
  border: 1px solid var(--border);
  box-shadow: 0 12px 32px rgba(15, 23, 42, 0.05);
}

.diagram-header {
  display: grid;
  gap: 6px;
  padding-bottom: 2px;
}

.diagram-title {
  margin: 0;
  font-size: 1.02rem;
}

.diagram-copy {
  margin: 0;
  color: var(--text-muted);
  max-width: 72ch;
  font-size: 0.92rem;
}

.diagram-rail,
.diagram-flow,
.diagram-compare,
.diagram-column,
.diagram-support {
  display: grid;
  gap: 12px;
}

.diagram-rail {
  grid-template-columns: 1fr;
}

.diagram-flow {
  grid-template-columns: repeat(7, minmax(0, 1fr));
  align-items: stretch;
}

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

.diagram-node,
.diagram-layer,
.diagram-loop,
.diagram-support-card {
  padding: 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg-soft);
  box-shadow: 0 8px 22px rgba(15, 23, 42, 0.04);
}

.diagram-node {
  display: grid;
  gap: 8px;
  min-height: 116px;
  align-content: start;
}

.diagram-node strong,
.diagram-layer strong,
.diagram-loop strong,
.diagram-support-card strong {
  display: block;
  font-size: 0.95rem;
}

.diagram-node span,
.diagram-layer span,
.diagram-loop span,
.diagram-support-card span {
  display: block;
  color: var(--text-muted);
  font-size: 0.88rem;
}

.diagram-layer {
  position: relative;
  padding-left: 22px;
}

.diagram-layer::before {
  content: "";
  position: absolute;
  left: 0;
  top: 14px;
  bottom: 14px;
  width: 6px;
  border-radius: 999px;
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.85), rgba(15, 118, 110, 0.85));
}

.diagram-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 42px;
  min-width: 42px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.18);
  background: rgba(37, 99, 235, 0.08);
  color: transparent;
  font-size: 0;
  position: relative;
}

.diagram-arrow::before {
  color: var(--blue);
  font-weight: 700;
  font-size: 1rem;
  line-height: 1;
}

.diagram-arrow.is-horizontal::before {
  content: "→";
}

.diagram-arrow.is-vertical::before {
  content: "↓";
}

.diagram-loop {
  border-style: dashed;
  border-color: rgba(15, 118, 110, 0.3);
  background: rgba(15, 118, 110, 0.06);
}

.diagram-loop-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

.diagram-loop-list span {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 10px;
  border-radius: 999px;
  background: rgba(15, 118, 110, 0.12);
  color: var(--teal);
  font-size: 0.8rem;
  font-weight: 700;
}

.diagram-column {
  padding: 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #fff;
  align-content: start;
}

.diagram-column-title {
  margin: 0;
  font-size: 0.98rem;
}

.diagram-column-copy {
  margin: 4px 0 0;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.diagram-node.is-accent,
.diagram-support-card.is-accent {
  border-color: rgba(37, 99, 235, 0.24);
  background: linear-gradient(180deg, rgba(37, 99, 235, 0.08) 0, rgba(37, 99, 235, 0.02) 100%);
}

.diagram-node.is-teal,
.diagram-support-card.is-teal {
  border-color: rgba(15, 118, 110, 0.28);
  background: linear-gradient(180deg, rgba(15, 118, 110, 0.08) 0, rgba(15, 118, 110, 0.02) 100%);
}

.diagram-node.is-amber,
.diagram-support-card.is-amber {
  border-color: rgba(217, 119, 6, 0.28);
  background: linear-gradient(180deg, rgba(217, 119, 6, 0.08) 0, rgba(217, 119, 6, 0.02) 100%);
}

.diagram-node.is-rose,
.diagram-support-card.is-rose {
  border-color: rgba(190, 24, 93, 0.24);
  background: linear-gradient(180deg, rgba(190, 24, 93, 0.08) 0, rgba(190, 24, 93, 0.02) 100%);
}

.diagram-support-card {
  min-height: 104px;
  background: #fff;
}

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

.pitfall-card {
  padding: 18px;
}

.chapter-next {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 18px;
}

.chapter-nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 16px;
}

.muted {
  color: var(--text-muted);
}

.back-to-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  min-width: 46px;
  height: 46px;
  padding: 0 14px;
  border: 1px solid rgba(37, 99, 235, 0.18);
  background: rgba(255, 255, 255, 0.96);
  box-shadow: var(--shadow);
  color: var(--blue);
  opacity: 0;
  pointer-events: none;
}

.back-to-top.is-visible {
  opacity: 1;
  pointer-events: auto;
}

@media (max-width: 1100px) {
  .stage-grid,
  .chapter-grid,
  .overview-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .hero-panel,
  .chapter-header-inner,
  .chapter-layout {
    grid-template-columns: 1fr;
  }

  .chapter-nav {
    position: static;
  }

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

  .roadmap-line::before {
    display: none;
  }

  .roadmap-step {
    padding-top: 34px;
  }

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

@media (max-width: 760px) {
  .header-inner,
  .section-inner,
  .chapter-header-inner,
  .chapter-layout,
  .site-footer-inner {
    width: min(calc(100% - 24px), var(--content-width));
  }

  .header-inner,
  .site-footer-inner {
    flex-direction: column;
    align-items: flex-start;
  }

  .header-nav,
  .hero-actions {
    width: 100%;
  }

  .hero-stats,
  .visual-caption,
  .milestones-grid,
  .advice-grid,
  .overview-phase-band,
  .guide-grid,
  .details-grid,
  .insight-grid,
  .resource-grid,
  .decision-grid,
  .scenario-grid,
  .diagram-compare,
  .diagram-support {
    grid-template-columns: 1fr 1fr;
  }

  .diagram-node,
  .diagram-support-card {
    min-height: 0;
  }

  .chapter-summary,
  .chapter-section,
  .card,
  .advice-card {
    padding: 20px;
  }

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

  .learning-nav-item:has(.prereq-links) {
    grid-column: 1 / -1;
  }

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

  .chapter-learning-nav .learning-nav-item:has(.prereq-links) {
    grid-column: 1 / -1;
  }
}

@media (max-width: 900px) {
  .diagram-flow {
    grid-template-columns: 1fr;
  }

  .diagram-compare,
  .diagram-support {
    grid-template-columns: 1fr;
  }

  .diagram-arrow.is-horizontal::before {
    content: "↓";
  }
}

@media (max-width: 560px) {
  .hero-stats,
  .stage-grid,
  .overview-grid,
  .chapter-grid,
  .advice-grid,
  .milestones-grid,
  .overview-phase-band,
  .visual-caption,
  .roadmap-line,
  .guide-grid,
  .details-grid,
  .insight-grid,
  .resource-grid,
  .decision-grid,
  .scenario-grid,
  .diagram-compare,
  .diagram-support,
  .diagram-flow {
    grid-template-columns: 1fr;
  }

  .hero {
    padding-top: 38px;
  }

  .hero h1 {
    font-size: 2rem;
  }

  .overview-card {
    min-height: 0;
  }

  .learning-nav {
    grid-template-columns: 1fr;
  }

  .learning-nav-item:has(.prereq-links) {
    grid-column: auto;
  }

  .chapter-learning-nav {
    grid-template-columns: 1fr;
  }

  .chapter-learning-nav .learning-nav-item:has(.prereq-links) {
    grid-column: auto;
  }
}