:root {
  color-scheme: light;
  --ink: #102b46;
  --ink-soft: #38516a;
  --blue: #164a9d;
  --blue-deep: #123b7b;
  --cyan: #00737d;
  --lime: #dfff62;
  --note-sage: #e5eee3;
  --paper: #f5f9fc;
  --white: #ffffff;
  --line: #b5c4d2;
  --focus: #09243d;
  --content-width: 74rem;
  font-family: "Segoe UI", "Yu Gothic UI", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

* {
  box-sizing: border-box;
}

html {
  scroll-padding-top: 1rem;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-size: 1rem;
  line-height: 1.75;
  overflow-wrap: anywhere;
}

a {
  color: var(--cyan);
  text-decoration-thickness: 0.1em;
  text-underline-offset: 0.18em;
}

a:hover {
  color: var(--blue-deep);
  text-decoration-thickness: 0.16em;
}

a:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 4px;
  border-radius: 2px;
}

::selection {
  background: var(--lime);
  color: var(--ink);
}

.skip-link {
  position: absolute;
  z-index: 10;
  top: 0.5rem;
  left: 0.5rem;
  padding: 0.75rem 1rem;
  transform: translateY(-160%);
  background: var(--lime);
  color: var(--ink);
  font-weight: 700;
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  background: var(--ink);
  color: var(--white);
}

.site-header__inner,
.opening__inner,
.reading-layout,
.sources__inner,
.site-footer__inner {
  width: min(100% - 3rem, var(--content-width));
  margin-inline: auto;
}

.site-header__inner {
  display: flex;
  min-height: 5rem;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
}

.wordmark {
  display: inline-flex;
  min-height: 3.25rem;
  align-items: center;
  padding: 0.25rem;
  background: var(--white);
  text-decoration: none;
}

.wordmark img {
  display: block;
  width: auto;
  height: 2.75rem;
  max-width: 100%;
}

.wordmark:hover {
  outline: 2px solid var(--lime);
  outline-offset: 3px;
}

.top-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 0.35rem 1.4rem;
}

.top-nav a {
  display: inline-flex;
  min-height: 2.75rem;
  align-items: center;
  color: var(--white);
  font-size: 0.95rem;
  font-weight: 650;
  text-decoration-color: transparent;
  text-underline-offset: 0.35em;
}

.top-nav a:hover {
  color: var(--lime);
  text-decoration-color: currentColor;
}

.top-nav a:focus-visible {
  outline-color: var(--lime);
}

.opening {
  position: relative;
  overflow: hidden;
  background-color: var(--white);
  background-image:
    linear-gradient(rgb(16 43 70 / 4%) 1px, transparent 1px),
    linear-gradient(90deg, rgb(16 43 70 / 4%) 1px, transparent 1px);
  background-size: 2.75rem 2.75rem;
  color: var(--ink);
}

.opening__inner {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(18rem, 0.8fr);
  align-items: center;
  gap: clamp(2rem, 6vw, 6rem);
  padding-block: clamp(3.5rem, 7vw, 6.5rem);
}

.opening h1 {
  max-width: 12ch;
  margin: 0;
  font-size: clamp(2.6rem, 5.7vw, 5.15rem);
  font-weight: 780;
  letter-spacing: -0.035em;
  line-height: 1.16;
  text-wrap: balance;
}

.opening h1:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 0.35rem;
}

.opening__intro {
  max-width: 57ch;
  margin: 1.5rem 0 0;
  color: var(--ink-soft);
  font-size: clamp(1.05rem, 1.5vw, 1.2rem);
}

.quick-note {
  position: relative;
  padding: 1.65rem clamp(1.25rem, 2.4vw, 2rem);
  border: 2px solid var(--ink);
  background: var(--note-sage);
  color: var(--ink);
  box-shadow: 0.4rem 0.45rem 0.55rem rgb(16 43 70 / 28%);
}

.quick-note::before,
.quick-note::after {
  position: absolute;
  top: 0.8rem;
  width: 0.55rem;
  height: 0.55rem;
  border: 2px solid var(--ink);
  border-radius: 50%;
  background: var(--paper);
  content: "";
}

.quick-note::before {
  left: 0.8rem;
}

.quick-note::after {
  right: 0.8rem;
}

.quick-note h2 {
  margin: 0 0 1rem;
  font-size: 1.2rem;
  letter-spacing: 0.01em;
}

.quick-list {
  display: grid;
  gap: 0.85rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.quick-list li {
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr);
  align-items: start;
  gap: 0.7rem;
}

.quick-list__number {
  display: grid;
  width: 2rem;
  height: 2rem;
  place-items: center;
  border: 2px solid var(--ink);
  border-radius: 50%;
  font-weight: 800;
  line-height: 1;
}

.quick-list strong,
.quick-list__detail {
  display: block;
}

.quick-list strong {
  font-size: 1rem;
}

.quick-list__detail {
  margin-top: 0.1rem;
  font-size: 0.93rem;
  line-height: 1.55;
}

.opening__rule {
  height: 1px;
  background: var(--line);
}

.reading-layout {
  display: grid;
  grid-template-columns: minmax(13rem, 0.72fr) minmax(0, 2fr);
  align-items: start;
  gap: clamp(2.5rem, 6vw, 6rem);
  padding-block: clamp(3.5rem, 7vw, 6rem);
}

.chapter-index {
  position: sticky;
  top: 1.5rem;
  padding-block: 0.5rem;
}

.chapter-index h2 {
  margin: 0 0 1rem;
  font-size: 1.05rem;
}

.chapter-index ol {
  display: grid;
  gap: 0.45rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.chapter-index a {
  display: flex;
  min-height: 2.9rem;
  align-items: center;
  gap: 0.75rem;
  padding: 0.4rem 0.65rem;
  border-bottom: 1px solid var(--line);
  color: var(--ink);
  font-weight: 650;
  text-decoration: none;
}

.chapter-index a:hover {
  background: #e4f2f5;
  color: var(--blue-deep);
  text-decoration: underline;
  text-underline-offset: 0.2em;
}

.chapter-index a span {
  color: var(--cyan);
  font-size: 0.9rem;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.chapter-index__note {
  margin: 1.3rem 0 0;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  background: var(--white);
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.chapters {
  min-width: 0;
}

.chapter {
  padding-block: 0 3.5rem;
  scroll-margin-top: 1rem;
}

.chapter + .chapter {
  padding-top: 3rem;
  border-top: 2px solid var(--line);
}

.chapter__header {
  display: grid;
  grid-template-columns: 4.5rem minmax(0, 1fr);
  align-items: start;
  gap: clamp(1rem, 2.5vw, 1.8rem);
}

.chapter__number {
  display: grid;
  width: 4.25rem;
  min-height: 4.25rem;
  place-items: center;
  border: 2px solid var(--blue);
  background: var(--blue);
  color: var(--white);
  font-size: 1.25rem;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  line-height: 1;
  box-shadow: 0.2rem 0.24rem 0.3rem rgb(16 43 70 / 24%);
}

.chapter__header h2 {
  margin: 0;
  font-size: clamp(1.65rem, 3vw, 2.35rem);
  font-weight: 760;
  letter-spacing: -0.025em;
  line-height: 1.3;
  text-wrap: balance;
}

.chapter__header h2:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 0.25rem;
}

.chapter__intro {
  max-width: 68ch;
  margin: 0.8rem 0 0;
  color: var(--ink-soft);
}

.practice-pair {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(1.25rem, 3vw, 2.25rem);
  margin-top: 1.75rem;
}

.practice {
  padding: 1.15rem 1.15rem 1rem;
  border-top: 4px solid var(--cyan);
  background: var(--white);
}

.practice--avoid {
  border-top-color: var(--blue-deep);
}

.practice h3 {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin: 0 0 0.75rem;
  font-size: 1.1rem;
}

.practice__mark {
  display: inline-grid;
  width: 1.65rem;
  height: 1.65rem;
  flex: 0 0 auto;
  place-items: center;
  border: 2px solid currentColor;
  border-radius: 50%;
  color: var(--cyan);
  font-size: 1.1rem;
  font-weight: 800;
  line-height: 1;
}

.practice--avoid .practice__mark {
  color: var(--blue-deep);
}

.practice ul,
.support-note ul {
  margin: 0;
  padding-left: 1.25rem;
}

.practice li + li,
.support-note li + li {
  margin-top: 0.55rem;
}

.practice li::marker,
.support-note li::marker {
  color: var(--cyan);
}

.practice--avoid li::marker {
  color: var(--blue-deep);
}

.chapter__footnote {
  margin: 1rem 0 0;
  padding-top: 0.85rem;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.support-note {
  margin-top: 1.75rem;
  padding: clamp(1.2rem, 3vw, 2rem);
  border: 2px solid var(--ink);
  background: #e3f3f3;
  box-shadow: 0.25rem 0.3rem 0.35rem rgb(0 115 125 / 22%);
}

.support-note h3 {
  margin: 0 0 0.75rem;
  font-size: 1.15rem;
}

.support-note > p {
  margin: 1rem 0 0;
  padding-top: 0.85rem;
  border-top: 1px solid #8daeb3;
}

.sources {
  background: var(--ink);
  color: var(--white);
}

.sources__inner {
  padding-block: clamp(2.5rem, 5vw, 4rem);
}

.sources h2 {
  margin: 0;
  color: var(--lime);
  font-size: clamp(1.5rem, 2.4vw, 2rem);
  letter-spacing: -0.02em;
}

.sources p {
  max-width: 72ch;
}

.sources__inner > p:first-of-type {
  margin: 0.75rem 0 1rem;
}

.sources ul {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  margin: 0;
  padding-left: 1.3rem;
}

.sources li::marker {
  color: var(--lime);
}

.sources a {
  color: var(--white);
  font-weight: 700;
}

.sources a:hover {
  color: var(--lime);
}

.sources a:focus-visible,
.site-footer a:focus-visible {
  outline-color: var(--lime);
}

.sources__note {
  margin: 1rem 0 0;
  color: #ffffff;
  font-size: 0.95rem;
}

.site-footer {
  background: var(--ink);
  color: var(--white);
}

.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 2rem;
  padding-block: 1.25rem;
}

.site-footer p {
  margin: 0;
}

.site-footer a {
  color: var(--white);
}

.site-footer a:hover {
  color: var(--lime);
}

@media (max-width: 54rem) {
  .site-header__inner {
    align-items: flex-start;
    flex-direction: column;
    gap: 0.2rem;
    padding-block: 0.75rem 0.55rem;
  }

  .top-nav {
    justify-content: flex-start;
    gap: 0.15rem 1rem;
  }

  .opening__inner {
    grid-template-columns: minmax(0, 1fr);
    gap: 2rem;
  }

  .opening h1 {
    max-width: 14ch;
  }

  .quick-note {
    max-width: 36rem;
  }

  .reading-layout {
    grid-template-columns: minmax(0, 1fr);
    gap: 2.5rem;
  }

  .chapter-index {
    position: static;
    padding: 1.2rem;
    border: 2px solid var(--ink);
    background: var(--white);
    box-shadow: 0.25rem 0.3rem 0.35rem rgb(16 43 70 / 18%);
  }

  .chapter-index ol {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.2rem 1rem;
  }

  .chapter-index__note {
    margin-top: 1rem;
  }
}

@media (max-width: 38rem) {
  .site-header__inner,
  .opening__inner,
  .reading-layout,
  .sources__inner,
  .site-footer__inner {
    width: min(100% - 2rem, var(--content-width));
  }

  .top-nav {
    gap: 0.1rem 0.75rem;
  }

  .top-nav a {
    min-height: 2.7rem;
    font-size: 0.9rem;
  }

  .opening__inner {
    padding-block: 3rem 3.5rem;
  }

  .opening h1 {
    font-size: clamp(2.45rem, 11vw, 3.65rem);
  }

  .opening__intro {
    margin-top: 1.2rem;
  }

  .quick-note {
    padding: 1.5rem 1rem 1.1rem;
  }

  .reading-layout {
    padding-block: 2.5rem 3rem;
  }

  .chapter-index {
    padding: 1rem;
  }

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

  .chapter {
    padding-bottom: 2.5rem;
  }

  .chapter + .chapter {
    padding-top: 2.3rem;
  }

  .chapter__header {
    grid-template-columns: 3.35rem minmax(0, 1fr);
    gap: 0.85rem;
  }

  .chapter__number {
    width: 3.2rem;
    min-height: 3.2rem;
    font-size: 1.05rem;
    box-shadow: 0.16rem 0.18rem 0.24rem rgb(16 43 70 / 24%);
  }

  .chapter__header h2 {
    font-size: 1.6rem;
  }

  .practice-pair {
    grid-template-columns: minmax(0, 1fr);
    gap: 1rem;
    margin-top: 1.25rem;
  }

  .practice {
    padding: 1rem;
  }

  .sources__inner {
    padding-block: 2.5rem;
  }

  .sources ul {
    display: grid;
    gap: 0.65rem;
  }

  .site-footer__inner {
    align-items: flex-start;
    flex-direction: column;
    padding-block: 1rem;
  }
}

@media (forced-colors: active) {
  .wordmark__dot,
  .quick-note,
  .quick-list__number,
  .chapter-index,
  .chapter-index__note,
  .chapter__number,
  .practice,
  .support-note {
    border: 1px solid CanvasText;
  }

  .opening,
  .site-header,
  .sources,
  .site-footer,
  .chapter__number {
    forced-color-adjust: auto;
  }

  a:focus-visible {
    outline: 3px solid Highlight;
  }
}

@media print {
  :root {
    color-scheme: light;
  }

  body {
    background: #ffffff;
    color: #000000;
    font-size: 11pt;
  }

  .site-header,
  .chapter-index,
  .opening__rule,
  .site-footer {
    display: none;
  }

  .opening,
  .sources {
    background: #ffffff;
    color: #000000;
  }

  .opening__inner,
  .sources__inner,
  .reading-layout {
    width: 100%;
    padding-block: 1rem;
  }

  .opening h1,
  .sources h2,
  .sources a {
    color: #000000;
  }

  .opening__inner,
  .reading-layout,
  .practice-pair {
    display: block;
  }

  .quick-note,
  .practice,
  .support-note {
    margin-block: 1rem;
    border: 1px solid #000000;
    box-shadow: none;
    break-inside: avoid;
  }

  .chapter {
    break-inside: avoid-page;
  }

  a {
    color: #000000;
  }
}