:root {
  color-scheme: light;
  --navy: #0c2532;
  --navy-soft: #173a47;
  --cyan: #72d2cf;
  --cyan-deep: #3aa8a8;
  --paper: #edf1ec;
  --white: #f8faf5;
  --ink: #132229;
  --muted: #5d6c70;
  --line: #cbd5d1;
  font-family: "Apple SD Gothic Neo", "Noto Sans KR", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  line-height: 1.68;
}

a {
  color: inherit;
}

.topbar {
  position: absolute;
  inset: 0 0 auto;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: center;
  padding: 18px clamp(20px, 5vw, 72px);
  color: var(--white);
  border-bottom: 1px solid rgba(236, 249, 245, 0.2);
}

.brand {
  font-weight: 850;
  text-decoration: none;
}

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  font-size: 14px;
}

nav a {
  text-decoration: none;
}

.book-hero {
  position: relative;
  min-height: min(82vh, 780px);
  display: flex;
  align-items: flex-end;
  overflow: hidden;
  background:
    radial-gradient(circle at 76% 28%, rgba(71, 191, 192, 0.2), transparent 25%),
    linear-gradient(135deg, #091c27 0%, var(--navy) 46%, #153b47 100%);
  color: var(--white);
}

.book-hero::after {
  content: "";
  position: absolute;
  inset: 0;
  opacity: 0.28;
  background-image:
    linear-gradient(rgba(114, 210, 207, 0.16) 1px, transparent 1px),
    linear-gradient(90deg, rgba(114, 210, 207, 0.14) 1px, transparent 1px);
  background-size: 72px 72px;
  mask-image: linear-gradient(90deg, transparent 12%, #000 70%);
}

.hero-inner {
  position: relative;
  z-index: 2;
  width: min(1180px, 100%);
  margin: 0 auto;
  padding: 132px clamp(20px, 5vw, 72px) clamp(54px, 8vw, 92px);
}

.circuit {
  position: absolute;
  z-index: 1;
  top: 24%;
  right: clamp(28px, 9vw, 140px);
  width: min(33vw, 390px);
  aspect-ratio: 1;
  border: 1px solid rgba(114, 210, 207, 0.3);
  transform: rotate(8deg);
}

.circuit::before,
.circuit::after {
  content: "";
  position: absolute;
  inset: 18%;
  border: 2px solid rgba(114, 210, 207, 0.42);
}

.circuit::after {
  inset: 38%;
  border-color: var(--cyan);
  background: rgba(114, 210, 207, 0.07);
}

.circuit span {
  position: absolute;
  width: 28%;
  height: 1px;
  background: rgba(114, 210, 207, 0.5);
}

.circuit span:nth-child(1) { top: 28%; left: -8%; }
.circuit span:nth-child(2) { top: 66%; right: -8%; }
.circuit span:nth-child(3) { top: 8%; right: 20%; transform: rotate(90deg); }
.circuit span:nth-child(4) { bottom: 8%; left: 20%; transform: rotate(90deg); }

.eyebrow {
  margin: 0 0 12px;
  color: var(--cyan-deep);
  font-size: 12px;
  font-weight: 850;
  letter-spacing: 0.09em;
  text-transform: uppercase;
}

.book-hero .eyebrow {
  color: var(--cyan);
}

h1,
h2,
p {
  letter-spacing: 0;
}

h1 {
  max-width: 900px;
  margin: 0;
  font-family: "KoPubWorldBatang", "Noto Serif KR", "AppleMyungjo", serif;
  font-size: clamp(54px, 9vw, 112px);
  line-height: 0.98;
  letter-spacing: -0.055em;
}

.subtitle {
  max-width: 680px;
  margin: 26px 0 0;
  color: #d4e7e3;
  font-size: clamp(18px, 2vw, 25px);
  font-weight: 700;
}

.byline {
  margin: 8px 0 0;
  color: #a9c1bf;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 30px;
}

.button {
  min-height: 46px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 17px;
  border: 1px solid rgba(236, 249, 245, 0.56);
  border-radius: 5px;
  color: var(--white);
  font-weight: 800;
  text-decoration: none;
}

.button.primary {
  border-color: var(--cyan);
  background: var(--cyan);
  color: var(--navy);
}

.overview {
  display: grid;
  grid-template-columns: minmax(220px, 320px) minmax(0, 720px);
  justify-content: center;
  gap: clamp(42px, 8vw, 110px);
  align-items: center;
  padding: clamp(72px, 11vw, 132px) clamp(20px, 5vw, 72px);
}

.book-object {
  aspect-ratio: 148 / 210;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 30px 27px;
  border: 1px solid #2f6872;
  background:
    linear-gradient(90deg, transparent 49.5%, rgba(114, 210, 207, 0.18) 50%, transparent 50.5%),
    linear-gradient(0deg, transparent 49.5%, rgba(114, 210, 207, 0.16) 50%, transparent 50.5%),
    var(--navy);
  color: var(--white);
  box-shadow: 20px 24px 0 #d7dfda;
}

.book-object p,
.book-object span,
.book-object small {
  margin: 0;
  font-size: 12px;
  font-weight: 750;
}

.book-object strong {
  align-self: flex-end;
  max-width: 180px;
  font-family: "KoPubWorldBatang", "Noto Serif KR", "AppleMyungjo", serif;
  font-size: clamp(42px, 5vw, 64px);
  line-height: 0.98;
  text-align: right;
}

.book-object span {
  color: var(--cyan);
}

.summary h2,
.section-heading h2,
.download-copy h2 {
  margin: 0;
  font-family: "KoPubWorldBatang", "Noto Serif KR", "AppleMyungjo", serif;
  font-size: clamp(34px, 4.5vw, 58px);
  line-height: 1.12;
  letter-spacing: -0.04em;
}

.summary .lead {
  margin-top: 26px;
  color: var(--ink);
  font-size: 19px;
}

.summary > p:not(.eyebrow):not(.lead) {
  color: var(--muted);
}

.facts {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  margin: 34px 0 0;
  border-block: 1px solid var(--line);
}

.facts div {
  padding: 16px 10px 16px 0;
}

.facts dt {
  color: var(--muted);
  font-size: 12px;
  font-weight: 800;
}

.facts dd {
  margin: 2px 0 0;
  font-size: 21px;
  font-weight: 850;
}

.contents-section {
  display: grid;
  grid-template-columns: minmax(240px, 0.72fr) minmax(0, 1.2fr);
  gap: clamp(40px, 8vw, 116px);
  padding: clamp(70px, 10vw, 120px) max(clamp(20px, 5vw, 72px), calc((100vw - 1180px) / 2));
  background: var(--navy);
  color: var(--white);
}

.contents-section .eyebrow {
  color: var(--cyan);
}

.part-list {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid rgba(218, 240, 235, 0.25);
}

.part-list li {
  display: grid;
  grid-template-columns: 50px 1fr;
  gap: 18px;
  align-items: center;
  padding: 19px 0;
  border-bottom: 1px solid rgba(218, 240, 235, 0.2);
}

.part-list > li > span {
  color: var(--cyan);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 13px;
}

.part-list strong {
  font-size: 20px;
}

.part-list p {
  margin: 2px 0 0;
  color: #a9c2c1;
  font-size: 14px;
}

.downloads-section {
  display: grid;
  grid-template-columns: minmax(240px, 0.75fr) minmax(0, 1.25fr);
  gap: clamp(42px, 8vw, 110px);
  align-items: end;
  padding: clamp(68px, 9vw, 106px) max(clamp(20px, 5vw, 72px), calc((100vw - 1180px) / 2));
  background: var(--white);
}

.download-copy > p:last-child {
  color: var(--muted);
}

.download-card {
  min-height: 128px;
  display: flex;
  justify-content: space-between;
  gap: 22px;
  align-items: center;
  padding: 24px;
  border: 1px solid var(--line);
  border-left: 5px solid var(--cyan-deep);
  border-radius: 5px;
  text-decoration: none;
}

.download-card:hover {
  border-color: var(--cyan-deep);
}

.download-card strong,
.download-card small {
  display: block;
}

.download-card strong {
  font-size: 21px;
}

.download-card small,
.download-card b {
  color: var(--muted);
  font-size: 13px;
}

footer {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  padding: 26px clamp(20px, 5vw, 72px);
  background: #dce4df;
  color: var(--muted);
  font-size: 14px;
}

footer p {
  margin: 0;
}

@media (max-width: 800px) {
  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .book-hero {
    min-height: 690px;
  }

  .circuit {
    top: 19%;
    right: -70px;
    width: 280px;
  }

  .overview,
  .contents-section,
  .downloads-section {
    grid-template-columns: 1fr;
  }

  .book-object {
    width: min(260px, 78vw);
  }

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

  footer {
    flex-direction: column;
  }
}

@media (max-width: 520px) {
  h1 {
    font-size: 52px;
  }

  .actions {
    flex-direction: column;
  }

  .button,
  .download-card {
    width: 100%;
  }

  .download-card {
    align-items: flex-start;
    flex-direction: column;
  }
}