:root {
  --ink: #10213e;
  --muted: #66728a;
  --line: #dce5f2;
  --paper: #ffffff;
  --soft: #f5f8fc;
  --accent: #1778f2;
  --accent-2: #19b8c8;
  --accent-3: #ffcf33;
  --accent-dark: #0b4eb4;
  --shadow: 0 24px 60px rgba(26, 63, 114, 0.14);
}

* { box-sizing: border-box; }
html { background: #e9eef5; scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: #e9eef5;
  font-family: "Noto Sans KR", "Malgun Gothic", "Apple SD Gothic Neo", Arial, sans-serif;
  letter-spacing: 0;
  word-break: keep-all;
}

img { display: block; max-width: 100%; }
.page { width: 1200px; margin: 0 auto; background: var(--paper); overflow: hidden; }
.inner { width: 1040px; margin: 0 auto; }

.hero {
  position: relative;
  min-height: 980px;
  padding: 72px 0 78px;
  background: linear-gradient(145deg, #fafdff 0%, #edf7ff 52%, #e6fff7 100%);
  border-bottom: 1px solid #d8e8f6;
}
.hero::after {
  content: "";
  position: absolute;
  inset: auto 0 0;
  height: 14px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
}
.hero-grid {
  display: grid;
  grid-template-columns: 438px 1fr;
  align-items: center;
  gap: 76px;
}
.cover-wrap { position: relative; padding: 14px 0 40px 22px; }
.cover-wrap::before {
  content: "";
  position: absolute;
  inset: 92px 42px 0 0;
  border: 2px solid rgba(23, 120, 242, 0.2);
  background: rgba(255, 255, 255, 0.62);
}
.cover {
  position: relative;
  z-index: 1;
  width: 386px;
  border: 1px solid rgba(16, 33, 62, 0.12);
  box-shadow: 22px 30px 54px rgba(33, 67, 109, 0.24);
}
.series-label {
  color: var(--accent-dark);
  font-size: 18px;
  font-weight: 800;
  text-transform: uppercase;
  margin-bottom: 22px;
}
.hero h1 { margin: 0 0 18px; font-size: 54px; line-height: 1.16; letter-spacing: 0; }
.hero h1 span { color: var(--accent); }
.subtitle { margin: 0 0 30px; font-size: 24px; line-height: 1.55; font-weight: 750; color: #25466f; }
.lead { margin: 0; font-size: 19px; line-height: 1.9; color: #53627b; }
.hero-facts {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0;
  margin-top: 38px;
  border-top: 1px solid #cbdcec;
  border-bottom: 1px solid #cbdcec;
}
.hero-fact { padding: 20px 8px 20px 0; }
.hero-fact:nth-child(odd) { border-right: 1px solid #cbdcec; }
.hero-fact:nth-child(even) { padding-left: 24px; }
.hero-fact strong { display: block; font-size: 14px; color: var(--accent-dark); margin-bottom: 7px; }
.hero-fact span { font-size: 17px; line-height: 1.45; font-weight: 700; }

.band { padding: 94px 0; }
.band.soft { background: var(--soft); }
.band.dark { color: #fff; background: #10284c; }
.section-kicker { color: var(--accent); font-size: 15px; font-weight: 900; text-transform: uppercase; margin-bottom: 12px; }
.section-title { margin: 0; font-size: 41px; line-height: 1.25; letter-spacing: 0; }
.section-copy { max-width: 820px; margin: 18px 0 0; color: var(--muted); font-size: 18px; line-height: 1.85; }
.dark .section-kicker { color: #59dddc; }
.dark .section-copy { color: #c8d5e9; }

.outcomes {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  margin-top: 54px;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.outcome { min-height: 222px; padding: 32px 24px 30px 0; border-right: 1px solid var(--line); }
.outcome + .outcome { padding-left: 24px; }
.outcome:last-child { border-right: 0; }
.outcome-num { display: block; margin-bottom: 23px; color: var(--accent); font: 900 27px/1 Arial, sans-serif; }
.outcome h3 { margin: 0 0 12px; font-size: 21px; line-height: 1.35; }
.outcome p { margin: 0; color: var(--muted); font-size: 15px; line-height: 1.75; }

.preview-grid { display: grid; grid-template-columns: 1.08fr 0.92fr; gap: 28px; margin-top: 54px; }
.preview-grid.three { grid-template-columns: 1.05fr 0.95fr; }
.preview-grid.volume-two { grid-template-columns: 1fr 1fr; }
.preview-stack { display: grid; gap: 28px; }
.preview {
  margin: 0;
  overflow: hidden;
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: 0 16px 40px rgba(22, 55, 99, 0.11);
}
.preview img { width: 100%; height: 100%; object-fit: contain; background: #fff; }
.preview picture { display: block; width: 100%; height: 100%; }
.preview.large .media { height: 720px; }
.preview.small .media { height: 346px; }
.preview.wide .media { height: 430px; }
.preview.standard .media { height: 500px; }
.preview.full-block { grid-column: 1 / -1; }
.preview.full-block .media { height: 480px; }
.preview .media { display: flex; align-items: center; justify-content: center; overflow: hidden; padding: 18px; background: #fff; }
.preview figcaption { min-height: 104px; padding: 22px 26px; border-top: 1px solid var(--line); }
.preview figcaption strong { display: block; font-size: 19px; margin-bottom: 7px; }
.preview figcaption span { color: var(--muted); font-size: 14px; line-height: 1.55; }
.source-note { margin-top: 24px; color: #768198; font-size: 14px; line-height: 1.7; }

.concept-previews { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; margin-top: 54px; }
.concept-preview { margin: 0; background: #fff; border: 1px solid var(--line); box-shadow: 0 16px 40px rgba(22, 55, 99, 0.11); }
.concept-image { display: block; width: 100%; aspect-ratio: 3 / 2; object-fit: cover; background: #eaf7fb; }
.concept-head { min-height: 136px; padding: 25px 26px 22px; color: #fff; background: var(--accent-dark); }
.concept-head span { display: block; margin-bottom: 12px; color: #8ef0dd; font: 900 16px/1 Arial, sans-serif; }
.concept-head strong { display: block; font-size: 23px; line-height: 1.35; }
.concept-flow { list-style: none; margin: 0; padding: 18px 26px 24px; counter-reset: flow; }
.concept-flow li { position: relative; min-height: 58px; padding: 17px 0 17px 48px; border-bottom: 1px solid var(--line); color: #40506a; font-size: 15px; line-height: 1.55; }
.concept-flow li:last-child { border-bottom: 0; }
.concept-flow li::before { counter-increment: flow; content: counter(flow, decimal-leading-zero); position: absolute; left: 0; top: 19px; color: var(--accent); font: 900 14px/1 Arial, sans-serif; }
.concept-preview figcaption { padding: 22px 26px 25px; color: var(--muted); border-top: 1px solid var(--line); font-size: 14px; line-height: 1.65; }

.toc-groups { display: grid; grid-template-columns: 1fr 1fr; gap: 26px; margin-top: 54px; align-items: start; }
.toc-group { background: rgba(255, 255, 255, 0.06); border: 1px solid rgba(255, 255, 255, 0.17); }
.toc-group.wide { grid-column: 1 / -1; }
.toc-heading { margin: 0; padding: 22px 24px; color: #fff; font-size: 20px; line-height: 1.35; background: rgba(255, 255, 255, 0.08); border-bottom: 1px solid rgba(255, 255, 255, 0.17); }
.toc-list { list-style: none; padding: 12px 24px 18px; margin: 0; columns: 1; }
.toc-group.wide .toc-list { columns: 2; column-gap: 42px; }
.toc-list li { display: grid; grid-template-columns: 45px 1fr auto; gap: 12px; padding: 10px 0; border-bottom: 1px solid rgba(255, 255, 255, 0.11); break-inside: avoid; font-size: 14px; line-height: 1.45; }
.toc-list li:last-child { border-bottom: 0; }
.toc-no { color: #58dbda; font-weight: 900; }
.toc-page { color: #9fb2ce; }

.book-info { display: grid; grid-template-columns: 1fr 1fr; gap: 0 70px; margin-top: 48px; border-top: 2px solid var(--ink); }
.info-row { display: grid; grid-template-columns: 130px 1fr; gap: 18px; padding: 20px 0; border-bottom: 1px solid var(--line); }
.info-row dt { font-weight: 850; color: var(--accent-dark); }
.info-row dd { margin: 0; color: #46556d; line-height: 1.65; }
.info-note { margin-top: 28px; color: #758198; font-size: 14px; line-height: 1.7; }

.series-strip { padding: 84px 0 90px; background: #eef5fb; }
.series-covers { display: grid; grid-template-columns: repeat(3, 1fr); gap: 56px; margin-top: 46px; align-items: end; }
.series-book { text-align: center; }
.series-book img { width: 218px; margin: 0 auto 22px; box-shadow: 10px 16px 30px rgba(26, 55, 94, 0.18); border: 1px solid rgba(16, 33, 62, 0.12); }
.series-book.active img { width: 252px; box-shadow: 12px 21px 40px rgba(23, 120, 242, 0.24); }
.series-book strong { display: block; font-size: 17px; margin-bottom: 6px; }
.series-book span { color: var(--muted); font-size: 14px; }
.series-book.active strong { color: var(--accent-dark); }

.footer { padding: 35px 0 40px; color: #718098; background: #fff; border-top: 1px solid var(--line); font-size: 13px; text-align: center; }

.volume-2 { --accent: #7557e8; --accent-2: #17b9cb; --accent-3: #ffbf36; --accent-dark: #4e32b9; }
.volume-3 { --accent: #0a9a79; --accent-2: #24b9cf; --accent-3: #ffcb3d; --accent-dark: #07715b; }
.volume-2 .hero { background: linear-gradient(145deg, #fbfdff 0%, #f0f0ff 53%, #e7fbff 100%); }
.volume-3 .hero { background: linear-gradient(145deg, #fbfffd 0%, #eaf9f4 53%, #e7f8ff 100%); }

html[lang="en"] body { font-family: Inter, "Segoe UI", Arial, sans-serif; word-break: normal; }
html[lang="en"] .hero h1 { font-size: 52px; }
html[lang="en"] .subtitle { font-size: 23px; }

@media (max-width: 900px) {
  .page { width: 100%; }
  .inner { width: min(100% - 40px, 720px); }
  .hero { min-height: 0; padding-top: 44px; }
  .hero-grid { grid-template-columns: 1fr; gap: 38px; }
  .cover-wrap { width: min(420px, 100%); margin: 0 auto; }
  .cover { width: 100%; }
  .hero h1, html[lang="en"] .hero h1 { font-size: 39px; }
  .subtitle, html[lang="en"] .subtitle { font-size: 20px; }
  .band { padding: 68px 0; }
  .section-title { font-size: 33px; }
  .outcomes, .preview-grid, .preview-grid.three, .preview-grid.volume-two, .concept-previews, .toc-groups, .book-info, .series-covers { grid-template-columns: 1fr; }
  .outcomes { border: 0; }
  .outcome, .outcome + .outcome { min-height: 0; padding: 26px 0; border-right: 0; border-bottom: 1px solid var(--line); }
  .toc-group.wide { grid-column: auto; }
  .toc-group.wide .toc-list { columns: 1; }
  .preview.full-block { grid-column: auto; }
  .preview.large .media, .preview.small .media, .preview.wide .media, .preview.standard .media, .preview.full-block .media { height: auto; min-height: 300px; }
  .preview.full-block picture, .preview.full-block img { height: auto; }
  .series-book.active img, .series-book img { width: 230px; }
}