:root {
  color-scheme: light;
  --paper: #fbfaf6;
  --ink: #20252b;
  --muted: #69727d;
  --line: #dfd8cc;
  --line-strong: #c8bba7;
  --panel: #ffffff;
  --panel-warm: #fff8ec;
  --accent: #355f5d;
  --accent-2: #a66a2c;
  --accent-3: #525f9a;
  --soft: #e8f0ee;
  --code: #f6f1e8;
  --shadow: 0 20px 60px rgba(32, 37, 43, 0.08);
  --radius: 8px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: linear-gradient(180deg, #fffdf8, var(--paper) 420px);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans KR", "Apple SD Gothic Neo", sans-serif;
  line-height: 1.68;
  overflow-wrap: break-word;
}

a {
  color: inherit;
}

button,
input {
  font: inherit;
}

.layout {
  width: min(1220px, calc(100% - 36px));
  margin: 0 auto;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid rgba(223, 216, 204, 0.9);
  background: rgba(251, 250, 246, 0.92);
  backdrop-filter: blur(14px);
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 64px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 900;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 7px;
  background: var(--accent);
  color: #fff;
  font-size: 15px;
}

.brand small {
  display: block;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
}

.portal-link {
  min-height: 38px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: rgba(255, 255, 255, 0.7);
  color: var(--muted);
  font-size: 14px;
  font-weight: 800;
  text-decoration: none;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 330px;
  gap: 32px;
  align-items: end;
  padding: 48px 0 28px;
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--accent);
  font-size: 13px;
  font-weight: 900;
}

.hero h1 {
  max-width: 780px;
  margin: 0;
  font-size: clamp(36px, 5vw, 66px);
  line-height: 1.06;
  letter-spacing: 0;
}

.hero p {
  max-width: 760px;
  margin: 18px 0 0;
  color: #4f5965;
  font-size: 18px;
}

.hero-card {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.factor-list {
  display: grid;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.factor-list li {
  display: grid;
  grid-template-columns: 82px 1fr;
  gap: 12px;
  align-items: center;
  min-height: 42px;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: #fbfaf7;
}

.factor-list strong {
  color: var(--accent);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 14px;
}

.factor-list span {
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.reader {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  gap: 22px;
  align-items: start;
  padding-bottom: 58px;
}

.sidebar {
  position: sticky;
  top: 84px;
  max-height: calc(100vh - 104px);
  overflow: auto;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.84);
}

.search-box {
  position: relative;
  margin-bottom: 12px;
}

.search-box input {
  width: 100%;
  min-height: 42px;
  padding: 10px 12px;
  border: 1px solid var(--line-strong);
  border-radius: 7px;
  background: #fff;
  outline: none;
}

.search-box input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 4px var(--soft);
}

.chapter-nav {
  display: grid;
  gap: 7px;
}

.chapter-button {
  width: 100%;
  min-height: 44px;
  padding: 9px 10px;
  border: 1px solid transparent;
  border-radius: 7px;
  background: transparent;
  color: #39434d;
  cursor: pointer;
  text-align: left;
}

.chapter-button:hover,
.chapter-button:focus {
  border-color: var(--line);
  background: #fbfaf7;
}

.chapter-button.active {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}

.chapter-button small {
  display: block;
  color: currentColor;
  opacity: 0.76;
  font-size: 11px;
  font-weight: 900;
}

.chapter-button span {
  display: block;
  font-size: 14px;
  font-weight: 900;
}

.section-pills {
  display: grid;
  gap: 5px;
  margin: 12px 0 0;
  padding: 12px 0 0;
  border-top: 1px solid var(--line);
}

.section-pills a {
  padding: 6px 8px;
  border-radius: 6px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
  text-decoration: none;
}

.section-pills a:hover,
.section-pills a:focus {
  background: var(--soft);
  color: var(--accent);
}

.content {
  min-width: 0;
}

.chapter {
  display: none;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: 0 16px 36px rgba(32, 37, 43, 0.06);
  overflow: clip;
}

.chapter.active {
  display: block;
}

.chapter > header,
.chapter-header {
  padding: 32px 34px 24px;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(135deg, var(--panel-warm), #ffffff);
}

.chapter-number {
  color: var(--accent);
  font-size: 13px;
  font-weight: 900;
}

.chapter > header h1,
.chapter h2 {
  margin: 8px 0 0;
  font-size: clamp(28px, 3vw, 42px);
  line-height: 1.16;
  letter-spacing: 0;
}

.chapter > header p,
.chapter-subtitle {
  max-width: 820px;
  margin: 14px 0 0;
  color: #4f5965;
  font-size: 17px;
}

.chapter-body {
  padding: 28px 34px 36px;
}

.section-block,
.chapter > section {
  padding: 22px 0;
  border-bottom: 1px solid var(--line);
}

.section-block:last-child,
.chapter > section:last-child {
  border-bottom: 0;
}

.section-block h3,
.chapter > section h2,
.chapter > section h3,
.chapter > aside h2,
.chapter > aside h3 {
  margin: 0 0 12px;
  color: #26313c;
  font-size: 22px;
  line-height: 1.28;
}

.section-block p,
.chapter > section p,
.chapter > aside p {
  margin: 10px 0;
}

.callout,
.recap,
.formula-box {
  margin: 18px 0;
  padding: 16px 18px;
  border-radius: 7px;
}

.callout,
.intuition {
  border: 1px solid #bdd6d7;
  background: var(--soft);
}

.recap {
  border: 1px solid #e6d3b7;
  background: #fff8ec;
}

.formula-box {
  overflow-x: auto;
  border: 1px solid var(--line);
  background: var(--code);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

.recap h3,
.recap h2,
.intuition h2,
.intuition h3,
.callout strong {
  margin-top: 0;
}

.recap ul,
.section-block ul,
.chapter > section ul {
  padding-left: 20px;
}

.chapter > section,
.chapter > aside {
  margin-left: 34px;
  margin-right: 34px;
}

.chapter > aside.intuition {
  margin-top: 24px;
  margin-bottom: 0;
  padding: 16px 18px;
  border-radius: 7px;
}

.chapter > section.recap {
  margin-top: 24px;
  margin-bottom: 34px;
  padding: 16px 18px;
  border-radius: 7px;
}

.tagline {
  display: inline-flex;
  min-height: 28px;
  align-items: center;
  padding: 4px 9px;
  border-radius: 6px;
  background: var(--soft);
  color: var(--accent);
  font-size: 12px;
  font-weight: 900;
}

.empty {
  display: none;
  padding: 30px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  color: var(--muted);
  text-align: center;
}

.empty.visible {
  display: block;
}

.footer {
  padding: 28px 0 44px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
}

@media (max-width: 980px) {
  .hero,
  .reader {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    max-height: none;
  }

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

  .section-pills {
    display: none;
  }
}

@media (max-width: 620px) {
  .layout {
    width: min(100% - 24px, 1220px);
  }

  .topbar-inner {
    align-items: flex-start;
    flex-direction: column;
    padding: 12px 0;
  }

  .portal-link {
    width: 100%;
    text-align: center;
  }

  .hero {
    padding-top: 32px;
  }

  .hero h1 {
    font-size: 34px;
  }

  .hero p {
    font-size: 16px;
  }

  .factor-list li {
    grid-template-columns: 1fr;
  }

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

  .chapter-header,
  .chapter-body,
  .chapter > header {
    padding-left: 20px;
    padding-right: 20px;
  }

  .chapter > section,
  .chapter > aside {
    margin-left: 20px;
    margin-right: 20px;
  }
}