/* =============================================================
   초보자를 위한 러닝 가이드 — Stripe Docs 스타일
   3단 레이아웃: 사이드바 · 본문 · 우측 TOC
   ============================================================= */
@import url("https://fonts.googleapis.com/css2?family=Noto+Serif+KR:wght@400;500;600;700&family=Pretendard:wght@400;500;600;700;800&display=swap");

/* ── Stripe 팔레트 → 기존 콘텐츠 토큰에 매핑 ───────────────── */
:root, [data-theme="light"] {
  /* Stripe 핵심 색 */
  --indigo: #635bff;
  --indigo-dark: #533afd;
  --navy: #0a2540;
  --slate: #425466;
  --slate-light: #697386;
  --page: #ffffff;
  --tint: #f6f9fc;
  --tint-2: #f0f4f8;
  --line: #e3e8ee;
  --line-soft: #ebeef3;

  /* 콘텐츠(마크다운 인라인 <style>·custom 클래스)에서 참조하는 토큰 */
  --paper: var(--page);
  --paper-soft: var(--tint);
  --ink: var(--navy);
  --fg: var(--slate);
  --text-color: var(--slate);
  --bg-color: var(--page);
  --ink-muted: var(--slate-light);
  --ink-faint: rgba(10, 37, 64, 0.18);
  --rule: var(--line);
  --border-color: var(--line);
  --sidebar-spacer: var(--line);
  --links: var(--indigo);
  --quote-bg: rgba(99, 91, 255, 0.06);

  --font-serif: "Noto Serif KR", serif;
  --font-sans: "Pretendard", system-ui, "Apple SD Gothic Neo", sans-serif;
  --font-mono: "SFMono-Regular", Consolas, Menlo, monospace;

  --sb-w: 300px;
  --toc-w: 240px;
  --topbar-h: 60px;
  --shadow-sm: 0 1px 2px rgba(10,37,64,.06), 0 1px 3px rgba(10,37,64,.08);
  --shadow-md: 0 4px 16px rgba(10,37,64,.10);
  --shadow-lg: 0 12px 40px rgba(10,37,64,.16);
}

/* ── 다크 테마 ───────────────────────────────────────────────── */
[data-theme="dark"] {
  --page: #0a1525;
  --tint: #0f1d31;
  --tint-2: #14233b;
  --line: #1e3050;
  --line-soft: #18283f;
  --navy: #e6ecf5;
  --slate: #b3c0d4;
  --slate-light: #8294ad;

  --paper: var(--page);
  --paper-soft: var(--tint);
  --ink: var(--navy);
  --fg: var(--slate);
  --text-color: var(--slate);
  --bg-color: var(--page);
  --ink-muted: var(--slate-light);
  --ink-faint: rgba(230, 236, 245, 0.22);
  --rule: var(--line);
  --border-color: var(--line);
  --sidebar-spacer: var(--line);
  --links: #8b85ff;
  --quote-bg: rgba(139, 133, 255, 0.10);
  --indigo: #8b85ff;
  --indigo-dark: #8b85ff;
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.7;
  color: var(--slate);
  background: var(--page);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

::selection { background: rgba(99,91,255,.18); }

a { color: var(--indigo); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Topbar ──────────────────────────────────────────────────── */
.topbar {
  position: sticky; top: 0; z-index: 100;
  height: var(--topbar-h);
  display: flex; align-items: center; gap: 14px;
  padding: 0 20px;
  background: rgba(255,255,255,.82);
  border-bottom: 1px solid var(--line);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
}
[data-theme="dark"] .topbar { background: rgba(10,21,37,.82); }

.brand { display: flex; align-items: center; gap: 10px; color: var(--navy); }
.brand:hover { text-decoration: none; }
.brand-mark { font-size: 22px; line-height: 1; }
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-text strong { font-size: 15px; font-weight: 700; color: var(--navy); letter-spacing: -.01em; }
.brand-text em { font-size: 11.5px; font-style: normal; color: var(--slate-light); }
.topbar-spacer { flex: 1; }

.menu-toggle { display: none; background: none; border: none; color: var(--slate); cursor: pointer; padding: 4px; }

/* 검색 */
.search-box { position: relative; }
.search-box input {
  width: 240px; height: 38px;
  padding: 0 34px 0 34px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--tint);
  color: var(--navy);
  font-family: inherit; font-size: 14px;
  transition: border-color .15s, box-shadow .15s, width .2s;
}
.search-box input:focus {
  outline: none; border-color: var(--indigo);
  box-shadow: 0 0 0 3px rgba(99,91,255,.16);
  background: var(--page);
}
.search-ico { position: absolute; left: 11px; top: 50%; transform: translateY(-50%); color: var(--slate-light); pointer-events: none; }
.search-kbd {
  position: absolute; right: 9px; top: 50%; transform: translateY(-50%);
  font-family: var(--font-mono); font-size: 11px; color: var(--slate-light);
  border: 1px solid var(--line); border-radius: 5px; padding: 1px 6px; background: var(--page);
}
.search-results {
  position: absolute; top: 46px; right: 0; width: 420px; max-width: 78vw;
  max-height: 60vh; overflow-y: auto;
  background: var(--page); border: 1px solid var(--line); border-radius: 12px;
  box-shadow: var(--shadow-lg); padding: 6px;
}
.sr-item { display: block; padding: 9px 12px; border-radius: 8px; color: var(--navy); }
.sr-item:hover, .sr-item.active { background: var(--tint); text-decoration: none; }
.sr-item .sr-page { font-size: 12px; color: var(--indigo); font-weight: 600; }
.sr-item .sr-head { font-size: 14px; font-weight: 600; color: var(--navy); margin: 1px 0; }
.sr-item .sr-snip { font-size: 12.5px; color: var(--slate-light); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.sr-empty { padding: 14px; color: var(--slate-light); font-size: 14px; text-align: center; }
mark { background: rgba(99,91,255,.22); color: inherit; border-radius: 2px; padding: 0 1px; }

.theme-toggle {
  display: inline-flex; align-items: center; justify-content: center;
  width: 38px; height: 38px; border: 1px solid var(--line); border-radius: 8px;
  background: var(--tint); color: var(--slate); cursor: pointer; transition: border-color .15s, color .15s;
}
.theme-toggle:hover { border-color: var(--indigo); color: var(--indigo); }
.ico-moon { display: none; }
[data-theme="dark"] .ico-sun { display: none; }
[data-theme="dark"] .ico-moon { display: inline; }

/* ── 3단 레이아웃 ────────────────────────────────────────────── */
.layout {
  display: grid;
  grid-template-columns: var(--sb-w) minmax(0, 1fr) var(--toc-w);
  max-width: 1440px;
  margin: 0 auto;
  align-items: start;
}

/* ── 사이드바 ────────────────────────────────────────────────── */
.sidebar {
  position: sticky; top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  padding: 26px 14px 60px 24px;
  border-right: 1px solid var(--line);
}
.sb-group { margin-bottom: 22px; }
.sb-group-title {
  font-size: 11px; font-weight: 700; letter-spacing: .09em; text-transform: uppercase;
  color: var(--slate-light); padding: 0 10px; margin-bottom: 8px;
}
.sb-nav ul { list-style: none; margin: 0; padding: 0; }
.sb-link {
  display: flex; flex-direction: column; gap: 1px;
  padding: 7px 10px; border-radius: 7px;
  color: var(--slate); border-left: 2px solid transparent;
}
.sb-link:hover { background: var(--tint); text-decoration: none; }
.sb-link-title { font-size: 14px; font-weight: 600; color: var(--navy); letter-spacing: -.01em; }
.sb-link-sub { font-size: 12px; color: var(--slate-light); }
.sb-link.active { background: rgba(99,91,255,.08); }
.sb-link.active .sb-link-title { color: var(--indigo); }
.sb-sub { margin: 4px 0 6px !important; padding-left: 12px !important; border-left: 1px solid var(--line); }
.sb-sublink {
  display: block; padding: 5px 10px; font-size: 13px; color: var(--slate-light);
  border-radius: 6px; line-height: 1.45;
}
.sb-sublink:hover { color: var(--indigo); background: var(--tint); text-decoration: none; }
.sb-sublink.active { color: var(--indigo); font-weight: 600; }

.sidebar-scrim { display: none; }

/* ── 본문 ────────────────────────────────────────────────────── */
.content {
  min-width: 0;
  padding: 44px clamp(28px, 4vw, 64px) 80px;
}
.article { max-width: 760px; }

/* 본문 타이포 — 가독성 위해 본문은 산세리프 기본, 헤딩은 navy */
.article { font-size: 16.5px; line-height: 1.78; color: var(--slate); }
.article p { margin: 1.05em 0; word-break: keep-all; text-wrap: pretty; }
.article strong { color: var(--navy); font-weight: 700; }

.md-heading { position: relative; scroll-margin-top: calc(var(--topbar-h) + 16px); color: var(--navy); }
.article h1 { font-size: 2.2em; font-weight: 800; line-height: 1.15; letter-spacing: -.025em; margin: .2em 0 .6em; color: var(--navy); }
.article h2 {
  font-size: 1.45em; font-weight: 700; letter-spacing: -.02em; color: var(--navy);
  margin: 2em 0 .55em; padding-top: .4em;
}
.article h3 { font-size: 1.15em; font-weight: 700; color: var(--navy); margin: 1.7em 0 .5em; letter-spacing: -.01em; }
.article h4 { font-size: 1em; font-weight: 700; color: var(--navy); margin: 1.4em 0 .4em; }

/* 헤딩 호버 앵커 */
.anchor {
  position: absolute; left: -1.1em; top: 0;
  color: var(--indigo); opacity: 0; font-weight: 400;
  text-decoration: none; transition: opacity .12s;
}
.md-heading:hover .anchor { opacity: .55; }
.anchor:hover { opacity: 1 !important; text-decoration: none; }

.article ul, .article ol { padding-left: 1.5em; margin: 1em 0; }
.article li { margin: .4em 0; text-wrap: pretty; }

/* 링크 — 본문 내 밑줄 */
.article a { border-bottom: 1px solid rgba(99,91,255,.3); }
.article a:hover { border-bottom-color: var(--indigo); text-decoration: none; }

/* 인용 */
.article blockquote {
  margin: 1.6em 0; padding: .2em 0 .2em 18px;
  border-left: 3px solid var(--indigo);
  color: var(--slate); font-size: .96em; background: transparent;
}
.article blockquote p { margin: .5em 0; }

/* 코드 */
.article code {
  font-family: var(--font-mono); font-size: .88em;
  background: var(--tint-2); color: var(--indigo-dark);
  padding: .15em .4em; border-radius: 5px;
}
.article pre {
  background: var(--navy); color: #e6ecf5;
  border-radius: 10px; padding: 16px 18px; overflow-x: auto;
  margin: 1.5em 0; font-size: 13.5px; line-height: 1.6;
}
[data-theme="dark"] .article pre { background: #060f1d; border: 1px solid var(--line); }
.article pre code { background: none; color: inherit; padding: 0; }

/* 표 — Stripe 카드형 */
.article table {
  width: 100%; border-collapse: collapse; margin: 1.6em 0;
  font-size: 14.5px; border: 1px solid var(--line); border-radius: 10px;
  overflow: hidden; box-shadow: var(--shadow-sm);
}
.article thead { background: var(--tint); }
.article th {
  text-align: left; padding: 11px 14px; font-weight: 700; color: var(--navy);
  font-size: 12.5px; letter-spacing: .03em; text-transform: uppercase;
  border-bottom: 1px solid var(--line);
}
.article td { padding: 11px 14px; border-bottom: 1px solid var(--line-soft); color: var(--slate); vertical-align: top; }
.article tbody tr:last-child td { border-bottom: none; }
.article tbody tr:hover { background: var(--tint); }

/* 이미지 / 일러스트 */
.article img { max-width: 100%; height: auto; margin: 1.6em 0; border-radius: 10px; }
.illus-full { display: block; width: 100%; margin: 2em 0; border-radius: 12px; box-shadow: var(--shadow-sm); }
.illus-center { display: block; width: 72%; max-width: 540px; margin: 2em auto; border-radius: 12px; box-shadow: var(--shadow-sm); }
.illus-half { float: right; width: 42%; max-width: 340px; margin: .4em 0 1.4em 1.8em; border-radius: 12px; box-shadow: var(--shadow-sm); }
.illus-caption { display: block; font-size: 12.5px; color: var(--slate-light); text-align: center; margin: -1.2em 0 2em; }
.illus-clear { clear: both; }

/* hr → 가는 구분선 */
.article hr { border: 0; border-top: 1px solid var(--line); margin: 2.4em 0; }
.article hr.hairline, .article .hairline {
  width: 40px; margin: 1em auto; border-top: 1px solid var(--ink-faint);
}

/* ── 챕터 오프닝 (.chapter-opener) — Stripe 히어로 톤 ────────── */
.chapter-opener {
  text-align: left; padding: 8px 0 26px; margin: 0 0 28px;
  border-bottom: 1px solid var(--line);
}
.chapter-opener .eyebrow {
  display: block; font-size: 12px; font-weight: 700; letter-spacing: .14em;
  text-transform: uppercase; color: var(--indigo); margin-bottom: 14px;
}
.chapter-opener h1 {
  font-size: clamp(1.9em, 3.4vw, 2.5em); font-weight: 800; line-height: 1.12;
  letter-spacing: -.03em; color: var(--navy); margin: 0 0 .15em; border: none; padding: 0;
}
.chapter-opener h1 br { display: none; }
.chapter-opener .opener-en {
  display: block; font-family: var(--font-serif); font-style: italic;
  color: var(--slate-light); font-size: .95em; margin-top: 6px;
}
.chapter-opener .hairline { display: none; }

/* 도입 에피소드 (.ch-episode) — Stripe 콜아웃 */
.ch-episode {
  background: var(--tint); border: 1px solid var(--line); border-left: 3px solid var(--indigo);
  border-radius: 10px; padding: 16px 20px; margin: 0 0 28px;
  font-size: 15px; line-height: 1.75; color: var(--slate);
}

.eyebrow { font-weight: 700; letter-spacing: .12em; text-transform: uppercase; color: var(--indigo); }
.opener-en { color: var(--slate-light); }

/* 톰뭉의 관점 (.perspective-box) */
.perspective-box {
  margin: 1.8em 0; padding: 16px 20px;
  border: 1px solid var(--line); border-radius: 12px;
  background: var(--quote-bg);
  font-size: 15px; line-height: 1.78;
}
.pb-label {
  font-size: 11px; font-weight: 800; letter-spacing: .08em; text-transform: uppercase;
  color: var(--indigo); margin-bottom: 8px;
}
.perspective-box p { margin: .5em 0; }

/* 클래식 커버 (preface 상단) → Stripe 히어로 카드 */
.classic-cover {
  margin: 0 0 32px; padding: 40px 32px;
  background: linear-gradient(135deg, #0a2540 0%, #1a3a5c 100%);
  color: #fff; border-radius: 16px;
  display: flex; flex-direction: column; min-height: 280px;
}
.classic-cover .eyebrow { color: rgba(255,255,255,.7); margin-bottom: 18px; font-size: 12px; }
.classic-cover .cover-title { font-size: 2.6em; font-weight: 800; line-height: 1.08; color: #fff; margin: 0 0 .3em; border: none; padding: 0; letter-spacing: -.03em; }
.classic-cover .hairline { width: 48px; height: 2px; background: rgba(255,255,255,.4); margin: 14px 0; border: 0; display: block; }
.classic-cover .cover-sub { font-size: 1.05em; color: rgba(255,255,255,.85); margin: 0 0 24px; font-style: normal; }
.classic-cover footer { margin-top: auto; font-size: 13px; color: rgba(255,255,255,.7); display: flex; justify-content: space-between; }

/* tip / warning 콜아웃 */
.tip, .warning {
  margin: 1.6em 0; padding: 14px 18px; border-radius: 10px;
  border: 1px solid var(--line); border-left: 3px solid var(--indigo);
  background: var(--tint); font-size: 15px;
}
.warning { border-left-color: #e0a020; }
.tip::before { content: "TIP"; display: block; font-size: 11px; font-weight: 700; letter-spacing: .1em; color: var(--indigo); margin-bottom: 6px; }
.warning::before { content: "주의"; display: block; font-size: 11px; font-weight: 700; letter-spacing: .1em; color: #c98a00; margin-bottom: 6px; }

/* ── 이전/다음 네비 ──────────────────────────────────────────── */
.page-nav { display: flex; gap: 16px; margin: 48px 0 0; padding-top: 24px; border-top: 1px solid var(--line); }
.pn {
  flex: 1; display: flex; flex-direction: column; gap: 4px;
  padding: 14px 18px; border: 1px solid var(--line); border-radius: 12px;
  color: var(--navy); transition: border-color .15s, box-shadow .15s, transform .15s;
}
.pn:hover { border-color: var(--indigo); box-shadow: var(--shadow-sm); text-decoration: none; transform: translateY(-1px); }
.pn-next { text-align: right; }
.pn-dir { font-size: 12px; color: var(--indigo); font-weight: 600; }
.pn-title { font-size: 14.5px; font-weight: 600; color: var(--navy); }
.pn-empty { flex: 1; border: none; pointer-events: none; }

.page-footer { margin-top: 40px; padding-top: 22px; border-top: 1px solid var(--line); }
.page-footer p { font-size: 12.5px; color: var(--slate-light); line-height: 1.6; }

/* ── 우측 TOC ────────────────────────────────────────────────── */
.toc {
  position: sticky; top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto; padding: 44px 22px 60px 8px;
}
.toc-title { font-size: 11px; font-weight: 700; letter-spacing: .09em; text-transform: uppercase; color: var(--slate-light); margin-bottom: 10px; }
.toc ul { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--line); }
.toc li a {
  display: block; padding: 4px 0 4px 14px; margin-left: -1px;
  font-size: 13px; line-height: 1.45; color: var(--slate-light);
  border-left: 2px solid transparent;
}
.toc li.toc-l3 a { padding-left: 26px; font-size: 12.5px; }
.toc li a:hover { color: var(--indigo); text-decoration: none; }
.toc li a.active { color: var(--indigo); font-weight: 600; border-left-color: var(--indigo); }

/* ── 홈(랜딩) ────────────────────────────────────────────────── */
.home-hero { padding: 24px 0 12px; }
.home-hero .eyebrow { display: block; font-size: 13px; margin-bottom: 14px; }
.home-hero h1 { font-size: clamp(2.4em, 5vw, 3.4em); font-weight: 800; letter-spacing: -.035em; color: var(--navy); margin: 0 0 .25em; line-height: 1.05; }
.home-lead { font-size: 1.15em; color: var(--slate); max-width: 60ch; margin: 0 0 26px; }
.home-cta { display: flex; gap: 12px; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; padding: 11px 22px; border-radius: 10px; font-size: 15px; font-weight: 600; transition: transform .12s, box-shadow .15s, background .15s; }
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn-primary { background: var(--indigo); color: #fff; box-shadow: 0 4px 14px rgba(99,91,255,.3); }
.btn-primary:hover { background: var(--indigo-dark); }
.btn-ghost { background: var(--tint); color: var(--navy); border: 1px solid var(--line); }
.btn-ghost:hover { border-color: var(--indigo); color: var(--indigo); }
.home-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; margin: 18px 0 0; }
.home-card {
  display: flex; flex-direction: column; gap: 3px; padding: 18px 20px;
  border: 1px solid var(--line); border-radius: 14px; background: var(--page);
  color: var(--navy); transition: border-color .15s, box-shadow .15s, transform .15s;
}
.home-card:hover { border-color: var(--indigo); box-shadow: var(--shadow-md); transform: translateY(-2px); text-decoration: none; }
.home-card-num { font-family: var(--font-mono); font-size: 13px; color: var(--indigo); font-weight: 700; }
.home-card-title { font-size: 16px; font-weight: 700; color: var(--navy); }
.home-card-label { font-size: 13.5px; color: var(--slate-light); }

/* ── 반응형 ──────────────────────────────────────────────────── */
@media (max-width: 1180px) {
  .layout { grid-template-columns: var(--sb-w) minmax(0, 1fr); }
  .toc { display: none; }
}
@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
  .menu-toggle { display: inline-flex; }
  .search-box input { width: 150px; }
  .search-kbd { display: none; }
  .sidebar {
    position: fixed; top: var(--topbar-h); left: 0; z-index: 90;
    width: 300px; max-width: 84vw; background: var(--page);
    transform: translateX(-105%); transition: transform .25s ease;
    box-shadow: var(--shadow-lg);
  }
  body.nav-open .sidebar { transform: translateX(0); }
  body.nav-open .sidebar-scrim {
    display: block; position: fixed; inset: var(--topbar-h) 0 0 0; z-index: 80;
    background: rgba(10,37,64,.35);
  }
  .content { padding: 28px 20px 64px; }
  .page-nav { flex-direction: column; }
  .brand-text em { display: none; }
}

/* float 컴포넌트 안전장치 */
.landing-cards, .posture-error-cards { clear: both; }