@import url('https://cdn.jsdelivr.net/gh/orioncactus/pretendard/dist/web/variable/pretendardvariable-dynamic-subset.css');
@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;500;600&display=swap');

/* A4 · Readable hypertext course (2026-07)
   Palette: #000000 · #233D4D · #FE7F2D · #EAECF0 */
:root {
  --a4-w: 210mm;
  --a4-h: 297mm;
  --pad-x: 17mm;
  --pad-y: 15mm;
  --palette-plum: #000000;
  --palette-slate: #233d4d;
  --palette-mint: #fe7f2d;
  --palette-ice: #eaecf0;
  --bg: var(--palette-ice);
  --paper: #fff;
  --panel: rgba(255, 255, 255, .74);
  --panel-hover: #fff;
  --border: rgba(35, 61, 77, .24);
  --border-strong: var(--palette-slate);
  --text: var(--palette-plum);
  --muted: var(--palette-slate);
  --faint: rgba(35, 61, 77, .72);
  --accent: var(--palette-mint);
  --accent-hover: var(--palette-mint);
  --link: var(--palette-slate);
  --link-hover: var(--palette-plum);
  --chip: var(--palette-ice);
  --code-bg: var(--palette-ice);
  --ok-bg: var(--palette-ice);
  --ok-border: var(--palette-slate);
  --warn-bg: rgba(254, 127, 45, .13);
  --warn-border: var(--palette-mint);
  --font: 'Pretendard Variable', Pretendard, 'Noto Sans KR',
    'Apple SD Gothic Neo', 'Malgun Gothic', system-ui, sans-serif;
  --mono: 'IBM Plex Mono', ui-monospace, monospace;
  --shadow: 0 2px 4px rgba(0, 0, 0, .04),
    0 18px 48px rgba(0, 0, 0, .11);
  --sidebar: 248px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.76;
  letter-spacing: -0.008em;
  font-kerning: normal;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--link);
  text-decoration-color: rgba(35, 61, 77, .42);
  text-decoration-thickness: 1px;
  text-underline-offset: .16em;
}
a:hover { color: var(--link-hover); }
a:focus-visible {
  outline: 3px solid var(--palette-mint);
  outline-offset: 3px;
  border-radius: 3px;
}
::selection {
  color: var(--palette-plum);
  background: var(--palette-mint);
}

.layout {
  display: grid;
  grid-template-columns: 1fr;
  min-height: 100vh;
}
@media (min-width: 960px) {
  .layout { grid-template-columns: var(--sidebar) 1fr; }
}

.sidebar {
  color: var(--palette-ice);
  background: var(--palette-plum);
  border-bottom: 1px solid var(--palette-slate);
  padding: 1.15rem;
  scrollbar-color: var(--palette-slate) transparent;
  scrollbar-width: thin;
}
@media (min-width: 960px) {
  .sidebar {
    border-bottom: 0;
    border-right: 1px solid var(--palette-slate);
    position: sticky;
    top: 0;
    height: 100vh;
    overflow: auto;
    padding: 1.45rem 1rem 2.5rem;
  }
}

.sidebar__brand {
  font-family: var(--mono);
  font-size: 0.67rem;
  letter-spacing: 0.055em;
  text-transform: uppercase;
  color: var(--palette-mint);
}
.sidebar__title {
  font-weight: 700;
  font-size: 1.08rem;
  line-height: 1.35;
  letter-spacing: -0.025em;
  margin: 0.3rem 0 0.2rem;
}
.sidebar__sub {
  font-size: 0.82rem;
  color: rgba(234, 236, 240, .78);
  margin: 0 0 1.1rem;
  line-height: 1.55;
  letter-spacing: -0.006em;
}

.sidebar h4 {
  font-family: var(--mono);
  font-size: 0.66rem;
  letter-spacing: 0.055em;
  text-transform: uppercase;
  color: var(--palette-mint);
  margin: 1.15rem 0 0.42rem;
  font-weight: 600;
}

.sidebar nav a {
  display: block;
  padding: 0.46rem 0.58rem;
  border-radius: 8px;
  color: rgba(234, 236, 240, .9);
  font-size: 0.875rem;
  text-decoration: none;
  line-height: 1.42;
  letter-spacing: -0.012em;
  transition: color .14s ease, background-color .14s ease;
}
.sidebar nav a:hover {
  background: rgba(254, 127, 45, .2);
  color: #fff;
}
.sidebar nav a.is-active {
  background: var(--palette-mint);
  color: var(--palette-plum);
  font-weight: 700;
}
.sidebar a:focus-visible { outline-color: var(--palette-mint); }
.sidebar nav a .n {
  font-family: var(--mono);
  font-size: 0.72rem;
  opacity: 0.82;
  margin-right: 0.34rem;
}

.main {
  padding: 1rem;
  display: flex;
  justify-content: center;
}
@media (min-width: 960px) {
  .main { padding: 2rem clamp(1.5rem, 3vw, 3.5rem) 4rem; }
}

.sheet {
  width: min(100%, var(--a4-w));
  min-height: var(--a4-h);
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: var(--pad-y) var(--pad-x);
}

.page-tools {
  display: flex;
  align-items: center;
  margin: 0 0 0.9rem;
}
.back-link {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.42rem 0.76rem;
  color: var(--palette-plum);
  background: var(--palette-ice);
  font-size: 0.84rem;
  font-weight: 700;
  letter-spacing: -0.015em;
  line-height: 1.3;
  text-decoration: none;
  transition: background-color .14s ease, border-color .14s ease, transform .14s ease;
}
.back-link:hover {
  border-color: var(--palette-slate);
  background: var(--palette-mint);
  transform: translateX(-1px);
}
.back-link:focus-visible {
  outline: 3px solid rgba(254, 127, 45, .55);
  outline-offset: 3px;
}

.sheet__label {
  display: flex;
  justify-content: space-between;
  gap: 0.5rem;
  font-family: var(--mono);
  font-size: 0.65rem;
  letter-spacing: 0.045em;
  text-transform: uppercase;
  color: var(--faint);
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.55rem;
  margin-bottom: 1.15rem;
}

h1 {
  color: var(--palette-plum);
  font-size: clamp(1.7rem, 3vw, 2.12rem);
  font-weight: 750;
  letter-spacing: -0.042em;
  line-height: 1.28;
  word-break: keep-all;
  overflow-wrap: break-word;
  margin: 0 0 0.7rem;
}
.lead {
  color: var(--muted);
  font-size: 1.04rem;
  font-weight: 450;
  letter-spacing: -0.016em;
  margin: 0 0 1.2rem;
  line-height: 1.72;
  word-break: keep-all;
  overflow-wrap: break-word;
}

.meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1.35rem;
}
.chip {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.025em;
  text-transform: uppercase;
  background: var(--chip);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.28rem 0.62rem;
  color: var(--palette-slate);
}

.prose {
  font-size: 1rem;
  line-height: 1.79;
  letter-spacing: -0.01em;
  word-break: keep-all;
  overflow-wrap: break-word;
}
.prose h2 {
  color: var(--palette-plum);
  font-size: 1.28rem;
  font-weight: 700;
  line-height: 1.42;
  letter-spacing: -0.032em;
  margin: 2.15rem 0 0.72rem;
  padding-bottom: 0.42rem;
  border-bottom: 1px solid var(--border);
}
.prose h3 {
  color: var(--palette-slate);
  font-size: 1.08rem;
  font-weight: 700;
  line-height: 1.48;
  letter-spacing: -0.025em;
  margin: 1.5rem 0 0.5rem;
}
.prose p { margin: 0 0 1rem; }
.prose ul, .prose ol {
  margin: 0 0 1.05rem;
  padding-left: 1.35rem;
}
.prose li { margin-bottom: 0.42rem; padding-left: 0.12rem; }
.prose li::marker { color: var(--palette-slate); }
.prose strong { color: var(--palette-plum); font-weight: 700; }
.prose code {
  font-family: var(--mono);
  font-size: 0.86em;
  color: var(--palette-plum);
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: 0.1em 0.36em;
  letter-spacing: 0;
}
.prose pre {
  color: var(--palette-plum);
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.95rem 1rem;
  overflow-x: auto;
  font-size: 0.85rem;
  line-height: 1.62;
  letter-spacing: 0;
  margin: 0.85rem 0 1.15rem;
}
.prose pre code { background: none; border: none; padding: 0; }
.prose table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  line-height: 1.6;
  margin: 0.85rem 0 1.2rem;
  display: block;
  overflow-x: auto;
  scrollbar-color: var(--border-strong) transparent;
  scrollbar-width: thin;
}
.prose th {
  text-align: left;
  font-family: var(--mono);
  color: var(--palette-plum);
  background: var(--panel);
  font-size: 0.75rem;
  letter-spacing: 0;
  border-bottom: 2px solid var(--border);
  padding: 0.55rem 0.62rem;
  white-space: nowrap;
}
.prose td {
  border-bottom: 1px solid var(--border);
  padding: 0.58rem 0.62rem;
  vertical-align: top;
}
.prose hr {
  border: 0;
  border-top: 1px solid var(--border);
  margin: 1.4rem 0;
}

/* 개념 링크 카드 */
.linkbox {
  display: grid;
  gap: 0.6rem;
  margin: 0.9rem 0 1.3rem;
}
@media (min-width: 520px) {
  .linkbox.cols-2 { grid-template-columns: 1fr 1fr; }
}
.linkbox a {
  display: block;
  border: 1px solid var(--border);
  background: var(--panel);
  border-radius: 11px;
  padding: 0.8rem 0.9rem;
  text-decoration: none;
  color: inherit;
  transition: transform .14s ease, border-color .14s ease,
    background-color .14s ease, box-shadow .14s ease;
}
.linkbox a:hover {
  border-color: var(--border-strong);
  background: var(--panel-hover);
  box-shadow: 0 8px 20px rgba(0, 0, 0, .08);
  transform: translateY(-1px);
}
.linkbox a strong {
  display: block;
  color: var(--link);
  font-size: 0.96rem;
  line-height: 1.48;
  letter-spacing: -0.018em;
  margin-bottom: 0.2rem;
}
.linkbox a span {
  font-size: 0.86rem;
  color: var(--muted);
  line-height: 1.55;
}

/* 인라인 개념 칩 링크 */
a.concept {
  font-family: var(--mono);
  font-size: 0.86em;
  color: var(--link-hover);
  background: var(--palette-ice);
  border: 1px solid var(--palette-slate);
  border-radius: 5px;
  padding: 0.07em 0.38em;
  text-decoration: none;
  letter-spacing: -0.01em;
  line-height: 1.58;
  white-space: normal;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
}
a.concept:hover {
  color: var(--palette-plum);
  background: var(--palette-mint);
}

.callout {
  border: 1px solid var(--border);
  border-left: 4px solid var(--palette-slate);
  border-radius: 10px;
  padding: 0.88rem 1rem;
  margin: 1rem 0 1.2rem;
  background: var(--panel);
  font-size: 0.95rem;
  line-height: 1.72;
  color: var(--muted);
}
.callout.ok {
  border-left-color: var(--ok-border);
  background: var(--ok-bg);
}
.callout.warn {
  border-left-color: var(--warn-border);
  background: var(--warn-bg);
}
.callout strong { color: var(--text); }

.diagram {
  margin: 0.9rem 0 1.2rem;
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: 11px;
  background: var(--paper);
}
.diagram svg { display: block; width: 100%; height: auto; max-height: 70mm; }
.diagram [font-family^="Inter"] { font-family: var(--font); }
.diagram [font-family^="IBM Plex Mono"] { font-family: var(--mono); }
.diagram [fill="#eef3f9"] { fill: var(--palette-ice); }
.diagram [fill="#e9f6ef"] { fill: var(--palette-mint); }
.diagram [fill="#faf3e6"] { fill: var(--palette-ice); }
.diagram [fill="#fff"] { fill: var(--paper); }
.diagram [fill="#5a574f"] { fill: var(--muted); }
.diagram [fill="#6a675f"] { fill: var(--palette-slate); }
.diagram [fill="#154a82"] { fill: var(--link); }
.diagram [stroke="#1a1917"] { stroke: var(--palette-plum); }
.diagram [stroke="#6a675f"] { stroke: var(--palette-slate); }
.diagram [stroke="#154a82"] { stroke: var(--link); }
.diagram__cap {
  text-align: center;
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--faint);
  margin-top: 0.5rem;
  letter-spacing: 0.015em;
  line-height: 1.5;
}

.see-also {
  margin-top: 1.9rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}
.see-also h3 {
  font-family: var(--mono);
  font-size: 0.73rem;
  letter-spacing: 0.045em;
  text-transform: uppercase;
  color: var(--faint);
  margin: 0 0 0.55rem;
  font-weight: 600;
}
.see-also ul {
  margin: 0;
  padding-left: 1.25rem;
  font-size: 0.93rem;
  line-height: 1.68;
}

.pager {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.75rem;
  margin-top: 2rem;
  padding-top: 1.1rem;
  border-top: 1px solid var(--border);
}
.pager a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  border: 1px solid var(--border);
  background: var(--panel);
  border-radius: 9px;
  padding: 0.58rem 0.85rem;
  text-decoration: none;
  color: var(--text);
  font-size: 0.91rem;
  font-weight: 600;
  line-height: 1.4;
}
.pager a:hover {
  border-color: var(--border-strong);
  background: var(--panel-hover);
}
.pager a.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--palette-plum);
}
.pager a.primary:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: var(--palette-plum);
}

.foot {
  margin-top: 1.7rem;
  text-align: center;
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--faint);
  letter-spacing: 0.025em;
  line-height: 1.55;
}

.checklist { list-style: none; padding: 0; }
.checklist li {
  padding: 0.4rem 0 0.4rem 1.55rem;
  position: relative;
  border-bottom: 1px solid var(--border);
}
.checklist li::before {
  content: '☐';
  position: absolute;
  left: 0;
  font-family: var(--mono);
  color: var(--palette-slate);
  font-weight: 600;
}

@media (max-width: 959px) {
  .sidebar {
    max-height: min(38vh, 340px);
    overflow-y: auto;
    box-shadow: 0 8px 24px rgba(0, 0, 0, .18);
  }
  .sidebar nav a {
    display: flex;
    align-items: center;
    min-height: 44px;
  }
  .main { padding: 0.8rem; }
  .sheet {
    min-height: auto;
    border-radius: 11px;
    padding: 2rem clamp(1.15rem, 5vw, 2.5rem);
  }
}

@media (max-width: 560px) {
  body { font-size: 15.75px; }
  .sidebar { padding: 1rem; }
  .sheet__label {
    align-items: flex-start;
    flex-direction: column;
    gap: 0.12rem;
  }
  h1 { font-size: 1.62rem; }
  .lead { font-size: 1rem; }
  .prose h2 {
    font-size: 1.2rem;
    margin-top: 1.85rem;
  }
  .prose h3 { font-size: 1.04rem; }
  .linkbox a { padding: 0.75rem 0.8rem; }
  .pager {
    align-items: stretch;
    flex-direction: column;
  }
  .pager > span:empty { display: none; }
  .pager a { justify-content: center; width: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    scroll-behavior: auto !important;
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
  }
}

@media print {
  @page { size: A4 portrait; margin: 12mm; }
  body {
    color: var(--palette-plum);
    background: #fff;
    font-size: 10.5pt;
    line-height: 1.62;
  }
  .sidebar, .pager, .page-tools { display: none !important; }
  .layout { display: block; }
  .main { padding: 0; display: block; }
  .sheet {
    width: 100%;
    min-height: auto;
    border: 0;
    border-radius: 0;
    box-shadow: none;
    padding: 0;
  }
  .callout,
  .diagram,
  .linkbox a,
  .prose pre,
  .prose table {
    break-inside: avoid;
  }
  .prose h2,
  .prose h3 {
    break-after: avoid;
  }
  a { color: var(--palette-slate); }
  a.concept,
  .linkbox a {
    color: var(--palette-plum);
    background: #fff;
    border-color: var(--palette-slate);
  }
  .callout {
    color: var(--palette-plum);
    background: #fff;
    border-color: var(--palette-slate);
  }
  .diagram { background: #fff; }
}