:root {
  --bg: #fbfaf7;
  --bg-alt: #f2f0ea;
  --card: #ffffff;
  --text: #1c1c22;
  --muted: #5d5d6a;
  --border: #e3e0d8;
  --accent: #2f5bea;
  --accent-soft: #e8eeff;
  --on-accent: #ffffff;
  --on-good: #ffffff;
  --warn: #c2410c;
  --warn-soft: #fff1e8;
  --good: #15803d;
  --good-soft: #e8f7ee;
  --highlight: #fff6d6;
  --radius: 16px;
  --shadow: 0 1px 2px rgba(0, 0, 0, .04), 0 4px 16px rgba(0, 0, 0, .04);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #131318;
    --bg-alt: #1a1a21;
    --card: #20202a;
    --text: #ececf1;
    --muted: #a3a3b2;
    --border: #2f2f3b;
    --accent: #7c9cff;
    --accent-soft: #232b48;
    --on-accent: #0f1530;
    --on-good: #0b1f12;
    --warn: #fb923c;
    --warn-soft: #33241a;
    --good: #4ade80;
    --good-soft: #1a2f22;
    --highlight: #33301c;
    --shadow: none;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 64px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo", "Noto Sans KR", "Malgun Gothic", "Segoe UI", sans-serif;
  font-size: 1.125rem;
  line-height: 1.75;
  word-break: keep-all;
  overflow-wrap: break-word;
  -webkit-text-size-adjust: 100%;
}

a { color: var(--accent); }

h1, h2, h3 { line-height: 1.35; margin: 0 0 .6em; }
h1 { font-size: clamp(2.2rem, 7vw, 3.4rem); letter-spacing: -.02em; }
h2 { font-size: clamp(1.6rem, 4.5vw, 2.2rem); letter-spacing: -.01em; }
h3 { font-size: 1.2rem; }
p { margin: 0 0 1em; }

.container { max-width: 880px; margin: 0 auto; padding: 0 20px; }

/* Hero */
.hero {
  padding: 72px 0 48px;
  background: linear-gradient(160deg, var(--accent-soft), var(--bg) 70%);
}
.eyebrow { color: var(--accent); font-weight: 700; margin-bottom: .4em; }
.lead { font-size: 1.2rem; color: var(--muted); }
.prep {
  display: flex; flex-wrap: wrap; gap: 6px 12px; align-items: baseline;
  margin-top: 24px; padding: 14px 18px;
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
}
.prep strong { color: var(--accent); }

/* Table of contents */
.toc {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.toc ol {
  display: flex; gap: 8px; margin: 0; padding: 10px 0;
  list-style: none; overflow-x: auto; scrollbar-width: none;
  counter-reset: toc;
}
.toc ol::-webkit-scrollbar { display: none; }
.toc a {
  display: block; white-space: nowrap;
  padding: 6px 14px; border-radius: 999px;
  font-size: .95rem; text-decoration: none; color: var(--text);
  background: var(--card); border: 1px solid var(--border);
}
.toc a:hover, .toc a:focus-visible { border-color: var(--accent); color: var(--accent); }

/* Sections */
section { padding: 64px 0; }
section.alt { background: var(--bg-alt); }
.section-no { color: var(--accent); font-weight: 800; letter-spacing: .08em; margin-bottom: .2em; }
h3.sub { margin-top: 2em; }
.note { color: var(--muted); font-size: .95rem; }
.bridge { font-size: 1.15rem; font-weight: 600; }

/* Cards */
.grid {
  display: grid; gap: 16px; margin: 24px 0;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}
.grid.small { grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); }
.grid.two { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.grid.three { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.card {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px 22px; box-shadow: var(--shadow);
}
.card p:last-child { margin-bottom: 0; }
.card.warn { border-top: 4px solid var(--warn); }
.card.use h3 { margin-bottom: .8em; }
.emoji { font-size: 2rem; line-height: 1; margin-bottom: .4em; }
.example {
  margin-top: .8em; padding: 10px 14px; border-radius: 10px;
  background: var(--accent-soft); font-weight: 600;
}

.pills { display: flex; flex-wrap: wrap; gap: 10px; padding: 0; list-style: none; }
.pills li {
  padding: 10px 16px; border-radius: 999px;
  background: var(--card); border: 1px solid var(--border); font-weight: 600;
}

/* Timeline */
.timeline { list-style: none; padding: 0; margin: 28px 0; position: relative; }
.timeline::before {
  content: ""; position: absolute; left: 7px; top: 8px; bottom: 8px;
  width: 2px; background: var(--border);
}
.timeline li { position: relative; padding: 0 0 22px 36px; }
.timeline li::before {
  content: ""; position: absolute; left: 0; top: 8px;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--card); border: 3px solid var(--accent);
}
.timeline .when { display: block; color: var(--muted); font-size: .92rem; font-weight: 600; }
.timeline strong { display: block; font-size: 1.1rem; }
.timeline p { margin: .2em 0 0; color: var(--muted); }
.timeline li.highlight {
  background: var(--highlight); border-radius: var(--radius);
  padding: 14px 16px 14px 36px; margin-bottom: 22px;
}
.timeline li.highlight::before { background: var(--accent); top: 22px; }

.tag {
  display: inline-block; margin-bottom: .8em; padding: 3px 12px;
  border-radius: 999px; background: var(--accent); color: var(--on-accent);
  font-size: .9rem; font-weight: 700;
}

.feature, .callout, .principle, .checklist, .practice, .demo {
  border-radius: var(--radius); padding: 24px; margin: 28px 0;
}
.feature { background: var(--card); border: 2px solid var(--accent); }
.callout { background: var(--warn-soft); border-left: 5px solid var(--warn); }
.callout p:last-child { margin-bottom: 0; }
.principle { background: var(--card); border: 1px solid var(--border); }
.checklist { background: var(--card); border: 1px solid var(--border); }
.practice { background: var(--good-soft); border: 1px solid color-mix(in srgb, var(--good) 30%, transparent); }
.practice .tag { background: var(--good); color: var(--on-good); }
.demo { background: var(--accent-soft); }

.checks, .checklist ul { list-style: none; padding: 0; margin: 0; }
.checks li, .checklist li { position: relative; padding-left: 30px; margin-bottom: .6em; }
.checks li::before, .checklist li::before {
  content: "✓"; position: absolute; left: 0; top: 0;
  color: var(--good); font-weight: 800;
}

/* Glossary and terms */
details { margin: 20px 0; }
summary { cursor: pointer; font-weight: 700; color: var(--accent); }
.glossary {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 22px;
}
.glossary dl { margin: 12px 0 0; }
dt { font-weight: 700; }
dd { margin: 0 0 12px; color: var(--muted); }
.terms { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.terms > div { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px 20px; }
.terms dd { margin: 0; }

/* Prediction bars */
.predict { background: var(--bg-alt); border-radius: 12px; padding: 18px; margin: 16px 0; }
.predict-q { font-weight: 700; font-size: 1.15rem; }
.bar { display: grid; grid-template-columns: 70px 1fr 48px; align-items: center; gap: 10px; margin: 8px 0; }
.bar i { display: block; height: 14px; border-radius: 7px; background: var(--border); position: relative; overflow: hidden; }
.bar i::after { content: ""; position: absolute; inset: 0; width: var(--w); background: var(--accent); border-radius: 7px; }
.bar b { text-align: right; font-variant-numeric: tabular-nums; }
.predict-note { font-size: .85rem; color: var(--muted); margin: 8px 0 0; }

/* Tables */
.table-wrap { overflow-x: auto; margin: 24px 0; border: 1px solid var(--border); border-radius: var(--radius); background: var(--card); }
table { width: 100%; border-collapse: collapse; min-width: 560px; }
th, td { padding: 14px 16px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); }
th { background: var(--bg-alt); font-size: .95rem; }
tr:last-child td { border-bottom: none; }
td:first-child { font-weight: 700; white-space: nowrap; }

/* Prompts */
.prompt {
  display: flex; gap: 12px; align-items: flex-start; justify-content: space-between;
  background: var(--card); border: 1px solid var(--border); border-radius: 12px;
  padding: 12px 12px 12px 16px; margin: 10px 0;
}
.prompt p { margin: 0; font-weight: 500; }
.copy {
  flex-shrink: 0; font: inherit; font-size: .85rem; font-weight: 700;
  padding: 6px 12px; border-radius: 8px; cursor: pointer;
  border: 1px solid var(--accent); background: transparent; color: var(--accent);
}
.copy:hover { background: var(--accent-soft); }
.copy.done { background: var(--accent); color: var(--on-accent); }

.compare { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }
.label { font-weight: 700; margin: 8px 0 0; }
.label.bad { color: var(--warn); }
.label.good { color: var(--good); }
.formula { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin: 22px 0; }
.formula span { padding: 8px 16px; border-radius: 10px; background: var(--card); border: 2px solid var(--good); font-weight: 700; }
.formula em { font-style: normal; font-weight: 800; color: var(--muted); }

.steps { padding-left: 1.4em; font-weight: 600; }
.steps li { margin-bottom: .4em; }

.summary { padding-left: 1.4em; font-size: 1.2rem; }
.summary li { margin-bottom: .8em; }

footer { padding: 40px 0 56px; color: var(--muted); font-size: .95rem; border-top: 1px solid var(--border); }
footer ul { padding-left: 1.2em; }

@media (max-width: 640px) {
  .table-wrap { border: none; background: none; overflow: visible; }
  table, tbody, tr, td { display: block; min-width: 0; }
  thead { display: none; }
  tr {
    background: var(--card); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 16px 18px; margin-bottom: 12px;
  }
  td { padding: 0; border: none; }
  td:first-child { font-size: 1.15rem; margin-bottom: 4px; }
  td:nth-child(3) { margin-top: 10px; color: var(--accent); font-weight: 700; font-size: .95rem; }
  td:nth-child(3)::before { content: "추천 대상 · "; color: var(--muted); font-weight: 600; }
}

@media (max-width: 520px) {
  body { font-size: 1.0625rem; }
  section { padding: 48px 0; }
  .hero { padding: 52px 0 36px; }
  .feature, .callout, .principle, .checklist, .practice, .demo { padding: 20px 18px; }
  .grid.small .card { padding: 16px; }
  .prompt { padding: 12px 10px 12px 14px; }
  .copy { padding: 5px 10px; }
}

@media print {
  .toc, .copy { display: none; }
  section, section.alt { background: none; padding: 24px 0; }
  details > *:not(summary) { display: block; }
}