:root {
  --bg: #090909;
  --bg-soft: #10100f;
  --surface: #171714;
  --surface-2: #20201b;
  --line: rgba(255,255,255,.11);
  --line-strong: rgba(235,157,110,.32);
  --text: #f7f3ed;
  --text-soft: #c7c0b7;
  --muted: #8d877f;
  --coral: #eb9d6e;
  --coral-strong: #f2b28b;
  --gold: #c9a84c;
  --green: #a9c78e;
  --max: 1180px;
  --font-ko: "Pretendard Variable", Pretendard, -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo", "Segoe UI", sans-serif;
  --font-display: Georgia, "Times New Roman", serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background:
    radial-gradient(circle at 80% -10%, rgba(235,157,110,.14), transparent 32rem),
    radial-gradient(circle at 0 36%, rgba(201,168,76,.08), transparent 28rem),
    var(--bg);
  color: var(--text);
  font-family: var(--font-ko);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
button, input { font: inherit; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid var(--line);
  background: rgba(9,9,9,.84);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}
.header-inner {
  max-width: var(--max);
  margin: 0 auto;
  min-height: 68px;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.brand { display: inline-flex; align-items: center; gap: 11px; }
.brand img { width: 34px; height: 34px; object-fit: contain; border-radius: 8px; background: #fff; padding: 3px; }
.brand strong { display: block; font-family: var(--font-display); font-size: 15px; line-height: 1.15; }
.brand span { display: block; margin-top: 2px; color: var(--muted); font-size: 10px; line-height: 1.2; }
.header-nav { display: flex; align-items: center; gap: 8px; }
.header-nav a {
  padding: 8px 12px;
  border-radius: 9px;
  color: var(--text-soft);
  font-size: 13px;
  font-weight: 700;
}
.header-nav a:hover, .header-nav a:focus-visible { background: var(--surface-2); color: var(--text); outline: none; }
.header-nav .home-link { border: 1px solid var(--line); }

.library-hero {
  max-width: var(--max);
  margin: 0 auto;
  padding: 92px 24px 62px;
}
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--coral-strong);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: .12em;
  text-transform: uppercase;
}
.eyebrow::before { content: "✦"; font-size: 18px; }
.library-hero h1 {
  max-width: 820px;
  margin: 18px 0 18px;
  font-size: clamp(42px, 7vw, 78px);
  line-height: 1.05;
  letter-spacing: -.055em;
}
.library-hero h1 em { color: var(--coral); font-family: var(--font-display); font-weight: 400; }
.hero-copy { max-width: 670px; margin: 0; color: var(--text-soft); font-size: clamp(17px, 2vw, 21px); }
.hero-copy strong { color: var(--text); }
.hero-meta { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 30px; }
.meta-chip {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 7px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--text-soft);
  background: rgba(255,255,255,.025);
  font-size: 13px;
  font-weight: 700;
}
.meta-chip.active { border-color: var(--line-strong); color: var(--coral-strong); }

.progress-panel {
  max-width: var(--max);
  margin: 0 auto 74px;
  padding: 0 24px;
}
.progress-card {
  display: grid;
  grid-template-columns: 160px 1fr auto;
  gap: 28px;
  align-items: center;
  padding: 24px 26px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: linear-gradient(135deg, rgba(235,157,110,.08), rgba(255,255,255,.018));
}
.progress-number { font-size: 36px; font-weight: 900; letter-spacing: -.04em; }
.progress-number small { display: block; color: var(--muted); font-size: 11px; letter-spacing: .08em; text-transform: uppercase; }
.progress-track { height: 9px; overflow: hidden; border-radius: 999px; background: rgba(255,255,255,.08); }
.progress-track span { display: block; width: 5.56%; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--coral), var(--gold)); }
.progress-copy { color: var(--muted); font-size: 13px; white-space: nowrap; }

.library-main { max-width: var(--max); margin: 0 auto; padding: 0 24px 100px; }
.level-section + .level-section { margin-top: 76px; }
.level-head { display: flex; align-items: end; justify-content: space-between; gap: 24px; margin-bottom: 22px; }
.level-kicker { color: var(--coral); font-family: var(--font-display); font-size: 14px; }
.level-head h2 { margin: 2px 0 0; font-size: clamp(28px, 4vw, 42px); line-height: 1.2; letter-spacing: -.035em; }
.level-head p { max-width: 470px; margin: 0; color: var(--muted); font-size: 14px; text-align: right; }
.lesson-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.lesson-card {
  position: relative;
  min-height: 230px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: 17px;
  background: linear-gradient(145deg, rgba(255,255,255,.04), rgba(255,255,255,.016));
  display: flex;
  flex-direction: column;
  transition: transform .2s ease, border-color .2s ease, background .2s ease;
}
a.lesson-card:hover, a.lesson-card:focus-visible {
  transform: translateY(-3px);
  border-color: var(--line-strong);
  background: linear-gradient(145deg, rgba(235,157,110,.09), rgba(255,255,255,.02));
  outline: none;
}
.lesson-card.is-upcoming { opacity: .68; }
.lesson-card.is-upcoming::after {
  content: "준비 중";
  position: absolute;
  top: 18px;
  right: 18px;
  padding: 4px 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  font-size: 10px;
  font-weight: 800;
}
.lesson-code { color: var(--coral-strong); font-family: var(--font-display); font-size: 13px; }
.lesson-card h3 { margin: 26px 0 10px; font-size: 21px; line-height: 1.4; letter-spacing: -.025em; }
.lesson-card p { margin: 0; color: var(--muted); font-size: 13px; }
.lesson-output { margin-top: auto; padding-top: 24px; color: var(--text-soft); font-size: 12px; font-weight: 700; }
.lesson-output span { color: var(--green); }
.lesson-arrow { margin-top: 12px; color: var(--coral-strong); font-size: 13px; font-weight: 800; }

.library-note {
  margin-top: 76px;
  padding: 26px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--surface);
}
.library-note strong { display: block; margin-bottom: 5px; font-size: 18px; }
.library-note p { margin: 0; color: var(--muted); font-size: 14px; }

.lesson-shell { max-width: var(--max); margin: 0 auto; padding: 38px 24px 100px; }
.breadcrumb { display: flex; flex-wrap: wrap; gap: 7px; color: var(--muted); font-size: 12px; }
.breadcrumb a:hover { color: var(--coral-strong); }
.lesson-hero { max-width: 890px; padding: 54px 0 46px; }
.lesson-hero h1 { margin: 15px 0 18px; font-size: clamp(36px, 6vw, 64px); line-height: 1.09; letter-spacing: -.05em; }
.lesson-hero p { max-width: 730px; margin: 0; color: var(--text-soft); font-size: 18px; }
.lesson-layout { display: grid; grid-template-columns: 230px minmax(0, 760px); gap: 56px; align-items: start; }
.toc { position: sticky; top: 98px; padding: 18px; border: 1px solid var(--line); border-radius: 15px; background: rgba(23,23,20,.72); }
.toc strong { display: block; margin-bottom: 10px; font-size: 12px; color: var(--coral-strong); letter-spacing: .08em; }
.toc a { display: block; padding: 7px 0; color: var(--muted); font-size: 12px; }
.toc a:hover { color: var(--text); }
.lesson-content section { scroll-margin-top: 96px; padding: 0 0 48px; border-bottom: 1px solid var(--line); }
.lesson-content section + section { padding-top: 48px; }
.lesson-content section:last-child { border-bottom: 0; }
.section-number { display: block; color: var(--coral); font-family: var(--font-display); font-size: 13px; margin-bottom: 7px; }
.lesson-content h2 { margin: 0 0 16px; font-size: 29px; line-height: 1.25; letter-spacing: -.035em; }
.lesson-content h3 { margin: 30px 0 10px; font-size: 19px; }
.lesson-content p { margin: 0; color: var(--text-soft); }
.lesson-content p + p { margin-top: 13px; }
.lesson-content ul, .lesson-content ol { margin: 15px 0 0; padding-left: 22px; color: var(--text-soft); }
.lesson-content li + li { margin-top: 8px; }
.result-card, .safety-box {
  padding: 20px 22px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--surface);
}
.result-card strong, .safety-box strong { color: var(--text); }
.safety-box { border-color: var(--line-strong); background: rgba(235,157,110,.06); }
.sample-note, .prompt-box {
  position: relative;
  margin-top: 17px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #10100e;
}
.sample-note pre, .prompt-box pre {
  margin: 0;
  color: #e5dfd6;
  white-space: pre-wrap;
  word-break: keep-all;
  font: 14px/1.75 var(--font-ko);
}
.prompt-box { padding-top: 52px; border-color: rgba(235,157,110,.25); }
.copy-button {
  position: absolute;
  top: 11px;
  right: 11px;
  min-height: 30px;
  padding: 5px 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--text-soft);
  background: var(--surface-2);
  cursor: pointer;
  font-size: 11px;
  font-weight: 800;
}
.copy-button:hover, .copy-button:focus-visible { border-color: var(--coral); color: var(--text); outline: none; }
.formula {
  margin: 20px 0;
  padding: 22px;
  border-radius: 14px;
  background: linear-gradient(135deg, rgba(235,157,110,.12), rgba(201,168,76,.06));
  color: var(--text);
  text-align: center;
  font-size: clamp(17px, 3vw, 23px);
  font-weight: 900;
}
.checklist { display: grid; gap: 10px; margin-top: 18px; }
.check-item {
  display: grid;
  grid-template-columns: 22px 1fr;
  gap: 11px;
  align-items: start;
  padding: 13px 14px;
  border: 1px solid var(--line);
  border-radius: 11px;
  background: rgba(255,255,255,.018);
  color: var(--text-soft);
  cursor: pointer;
}
.check-item input { width: 17px; height: 17px; margin-top: 3px; accent-color: var(--coral); }
.check-item:has(input:checked) { color: var(--muted); text-decoration: line-through; }
.local-note { margin-top: 12px; color: var(--muted); font-size: 11px; }
.official-links { display: grid; gap: 10px; }
.official-links a { padding: 15px 16px; border: 1px solid var(--line); border-radius: 11px; color: var(--text-soft); font-size: 13px; }
.official-links a:hover { border-color: var(--line-strong); color: var(--text); }

.lesson-navigation {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  margin-top: 36px;
}
.lesson-navigation a {
  min-height: 92px;
  padding: 17px 18px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(255,255,255,.02);
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.lesson-navigation a:hover, .lesson-navigation a:focus-visible {
  border-color: var(--line-strong);
  background: rgba(235,157,110,.06);
  outline: none;
}
.lesson-navigation span { color: var(--muted); font-size: 11px; }
.lesson-navigation strong { margin-top: 5px; color: var(--text-soft); font-size: 13px; line-height: 1.45; }
.lesson-navigation .lesson-next { text-align: right; }

.page-footer { border-top: 1px solid var(--line); background: #070707; }
.footer-inner { max-width: var(--max); margin: 0 auto; padding: 32px 24px; display: flex; justify-content: space-between; gap: 20px; color: var(--muted); font-size: 12px; }
.footer-inner a:hover { color: var(--text); }

@media (max-width: 900px) {
  .lesson-grid { grid-template-columns: repeat(2, 1fr); }
  .lesson-layout { grid-template-columns: 1fr; }
  .toc { position: static; display: none; }
  .level-head { display: block; }
  .level-head p { margin-top: 8px; text-align: left; }
  .progress-card { grid-template-columns: 110px 1fr; }
  .progress-copy { grid-column: 1 / -1; white-space: normal; }
}

@media (max-width: 620px) {
  .header-inner { min-height: 60px; padding: 0 16px; }
  .brand span { display: none; }
  .header-nav a:not(.home-link) { display: none; }
  .library-hero { padding: 66px 18px 44px; }
  .library-hero h1 { font-size: 44px; }
  .progress-panel, .library-main, .lesson-shell { padding-left: 18px; padding-right: 18px; }
  .progress-card { grid-template-columns: 1fr; gap: 14px; }
  .lesson-grid { grid-template-columns: 1fr; }
  .lesson-card { min-height: 205px; }
  .level-section + .level-section { margin-top: 56px; }
  .lesson-hero { padding-top: 42px; }
  .lesson-hero h1 { font-size: 39px; }
  .lesson-content h2 { font-size: 25px; }
  .lesson-navigation { grid-template-columns: 1fr; }
  .lesson-navigation > span:empty { display: none; }
  .footer-inner { display: block; text-align: center; }
  .footer-inner span { display: block; margin-top: 6px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; }
}