/* Math Atlas — 사이트 전역 스타일. 빌드 시 site/assets/로 복사됨. */

:root {
  --bg: #faf9f6;
  --surface: #ffffff;
  --ink: #1d2433;
  --muted: #5b6472;
  --border: #e4e1d8;
  --border-soft: #edeae2;
  --accent: #24549c;
  --accent-ink: #1b4079;
  --accent-soft: #edf3fc;
  --code-bg: #f1efe9;
  --shadow: 0 1px 3px rgba(29, 36, 51, 0.07), 0 8px 24px -12px rgba(29, 36, 51, 0.12);
  --tier-warmup: #64748c;
  --tier-core: #24549c;
  --tier-challenge: #b0531f;
  --tier-contest: #71399e;
  --ok: #2e7d4f;
}

/* 다크 팔레트. 기본은 시스템 설정을 따르고(data-theme 없음),
   버튼으로 고정하면 html[data-theme="dark"|"light"]가 우선한다. */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14171d;
    --surface: #1d222b;
    --ink: #e7eaf0;
    --muted: #9aa3b0;
    --border: #303747;
    --border-soft: #272d3a;
    --accent: #82aae6;
    --accent-ink: #a9c6f0;
    --accent-soft: #202b3d;
    --code-bg: #262c38;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
    --tier-warmup: #8b99ad;
    --tier-core: #82aae6;
    --tier-challenge: #d98b57;
    --tier-contest: #b083d6;
    --ok: #6cbd90;
  }
}

:root[data-theme="dark"] {
  --bg: #14171d;
  --surface: #1d222b;
  --ink: #e7eaf0;
  --muted: #9aa3b0;
  --border: #303747;
  --border-soft: #272d3a;
  --accent: #82aae6;
  --accent-ink: #a9c6f0;
  --accent-soft: #202b3d;
  --code-bg: #262c38;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  --tier-warmup: #8b99ad;
  --tier-core: #82aae6;
  --tier-challenge: #d98b57;
  --tier-contest: #b083d6;
  --ok: #6cbd90;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Apple SD Gothic Neo",
    "Noto Sans KR", "Malgun Gothic", sans-serif;
  font-size: 16.5px;
  line-height: 1.72;
  word-break: keep-all;
  overflow-wrap: break-word;
}

/* ---- 언어 전환: html[data-lang]에 따라 반대 언어 요소를 숨김 ---- */
html[data-lang="ko"] [data-l="en"] { display: none !important; }
html[data-lang="en"] [data-l="ko"] { display: none !important; }

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

/* ---- 헤더 ---- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.55rem 1.1rem;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  font-weight: 750;
  font-size: 1.02rem;
  letter-spacing: 0.01em;
  color: var(--ink);
  white-space: nowrap;
}
.brand:hover { text-decoration: none; color: var(--accent); }

.crumbs {
  flex: 1;
  min-width: 0;
  font-size: 0.86rem;
  color: var(--muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.crumbs a { color: var(--muted); }
.crumbs .sep { margin: 0 0.4rem; opacity: 0.5; }

.topbar .controls { display: flex; gap: 0.45rem; align-items: center; }

.btn {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--ink);
  font: inherit;
  font-size: 0.83rem;
  padding: 0.32rem 0.72rem;
  border-radius: 8px;
  cursor: pointer;
  white-space: nowrap;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn[aria-pressed="true"] {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

/* ---- 레이아웃 ---- */
.layout {
  display: grid;
  grid-template-columns: 268px minmax(0, 1fr);
  max-width: 1240px;
  margin: 0 auto;
  gap: 2.2rem;
  padding: 1.6rem 1.2rem 4rem;
}
.layout.no-side { grid-template-columns: minmax(0, 1fr); }
.layout.no-side .content { margin: 0 auto; }

.sidebar {
  position: sticky;
  top: 4.2rem;
  align-self: start;
  max-height: calc(100vh - 5.5rem);
  overflow-y: auto;
  font-size: 0.9rem;
  padding-right: 0.4rem;
}
.sidebar .side-course {
  font-weight: 700;
  font-size: 0.95rem;
  margin: 0.2rem 0 0.7rem;
  display: block;
}
.sidebar .unit { margin: 0.9rem 0 0.3rem; }
.sidebar .unit-name {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  margin-bottom: 0.25rem;
}
.sidebar ul { list-style: none; margin: 0; padding: 0; }
.sidebar li a, .sidebar li .planned-item {
  display: block;
  padding: 0.28rem 0.55rem;
  border-radius: 7px;
  color: var(--ink);
}
.sidebar li a:hover { background: var(--accent-soft); text-decoration: none; }
.sidebar li a.current {
  background: var(--accent-soft);
  color: var(--accent-ink);
  font-weight: 650;
}
.sidebar .planned-item { color: var(--muted); cursor: default; }

main { min-width: 0; }
.content { max-width: 46.5rem; }

/* ---- 타이포그래피 ---- */
h1 { font-size: 1.85rem; line-height: 1.3; margin: 0.4rem 0 0.5rem; letter-spacing: -0.01em; }
h2 {
  font-size: 1.32rem;
  margin: 2.4rem 0 0.8rem;
  padding-bottom: 0.35rem;
  border-bottom: 1px solid var(--border-soft);
  letter-spacing: -0.005em;
}
h3 { font-size: 1.08rem; margin: 1.8rem 0 0.5rem; }
p { margin: 0.75rem 0; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2.2rem 0; }
strong { font-weight: 700; }

ul, ol { padding-left: 1.5rem; margin: 0.75rem 0; }
li { margin: 0.3rem 0; }

table { border-collapse: collapse; margin: 1rem 0; font-size: 0.95em; }
th, td { border: 1px solid var(--border); padding: 0.45rem 0.8rem; text-align: left; }
th { background: var(--code-bg); font-weight: 700; }

code {
  background: var(--code-bg);
  border-radius: 5px;
  padding: 0.1em 0.35em;
  font-size: 0.9em;
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
}

blockquote {
  margin: 1rem 0;
  padding: 0.2rem 1.1rem;
  border-left: 3px solid var(--border);
  color: var(--muted);
}

.lesson-meta {
  font-size: 0.86rem;
  color: var(--muted);
  margin-bottom: 1.4rem;
}

/* ---- 수식 ---- */
.katex { font-size: 1.08em; }
.math-display { overflow-x: auto; padding: 0.35rem 0; margin: 0.9rem 0; }

/* ---- 그림 (빌드가 SVG를 인라인으로 심음 → CSS 변수로 테마 자동 대응) ---- */
.fig { margin: 1.7rem auto; text-align: center; }
.fig svg { max-width: 100%; height: auto; font-family: inherit; }
.fig figcaption { font-size: 0.85rem; color: var(--muted); margin-top: 0.55rem; }

/* ---- 콜아웃 ---- */
.co {
  border: 1px solid var(--border);
  border-left-width: 4px;
  border-radius: 10px;
  padding: 0.85rem 1.15rem;
  margin: 1.3rem 0;
  background: var(--surface);
}
.co > :first-child { margin-top: 0; }
.co > :last-child { margin-bottom: 0; }
.co-tag {
  display: block;
  font-size: 0.76rem;
  font-weight: 750;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.35rem;
}
.co-title { font-weight: 700; display: block; margin-bottom: 0.3rem; font-size: 1.02rem; }

.co.goal { border-left-color: var(--ok); }
.co.goal .co-tag { color: var(--ok); }
.co.definition { border-left-color: var(--accent); background: var(--accent-soft); }
.co.definition .co-tag { color: var(--accent-ink); }
.co.example { border-left-color: var(--tier-contest); }
.co.example .co-tag { color: var(--tier-contest); }
.co.note { border-left-color: var(--tier-warmup); }
.co.note .co-tag { color: var(--tier-warmup); }
.co.warn { border-left-color: var(--tier-challenge); }
.co.warn .co-tag { color: var(--tier-challenge); }

/* ---- 탭 ---- */
.tabs {
  display: flex;
  gap: 0.4rem;
  margin: 1.3rem 0 1.7rem;
  border-bottom: 1px solid var(--border);
}
.tab-btn {
  appearance: none;
  background: none;
  border: 0;
  border-bottom: 2.5px solid transparent;
  font: inherit;
  font-size: 0.98rem;
  font-weight: 650;
  color: var(--muted);
  padding: 0.45rem 0.9rem;
  cursor: pointer;
  margin-bottom: -1px;
}
.tab-btn:hover { color: var(--ink); }
.tab-btn[aria-selected="true"] { color: var(--accent-ink); border-bottom-color: var(--accent); }
.tab-panel[hidden] { display: none; }
.count-pill {
  display: inline-block;
  font-size: 0.72rem;
  background: var(--code-bg);
  border-radius: 99px;
  padding: 0 0.5em;
  margin-left: 0.3em;
  color: var(--muted);
}

/* ---- 문제 카드 ---- */
.tier-head {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  margin: 2.2rem 0 0.9rem;
}
.tier-head h2 { margin: 0; border: 0; padding: 0; font-size: 1.2rem; }
.tier-head .tier-desc { font-size: 0.85rem; color: var(--muted); }

.prob {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.05rem 1.25rem;
  margin: 0.9rem 0;
  box-shadow: var(--shadow);
}
.prob-head {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  margin-bottom: 0.5rem;
}
.prob-num { font-weight: 750; font-size: 0.95rem; }
.badge {
  font-size: 0.7rem;
  font-weight: 750;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  padding: 0.1rem 0.5rem;
  border-radius: 99px;
  border: 1px solid currentColor;
}
.badge.warmup { color: var(--tier-warmup); }
.badge.core { color: var(--tier-core); }
.badge.challenge { color: var(--tier-challenge); }
.badge.contest { color: var(--tier-contest); }
.badge.type-chip { color: var(--muted); border-style: dashed; text-transform: none; letter-spacing: 0; }
.prob-src { font-size: 0.78rem; color: var(--muted); margin-left: auto; }

.prob-statement > :first-child { margin-top: 0; }
.prob-statement > :last-child { margin-bottom: 0; }

details.reveal {
  margin-top: 0.7rem;
  border: 1px solid var(--border-soft);
  border-radius: 9px;
  background: var(--bg);
}
details.reveal > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.42rem 0.85rem;
  font-size: 0.85rem;
  font-weight: 650;
  color: var(--muted);
  user-select: none;
}
details.reveal > summary::-webkit-details-marker { display: none; }
details.reveal > summary::before { content: "▸ "; }
details.reveal[open] > summary::before { content: "▾ "; }
details.reveal[open] > summary { color: var(--accent-ink); border-bottom: 1px dashed var(--border); }
details.reveal .reveal-body { padding: 0.65rem 0.95rem 0.8rem; }
details.reveal .reveal-body > :first-child { margin-top: 0; }
details.reveal .reveal-body > :last-child { margin-bottom: 0; }

.answer-line {
  font-weight: 650;
  background: var(--accent-soft);
  border-radius: 7px;
  padding: 0.35rem 0.7rem;
  display: inline-block;
  margin-bottom: 0.5rem;
}

.problems-toolbar { display: flex; gap: 0.5rem; margin: 0.4rem 0 1.2rem; }

/* ---- 카탈로그 (홈) ---- */
.hero { margin: 1.2rem 0 2.2rem; max-width: 44rem; }
.hero h1 { font-size: 2.1rem; }
.hero p { color: var(--muted); font-size: 1.02rem; }

.track-title { font-size: 1.25rem; margin: 2.3rem 0 1rem; }
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(285px, 1fr));
  gap: 1rem;
}
.course-card {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.15rem 1.25rem;
  color: var(--ink);
  box-shadow: var(--shadow);
  transition: border-color 0.15s ease, transform 0.15s ease;
}
a.course-card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-2px); }
.course-card.planned { opacity: 0.62; }
.course-card h3 { margin: 0; font-size: 1.06rem; }
.course-card p { margin: 0; font-size: 0.87rem; color: var(--muted); }
.card-status { font-size: 0.75rem; font-weight: 700; }
.card-status.open { color: var(--ok); }
.card-status.soon { color: var(--muted); }

/* ---- 코스 목차 ---- */
.unit-block { margin: 1.9rem 0; }
.unit-block h2 { border: 0; padding: 0; margin-bottom: 0.6rem; }
.lesson-list { list-style: none; padding: 0; margin: 0; }
.lesson-list li { margin: 0.4rem 0; }
.lesson-list a, .lesson-list .planned-row {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.62rem 1rem;
  color: var(--ink);
}
.lesson-list a:hover { border-color: var(--accent); text-decoration: none; }
.lesson-list .planned-row { color: var(--muted); border-style: dashed; background: none; }
.lesson-list .lnum { font-weight: 700; color: var(--muted); font-size: 0.85rem; min-width: 2.1rem; }
.chip {
  margin-left: auto;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 99px;
  padding: 0.08rem 0.55rem;
  white-space: nowrap;
}
.unit-soon { color: var(--muted); font-size: 0.88rem; margin: 0.3rem 0 0; }

/* ---- 이전/다음 ---- */
.pager { display: flex; justify-content: space-between; gap: 1rem; margin-top: 3rem; }
.pager a {
  flex: 1;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.6rem 0.9rem;
  font-size: 0.88rem;
  background: var(--surface);
}
.pager a:hover { border-color: var(--accent); text-decoration: none; }
.pager .next { text-align: right; }
.pager .dir { display: block; font-size: 0.72rem; color: var(--muted); }

footer.site-foot {
  max-width: 1240px;
  margin: 0 auto;
  padding: 1.2rem;
  font-size: 0.8rem;
  color: var(--muted);
  border-top: 1px solid var(--border-soft);
}

/* ---- 문제집 (인쇄용 숙제 시트) ---- */
.worksheet-meta { display: flex; align-items: baseline; gap: 0.8rem; flex-wrap: wrap; }
.worksheet-blank {
  height: 11rem;
  border: 1.5px dashed var(--border);
  border-radius: 10px;
  margin-top: 0.9rem;
}
.worksheet .prob { box-shadow: none; }
.name-line { color: var(--muted); font-size: 0.9rem; margin: 0.2rem 0 1.2rem; }

@media print {
  .worksheet-blank { border-color: #bbb; }
  .worksheet .prob { border-color: #ccc; }
}

/* ---- 수업 모드: 큰 글씨, 사이드바 숨김 ---- */
html.classmode body { font-size: 21px; }
html.classmode .layout { grid-template-columns: minmax(0, 1fr); max-width: 62rem; }
html.classmode .sidebar { display: none; }
html.classmode .content { max-width: none; }
html.classmode .katex { font-size: 1.12em; }

/* ---- 반응형 ---- */
@media (max-width: 900px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  .sidebar { position: static; max-height: none; order: 2; border-top: 1px solid var(--border); padding-top: 1rem; }
  .crumbs { display: none; }
}

/* ---- 인쇄 ---- */
@media print {
  .topbar, .sidebar, .problems-toolbar, .pager, .tabs { display: none !important; }
  .layout { display: block; padding: 0; }
  body { background: #fff; color: #000; font-size: 12pt; }
  .prob, .co { box-shadow: none; break-inside: avoid; }
  .tab-panel[hidden] { display: block !important; }
  a { color: inherit; }
}