:root {
  --bg: #fdfcfa;
  --surface: #ffffff;
  --text: #24292f;
  --text-soft: #6b7280;
  --border: #e5e3de;
  --accent: #2563eb;
  --accent-soft: #eff4ff;
  --l1: #0e7490;
  --l3: #15803d;
  --l5: #b45309;
  --l7: #b91c1c;
  --l1-bg: #ecfeff;
  --l3-bg: #f0fdf4;
  --l5-bg: #fffbeb;
  --l7-bg: #fef2f2;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #16181d;
    --surface: #1e2127;
    --text: #e6e6e3;
    --text-soft: #9ca3af;
    --border: #32363e;
    --accent: #7ba7f7;
    --accent-soft: #232c3f;
    --l1: #67e8f9;
    --l3: #86efac;
    --l5: #fcd34d;
    --l7: #fca5a5;
    --l1-bg: #164e63aa;
    --l3-bg: #14532daa;
    --l5-bg: #78350faa;
    --l7-bg: #7f1d1daa;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Noto Sans KR", "Apple SD Gothic Neo", "Malgun Gothic",
    -apple-system, "Segoe UI", sans-serif;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

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

/* Header / footer */
.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}
.header-inner { display: flex; align-items: baseline; gap: 0.75rem; padding: 1rem 1.25rem; }
.brand { display: flex; align-items: baseline; gap: 0.6rem; color: var(--text); }
.brand:hover { text-decoration: none; }
.brand-name { font-size: 1.2rem; font-weight: 700; }
.brand-tagline { font-size: 0.85rem; color: var(--text-soft); }

.site-nav { margin-left: auto; display: flex; gap: 1.1rem; }
.site-nav a { color: var(--text-soft); font-size: 0.92rem; font-weight: 500; }
.site-nav a:hover { color: var(--accent); text-decoration: none; }

.site-footer {
  margin-top: 4rem;
  padding: 1.5rem 0 2.5rem;
  border-top: 1px solid var(--border);
  color: var(--text-soft);
  font-size: 0.85rem;
}

/* Home */
.home-body { padding-top: 0.5rem; }
.home-nav {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 0.9rem;
  margin-top: 2rem;
}
.home-nav-card {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  padding: 1rem 1.1rem;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, transform 0.15s ease;
}
.home-nav-card:hover {
  text-decoration: none;
  border-color: var(--accent);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.07);
  transform: translateY(-2px);
}
.home-nav-card strong { color: var(--accent); }
.home-nav-card span { color: var(--text-soft); font-size: 0.88rem; }

/* Archive */
.hero { margin-top: 1.5rem; }
.hero img {
  display: block;
  width: 100%;
  height: auto;
  max-height: 220px;
  object-fit: cover;
  border-radius: 12px;
}

.archive-head { padding-top: 1.5rem; }
.archive-head h1 { margin: 0 0 0.25rem; font-size: 1.7rem; }
.archive-sub { margin: 0 0 1.25rem; color: var(--text-soft); }

.archive-controls { display: flex; flex-wrap: wrap; gap: 0.75rem; margin-bottom: 1.5rem; }
#search {
  flex: 1 1 220px;
  padding: 0.55rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.95rem;
}
#search:focus { outline: 2px solid var(--accent); outline-offset: -1px; }

.level-filter { display: flex; gap: 0.4rem; }
.level-btn {
  padding: 0.45rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--text-soft);
  font-size: 0.85rem;
  cursor: pointer;
}
.level-btn.is-active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

.post-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.9rem;
}
.post-item[hidden] { display: none; }
.post-card {
  display: flex;
  flex-direction: column;
  height: 100%;
  gap: 0.45rem;
  padding: 1rem 1.1rem 1.1rem;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  transition: border-color 0.15s ease, box-shadow 0.15s ease, transform 0.15s ease;
}
.post-card:hover {
  text-decoration: none;
  border-color: var(--accent);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.07);
  transform: translateY(-2px);
}
.post-card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.78rem;
  color: var(--text-soft);
}
.post-card-title { margin: 0; font-size: 1.05rem; font-weight: 600; line-height: 1.45; }
.post-card-excerpt {
  margin: 0;
  color: var(--text-soft);
  font-size: 0.88rem;
  line-height: 1.6;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.empty-note { color: var(--text-soft); padding: 2rem 0; text-align: center; }

/* Level badges */
.level-badge {
  display: inline-block;
  padding: 0.1rem 0.55rem;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
  white-space: nowrap;
}
.level-l1 { color: var(--l1); background: var(--l1-bg); }
.level-l3 { color: var(--l3); background: var(--l3-bg); }
.level-l5 { color: var(--l5); background: var(--l5-bg); }
.level-l7 { color: var(--l7); background: var(--l7-bg); }

/* Post page */
.post-header { padding: 2.25rem 0 1rem; border-bottom: 1px solid var(--border); }
.post-header h1 { margin: 0 0 0.6rem; font-size: 1.75rem; line-height: 1.35; }
.post-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
  color: var(--text-soft);
  font-size: 0.85rem;
}

.post-body { padding-top: 1.25rem; font-size: 1.02rem; }
.post-body h1, .post-body h2, .post-body h3 { line-height: 1.4; margin: 1.8em 0 0.6em; }
.post-body p { margin: 0.9em 0; }
.post-body img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  display: block;
  margin: 1.25rem auto;
}
.post-body blockquote {
  margin: 1rem 0;
  padding: 0.25rem 1rem;
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  border-radius: 0 8px 8px 0;
  color: var(--text-soft);
}
.post-body pre {
  overflow-x: auto;
  padding: 0.9rem 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
}
.post-body code { font-family: ui-monospace, "SFMono-Regular", Consolas, monospace; }
.post-body table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.25rem 0;
  font-size: 0.95rem;
  display: block;
  overflow-x: auto;
}
.post-body th, .post-body td {
  border: 1px solid var(--border);
  padding: 0.45rem 0.7rem;
}
.post-body th { background: var(--surface); }

.math-block { margin: 1.25rem 0; overflow-x: auto; text-align: center; }
.math-inline { white-space: nowrap; }

.post-footer-nav { margin-top: 3rem; }

/* Concept map (mind map) */
.cm-toolbar { display: flex; flex-wrap: wrap; gap: 0.4rem; margin: 0 0 0.9rem; }
.cm-toolbar button {
  padding: 0.4rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--text-soft);
  font-size: 0.85rem;
  cursor: pointer;
}
.cm-toolbar button:hover { border-color: var(--accent); color: var(--accent); }
.cm-toolbar button.is-active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

.cm-stage {
  /* 본문 폭(760px)을 벗어나 화면 전체 폭 사용 */
  width: 100vw;
  margin-left: calc(50% - 50vw);
  height: 78vh;
  min-height: 480px;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}
#cm-svg { width: 100%; height: 100%; color: var(--text); }
#cm-svg a { color: var(--accent); }
.cm-chip { font-size: 0.62rem; padding: 0.05rem 0.4rem; vertical-align: 1px; }

.concept-map-fallback h2 { margin-top: 2rem; }
.concept-map-fallback .level-badge { margin-left: 0.3rem; }

/* 404 */
.not-found { text-align: center; padding: 5rem 0; }
.not-found h1 { font-size: 3rem; margin-bottom: 0.5rem; }