/* Leo Design Notes · Knowledge Anthology */
:root {
  --ink: #0a0e17;
  --ink-soft: #1a2233;
  --muted: #5a6578;
  --line: #d8dee8;
  --paper: #f4f6fa;
  --white: #ffffff;
  --blue: #1a4fd6;
  --blue-deep: #0d2f8a;
  --blue-soft: #e8effc;
  --accent: #1a4fd6;
  --ok: #1a7a4c;
  --warn: #b45309;
  --radius: 2px;
  --max: 920px;
  --font-display: "Syne", "Noto Sans SC", sans-serif;
  --font-body: "DM Sans", "Noto Sans SC", sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(ellipse 80% 50% at 10% -10%, rgba(26, 79, 214, 0.08), transparent 50%),
    radial-gradient(ellipse 60% 40% at 100% 0%, rgba(13, 47, 138, 0.06), transparent 45%),
    linear-gradient(180deg, #eef1f7 0%, var(--paper) 28%, #e9edf5 100%);
  background-attachment: fixed;
  line-height: 1.65;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

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

/* —— Layout —— */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(14px);
  background: rgba(244, 246, 250, 0.85);
  border-bottom: 1px solid var(--line);
}

.site-header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.brand {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.04em;
  color: var(--ink);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.brand-mark {
  width: 10px;
  height: 10px;
  background: var(--blue);
  display: inline-block;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.9rem;
  font-size: 0.8rem;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.nav-links a {
  color: var(--muted);
  text-decoration: none;
}

.nav-links a:hover,
.nav-links a.active { color: var(--blue); }

.wrap {
  max-width: var(--max);
  margin: 0 auto;
  padding: 2.5rem 1.5rem 5rem;
}

.wrap-wide {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 5rem;
}

/* —— Hero —— */
.hero {
  padding: 3.5rem 0 2.5rem;
  border-bottom: 1px solid var(--line);
  margin-bottom: 2.5rem;
  position: relative;
}

.hero-meta {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--blue);
  margin-bottom: 1rem;
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.hero h1 {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(2rem, 5vw, 3.2rem);
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
  max-width: 16ch;
}

.hero .lead {
  font-size: 1.1rem;
  color: var(--muted);
  max-width: 38em;
  margin-bottom: 1.5rem;
}

.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.04em;
  padding: 0.35rem 0.65rem;
  background: var(--white);
  border: 1px solid var(--line);
  color: var(--ink-soft);
}

.tag.blue {
  background: var(--blue);
  border-color: var(--blue);
  color: white;
}

/* —— Sections —— */
.section {
  margin-bottom: 3rem;
  scroll-margin-top: 4.5rem;
}

.section-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--blue);
  margin-bottom: 0.5rem;
}

.section h2 {
  font-family: var(--font-display);
  font-size: 1.65rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.6rem;
  line-height: 1.25;
}

.section h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 700;
  margin: 1.75rem 0 0.75rem;
}

.claim {
  font-size: 1.05rem;
  color: var(--ink-soft);
  border-left: 3px solid var(--blue);
  padding-left: 1rem;
  margin: 1rem 0 1.5rem;
  max-width: 42em;
}

.quote {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1.45;
  color: var(--blue-deep);
  margin: 1.5rem 0;
  padding: 1.25rem 1.5rem;
  background: var(--blue-soft);
  border: 1px solid rgba(26, 79, 214, 0.15);
}

.quote cite {
  display: block;
  margin-top: 0.75rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 400;
  font-style: normal;
  letter-spacing: 0.08em;
  color: var(--muted);
}

/* —— Cards / grids —— */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.topic-card {
  background: var(--white);
  border: 1px solid var(--line);
  padding: 1.35rem 1.4rem 1.5rem;
  transition: border-color 0.2s, transform 0.2s;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  text-decoration: none;
  color: inherit;
  min-height: 180px;
}

.topic-card:hover {
  border-color: var(--blue);
  transform: translateY(-2px);
  text-decoration: none;
}

.topic-card .num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--blue);
  letter-spacing: 0.1em;
}

.topic-card h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin: 0;
  line-height: 1.3;
}

.topic-card p {
  font-size: 0.9rem;
  color: var(--muted);
  flex: 1;
}

.topic-card .go {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  color: var(--blue);
  text-transform: uppercase;
}

/* —— Checklist / tables —— */
.checklist {
  list-style: none;
  margin: 1rem 0;
}

.checklist li {
  display: grid;
  grid-template-columns: 2.2rem 1fr;
  gap: 0.75rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--line);
  align-items: start;
}

.checklist li:last-child { border-bottom: none; }

.checklist .n {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--blue);
  font-weight: 500;
  padding-top: 0.15rem;
}

.checklist strong {
  display: block;
  font-family: var(--font-display);
  font-size: 1rem;
  margin-bottom: 0.25rem;
}

.checklist .desc {
  font-size: 0.92rem;
  color: var(--ink-soft);
}

.checklist .check {
  font-size: 0.82rem;
  color: var(--muted);
  margin-top: 0.4rem;
  padding-left: 0.75rem;
  border-left: 2px solid var(--line);
}

.panel {
  background: var(--white);
  border: 1px solid var(--line);
  padding: 1.5rem;
  margin: 1.25rem 0;
}

.panel-title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 1rem;
}

.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

@media (max-width: 700px) {
  .two-col { grid-template-columns: 1fr; }
}

.compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--line);
  margin: 1.25rem 0;
  overflow: hidden;
}

.compare > div { padding: 1.25rem; }
.compare .before { background: #f0f1f4; }
.compare .after { background: var(--blue-soft); }
.compare h4 {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
  color: var(--muted);
}
.compare .after h4 { color: var(--blue); }
.compare ul { padding-left: 1.1rem; font-size: 0.9rem; }
.compare li { margin-bottom: 0.35rem; }

@media (max-width: 600px) {
  .compare { grid-template-columns: 1fr; }
}

.trap-grid {
  display: grid;
  gap: 0.75rem;
  margin: 1rem 0;
}

.trap {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.75rem 1rem;
  padding: 1rem 1.1rem;
  background: var(--white);
  border: 1px solid var(--line);
  border-left: 3px solid var(--warn);
}

.trap .label {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  color: var(--warn);
  text-transform: uppercase;
  grid-column: 1 / -1;
}

.pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1rem 0;
}

.pill {
  font-size: 0.85rem;
  padding: 0.4rem 0.85rem;
  background: var(--white);
  border: 1px solid var(--line);
}

.pill strong { color: var(--blue); }

.formula {
  font-family: var(--font-display);
  font-size: 1.35rem;
  font-weight: 700;
  text-align: center;
  padding: 1.5rem;
  background: var(--ink);
  color: white;
  margin: 1.5rem 0;
  letter-spacing: 0.02em;
}

.formula span { color: #7ba3ff; }

.footer {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem 3rem;
  border-top: 1px solid var(--line);
  font-size: 0.8rem;
  color: var(--muted);
  font-family: var(--font-mono);
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 1.5rem;
  color: var(--muted);
  text-decoration: none;
}

.back-link:hover { color: var(--blue); }

.toc {
  background: var(--white);
  border: 1px solid var(--line);
  padding: 1.25rem 1.5rem;
  margin-bottom: 2rem;
}

.toc ol {
  margin: 0.75rem 0 0 1.2rem;
  font-size: 0.95rem;
}

.toc li { margin-bottom: 0.35rem; }

.stat-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.75rem;
  margin: 2rem 0;
}

@media (max-width: 700px) {
  .stat-row { grid-template-columns: repeat(2, 1fr); }
}

.stat {
  background: var(--white);
  border: 1px solid var(--line);
  padding: 1.1rem;
  text-align: center;
}

.stat .v {
  font-family: var(--font-display);
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--blue);
  line-height: 1;
}

.stat .l {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-top: 0.4rem;
}

.sub-block {
  margin: 2.5rem 0;
  padding-top: 1.5rem;
  border-top: 1px dashed var(--line);
}

.sub-block:first-of-type { border-top: none; padding-top: 0; }

kbd {
  font-family: var(--font-mono);
  font-size: 0.8em;
  background: var(--paper);
  border: 1px solid var(--line);
  padding: 0.1em 0.35em;
}