/* ── RESET & BASE ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --ink:  #0d0d0d;
  --ink2: #444;
  --ink3: #777;
  --ink4: #aaa;
  --rule: #e5e2db;
  --bg:   #f8f7f4;
  --white:#fff;
  --blue:       #2348c4;
  --blue-soft:  #eef2ff;
  --green:      #0a7a5e;
  --green-soft: #d4f0dc;
  --purple:      #6d28c4;
  --purple-soft: #ece5ff;
  --amber:      #b34500;
  --amber-soft: #ffe5d2;
  --teal:       #1a6e34;
  --teal-soft:  #d4f0dc;
  --pink:       #a0186e;
  --pink-soft:  #fde2f2;
  --mono:  'JetBrains Mono', monospace;
  --serif: 'EB Garamond', serif;
  --sans:  'Inter', sans-serif;
  --r:    8px;
  --r-lg: 12px;
}

html, body {
  height: 100%;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 14px;
  line-height: 1.6;
}

a { color: var(--blue); }
code {
  font-family: var(--mono);
  font-size: 0.75em;
  background: #f0ede8;
  padding: 0.1rem 0.35rem;
  border-radius: 3px;
  color: #444;
}

/* ── TOP NAV ── */
.topnav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.75rem;
  height: 48px;
  border-bottom: 1px solid var(--rule);
  background: rgba(248,247,244,0.95);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 100;
}
.logo {
  font-family: var(--serif);
  font-size: 1.05rem;
  color: var(--ink);
  text-decoration: none;
}
.logo em { font-style: italic; color: var(--blue); }
.nav-links {
  display: flex;
  gap: 1.75rem;
}
.nav-links a {
  font-size: 0.7rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--ink4);
  text-decoration: none;
  transition: color 0.15s;
}
.nav-links a:hover { color: var(--ink); }

/* ── FOOTER ── */
.site-footer {
  border-top: 1px solid var(--rule);
  background: rgba(248,247,244,0.95);
  padding: 0 1.75rem;
  height: 44px;
  display: flex;
  align-items: center;
}
.footer-inner {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.footer-logo {
  font-family: var(--serif);
  font-size: 0.95rem;
}
.footer-logo em { font-style: italic; color: var(--blue); }
.footer-links {
  display: flex;
  gap: 1.5rem;
}
.footer-links a {
  font-size: 0.68rem;
  color: var(--ink4);
  text-decoration: none;
}
.footer-links a:hover { color: var(--ink); }
.footer-note { font-size: 0.65rem; color: var(--ink4); }

/* ── HOMEPAGE ── */
.landing-shell {
  height: calc(100vh - 48px);
  display: flex;
}
.l-graph-area {
  flex: 1;
  min-height: 0;
  position: relative;
  overflow: hidden;
}
#landing-svg { width: 100%; height: 100%; }
.l-headline {
  position: absolute;
  top: 50%;
  left: 1.75rem;
  transform: translateY(-50%);
  z-index: 5;
  pointer-events: none;
  max-width: 230px;
}
.l-headline h1 {
  font-family: var(--serif);
  font-size: 2rem;
  line-height: 1.12;
  font-weight: 400;
  color: var(--ink);
}
.l-headline h1 em { font-style: italic; color: var(--blue); }
.l-headline p { font-size: 0.68rem; color: var(--ink4); margin-top: 0.5rem; line-height: 1.65; }
.l-headline-sub { font-size: 0.85rem !important; color: var(--ink3) !important; margin-top: 0.4rem !important; }
.l-headline-sub em { font-style: italic; color: var(--blue); }

.l-hero-eq {
  margin-top: 1.25rem;
  opacity: 1;
  transition: opacity 0.4s ease-in-out;
  will-change: opacity;
}
.l-eq-lbl {
  display: block;
  font-size: 0.56rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink4);
  margin-bottom: 0.3rem;
}
#l-eq-out { font-size: 0.9rem; color: var(--ink2); }

/* landing tooltip */
#l-tt {
  position: absolute;
  z-index: 30;
  pointer-events: none;
  display: none;
  background: var(--white);
  border: 1px solid var(--rule);
  border-radius: 10px;
  padding: 0.85rem 1rem;
  box-shadow: 0 12px 40px rgba(0,0,0,0.09);
  width: 210px;
}
.l-tt-cat  { font-size: 0.58rem; letter-spacing: 0.1em; text-transform: uppercase; font-weight: 500; margin-bottom: 0.25rem; }
.l-tt-name { font-family: var(--serif); font-size: 1rem; color: var(--ink); margin-bottom: 0.4rem; }
.l-tt-eq   { font-size: 0.72rem; margin-bottom: 0.4rem; min-height: 18px; }
.l-tt-sep  { height: 1px; background: #f0ede8; margin: 0.4rem 0; }
.l-tt-cl   { font-size: 0.56rem; letter-spacing: 0.08em; text-transform: uppercase; color: #ccc; margin-bottom: 0.3rem; }
.l-tt-tags { display: flex; flex-wrap: wrap; gap: 0.25rem; }
.l-tt-tag  { font-size: 0.6rem; padding: 0.12rem 0.45rem; border-radius: 20px; background: #f4f2ee; color: #666; }

/* ── FIELDS INDEX PAGE ── */
.fields-page { max-width: 960px; margin: 0 auto; padding: 2.5rem 2rem; }
.category-section { margin-bottom: 2.5rem; }
.category-eyebrow {
  font-size: 0.6rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  font-weight: 500;
  margin-bottom: 0.85rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--rule);
}
.fields-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 0.75rem;
}
.field-card {
  background: var(--white);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--fc, var(--rule));
  border-radius: var(--r);
  padding: 1rem 1rem 1rem calc(1rem - 2px);
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s, box-shadow 0.15s;
  display: block;
}
.field-card:hover { border-color: var(--fc, var(--blue)); box-shadow: 0 2px 12px rgba(0,0,0,0.07); }
.field-card-icon { font-size: 1.1rem; margin-bottom: 0.5rem; color: var(--fc, var(--ink3)); }
.field-card-name { font-size: 0.85rem; font-weight: 500; color: var(--ink); margin-bottom: 0.3rem; }
.field-card-desc { font-size: 0.68rem; color: var(--ink3); line-height: 1.55; }

/* ── CONCEPTS INDEX PAGE ── */
.concepts-page { max-width: 960px; margin: 0 auto; padding: 2.5rem 2rem; }
.concepts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 0.6rem;
}
.concept-card {
  background: var(--white);
  border: 1px solid var(--rule);
  border-radius: var(--r);
  padding: 0.75rem 1rem;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s;
}
.concept-card:hover { border-color: var(--purple); }
.concept-card-name { font-size: 0.8rem; font-weight: 500; color: var(--ink); }
.concept-card-count { font-size: 0.65rem; color: var(--ink4); margin-top: 0.2rem; }

/* ── FIELD / TOPIC / CONCEPT PAGES ── */
.field-page-shell {
  display: grid;
  grid-template-rows: 48px 1fr;
  height: calc(100vh - 48px);
  overflow: hidden;
}
.fp-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.75rem;
  border-bottom: 1px solid var(--rule);
  background: rgba(248,247,244,0.92);
  flex-shrink: 0;
}
.breadcrumb { font-size: 0.7rem; color: var(--ink3); display: flex; align-items: center; gap: 0.4rem; }
.breadcrumb a { color: var(--blue); text-decoration: none; }
.breadcrumb span { color: var(--ink4); }
.fp-body { display: grid; grid-template-columns: 1fr 240px; overflow: hidden; height: 100%; }
.fp-main { overflow-y: auto; padding: 2rem; }
.fp-sidebar { overflow-y: auto; border-left: 1px solid var(--rule); padding: 1.25rem; background: #fafaf8; }

/* ── ARTICLE STYLES ── */
.art-eyebrow { font-size: 0.6rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--blue); margin-bottom: 0.5rem; font-weight: 500; }
.art-title   { font-family: var(--serif); font-size: 2rem; font-weight: 400; color: var(--ink); margin-bottom: 0.3rem; line-height: 1.15; }
.art-meta    { font-size: 0.68rem; color: var(--ink4); margin-bottom: 1.5rem; display: flex; gap: 1rem; flex-wrap: wrap; }
.art-meta span { display: flex; align-items: center; gap: 0.3rem; }
.art-meta i  { font-size: 12px; }
.art-intro   { font-size: 1rem; line-height: 1.8; color: var(--ink2); margin-bottom: 1.5rem; border-left: 2px solid var(--rule); padding-left: 1rem; font-family: var(--serif); }
.art-h2      { font-family: var(--serif); font-size: 1.3rem; font-weight: 400; color: var(--ink); margin: 2rem 0 0.75rem; border-bottom: 1px solid var(--rule); padding-bottom: 0.4rem; }
.art-p       { font-size: 0.83rem; line-height: 1.8; color: var(--ink2); margin-bottom: 1rem; }
.art-eq      { background: var(--white); border: 1px solid var(--rule); border-radius: var(--r); padding: 1.1rem 1.5rem; margin: 1.25rem 0; text-align: center; overflow-x: auto; }
.art-eq-label { font-size: 0.6rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink4); margin-bottom: 0.5rem; }

/* topic content from markdown */
.fp-main h2 { font-family: var(--serif); font-size: 1.3rem; font-weight: 400; color: var(--ink); margin: 2rem 0 0.75rem; border-bottom: 1px solid var(--rule); padding-bottom: 0.4rem; }
.fp-main h3 { font-size: 0.9rem; font-weight: 500; margin: 1.5rem 0 0.5rem; }
.fp-main p  { font-size: 0.83rem; line-height: 1.8; color: var(--ink2); margin-bottom: 1rem; }
.fp-main ul, .fp-main ol { font-size: 0.83rem; color: var(--ink2); padding-left: 1.5rem; margin-bottom: 1rem; }
.fp-main li { margin-bottom: 0.3rem; line-height: 1.7; }
.fp-main table { width: 100%; border-collapse: collapse; font-size: 0.78rem; margin: 1.25rem 0; }
.fp-main th { background: #f4f2ee; padding: 0.5rem 0.75rem; text-align: left; font-weight: 500; border: 1px solid var(--rule); }
.fp-main td { padding: 0.5rem 0.75rem; border: 1px solid var(--rule); color: var(--ink2); }
.fp-main blockquote { border-left: 2px solid var(--rule); padding-left: 1rem; font-family: var(--serif); font-size: 1rem; color: var(--ink3); margin: 1.25rem 0; }
.fp-main strong { color: var(--ink); }
.fp-main em { font-style: italic; }
.fp-main a  { color: var(--blue); }

/* ── WIDGETS ── */
.art-widget { background: var(--blue-soft); border: 1px solid #c7d4f5; border-radius: var(--r-lg); padding: 1.1rem; margin: 1.5rem 0; }
.art-widget-header { display: flex; align-items: center; gap: 0.5rem; margin-bottom: 0.85rem; }
.art-widget-icon   { width: 28px; height: 28px; background: var(--blue); border-radius: 6px; display: flex; align-items: center; justify-content: center; color: var(--white); font-size: 14px; flex-shrink: 0; }
.art-widget-title  { font-size: 0.72rem; font-weight: 500; color: var(--blue); }
.art-widget-sub    { font-size: 0.65rem; color: #6680cc; }
.widget-canvas { background: var(--white); border-radius: var(--r); border: 1px solid #dde5ff; padding: 1rem; }

/* ── TOPICS GRID (on field page) ── */
.topics-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; }
.topic-card {
  background: var(--white);
  border: 1px solid var(--rule);
  border-radius: var(--r);
  padding: 0.85rem 1rem;
  cursor: pointer;
  transition: border-color 0.15s;
  text-decoration: none;
  display: block;
  color: inherit;
}
.topic-card:hover { border-color: var(--blue); }
.topic-card-title { font-size: 0.82rem; font-weight: 500; color: var(--ink); margin-bottom: 0.25rem; }
.topic-card-desc  { font-size: 0.68rem; color: var(--ink3); line-height: 1.5; margin-bottom: 0.5rem; }
.topic-card-tags  { display: flex; flex-wrap: wrap; gap: 0.3rem; }

/* ── SIDEBAR ── */
.sb-section { margin-bottom: 1.25rem; }
.sb-label { font-size: 0.58rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink4); margin-bottom: 0.5rem; display: block; }
.sb-concept, .sb-field, .sb-widget-link {
  display: block;
  font-size: 0.7rem;
  padding: 0.3rem 0.6rem;
  border-radius: 6px;
  margin-bottom: 0.3rem;
  text-decoration: none;
  cursor: pointer;
}
.sb-concept     { border: 1px solid var(--green-soft);  color: var(--green);  background: #f0fdf5; }
.sb-field       { border: 1px solid var(--purple-soft); color: var(--purple); background: #faf7ff; }
.sb-widget-link { border: 1px solid var(--amber-soft);  color: var(--amber);  background: #fff8f4; }
.sb-concept:hover     { border-color: var(--green);  }
.sb-field:hover       { border-color: var(--purple); }
.sb-widget-link:hover { border-color: var(--amber);  }
.sb-divider { height: 1px; background: var(--rule); margin: 1rem 0; }
.difficulty-bar { display: flex; gap: 3px; margin-top: 0.35rem; }
.diff-pip     { height: 4px; flex: 1; border-radius: 2px; background: var(--rule); }
.diff-pip.on  { background: var(--blue); }

/* ── CHIPS ── */
.chip { display: inline-block; font-size: 0.6rem; padding: 0.15rem 0.55rem; border-radius: 20px; font-weight: 400; letter-spacing: 0.02em; }
.chip-blue   { background: var(--blue-soft);   color: var(--blue); }
.chip-green  { background: var(--green-soft);  color: var(--green); }
.chip-purple { background: var(--purple-soft); color: var(--purple); }
.chip-amber  { background: var(--amber-soft);  color: var(--amber); }
.chip-pink   { background: var(--pink-soft);   color: var(--pink); }
.chip-teal   { background: var(--teal-soft);   color: var(--teal); }
.chip-gray   { background: #f0ede8;            color: #666; }
/* category colour aliases */
.chip-cs      { background: var(--blue-soft);   color: var(--blue); }
.chip-finance { background: var(--green-soft);  color: var(--green); }
.chip-life    { background: var(--purple-soft); color: var(--purple); }
.chip-physics { background: var(--amber-soft);  color: var(--amber); }
.chip-earth   { background: #ccfbf1;            color: #0f766e; }
.chip-social  { background: var(--pink-soft);   color: var(--pink); }

/* ── NOTE BLOCK ── */
.note-block {
  background: var(--white);
  border-left: 2px solid var(--blue);
  padding: 0.75rem 1rem;
  font-size: 0.72rem;
  color: var(--ink2);
  line-height: 1.7;
  border-radius: 0 var(--r) var(--r) 0;
  margin-top: 1rem;
}
.note-block strong { color: var(--blue); }

/* ── PAGE WRAPPERS ── */
.page-wrap { max-width: 960px; margin: 0 auto; padding: 2.5rem 2rem; }
.section-eyebrow { font-size: 0.6rem; letter-spacing: 0.14em; text-transform: uppercase; color: var(--blue); font-weight: 500; margin-bottom: 0.5rem; }
.section-title   { font-family: var(--serif); font-size: 1.75rem; font-weight: 400; color: var(--ink); margin-bottom: 0.4rem; }
.section-sub     { font-size: 0.78rem; color: var(--ink3); margin-bottom: 2rem; line-height: 1.6; }
.rule-h { border: none; border-top: 1px solid var(--rule); margin: 2rem 0; }

/* ── 404 ── */
.error-page { text-align: center; padding: 6rem 2rem; }
.error-page h1 { font-family: var(--serif); font-size: 4rem; font-weight: 400; color: var(--ink); }
.error-page p  { font-size: 0.85rem; color: var(--ink3); margin: 1rem 0 2rem; }

/* ── RESPONSIVE ── */
@media (max-width: 720px) {
  .fp-body { grid-template-columns: 1fr; }
  .fp-sidebar { display: none; }
  .topics-grid { grid-template-columns: 1fr; }
  .fields-grid { grid-template-columns: 1fr 1fr; }
  .nav-links { gap: 1rem; }

  /* Stack hero above graph on mobile */
  .l-graph-area { display: flex; flex-direction: column; }
  .l-headline {
    position: relative !important;
    top: auto !important;
    left: auto !important;
    transform: none !important;
    flex-shrink: 0;
    text-align: center;
    max-width: 100%;
    padding: 0.6rem 1.25rem 0.4rem;
    pointer-events: auto;
  }
  .l-headline h1 { font-size: 1.3rem; }
  .l-headline p  { font-size: 0.62rem; }
  .l-hero-eq { display: none; }
  #landing-svg { flex: 1; min-height: 0; }
}