@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Serif:ital,wght@0,300;0,400;0,600;1,300;1,400&family=IBM+Plex+Mono:wght@400;500&family=Source+Sans+3:wght@300;400;600&display=swap');

:root {
  --ink:         #1a1a1a;
  --ink-mid:     #444;
  --ink-light:   #777;
  --rule:        #ddd;
  --bg:          #fafaf8;
  --bg-surface:  #ffffff;
  --bg-tint:     #f4f4f0;
  --accent:      #1a3a5c;
  --accent-mid:  #2a5a8c;
  --accent-light:#e8eef5;
  --red:         #c0392b;
  --green:       #1a6640;
  --amber:       #8a5a00;
  --serif:       'IBM Plex Serif', Georgia, serif;
  --sans:        'Source Sans 3', system-ui, sans-serif;
  --mono:        'IBM Plex Mono', 'Courier New', monospace;
  --max-w:       860px;
  --nav-h:       56px;
  --radius:      4px;
  --transition:  0.18s ease;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body { font-family: var(--sans); font-weight: 400; color: var(--ink); background: var(--bg); line-height: 1.7; -webkit-font-smoothing: antialiased; }
img { max-width: 100%; display: block; }
a { color: var(--accent-mid); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent); }

/* ── Nav ──────────────────────────────────────────────────── */
.site-nav {
  position: sticky; top: 0; z-index: 100;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--rule);
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.25rem;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  gap: 0;
}
.nav-brand {
  font-family: var(--serif); font-weight: 600; font-size: 0.95rem;
  color: var(--accent); text-decoration: none;
  margin-right: 1.25rem; white-space: nowrap; flex-shrink: 0;
}
.nav-brand span { font-weight: 300; color: var(--ink-mid); }

.nav-links {
  display: flex; list-style: none; align-items: stretch;
  flex: 1; overflow: hidden;
}
.nav-links li { display: flex; align-items: stretch; }
.nav-links a {
  display: flex; align-items: center;
  padding: 0 0.55rem;
  font-size: 0.68rem; font-weight: 600;
  letter-spacing: 0.05em; text-transform: uppercase;
  color: var(--ink-mid); text-decoration: none;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  transition: color var(--transition), border-color var(--transition);
  height: var(--nav-h);
}
.nav-links a:hover, .nav-links a.active {
  color: var(--accent); border-bottom-color: var(--accent);
}
.nav-links a.external::after { content: ' ↗'; font-size: 0.7em; opacity: 0.6; }

/* Hamburger button — hidden on desktop */
.nav-toggle {
  display: none;
  margin-left: auto;
  background: none; border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 0.3rem 0.5rem; cursor: pointer;
  color: var(--ink-mid); font-size: 1rem; line-height: 1;
}

/* Mobile nav drawer */
@media (max-width: 820px) {
  .nav-inner { height: var(--nav-h); }
  .nav-toggle { display: flex; align-items: center; }
  .nav-links {
    display: none;
    position: absolute; top: var(--nav-h); left: 0; right: 0;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--rule);
    flex-direction: column;
    padding: 0.5rem 0;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    overflow: visible;
  }
  .nav-links.open { display: flex; }
  .nav-links li { width: 100%; }
  .nav-links a {
    height: auto; padding: 0.65rem 1.5rem;
    font-size: 0.75rem; border-bottom: none;
    border-left: 3px solid transparent;
  }
  .nav-links a:hover, .nav-links a.active {
    border-bottom: none; border-left-color: var(--accent);
    background: var(--accent-light);
  }
}

/* ── Hero ─────────────────────────────────────────────────── */
.hero { background: var(--bg-surface); border-bottom: 1px solid var(--rule); padding: 4rem 1.5rem 3.5rem; }
.hero-inner { max-width: var(--max-w); margin: 0 auto; }
.hero-label { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--accent-mid); margin-bottom: 1rem; }
.hero h1 { font-family: var(--serif); font-weight: 300; font-size: clamp(1.8rem, 4vw, 2.6rem); line-height: 1.2; color: var(--ink); margin-bottom: 0.5rem; max-width: 680px; }
.hero h1 em { font-style: italic; color: var(--accent); }
.hero-subtitle { font-size: 1rem; color: var(--ink-mid); max-width: 560px; margin-bottom: 2rem; }
.hero-meta { display: flex; flex-wrap: wrap; gap: 1.5rem; margin-bottom: 2rem; font-size: 0.85rem; color: var(--ink-light); }
.hero-meta strong { color: var(--ink-mid); font-weight: 600; }
.hero-badges { display: flex; flex-wrap: wrap; gap: 0.5rem; }

/* ── Badges ───────────────────────────────────────────────── */
.badge { display: inline-flex; align-items: center; gap: 0.3rem; padding: 0.3rem 0.75rem; border-radius: var(--radius); font-family: var(--mono); font-size: 0.72rem; font-weight: 500; text-decoration: none; transition: opacity var(--transition); }
.badge:hover { opacity: 0.8; text-decoration: none; }
.badge-primary { background: var(--accent); color: #fff; }
.badge-outline  { background: transparent; border: 1px solid var(--rule); color: var(--ink-mid); }
.badge-green    { background: #e8f5ee; color: var(--green); border: 1px solid #b8ddc8; }
.badge-amber    { background: #fef9e7; color: var(--amber); border: 1px solid #f5d98a; }

/* ── Tags ─────────────────────────────────────────────────── */
.tag { font-family: var(--mono); font-size: 0.62rem; padding: 0.15rem 0.45rem; border-radius: 2px; border: 1px solid var(--rule); color: var(--ink-light); background: var(--bg-tint); }
.tag[href] { text-decoration: none; }
.tag[href]:hover { color: var(--accent); border-color: var(--accent-mid); }
.tag-temporal   { border-color: #aac4e0; color: #1a4a7a; background: #eef4fb; }
.tag-structural { border-color: #b8d4b8; color: #1a5a1a; background: #eef6ee; }
.tag-semantic   { border-color: #e0c8a0; color: #7a5a00; background: #fdf6e8; }

/* ── Abstract section ─────────────────────────────────────── */
.abstract-section { background: var(--bg-tint); border-top: 1px solid var(--rule); border-bottom: 1px solid var(--rule); padding: 2.5rem 1.5rem; }
.abstract-inner { width: min(100%, var(--max-w)); max-width: var(--max-w); margin: 0 auto; }
.abstract-label { font-family: var(--serif); font-style: italic; font-weight: 300; font-size: 1.1rem; color: var(--ink-light); padding-top: 0.15rem; }
.abstract-text { display: block; width: 100%; max-width: 100%; font-size: 0.95rem; color: var(--ink-mid); line-height: 1.8; text-align: left; }

/* ── Highlights strip ─────────────────────────────────────── */
.highlights { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 1px; background: var(--rule); border: 1px solid var(--rule); border-radius: var(--radius); overflow: hidden; margin: 1.5rem 0; }
.highlight-item { background: var(--bg-surface); padding: 1.25rem 1rem; text-align: center; }
.highlight-num { font-family: var(--serif); font-weight: 300; font-size: 2rem; color: var(--accent); line-height: 1; margin-bottom: 0.25rem; }
.highlight-label { font-size: 0.75rem; color: var(--ink-light); line-height: 1.3; }

/* ── Section headers ──────────────────────────────────────── */
.section { padding: 3rem 1.5rem; max-width: var(--max-w); margin: 0 auto; }
.section-header { display: flex; align-items: baseline; gap: 1rem; margin-bottom: 1.75rem; padding-bottom: 0.75rem; border-bottom: 1px solid var(--rule); }
.section-header h2 { font-family: var(--serif); font-weight: 600; font-size: 1.15rem; color: var(--ink); }
.section-count { font-family: var(--mono); font-size: 0.72rem; color: var(--ink-light); margin-left: auto; text-decoration: none; }
.section-count:hover { color: var(--accent); }

/* ── Cards ────────────────────────────────────────────────── */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 1rem; }
.card { background: var(--bg-surface); border: 1px solid var(--rule); border-radius: var(--radius); padding: 1.25rem 1.25rem 1rem; text-decoration: none; color: inherit; display: block; transition: border-color var(--transition), box-shadow var(--transition); }
.card:hover { border-color: var(--accent-mid); box-shadow: 0 2px 8px rgba(26,58,92,0.08); text-decoration: none; }
.card-tag { font-family: var(--mono); font-size: 0.65rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent-mid); margin-bottom: 0.4rem; }
.card h3 { font-family: var(--serif); font-weight: 600; font-size: 0.95rem; color: var(--ink); margin-bottom: 0.4rem; line-height: 1.3; }
.card p { font-size: 0.82rem; color: var(--ink-light); line-height: 1.5; margin-bottom: 0.75rem; }
.card-footer { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.card-contrib { font-size: 0.72rem; color: var(--ink-light); margin-top: 0.6rem; font-family: var(--mono); }

/* ── Detail pages ─────────────────────────────────────────── */
.page-wrap { max-width: var(--max-w); margin: 0 auto; padding: 2.5rem 1.5rem; }
.page-title { font-family: var(--serif); font-weight: 300; font-size: 1.8rem; color: var(--ink); margin-bottom: 0.25rem; }
.page-subtitle { font-size: 0.9rem; color: var(--ink-light); margin-bottom: 2rem; padding-bottom: 1.5rem; border-bottom: 1px solid var(--rule); }
.back-link { font-size: 0.82rem; color: var(--ink-light); text-decoration: none; }
.back-link:hover { color: var(--accent-mid); }

.detail-header { margin: 1.25rem 0 1.5rem; padding-bottom: 1.25rem; border-bottom: 1px solid var(--rule); }
.detail-id { font-family: var(--mono); font-size: 0.72rem; color: var(--accent-mid); letter-spacing: 0.08em; text-transform: uppercase; margin-bottom: 0.4rem; }
.detail-title { font-family: var(--serif); font-weight: 600; font-size: 1.5rem; color: var(--ink); margin-bottom: 0.75rem; }
.detail-meta { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 0.6rem; }
.contrib-line { font-size: 0.78rem; color: var(--ink-light); margin-top: 0.5rem; }
.contrib-line strong { color: var(--ink-mid); font-weight: 600; }
.contrib-line a { color: var(--accent-mid); }

/* ── Artifact strip ───────────────────────────────────────── */
.artifact-strip { display: flex; flex-wrap: wrap; align-items: center; gap: 0.4rem; margin-bottom: 1.5rem; padding: 0.75rem 1rem; background: var(--bg-tint); border: 1px solid var(--rule); border-radius: var(--radius); }
.artifact-strip-label { font-family: var(--mono); font-size: 0.65rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-light); margin-right: 0.25rem; }

/* ── Invariant box ────────────────────────────────────────── */
.invariant-box { background: var(--accent-light); border: 1px solid #c0d4e8; border-left: 3px solid var(--accent); border-radius: var(--radius); padding: 1rem 1.25rem; margin-bottom: 1.5rem; }
.invariant-label { font-family: var(--mono); font-size: 0.65rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent-mid); margin-bottom: 0.3rem; }
.invariant-value { font-family: var(--mono); font-size: 0.84rem; color: var(--ink); }

/* ── Steps ────────────────────────────────────────────────── */
.steps { display: flex; flex-direction: column; }
.step { display: grid; grid-template-columns: 2.5rem 1fr; gap: 1rem; padding: 1.25rem 0; border-bottom: 1px solid var(--rule); }
.step:last-child { border-bottom: none; }
.step-num { width: 2rem; height: 2rem; border-radius: 50%; border: 1.5px solid var(--accent); display: flex; align-items: center; justify-content: center; font-family: var(--mono); font-size: 0.75rem; font-weight: 500; color: var(--accent); flex-shrink: 0; margin-top: 0.1rem; }
.step-content h3 { font-family: var(--sans); font-weight: 600; font-size: 0.95rem; margin-bottom: 0.35rem; color: var(--ink); }
.step-content p { font-size: 0.88rem; color: var(--ink-mid); margin-bottom: 0.5rem; }

/* ── Code ─────────────────────────────────────────────────── */
pre, code { font-family: var(--mono); font-size: 0.82rem; }
pre { background: #f0f0ec; border: 1px solid #ddd; border-left: 3px solid var(--accent); border-radius: var(--radius); padding: 1rem 1.1rem; overflow-x: auto; line-height: 1.6; margin: 0.75rem 0; }
code { background: #f0f0ec; padding: 0.1em 0.35em; border-radius: 2px; color: var(--accent); }
pre code { background: none; padding: 0; color: inherit; }

/* ── Prose ────────────────────────────────────────────────── */
.prose h2 { font-family: var(--serif); font-weight: 600; font-size: 1.1rem; margin: 2rem 0 0.6rem; color: var(--ink); }
.prose h3 { font-family: var(--sans); font-weight: 600; font-size: 0.95rem; margin: 1.5rem 0 0.4rem; color: var(--ink-mid); }
.prose p  { margin-bottom: 0.9rem; font-size: 0.92rem; line-height: 1.8; color: var(--ink-mid); }
.prose ul, .prose ol { margin: 0.5rem 0 0.9rem 1.4rem; font-size: 0.92rem; color: var(--ink-mid); }
.prose li { margin-bottom: 0.25rem; }
.prose table { width: 100%; border-collapse: collapse; margin: 1rem 0; font-size: 0.82rem; }
.prose th { background: var(--bg-tint); border: 1px solid var(--rule); padding: 0.5rem 0.75rem; text-align: left; font-weight: 600; color: var(--ink); }
.prose td { border: 1px solid var(--rule); padding: 0.45rem 0.75rem; color: var(--ink-mid); }

/* ── Citation ─────────────────────────────────────────────── */
.citation-box { background: var(--bg-tint); border: 1px solid var(--rule); border-left: 3px solid var(--accent); border-radius: var(--radius); padding: 1.1rem 1.25rem; font-family: var(--mono); font-size: 0.75rem; line-height: 1.8; color: var(--ink-mid); }
.citation-copy { background: none; border: 1px solid var(--rule); border-radius: var(--radius); padding: 0.25rem 0.6rem; font-family: var(--mono); font-size: 0.65rem; color: var(--ink-light); cursor: pointer; margin-top: 0.5rem; transition: all var(--transition); }
.citation-copy:hover { background: var(--accent); color: #fff; border-color: var(--accent); }

/* ── Filter bar ───────────────────────────────────────────── */
.filter-bar { display: flex; gap: 0.5rem; flex-wrap: wrap; margin-bottom: 1.75rem; }
.filter-btn { font-family: var(--mono); font-size: 0.72rem; padding: 0.3rem 0.75rem; border-radius: 3px; cursor: pointer; transition: all var(--transition); }
.filter-btn.active-filter { background: var(--accent) !important; color: #fff !important; border-color: var(--accent) !important; }

/* ── Instantiator list (index) ────────────────────────────── */
.inst-list { display: flex; flex-direction: column; gap: 0; border: 1px solid var(--rule); border-radius: var(--radius); overflow: hidden; }
.inst-row {
  display: flex; align-items: flex-start; justify-content: space-between; gap: 1.5rem;
  padding: 1rem 1.25rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--rule);
  text-decoration: none; color: inherit;
  transition: background var(--transition);
}
.inst-row:last-child { border-bottom: none; }
.inst-row:hover { background: var(--accent-light); text-decoration: none; }
.inst-row-left { flex: 1; min-width: 0; }
.inst-row-id { font-family: var(--mono); font-size: 0.62rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent-mid); margin-bottom: 0.2rem; }
.inst-row-title { font-family: var(--serif); font-weight: 600; font-size: 0.95rem; color: var(--ink); margin-bottom: 0.25rem; }
.inst-row-note { font-size: 0.78rem; color: var(--ink-light); line-height: 1.5; }
.inst-row-right { display: flex; flex-wrap: wrap; align-items: center; gap: 0.35rem; flex-shrink: 0; padding-top: 0.15rem; }

/* ── Instantiator detail ──────────────────────────────────── */
.inst-note-box {
  background: var(--bg-tint); border: 1px solid var(--rule);
  border-left: 3px solid var(--accent-mid);
  border-radius: var(--radius); padding: 0.75rem 1rem; margin-bottom: 1.25rem;
}
.inst-note-label { font-family: var(--mono); font-size: 0.62rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-light); margin-bottom: 0.2rem; }
.inst-note-text { font-size: 0.84rem; color: var(--ink-mid); line-height: 1.6; }

.inst-action-row { display: flex; gap: 0.75rem; flex-wrap: wrap; margin-bottom: 1.25rem; }
.inst-dl-btn {
  display: inline-flex; align-items: center; gap: 0.6rem;
  padding: 0.55rem 1rem;
  background: var(--bg-surface); border: 1px solid var(--rule);
  border-radius: var(--radius);
  text-decoration: none; color: inherit;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.inst-dl-btn:hover { border-color: var(--accent-mid); box-shadow: 0 1px 4px rgba(26,58,92,0.1); text-decoration: none; }
.inst-dl-icon { font-size: 1rem; color: var(--accent-mid); line-height: 1; }
.inst-dl-label { display: block; font-family: var(--mono); font-size: 0.6rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-light); }
.inst-dl-name { display: block; font-family: var(--mono); font-size: 0.78rem; color: var(--accent-mid); font-weight: 500; }

.inst-deps {
  font-size: 0.8rem; color: var(--ink-light); margin-bottom: 1.5rem;
  display: flex; align-items: center; gap: 0.4rem; flex-wrap: wrap;
}
.inst-deps-label {
  font-family: var(--mono); font-size: 0.62rem; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--ink-light);
  margin-right: 0.25rem;
}
.inst-deps code { font-size: 0.78rem; }

/* ── Contribution level cards ─────────────────────────────── */
.contrib-levels { display:flex; flex-direction:column; gap:0; border:1px solid var(--rule); border-radius:var(--radius); overflow:hidden; margin-bottom:0; }
.contrib-level { display:flex; gap:1.25rem; padding:1.25rem 1.5rem; background:var(--bg-surface); border-bottom:1px solid var(--rule); align-items:flex-start; }
.contrib-level:last-child { border-bottom:none; }
.contrib-level-badge {
  flex-shrink:0; width:4.5rem; text-align:center;
  font-family:var(--mono); font-size:0.62rem; font-weight:500;
  letter-spacing:0.06em; text-transform:uppercase;
  padding:0.3rem 0.5rem; border-radius:var(--radius);
  border:1px solid var(--rule); color:var(--ink-light);
  background:var(--bg-tint); margin-top:0.1rem;
}
.contrib-level-badge.level-2 { background:#eef4fb; border-color:#aac4e0; color:#1a4a7a; }
.contrib-level-badge.level-3 { background:#eef6ee; border-color:#b8d4b8; color:#1a5a1a; }
.contrib-level-body { flex:1; min-width:0; }
.contrib-level-title { font-family:var(--serif); font-weight:600; font-size:0.98rem; color:var(--ink); margin-bottom:0.4rem; }
.contrib-level-desc { font-size:0.86rem; color:var(--ink-mid); line-height:1.7; margin-bottom:0; }

/* ── Footer ───────────────────────────────────────────────── */
.site-footer { margin-top: 4rem; border-top: 1px solid var(--rule); background: var(--bg-surface); padding: 2rem 1.5rem; }
.footer-inner { max-width: var(--max-w); margin: 0 auto; display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 1rem; font-size: 0.78rem; color: var(--ink-light); }
.footer-inner a { color: var(--ink-light); }
.footer-links { display: flex; gap: 1.5rem; }

/* ── Responsive ───────────────────────────────────────────── */
@media (max-width: 640px) {
  .abstract-inner { grid-template-columns: 1fr; gap: 0.5rem; }
  .hero { padding: 2.5rem 1.25rem 2rem; }
  .card-grid { grid-template-columns: 1fr; }
}