/* ==========================================================================
   OrientDig Spreadsheet — Research Strata / Source Dig theme
   Light sandstone · deep coal black · mineral teal · terracotta · ultramarine · magenta
   ========================================================================== */

:root {
  /* palette */
  --sand:        #EFE9DC;
  --sand-2:      #E6DFCF;
  --sand-3:      #DCD3BF;
  --ink:         #201E1B;
  --ink-2:       #161512;
  --ink-soft:    #4E4A43;
  --ink-faint:   #948C7E;
  --teal:        #208A6E;
  --teal-d:      #176D55;
  --teal-s:      #DDF0E9;
  --terra:       #C4582A;
  --terra-d:     #A84622;
  --terra-s:     #F7E2D6;
  --ultra:       #3546B5;
  --ultra-d:     #273492;
  --ultra-s:     #E3E7F8;
  --magenta:     #C23B72;
  --magenta-s:   #F8E0EC;
  --line:        #DDD4C2;
  --line-soft:   #E8E0D0;

  /* typography */
  --serif: Georgia, 'Times New Roman', Times, serif;
  --sans: system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, monospace;

  /* geometry */
  --radius: 14px;
  --radius-sm: 8px;
  --container: 1140px;
  --shadow-sm: 0 1px 2px rgba(32, 30, 27, 0.05), 0 2px 8px rgba(32, 30, 27, 0.06);
  --shadow-md: 0 4px 14px rgba(32, 30, 27, 0.10), 0 12px 32px rgba(32, 30, 27, 0.08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--sans);
  font-size: 16.5px;
  line-height: 1.65;
  color: var(--ink);
  background: var(--sand);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ---------- accessibility ---------- */
.skip-link { position: absolute; left: -9999px; top: 0; background: var(--ink); color: #fff; padding: 10px 16px; z-index: 200; border-radius: 0 0 var(--radius-sm) 0; }
.skip-link:focus { left: 0; }
:focus-visible { outline: 3px solid var(--teal); outline-offset: 2px; border-radius: 3px; }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; margin: -1px; padding: 0; border: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------- layout ---------- */
.container { max-width: var(--container); margin: 0 auto; padding: 0 22px; }

/* ---------- header ---------- */
.site-header { position: sticky; top: 0; z-index: 100; background: rgba(239, 233, 220, 0.92); backdrop-filter: saturate(140%) blur(8px); border-bottom: 1px solid var(--line-soft); }
.header-inner { display: flex; align-items: center; gap: 20px; height: 66px; }
.brand { display: flex; align-items: center; gap: 11px; text-decoration: none; color: var(--ink); }
.brand img { width: 34px; height: 34px; display: block; border-radius: 7px; }
.brand-name { font-family: var(--serif); font-weight: 700; font-size: 1.06rem; letter-spacing: 0.01em; }
.brand-name small { display: block; font-family: var(--sans); font-weight: 600; font-size: 0.66rem; color: var(--ink-faint); letter-spacing: 0.14em; text-transform: uppercase; }

.main-nav { margin-left: auto; }
.main-nav ul { display: flex; align-items: center; gap: 4px; list-style: none; margin: 0; padding: 0; }
.main-nav a { display: block; padding: 8px 12px; text-decoration: none; color: var(--ink-soft); font-weight: 600; font-size: 0.9rem; border-radius: var(--radius-sm); }
.main-nav a:hover { background: var(--sand-2); color: var(--ink); }
.main-nav a.active { color: var(--terra-d); background: var(--terra-s); }

.mobile-nav-toggle { display: none; margin-left: auto; width: 44px; height: 44px; border: 1px solid var(--line); background: #fff; border-radius: var(--radius-sm); cursor: pointer; color: var(--ink); }
.mobile-nav-toggle svg { display: block; margin: 0 auto; }

@media (max-width: 860px) {
  .main-nav { display: none; }
  .mobile-nav-toggle { display: block; }
  .main-nav.open { display: block; position: absolute; left: 0; right: 0; top: 66px; background: #fff; border-bottom: 1px solid var(--line); box-shadow: var(--shadow-md); }
  .main-nav.open ul { flex-direction: column; align-items: stretch; gap: 2px; padding: 8px; }
  .main-nav.open a { padding: 12px 14px; }
}

/* ---------- buttons ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 12px 22px; border-radius: 999px; text-decoration: none; font-weight: 700; font-size: 0.98rem; line-height: 1.2; border: 1.5px solid transparent; transition: transform 0.12s ease, box-shadow 0.12s ease, background 0.12s ease; }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--terra); color: #fff; box-shadow: 0 4px 14px rgba(196, 88, 42, 0.30); }
.btn-primary:hover { background: var(--terra-d); box-shadow: 0 6px 18px rgba(196, 88, 42, 0.38); }
.btn-secondary { background: #fff; color: var(--ink); border-color: var(--line); box-shadow: var(--shadow-sm); }
.btn-secondary:hover { border-color: var(--ink-soft); background: #fff; }
.btn-sm { padding: 9px 16px; font-size: 0.88rem; }

/* ---------- hero ---------- */
.hero-section { padding: 56px 0 44px; position: relative; overflow: hidden; background: radial-gradient(circle at 85% 8%, var(--teal-s) 0, transparent 42%), radial-gradient(circle at 6% 92%, var(--ultra-s) 0, transparent 40%); }
.hero-grid { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 44px; align-items: center; }
.hero-badge { display: inline-block; padding: 5px 13px; border-radius: 999px; background: var(--teal-s); color: var(--teal-d); font-weight: 700; font-size: 0.76rem; letter-spacing: 0.08em; text-transform: uppercase; }
.hero-title { font-family: var(--serif); font-size: clamp(2.05rem, 4.6vw, 3.1rem); line-height: 1.12; color: var(--ink-2); margin: 18px 0 16px; font-weight: 700; }
.hero-title em { font-style: normal; color: var(--terra); }
.hero-description { font-size: 1.08rem; color: var(--ink-soft); max-width: 34em; margin: 0 0 26px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; }

/* hero strata cross-section visual */
.hero-visual { position: relative; display: flex; justify-content: center; }
.strata-hero { position: relative; width: 240px; }
.sh-band { position: relative; height: 64px; border-radius: 6px; margin-bottom: 6px; display: flex; align-items: center; padding: 0 14px; font-family: var(--mono); font-size: 0.72rem; font-weight: 700; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink); border: 1px solid rgba(32,30,27,0.12); }
.sh-surface { background: repeating-linear-gradient(0deg, #EADFC8 0 6px, #F1E8D2 6px 12px); color: #5c5340; }
.sh-context { background: var(--teal-s); color: var(--teal-d); }
.sh-destination { background: var(--ultra-s); color: var(--ultra-d); }
.sh-unknown { background: repeating-linear-gradient(-45deg, #F3D8E6 0 6px, #F8E0EC 6px 12px); color: #9c2f5f; }
.sh-coreline { position: absolute; top: 6px; bottom: 6px; left: 50%; transform: translateX(-50%); width: 0; border-left: 2px dashed var(--ink-faint); }
.sh-coreline::before, .sh-coreline::after { content: ""; position: absolute; left: -4px; width: 6px; height: 6px; border-radius: 50%; background: var(--terra); }
.sh-coreline::before { top: -3px; }
.sh-coreline::after { bottom: -3px; }

@media (max-width: 860px) {
  .hero-grid { grid-template-columns: 1fr; gap: 26px; }
  .hero-section { padding-top: 34px; }
}

/* ---------- section scaffolding ---------- */
.section { padding: 46px 0; }
.section-alt { background: var(--sand-2); }
.section-header { max-width: 680px; margin: 0 auto 34px; text-align: center; }
.eyebrow { display: inline-block; font-size: 0.76rem; font-weight: 700; letter-spacing: 0.14em; text-transform: uppercase; color: var(--teal-d); }
.section-title { font-family: var(--serif); font-size: clamp(1.6rem, 3.4vw, 2.15rem); color: var(--ink-2); margin: 10px 0 12px; line-height: 1.2; }
.section-lead { color: var(--ink-soft); font-size: 1.02rem; margin: 0; }

/* ---------- category grid (specimen archive labels) ---------- */
.categories-section { padding-top: 10px; }
.cat-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.cat-card {
  position: relative; display: flex; flex-direction: column; gap: 9px;
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  padding: 15px 16px 14px; text-decoration: none; color: var(--ink);
  box-shadow: var(--shadow-sm); transition: transform 0.14s ease, box-shadow 0.14s ease, border-color 0.14s ease;
}
.cat-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--teal); }
.cat-top { display: flex; align-items: flex-start; justify-content: space-between; }
.cat-code { font-family: var(--mono); font-size: 0.72rem; color: var(--ink-faint); letter-spacing: 0.06em; }
.cat-spec { font-family: var(--serif); font-size: 1.5rem; font-weight: 800; color: var(--ink-2); line-height: 1; }
.cat-icon { width: 28px; height: 28px; color: var(--teal-d); }
.cat-icon svg { width: 100%; height: 100%; }
.cat-name { font-weight: 700; color: var(--ink-2); font-size: 0.97rem; line-height: 1.3; }
.cat-card .cat-arrow { margin-top: auto; font-size: 0.8rem; font-weight: 700; color: var(--teal-d); }
.cat-card::after { content: ""; position: absolute; top: 8px; right: 8px; width: 9px; height: 9px; border: 1.5px solid var(--ink-faint); border-radius: 50%; opacity: 0.45; }

@media (max-width: 900px) {
  .cat-grid { grid-template-columns: repeat(2, 1fr); gap: 12px; }
  .cat-card { padding: 13px 13px 12px; }
}

/* ---------- four-layer strata module ---------- */
.strata { display: flex; align-items: stretch; gap: 0; max-width: 920px; margin: 0 auto; }
.strata-step { flex: 1; display: flex; flex-direction: column; align-items: center; text-align: center; gap: 8px; padding: 0 8px; }
.strata-band { width: 100%; height: 14px; border-radius: 4px; }
.strata-step[data-s="1"] .strata-band { background: repeating-linear-gradient(0deg, #E4D8BF 0 4px, #F1E8D2 4px 8px); }
.strata-step[data-s="2"] .strata-band { background: var(--teal); }
.strata-step[data-s="3"] .strata-band { background: var(--ultra); }
.strata-step[data-s="4"] .strata-band { background: repeating-linear-gradient(-45deg, #E8A6C4 0 4px, #F3D8E6 4px 8px); }
.strata-dot { width: 38px; height: 38px; border-radius: 50%; display: grid; place-items: center; font-family: var(--mono); font-weight: 800; font-size: 0.8rem; color: #fff; background: var(--ink-2); }
.strata-label { font-weight: 700; color: var(--ink-2); font-size: 0.92rem; }
.strata-desc { color: var(--ink-soft); font-size: 0.84rem; }
.strata-arrow { flex: none; align-self: center; color: var(--terra); font-size: 1.4rem; font-weight: 800; padding: 0 2px; }
@media (max-width: 720px) {
  .strata { flex-direction: column; gap: 0; }
  .strata-step { flex-direction: row; align-items: center; text-align: left; gap: 12px; padding: 8px 0; }
  .strata-band { width: 14px; height: 40px; flex: none; }
  .strata-arrow { transform: rotate(90deg); align-self: center; }
}

/* ---------- signatures ---------- */
.sample-code { display: inline-block; font-family: var(--mono); font-size: 0.68rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; padding: 3px 8px; border-radius: 4px; background: var(--sand-2); color: var(--ink-soft); border: 1px solid var(--line); }
.archive-stamp { display: inline-block; font-family: var(--mono); font-size: 0.66rem; font-weight: 800; letter-spacing: 0.08em; text-transform: uppercase; padding: 4px 10px; border: 2px solid var(--terra); color: var(--terra-d); border-radius: 4px; transform: rotate(-3deg); }
.grid-coord { font-family: var(--mono); font-size: 0.74rem; color: var(--ink-faint); letter-spacing: 0.08em; }
.field-note { border-left: 3px solid var(--teal); background: var(--teal-s); padding: 14px 16px; border-radius: 0 var(--radius-sm) var(--radius-sm) 0; margin: 18px 0; font-size: 0.94rem; color: #12503D; }
.field-note strong { display: block; font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase; margin-bottom: 4px; color: var(--teal-d); }

.open-note { display: inline-flex; align-items: center; gap: 9px; padding: 10px 14px; border: 1px dashed var(--magenta); border-radius: var(--radius-sm); background: var(--magenta-s); color: #8A2152; font-weight: 600; font-size: 0.92rem; margin: 10px 0; }
.open-note .qmark { flex: none; width: 24px; height: 24px; border-radius: 50%; background: var(--magenta); color: #fff; display: grid; place-items: center; font-weight: 800; }

.example-flag { display: inline-block; margin-top: 14px; font-size: 0.74rem; color: var(--ink-faint); font-style: italic; border-top: 1px dashed var(--line); padding-top: 8px; }

/* ---------- duo grid ---------- */
.duo-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.duo-col { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 22px; }
.duo-col h3 { margin: 0 0 10px; font-size: 1.02rem; display: flex; align-items: center; gap: 9px; color: var(--ink-2); }
.duo-col ul { margin: 0; padding-left: 18px; color: var(--ink-soft); font-size: 0.94rem; }
.duo-col ul li { margin: 6px 0; }
.duo-col .mark { flex: none; width: 22px; height: 22px; border-radius: 5px; display: grid; place-items: center; font-size: 0.78rem; color: #fff; font-family: var(--mono); }
.duo-col.is-a .mark { background: var(--teal); }
.duo-col.is-b .mark { background: var(--ultra); }
@media (max-width: 720px) { .duo-grid { grid-template-columns: 1fr; } }

/* ---------- stop digging when ---------- */
.stop-list { list-style: none; margin: 0; padding: 0; max-width: 760px; margin-inline: auto; }
.stop-list li { display: flex; gap: 14px; align-items: flex-start; padding: 14px 16px; margin: 10px 0; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow-sm); }
.stop-list .s-num { flex: none; width: 30px; height: 30px; border-radius: 50%; display: grid; place-items: center; background: var(--magenta-s); color: var(--magenta); font-weight: 800; font-size: 0.82rem; font-family: var(--mono); }
.stop-list p { margin: 0; color: var(--ink-soft); font-size: 0.96rem; }
.stop-list strong { color: var(--ink-2); }

/* ---------- guide entry cards ---------- */
.guide-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.guide-card { display: flex; flex-direction: column; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 24px 22px; text-decoration: none; color: var(--ink); box-shadow: var(--shadow-sm); transition: transform 0.14s ease, box-shadow 0.14s ease; }
.guide-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); }
.guide-card .guide-num { font-family: var(--mono); font-size: 0.78rem; color: var(--ultra-d); letter-spacing: 0.1em; }
.guide-card h3 { font-family: var(--serif); font-size: 1.24rem; color: var(--ink-2); margin: 8px 0 10px; }
.guide-card p { color: var(--ink-soft); font-size: 0.95rem; margin: 0 0 16px; }
.guide-card .guide-cta { margin-top: auto; font-weight: 700; color: var(--terra-d); font-size: 0.9rem; }
@media (max-width: 900px) { .guide-grid { grid-template-columns: 1fr; } }

/* ---------- FAQ ---------- */
.faq-list { max-width: 760px; margin: 0 auto; }
details.faq-item { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); margin: 10px 0; box-shadow: var(--shadow-sm); overflow: hidden; }
details.faq-item summary { cursor: pointer; list-style: none; padding: 16px 20px; font-weight: 700; color: var(--ink-2); display: flex; align-items: center; justify-content: space-between; gap: 14px; }
details.faq-item summary::-webkit-details-marker { display: none; }
details.faq-item summary::after { content: "+"; font-size: 1.5rem; font-weight: 400; color: var(--terra); line-height: 1; }
details.faq-item[open] summary::after { content: "–"; }
.faq-item .faq-body { padding: 0 20px 18px; color: var(--ink-soft); font-size: 0.96rem; }
.faq-item .faq-body p { margin: 0 0 10px; }

/* ---------- final CTA ---------- */
.final-cta { background: var(--ink-2); color: #fff; border-radius: 20px; padding: 44px 40px; text-align: center; position: relative; overflow: hidden; }
.final-cta::before { content: ""; position: absolute; inset: 0; opacity: 0.35; background: radial-gradient(circle at 15% 20%, var(--teal) 0, transparent 40%), radial-gradient(circle at 85% 80%, var(--ultra) 0, transparent 40%); }
.final-cta h2 { font-family: var(--serif); font-size: clamp(1.5rem, 3.2vw, 2.1rem); margin: 0 0 12px; position: relative; }
.final-cta p { color: rgba(255,255,255,0.82); max-width: 30em; margin: 0 auto 24px; position: relative; }
.final-cta .btn-primary { position: relative; }

/* ---------- footer ---------- */
.site-footer { border-top: 1px solid var(--line); background: var(--sand-2); padding: 44px 0 30px; margin-top: 30px; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 30px; }
.footer-brand p { color: var(--ink-soft); font-size: 0.92rem; max-width: 34em; }
.footer-col h4 { font-size: 0.78rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-faint); margin: 0 0 12px; }
.footer-col ul { list-style: none; margin: 0; padding: 0; }
.footer-col a { color: var(--ink-soft); text-decoration: none; font-size: 0.94rem; line-height: 2.1; }
.footer-col a:hover { color: var(--terra-d); }
.footer-bottom { margin-top: 28px; padding-top: 20px; border-top: 1px solid var(--line-soft); font-size: 0.82rem; color: var(--ink-faint); display: flex; flex-wrap: wrap; gap: 8px 20px; justify-content: space-between; }
@media (max-width: 720px) { .footer-grid { grid-template-columns: 1fr; } }

/* ---------- article / guide pages ---------- */
.page-hero { background: radial-gradient(circle at 80% 10%, var(--teal-s) 0, transparent 45%), var(--ink-2); color: #fff; padding: 48px 0 40px; position: relative; overflow: hidden; }
.page-hero .container { position: relative; }
.page-hero h1 { font-family: var(--serif); font-size: clamp(1.8rem, 4vw, 2.6rem); margin: 12px 0 12px; line-height: 1.15; color: #fff; }
.page-hero p { color: rgba(255,255,255,0.82); max-width: 40em; font-size: 1.05rem; }

.article-body { max-width: 760px; margin: 0 auto; padding: 40px 22px 60px; }
.article-body h2 { font-family: var(--serif); font-size: 1.5rem; color: var(--ink-2); margin: 38px 0 12px; }
.article-body h3 { font-size: 1.12rem; color: var(--ink-2); margin: 26px 0 8px; }
.article-body p { color: var(--ink-soft); margin: 0 0 16px; }
.article-body ul, .article-body ol { color: var(--ink-soft); margin: 0 0 18px; padding-left: 22px; }
.article-body li { margin: 6px 0; }
.article-body blockquote { margin: 22px 0; padding: 16px 20px; background: var(--sand-2); border-left: 4px solid var(--teal); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; color: var(--ink-soft); font-family: var(--serif); font-size: 1.06rem; }

.back-link { display: inline-flex; align-items: center; gap: 6px; color: var(--teal-s); font-weight: 700; text-decoration: none; font-size: 0.9rem; margin-bottom: 6px; }
.back-link:hover { text-decoration: underline; }

/* legal pages */
.legal-body { max-width: 720px; margin: 0 auto; padding: 40px 22px 60px; }
.legal-body h1 { font-family: var(--serif); color: var(--ink-2); font-size: 2rem; margin: 0 0 6px; }
.legal-body .legal-date { color: var(--ink-faint); font-size: 0.85rem; margin-bottom: 24px; }
.legal-body h2 { font-family: var(--serif); font-size: 1.25rem; color: var(--ink-2); margin: 28px 0 8px; }
.legal-body p, .legal-body li { color: var(--ink-soft); }
.legal-body ul { padding-left: 22px; }

/* 404 */
.notfound { text-align: center; padding: 70px 22px 80px; }
.notfound .big { font-family: var(--serif); font-size: clamp(4rem, 14vw, 7rem); color: var(--ink-2); margin: 0; line-height: 1; }
.notfound h1 { font-family: var(--serif); color: var(--ink-2); margin: 8px 0 12px; }
.notfound p { color: var(--ink-soft); max-width: 30em; margin: 0 auto 24px; }