/* ==========================================================
   GHK-Cu Doctor — cyanotype-archive
   Palette: Prussian-blue ground + warm cream paper inset + copper accent
   ========================================================== */

:root {
  --primary: #0E2A4A;
  --primary-50: #E6ECF3;
  --primary-900: #061629;
  --secondary: #1F4D7A;
  --accent: #B97A2A;
  --accent-deep: #A06820;
  --neutral-50: #F6F1E6;
  --neutral-200: #E0D9C7;
  --neutral-500: #7A7363;
  --neutral-900: #13110D;
  --bg: #0E2A4A;
  --surface: #102E50;
  --surface-paper: #F6F1E6;
  --text: #F6F1E6;
  --text-on-paper: #13110D;
  --text-muted: #B6C7DA;
  --text-muted-paper: #5E5A52;
  --rule: #C9D6E4;
  --rule-paper: #13110D;
  --success: #7FB28A;
  --warning: #B97A2A;
  --danger: #C45A4E;

  --max-width: 70rem;
  --container-px: clamp(1rem, 3vw, 2rem);

  --font-heading: 'DM Serif Display', 'Playfair Display', Georgia, serif;
  --font-body: 'IBM Plex Sans', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-mono: 'IBM Plex Mono', 'Courier New', monospace;
}

/* Reset */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
img, svg { max-width: 100%; height: auto; display: block; }
a { color: inherit; }
a:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

/* Typography */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: 400;
  line-height: 1.05;
  margin: 0 0 0.75em;
  letter-spacing: 0;
}
h1 { font-size: clamp(2.5rem, 5.5vw, 4.25rem); }
h2 { font-size: clamp(1.75rem, 3.5vw, 2.5rem); line-height: 1.1; }
h3 { font-size: 1.375rem; line-height: 1.2; }
p { margin: 0 0 1.1em; }
strong { font-weight: 600; }
em { font-style: italic; }

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 1.25em;
}

.subheadline {
  font-size: clamp(1.125rem, 1.6vw, 1.25rem);
  line-height: 1.55;
  color: var(--text-muted);
  max-width: 38em;
  margin: 0 0 1.75em;
}

/* Container */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding-left: var(--container-px);
  padding-right: var(--container-px);
}

/* Skip link */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent);
  color: var(--primary);
  padding: 0.5rem 1rem;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  text-decoration: none;
}
.skip-link:focus { left: 1rem; top: 1rem; z-index: 100; }

/* Header */
.site-header {
  background: var(--primary);
  border-bottom: 1px solid var(--accent);
  padding: 1.25rem 0;
}
.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
}
.site-brand {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  color: var(--neutral-50);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.site-brand-mark {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  letter-spacing: 0.22em;
  color: var(--accent);
  text-transform: uppercase;
  margin-top: 0.125rem;
}

.site-nav { font-family: var(--font-body); }
.site-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 1.25rem;
}
.site-nav li { display: flex; align-items: baseline; gap: 0.5rem; }
.site-nav a {
  color: var(--neutral-50);
  text-decoration: none;
  font-size: 0.9375rem;
  border-bottom: 1px solid transparent;
  transition: border-color 150ms ease-out;
}
.site-nav a:hover { border-bottom-color: var(--accent); }
.site-nav .nav-index {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--accent);
}

/* Hero — dark Prussian-blue band */
.hero {
  background: var(--primary);
  padding: clamp(3rem, 7vw, 5.5rem) 0 clamp(3rem, 6vw, 4.5rem);
  position: relative;
}
.hero::after {
  content: "";
  display: block;
  height: 1px;
  background: var(--accent);
  width: 100%;
  position: absolute;
  bottom: 0;
  left: 0;
}
.hero-inner { display: grid; gap: 2rem; }
.hero-figure {
  margin: 0;
  padding: 6px;
  background: var(--neutral-50);
  border: 1px solid var(--accent);
}
.hero-figure img {
  width: 100%;
  height: auto;
  display: block;
  border: 1px solid var(--accent);
}
.hero-figure figcaption {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--primary);
  padding: 0.625rem 0.75rem 0.25rem;
  text-align: center;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-top: 1.25rem;
}
.cta-row-center { justify-content: center; }
.btn {
  display: inline-flex;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  text-decoration: none;
  padding: 0.875rem 1.5rem;
  border-radius: 0;
  border: 1.5px solid transparent;
  transition: border-color 150ms ease-out, background-color 150ms ease-out, color 150ms ease-out;
  cursor: pointer;
}
.btn-primary {
  background: var(--accent);
  color: var(--primary);
  border-color: var(--accent);
}
.btn-primary:hover, .btn-primary:focus-visible {
  background: var(--accent-deep);
  border-color: var(--accent-deep);
}
.btn-secondary {
  background: transparent;
  color: var(--neutral-50);
  border-color: var(--neutral-50);
}
.btn-secondary:hover, .btn-secondary:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
}

/* Paper panel — body reading surface */
main { display: block; }
.paper-panel {
  background: var(--surface-paper);
  color: var(--text-on-paper);
  border-top: 1px solid var(--accent);
  border-bottom: 1px solid var(--accent);
  padding: clamp(2.5rem, 6vw, 4.5rem) 0;
}
.paper-panel a {
  color: var(--primary);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}
.paper-panel a:hover {
  color: var(--accent-deep);
}
.paper-panel h2, .paper-panel h3 { color: var(--text-on-paper); }
.paper-panel .eyebrow { color: var(--accent-deep); }

.article-body {
  max-width: 44rem;
  margin: 0 auto;
}
.article-body > section {
  padding: 1.75rem 0;
  border-bottom: 1px solid var(--neutral-200);
}
.article-body > section:last-child { border-bottom: none; }
.article-body h2 {
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top: 2px solid var(--accent);
  display: block;
  padding-bottom: 0.25rem;
}
.article-body h3 { margin-top: 1.5rem; }

.article-body sup a {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  color: var(--accent-deep);
  text-decoration: none;
  border-bottom: 1px dotted var(--accent-deep);
  padding: 0 1px;
}
.article-body sup a:hover { color: var(--primary); border-bottom-color: var(--primary); }

/* Plate figure inside paper panel */
.plate {
  margin: 2.25rem auto;
  padding: 6px;
  background: var(--neutral-50);
  border: 1px solid var(--rule-paper);
  max-width: 38rem;
}
.plate img {
  width: 100%;
  display: block;
  border: 1px solid var(--neutral-200);
}
.plate figcaption {
  text-align: center;
  padding: 0.75rem 0.5rem 0.25rem;
  color: var(--text-on-paper);
}
.plate .plate-label {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--accent-deep);
  display: block;
  margin-bottom: 0.25rem;
}
.plate .plate-title {
  font-family: var(--font-heading);
  font-style: italic;
  font-size: 0.9375rem;
}

/* Callout / note */
.callout {
  border: 1px solid var(--rule-paper);
  border-top: 2px solid var(--accent);
  padding: 1.25rem 1.5rem;
  margin: 2rem 0;
  background: var(--neutral-50);
}
.callout .eyebrow {
  margin-bottom: 0.5rem;
  color: var(--accent-deep);
}

/* Inline code & DOI */
code, .mono {
  font-family: var(--font-mono);
  font-size: 0.9em;
}
.paper-panel code {
  background: var(--neutral-200);
  padding: 0.125rem 0.375rem;
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.9375rem;
}
.paper-panel table th {
  border-top: 2px solid var(--accent);
  border-bottom: 2px solid var(--rule-paper);
  text-align: left;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  padding: 0.625rem 0.75rem;
}
.paper-panel table td {
  border-bottom: 1px solid var(--neutral-200);
  padding: 0.625rem 0.75rem;
  vertical-align: top;
}

/* References list */
.references-list {
  list-style: none;
  counter-reset: ref;
  padding: 0;
  margin: 2rem 0;
}
.references-list li {
  counter-increment: ref;
  position: relative;
  padding-left: 3.5rem;
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--neutral-200);
  padding-bottom: 1.25rem;
}
.references-list li::before {
  content: "[" counter(ref, decimal-leading-zero) "]";
  position: absolute;
  left: 0;
  top: 0;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  letter-spacing: 0.1em;
  color: var(--accent-deep);
}
.references-list .ref-doi {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--text-muted-paper);
  margin-top: 0.25rem;
}
.references-list .ref-link {
  margin-left: 0.5rem;
}

/* FAQ */
.faq-entries h3 {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 1.0625rem;
  margin: 2rem 0 0.5rem;
  color: var(--primary);
}
.faq-entries h3::before {
  content: "Q. ";
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  color: var(--accent-deep);
  vertical-align: 0.125em;
  margin-right: 0.25rem;
}

/* Contact */
.contact-form {
  display: grid;
  gap: 1rem;
  max-width: 32rem;
  margin: 2rem 0;
}
.contact-form label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent-deep);
}
.contact-form input, .contact-form textarea {
  font-family: var(--font-body);
  font-size: 1rem;
  padding: 0.75rem;
  border: 1px solid var(--rule-paper);
  border-radius: 0;
  background: var(--neutral-50);
  color: var(--text-on-paper);
  width: 100%;
}
.contact-form textarea { min-height: 8rem; resize: vertical; }
.contact-form input:focus, .contact-form textarea:focus {
  outline: 2px solid var(--accent);
  outline-offset: 0;
}
.contact-form button {
  justify-self: start;
}

/* Breadcrumb */
.breadcrumb {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin: 0 0 1rem;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}
.breadcrumb li { display: flex; gap: 0.5rem; align-items: center; }
.breadcrumb li + li::before { content: "/"; color: var(--accent); }
.breadcrumb a { color: var(--text-muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--accent); }

/* Footer */
.site-footer {
  background: var(--primary);
  color: var(--neutral-50);
  padding: clamp(3rem, 5vw, 4rem) 0 2rem;
  position: relative;
}
.site-footer::before {
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 5px;
  border-top: 1px solid var(--accent);
  border-bottom: 1px solid var(--accent);
}
.footer-grid {
  display: grid;
  gap: 2.5rem;
  grid-template-columns: 1fr;
}
@media (min-width: 720px) {
  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr 1fr;
  }
}
.footer-col h4 {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 0.75rem;
}
.footer-col ul { list-style: none; margin: 0; padding: 0; }
.footer-col li { margin: 0.4rem 0; }
.footer-col a {
  color: var(--neutral-50);
  text-decoration: none;
  font-size: 0.9375rem;
  border-bottom: 1px solid transparent;
}
.footer-col a:hover { border-bottom-color: var(--accent); }

.footer-disclaimer {
  font-size: 0.875rem;
  color: var(--text-muted);
  max-width: 36em;
  margin: 0 0 1rem;
}
.colophon {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--secondary);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  display: flex;
  flex-wrap: wrap;
  gap: 1rem 2rem;
}
.colophon span strong {
  color: var(--accent);
  font-weight: 500;
  margin-right: 0.4rem;
}

/* Section header (non-hero pages) */
.page-header {
  background: var(--primary);
  padding: clamp(2.5rem, 5vw, 4rem) 0 clamp(2rem, 4vw, 3rem);
  border-bottom: 1px solid var(--accent);
}

/* 404 */
.error-page {
  text-align: center;
  padding: 5rem 0;
}
.error-page h1 {
  font-size: clamp(3rem, 7vw, 5rem);
  margin-bottom: 0.5rem;
}
.error-page .eyebrow { display: block; margin: 0 0 2rem; }

/* Responsive */
@media (min-width: 768px) {
  .hero-inner {
    grid-template-columns: 1.1fr 1fr;
    align-items: center;
    gap: 3rem;
  }
}

/* Tippy theme overrides */
.tippy-box[data-theme~='ghkcu'] {
  background: var(--primary);
  color: var(--neutral-50);
  font-family: var(--font-body);
  font-size: 0.875rem;
  border: 1px solid var(--accent);
  border-radius: 0;
  padding: 0.5rem 0.75rem;
  max-width: 22rem !important;
  line-height: 1.45;
}
.tippy-box[data-theme~='ghkcu'] .tippy-arrow { color: var(--primary); }
.tippy-box[data-theme~='ghkcu'] .tippy-arrow::before { color: var(--primary); }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
}