:root {
  --primary-color: #67247d;
  --secondary-color: #bd47e6;
  --dark-purple: #270d37;
  --black: #040101;
  --white: #ffffff;
  --light-gray: #afafaf;
  --medium-gray: #7d7d7d;
  --gray: #969696;
  --background-gray: #f5f7f9;
  --font-main: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Newsreader', Georgia, 'Times New Roman', Times, serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-main);
  font-size: 12pt;
  color: var(--black);
  line-height: 1.55;
  background-color: var(--white);
  scroll-padding-top: 80px;
}
a { text-decoration: none; color: var(--primary-color); transition: color 0.2s ease; }
a:hover { color: var(--secondary-color); }
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 500;
  margin-bottom: 0.75rem;
  line-height: 1.25;
  color: var(--black);
}
h1 { font-size: 22pt; }
h2 { font-size: 17pt; margin-top: 2rem; }
h3 { font-size: 14pt; margin-top: 1.5rem; }
h4 { font-size: 12pt; margin-top: 1.25rem; font-weight: 600; }
p { margin-bottom: 1rem; }
ul, ol { margin-bottom: 1rem; padding-left: 1.5rem; }
li { margin-bottom: 0.4rem; }
img { max-width: 100%; height: auto; display: block; }

/* Header */
header {
  background-color: var(--white);
  border-bottom: 1px solid var(--light-gray);
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 1000;
}
.header-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1600px;
  margin: 0 auto;
  padding: 0 2rem;
}
.site-logo {
  text-transform: uppercase;
  letter-spacing: 1px;
  font-weight: bold;
  font-size: 1.25rem;
}
.site-logo a { color: var(--black); }
.version-chip {
  display: inline-block;
  margin-left: 0.75rem;
  padding: 0.15rem 0.5rem;
  background-color: var(--background-gray);
  border: 1px solid var(--light-gray);
  border-radius: 999px;
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--medium-gray);
  text-transform: none;
  letter-spacing: 0;
  vertical-align: middle;
}
.header-actions { display: flex; align-items: center; }
.download-btn {
  background-color: var(--white);
  color: var(--black);
  border: 1px solid var(--black);
  padding: 0.5rem 1rem;
  border-radius: 4px;
  display: flex;
  align-items: center;
  transition: all 0.3s ease;
  font-size: 0.9rem;
}
.download-btn:hover { background-color: var(--black); color: var(--white); }
.download-btn svg { margin-left: 0.5rem; }

/* Container */
.container {
  display: flex;
  max-width: 1600px;
  margin: 0 auto;
  min-height: calc(100vh - 130px);
}

/* Sidebar */
.sidebar {
  width: 310px;
  background-color: var(--background-gray);
  border-right: 1px solid var(--light-gray);
  padding: 0;
  flex-shrink: 0;
  height: calc(100vh - 65px);
  overflow-y: auto;
  position: sticky;
  top: 65px;
}
.sidebar-title {
  text-transform: uppercase;
  letter-spacing: 1px;
  padding: 1rem 1.5rem;
  font-size: 1rem;
  font-weight: bold;
  border-bottom: 1px solid var(--light-gray);
}
.nav-menu { list-style: none; }
.nav-item { border-bottom: 1px solid var(--light-gray); }
.nav-item.has-children > .nav-link::after {
  content: '▾';
  margin-left: auto;
  opacity: 0.5;
  font-size: 0.8rem;
}
.nav-item.has-children.open > .nav-link::after { content: '▴'; }
.nav-children {
  list-style: none;
  padding: 0;
  margin: 0;
  background-color: rgba(255,255,255,0.4);
  display: none;
}
.nav-item.open .nav-children { display: block; }
.nav-children li { border-top: 1px dashed var(--light-gray); margin: 0; }
.nav-children .nav-link {
  padding-left: 2.5rem;
  font-size: 0.88rem;
  color: var(--medium-gray);
}
.nav-link {
  display: flex;
  align-items: center;
  padding: 0.85rem 1.5rem;
  color: var(--black);
  transition: all 0.3s ease;
  font-size: 0.95rem;
}
.nav-link:hover { background-color: rgba(189, 71, 230, 0.05); }
.nav-link.active {
  background-color: var(--white);
  font-weight: 500;
  border-left: 3px solid var(--primary-color);
  padding-left: calc(1.5rem - 3px);
}
.nav-children .nav-link.active { padding-left: calc(2.5rem - 3px); }

/* Main content */
.main-content {
  flex: 1;
  padding: 3rem 5rem;
  max-width: 1100px;
}
section[id] { scroll-margin-top: 80px; }
.content-header {
  text-align: center;
  margin-bottom: 3rem;
  border-bottom: 1px solid var(--light-gray);
  padding-bottom: 2rem;
}
.content-title {
  font-family: var(--font-heading);
  font-size: 28pt;
  margin-bottom: 0.75rem;
  color: var(--black);
  line-height: 1.15;
  font-weight: 500;
}
.page-subtitle { color: var(--medium-gray); font-style: italic; margin-bottom: 0; font-size: 11pt; }
.authors { margin-bottom: 0; color: var(--medium-gray); font-size: 11pt; }
.last-reviewed {
  display: inline-block;
  margin-top: 0.4rem;
  font-size: 9pt;
  color: var(--medium-gray);
}
.section-divider {
  display: flex;
  align-items: center;
  margin: 3rem 0 2rem;
}
.section-divider-title {
  text-transform: uppercase;
  letter-spacing: 2px;
  font-size: 0.9rem;
  margin-right: 1rem;
  color: var(--medium-gray);
}
.section-divider hr { flex: 1; border: none; height: 1px; background-color: var(--light-gray); }
.content-text { font-size: 12pt; line-height: 1.55; }

/* Page navigation (prev/next) */
.page-nav {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin: 4rem 0 1rem;
  padding-top: 2rem;
  border-top: 1px solid var(--light-gray);
}
.page-nav a {
  flex: 1;
  padding: 1rem 1.25rem;
  border: 1px solid var(--light-gray);
  border-radius: 4px;
  background-color: var(--background-gray);
  color: var(--black);
  font-size: 0.9rem;
}
.page-nav a:hover { border-color: var(--primary-color); }
.page-nav .nav-prev { text-align: left; }
.page-nav .nav-next { text-align: right; }
.page-nav .nav-label {
  display: block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--medium-gray);
  margin-bottom: 0.25rem;
}

/* Callouts */
.callout {
  background-color: var(--background-gray);
  border-left: 4px solid var(--primary-color);
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  border-radius: 0 4px 4px 0;
}
.callout.callout-warning { border-left-color: #d97706; }
.callout.callout-update { border-left-color: var(--secondary-color); }
.callout strong { color: var(--primary-color); }

/* Term definitions */
.term-block {
  background-color: var(--background-gray);
  border-left: 4px solid var(--primary-color);
  padding: 1.5rem;
  margin: 2rem 0;
  border-radius: 0 4px 4px 0;
}
.term-title { font-weight: 600; color: var(--primary-color); margin-bottom: 0.5rem; }
.iso-citation {
  font-size: 0.85em;
  color: var(--medium-gray);
  margin-top: 0.5rem;
  display: block;
}

/* Tables */
.maturity-table, table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 10.5pt;
  border: 1px solid var(--light-gray);
}
.maturity-table th, .maturity-table td,
table th, table td {
  border: 1px solid var(--light-gray);
  padding: 0.5rem 0.65rem;
  text-align: left;
  vertical-align: top;
}
.maturity-table th, table th { background-color: var(--background-gray); font-weight: bold; }
.maturity-table tr:nth-child(even), table tr:nth-child(even) { background-color: rgba(245, 247, 249, 0.5); }

/* Figures */
.figure { margin: 2rem 0; text-align: center; }
.figure img {
  max-width: 100%;
  border-radius: 4px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
  border: 1px solid var(--light-gray);
}
.figure-caption {
  margin-top: 0.75rem;
  font-size: 10pt;
  color: var(--medium-gray);
  font-style: italic;
}

/* Audience cards */
.audience-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
  margin: 3rem 0;
}
.audience-card {
  background-color: var(--white);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
  border: 1px solid var(--light-gray);
  display: flex;
  flex-direction: column;
}
.audience-card-header {
  background-color: var(--primary-color);
  color: var(--white);
  padding: 1.5rem;
  text-align: center;
}
.audience-card-header h3 { color: var(--white); }
.audience-card-content { padding: 1.5rem; flex-grow: 1; }
.audience-card ul { padding-left: 1.5rem; margin-bottom: 1rem; }
.audience-card li { margin-bottom: 0.5rem; }

/* Hero (landing) */
.hero {
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--dark-purple) 100%);
  color: var(--white);
  padding: 5rem 2rem;
  text-align: center;
  border-radius: 8px;
  margin-bottom: 3rem;
}
.hero h1 { color: var(--white); font-family: var(--font-heading); font-size: 32pt; margin-bottom: 0.75rem; }
.hero p { color: rgba(255,255,255,0.85); font-size: 13pt; max-width: 700px; margin: 0 auto 1.5rem; }
.hero .hero-meta { font-size: 0.9rem; opacity: 0.7; }
.hero-actions { display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap; }
.btn-primary {
  background-color: var(--white);
  color: var(--primary-color);
  padding: 0.75rem 1.5rem;
  border-radius: 4px;
  font-weight: 500;
}
.btn-primary:hover { background-color: var(--secondary-color); color: var(--white); }
.btn-secondary {
  background-color: transparent;
  color: var(--white);
  padding: 0.75rem 1.5rem;
  border-radius: 4px;
  border: 1px solid var(--white);
  font-weight: 500;
}
.btn-secondary:hover { background-color: var(--white); color: var(--primary-color); }

/* TOC grid on landing */
.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1rem;
  margin: 2rem 0;
}
.toc-card {
  border: 1px solid var(--light-gray);
  border-radius: 6px;
  padding: 1.25rem;
  background-color: var(--white);
  transition: border-color 0.2s ease, transform 0.2s ease;
}
.toc-card:hover { border-color: var(--primary-color); transform: translateY(-2px); }
.toc-card h3 { margin: 0 0 0.5rem; font-size: 1.05rem; }
.toc-card h3 a { color: var(--primary-color); }
.toc-card p { margin: 0; font-size: 0.9rem; color: var(--medium-gray); }

/* Footnotes (markdown-it-footnote) */
.footnotes {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--light-gray);
  font-size: 10pt;
  color: var(--medium-gray);
}
.footnotes hr { display: none; }
.footnotes ol { padding-left: 2.5em; }
.footnotes li { margin-bottom: 0.75rem; line-height: 1.5; }
.footnote-ref a, a.footnote-backref {
  text-decoration: none;
  color: var(--secondary-color);
  font-weight: bold;
}
sup.footnote-ref { font-size: 0.75em; }

/* Collapsible details */
details {
  margin-bottom: 1.5rem;
  border: 1px solid var(--light-gray);
  border-radius: 4px;
  background-color: var(--background-gray);
}
details summary {
  padding: 1rem 1.5rem;
  cursor: pointer;
  font-weight: 500;
  color: var(--black);
  background-color: rgba(189, 71, 230, 0.05);
  border-radius: 4px 4px 0 0;
  list-style: none;
  position: relative;
}
details summary::-webkit-details-marker { display: none; }
details summary::marker { display: none; }
details summary::after {
  content: '►';
  position: absolute;
  right: 1.5rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.8em;
  color: var(--medium-gray);
  transition: transform 0.2s ease-in-out;
}
details[open] summary::after { transform: translateY(-50%) rotate(90deg); }
details summary h4 { display: inline; margin: 0; }
details[open] summary { border-bottom: 1px solid var(--light-gray); }
.maturity-details { padding: 1.5rem; background-color: var(--white); border-radius: 0 0 4px 4px; }
.maturity-details p { margin-bottom: 1rem; }
.maturity-details strong { color: var(--primary-color); }

/* Author card */
.author-grid { margin-top: 2rem; }
.author-card {
  display: flex;
  align-items: flex-start;
  gap: 2rem;
  background-color: var(--background-gray);
  padding: 2rem;
  border-radius: 8px;
  border: 1px solid var(--light-gray);
}
.author-image-container { flex-shrink: 0; width: 150px; height: 150px; }
.author-image-container img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 50%;
  border: 3px solid var(--white);
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}
.author-info h3 { margin-top: 0; color: var(--primary-color); }
.author-title { font-weight: 500; color: var(--medium-gray); margin-bottom: 1rem; }
.author-bio { font-size: 0.95rem; margin-bottom: 1.5rem; }
.author-links a { margin-right: 1rem; font-size: 0.9rem; text-decoration: underline; }

/* Footer */
footer {
  background-color: var(--black);
  color: white;
  padding: 3rem 0;
  margin-top: 4rem;
}
.footer-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 2rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 3rem;
}
.footer-column h3 { color: white; margin-bottom: 1.5rem; font-size: 1.2rem; }
.footer-links { list-style: none; padding-left: 0; }
.footer-links li { margin-bottom: 0.75rem; }
.footer-links a { color: var(--light-gray); transition: color 0.3s ease; }
.footer-links a:hover { color: var(--secondary-color); }
.footer-social { display: flex; gap: 1rem; margin-top: 1rem; }
.footer-social a {
  display: flex; align-items: center; justify-content: center;
  width: 36px; height: 36px; border-radius: 50%;
  background-color: rgba(255, 255, 255, 0.1);
  color: white;
  transition: background-color 0.3s ease;
}
.footer-social a:hover { background-color: var(--secondary-color); }
.footer-bottom {
  max-width: 1400px;
  margin: 2rem auto 0;
  padding: 2rem 2rem 0;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.footer-copyright { color: var(--light-gray); font-size: 0.9rem; }
.footer-bottom-links { display: flex; gap: 1.5rem; }
.footer-bottom-links a { color: var(--light-gray); font-size: 0.9rem; }

/* Back to top */
.back-to-top {
  position: fixed;
  bottom: 2rem; right: 2rem;
  width: 50px; height: 50px;
  border-radius: 50%;
  background-color: var(--primary-color);
  color: white;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  opacity: 0; visibility: hidden;
  transition: all 0.3s ease;
  z-index: 100;
}
.back-to-top.visible { opacity: 1; visibility: visible; }
.back-to-top:hover { background-color: var(--secondary-color); }

/* Print stylesheet (used by WeasyPrint for PDF generation) */
@media print {
  header, .sidebar, .back-to-top, footer, .page-nav { display: none !important; }
  body, .content-text { font-family: var(--font-main); font-size: 10pt; line-height: 1.4; color: #000; }
  .container { display: block; max-width: none; }
  .main-content { padding: 0; max-width: none; }
  .content-title { font-size: 20pt; }
  h1 { font-size: 18pt; page-break-after: avoid; }
  h2 { font-size: 13.5pt; page-break-after: avoid; margin-top: 1rem; }
  h3 { font-size: 11.5pt; page-break-after: avoid; margin-top: 0.8rem; }
  h4 { font-size: 10pt; page-break-after: avoid; margin-top: 0.6rem; }
  p { margin-bottom: 0.5rem; }
  ul, ol { margin-bottom: 0.5rem; padding-left: 1.1rem; }
  li { margin-bottom: 0.15rem; }
  .figure, table { page-break-inside: avoid; }
  .figure { margin: 1rem 0; }
  .figure img { max-height: 14cm; width: auto; box-shadow: none; border: 1px solid #ccc; }
  .maturity-table, table { font-size: 9pt; margin: 0.75rem 0; }
  .maturity-table th, .maturity-table td, table th, table td { padding: 0.3rem 0.4rem; }
  .figure-caption { font-size: 8.5pt; margin-top: 0.4rem; }
  .footnotes { font-size: 8.5pt; margin-top: 1.5rem; padding-top: 0.75rem; }
  .footnotes li { margin-bottom: 0.3rem; }
  .last-reviewed { display: none; }
  a { color: #000; text-decoration: none; }
  @page { margin: 1.75cm 2cm 2cm; size: Letter; }
  .pdf-cover {
    page-break-after: always;
    min-height: 90vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
  }
  .pdf-cover h1 { font-family: var(--font-heading); font-size: 26pt; margin-bottom: 0.5rem; font-weight: 500; }
  .pdf-cover .subtitle { color: #555; font-style: italic; margin-bottom: 1.5rem; font-size: 11pt; }
  .pdf-cover .author { font-size: 11pt; margin-top: 0.75rem; }
  .pdf-cover .meta { margin-top: 2rem; color: #555; font-size: 9pt; }
  .pdf-chapter { page-break-before: always; padding-top: 0; }
  .term-block { padding: 0.6rem 0.85rem; margin: 0.75rem 0; }
}

/* Larger screens */
@media (min-width: 768px) {
  .container { flex-direction: row; }
  .sidebar { width: 310px; height: calc(100vh - 65px); position: sticky; }
  .main-content { padding: 3rem 5rem; }
}
@media (min-width: 1200px) {
  .main-content { padding: 4rem 6rem; }
}

/* Mobile */
@media (max-width: 767px) {
  .header-container { flex-direction: column; align-items: center; text-align: center; }
  .site-logo { margin-bottom: 1rem; }
  .container { flex-direction: column; }
  .sidebar {
    position: static;
    width: 100%;
    height: auto;
    overflow-y: visible;
    border-right: none;
    border-bottom: 1px solid var(--light-gray);
    top: 0;
  }
  .sidebar-title { text-align: center; cursor: pointer; padding: 1rem; border-bottom: none; }
  .sidebar-title::after { content: ' ▼'; font-size: 0.8em; margin-left: 0.5rem; }
  .sidebar-title.open::after { content: ' ▲'; }
  .nav-menu { display: none; border-top: 1px solid var(--light-gray); }
  .nav-menu.active { display: block; }
  .main-content { padding: 2rem 1.5rem; }
  .hero { padding: 3rem 1rem; }
  .hero h1 { font-size: 2rem; }
  .footer-container { grid-template-columns: 1fr; text-align: center; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .author-card { flex-direction: column; align-items: center; text-align: center; }
}