:root {
  --side-width: 17.5rem;
  --reading-width: 45rem;
  --rail-width: 7rem;
  --space-1: 0.5rem;
  --space-2: 0.875rem;
  --space-3: 1.25rem;
  --space-4: 2rem;
  --space-5: 3rem;
  --space-6: 5rem;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 0;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

.site-shell {
  display: grid;
  grid-template-columns: var(--side-width) minmax(0, 1fr);
  min-height: 100vh;
}

.side-index {
  position: sticky;
  top: 0;
  z-index: 5;
  align-self: start;
  height: 100vh;
  overflow-y: auto;
  padding: var(--space-4) var(--space-3);
}

.index-mark {
  display: grid;
  gap: 0.15rem;
  margin-bottom: var(--space-4);
}

.index-mark span,
.index-mark strong {
  display: block;
}

.index-list {
  display: grid;
  gap: 0.35rem;
  padding: 0;
  margin: 0;
  list-style: none;
}

.mobile-index {
  display: none;
}

.index-link {
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr);
  align-items: center;
  min-height: 3rem;
  padding: 0.5rem 0.65rem;
}

.page-frame {
  position: relative;
  min-width: 0;
  overflow: hidden;
}

.page-frame::before,
.page-frame::after {
  position: fixed;
  z-index: -1;
  right: 2.75rem;
  width: 3rem;
  height: 145vh;
  content: "";
  border-left: 1px solid currentColor;
  border-right: 1px solid currentColor;
  transform: rotate(8deg) translateY(-16vh);
  opacity: 0.35;
}

.page-frame::after {
  right: 5.75rem;
  transform: rotate(-8deg) translateY(-12vh);
}

.content-grid {
  display: grid;
  grid-template-columns: minmax(0, var(--reading-width)) var(--rail-width);
  gap: var(--space-5);
  width: min(calc(100% - 3rem), 59rem);
  margin: 0 auto;
  padding: var(--space-4) 0 var(--space-6);
}

.reading-column {
  min-width: 0;
}

.breadcrumb {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  margin-bottom: var(--space-4);
}

.hero {
  padding: var(--space-5) 0 var(--space-4);
}

.hero-copy {
  max-width: 43rem;
}

.hero-actions,
.next-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: var(--space-4);
}

.action-link,
.next-link,
.text-link {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  padding: 0.55rem 0.8rem;
}

.side-figure {
  display: grid;
  align-content: start;
  gap: var(--space-3);
  padding-top: 7.25rem;
}

.helix-glyph {
  position: sticky;
  top: 5rem;
  width: 5rem;
  height: 24rem;
  margin-inline: auto;
}

.helix-glyph::before,
.helix-glyph::after {
  position: absolute;
  inset: 0 1rem;
  content: "";
  border-left: 2px solid currentColor;
  border-right: 2px solid currentColor;
  border-radius: 50%;
  transform: skewY(-24deg);
}

.helix-glyph::after {
  transform: skewY(24deg);
}

.rail-rule {
  height: 1px;
  margin: 2.2rem 0;
}

.section-block {
  padding: var(--space-5) 0;
}

.section-block + .section-block {
  border-top: 1px solid;
}

.brief {
  max-width: 42rem;
  margin-bottom: var(--space-3);
}

.plain-list,
.check-list,
.source-list {
  display: grid;
  gap: 0.7rem;
  padding-left: 1.2rem;
}

.pathway-list {
  display: grid;
  gap: 0;
  padding: 0;
  margin: var(--space-4) 0;
  list-style: none;
  counter-reset: pathway;
}

.pathway-list > li {
  display: grid;
  grid-template-columns: 3rem minmax(0, 1fr);
  gap: var(--space-3);
  padding: var(--space-3) 0;
  border-top: 1px solid;
  counter-increment: pathway;
}

.pathway-list > li::before {
  content: "0" counter(pathway);
}

.keyline-card,
.callout,
.notes-panel,
.source-drawer,
.image-panel {
  margin: var(--space-4) 0;
  padding: var(--space-3);
  border: 1px solid;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-3);
}

.keyline-card {
  margin: 0;
}

.keyline-card a {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  margin-top: 0.35rem;
}

.source-drawer summary {
  display: flex;
  align-items: center;
  min-height: 2.75rem;
  cursor: pointer;
}

.source-drawer[open] summary {
  margin-bottom: var(--space-2);
}

.source-list a,
.footer-link {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  padding-block: 0.35rem;
}

.table-wrap {
  max-width: 100%;
  overflow-x: auto;
  margin: var(--space-4) 0;
}

.ruled-table {
  width: 100%;
  border-collapse: collapse;
}

.ruled-table th,
.ruled-table td {
  padding: 0.9rem 0.75rem;
  text-align: left;
  vertical-align: top;
  border-top: 1px solid;
  border-bottom: 1px solid;
}

.term-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: var(--space-4) 0;
}

.term-card {
  margin: 0;
  padding: var(--space-3);
}

.term-card dt {
  margin-bottom: 0.45rem;
}

.term-card dd {
  margin: 0;
}

.notes-label,
.notes-area,
.notes-actions,
.save-status {
  display: block;
}

.notes-area {
  width: 100%;
  min-height: 8rem;
  margin: 0.65rem 0;
  padding: 0.8rem;
  resize: vertical;
}

.notes-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
}

.notes-button {
  min-width: 7rem;
  min-height: 2.75rem;
  padding: 0.55rem 0.85rem;
}

.save-status {
  min-height: 1.6rem;
  margin-top: 0.65rem;
}

.image-panel {
  padding: 0;
  overflow: hidden;
}

.image-panel figcaption {
  padding: 0.8rem 1rem;
}

.site-footer {
  display: grid;
  gap: var(--space-3);
  padding: var(--space-4) 0 0;
  margin-top: var(--space-5);
  border-top: 1px solid;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.25rem;
}

.skip-link {
  position: fixed;
  z-index: 20;
  top: 0.5rem;
  left: 0.5rem;
  min-height: 2.75rem;
  padding: 0.65rem 1rem;
  transform: translateY(-160%);
}

.skip-link:focus {
  transform: translateY(0);
}

@media (max-width: 900px) {
  .site-shell {
    grid-template-columns: 1fr;
  }

  .side-index {
    position: relative;
    height: auto;
    overflow: visible;
    padding: 1rem;
  }

  .index-mark {
    margin-bottom: 0.5rem;
  }

  .desktop-index {
    display: none;
  }

  .mobile-index {
    display: block;
  }

  .mobile-index summary {
    display: flex;
    align-items: center;
    min-height: 2.75rem;
    cursor: pointer;
  }

  .mobile-index[open] summary {
    margin-bottom: 0.65rem;
  }

  .mobile-index .index-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .content-grid {
    grid-template-columns: minmax(0, 1fr);
    width: min(calc(100% - 2rem), var(--reading-width));
    padding-top: var(--space-3);
  }

  .side-figure {
    display: none;
  }

  .page-frame::before,
  .page-frame::after {
    position: absolute;
    right: -1.5rem;
    height: 42rem;
  }

  .page-frame::after {
    right: 1.5rem;
  }
}

@media (max-width: 600px) {
  .mobile-index .index-list,
  .card-grid,
  .term-grid {
    grid-template-columns: 1fr;
  }

  .index-link {
    min-height: 2.75rem;
  }

  .hero {
    padding-top: var(--space-4);
  }

  .section-block {
    padding: var(--space-4) 0;
  }

  .pathway-list > li {
    grid-template-columns: 2.5rem minmax(0, 1fr);
    gap: 0.75rem;
  }

  /* Phones: each table row becomes a short stacked card; the column name rides above each cell. */
  .ruled-table thead {
    display: none;
  }

  .ruled-table,
  .ruled-table tbody,
  .ruled-table tr,
  .ruled-table th,
  .ruled-table td {
    display: block;
    width: 100%;
  }

  .ruled-table tbody tr {
    border-top: 1px solid;
  }

  .ruled-table th,
  .ruled-table td {
    border: 0;
    padding: 0.6rem 0.75rem;
  }

  .ruled-table th[scope="row"] {
    padding-top: 0.9rem;
  }

  .ruled-table td::before {
    display: block;
    margin-bottom: 0.2rem;
    content: attr(data-label);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}