/* See REFERENCES.md [C1]-[C5] [A4]-[A5] for responsive, focus, contrast and transition techniques. */
:root {
  --colour-bg: #f5f7f8; --colour-surface: #ffffff; --colour-text: #182126;
  --colour-muted: #53616a; --colour-border: #c6d0d5; --colour-control-border: #718087; --colour-primary: #075e66;
  --colour-primary-dark: #04474d; --colour-accent: #d9eff1; --colour-error: #a11a1a;
  --colour-focus: #ffbf47; --radius: 0.5rem; --content-width: 68rem;
  font-family: Arial, Helvetica, sans-serif; color: var(--colour-text); background: var(--colour-bg);
}
* { box-sizing: border-box; }
body { margin: 0; line-height: 1.5; }
a { color: var(--colour-primary); }
a:hover { color: var(--colour-primary-dark); }
/* [C1] [A4] [A5]: visible, high-contrast keyboard focus. */
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible {
  outline: 3px solid var(--colour-text); outline-offset: 2px; box-shadow: 0 0 0 5px var(--colour-focus);
}
.skip-link {
  position: absolute; left: 0.75rem; top: -5rem; z-index: 10;
  padding: 0.65rem 0.9rem; background: var(--colour-text); color: #fff;
}
.skip-link:focus { top: 0.75rem; }
.site-header { background: var(--colour-surface); border-bottom: 1px solid var(--colour-border); }
.header-inner, main, .site-footer { width: min(100% - 2rem, var(--content-width)); margin-inline: auto; }
.header-inner { position: relative; padding-block: 0.9rem; }
.site-name { display: inline-block; font-size: 1.15rem; font-weight: 700; text-decoration: none; view-transition-name: site-name; }
.menu-toggle {
  float: right; padding: 0.5rem 0.75rem; border: 1px solid var(--colour-control-border);
  border-radius: var(--radius); background: var(--colour-surface); color: var(--colour-text);
  font: inherit; cursor: pointer;
}
.site-nav { display: none; clear: both; padding-top: 0.75rem; }
.site-nav.is-open { display: block; }
.site-nav ul { margin: 0; padding: 0; list-style: none; }
.site-nav a { display: block; padding: 0.6rem 0; text-decoration: none; }
.site-nav a[aria-current="page"] { font-weight: 700; text-decoration: underline; text-underline-offset: 0.25rem; }
main { padding-block: 2rem 3rem; view-transition-name: page-content; }
.intro { max-width: 46rem; margin-bottom: 1.75rem; }
.eyebrow { margin: 0 0 0.25rem; color: var(--colour-primary); font-weight: 700; }
h1, h2, h3 { line-height: 1.2; }
h1 { margin: 0; font-size: clamp(2rem, 7vw, 3rem); }
h2 { margin-top: 0; }
.search-panel, .result-card { background: var(--colour-surface); border: 1px solid var(--colour-border); border-radius: var(--radius); }
.search-panel { padding: 1rem; }
.field { margin-bottom: 1rem; }
label, legend { font-weight: 700; }
input[type="search"], input[type="number"], select, textarea {
  display: block; width: 100%; margin-top: 0.35rem; padding: 0.7rem;
  border: 1px solid var(--colour-control-border); border-radius: 0.35rem;
  background: #fff; color: var(--colour-text); font: inherit;
}
fieldset { margin: 0 0 1rem; padding: 0; border: 0; }
.choice-list { display: grid; gap: 0.5rem; margin-top: 0.45rem; }
.choice-list label, .checkbox-row { font-weight: 400; }
.checkbox-row { display: flex; gap: 0.55rem; align-items: flex-start; margin-bottom: 1rem; }
.checkbox-row input { margin-top: 0.25rem; }
.hint, .form-error { margin: 0.3rem 0 0; font-size: 0.9rem; }
.hint { color: var(--colour-muted); }
.form-error { color: var(--colour-error); font-weight: 700; }
input[aria-invalid="true"] { border-color: var(--colour-error); border-width: 2px; }
.primary-button {
  min-height: 2.75rem; padding: 0.65rem 1rem; border: 0; border-radius: var(--radius);
  background: var(--colour-primary); color: #fff; font: inherit; font-weight: 700; cursor: pointer;
}
#search-button:hover { background: var(--colour-primary-dark); }
.primary-button:disabled { cursor: wait; opacity: 0.65; }
.secondary-button { padding: 0.55rem 0.85rem; border: 1px solid var(--colour-control-border); border-radius: var(--radius); background: var(--colour-surface); color: var(--colour-text); font: inherit; cursor: pointer; }
.secondary-button:hover { border-color: var(--colour-primary); }
.results-section { margin-top: 2rem; container-type: inline-size; }
.results-heading-row { display: flex; gap: 1rem; align-items: baseline; justify-content: space-between; }
.results-heading-row p { margin: 0; color: var(--colour-muted); }
.status { padding: 0.8rem; border-left: 4px solid var(--colour-primary); background: var(--colour-accent); }
.status.error { border-left-color: var(--colour-error); }
.results-list { display: grid; gap: 1rem; margin: 1rem 0 0; padding: 0; list-style: none; }
.result-card { padding: 1rem; }
.paper-detail { display: grid; gap: 2rem; }
.paper-detail > header, .paper-detail section { background: var(--colour-surface); border: 1px solid var(--colour-border); border-radius: var(--radius); padding: 1rem; }
.paper-meta { margin: 1rem 0; padding-left: 1.25rem; }
.notes-panel textarea { resize: vertical; min-height: 9rem; }
.save-status { min-height: 1.5rem; font-weight: 700; }
.reading-notes { margin-block: 0.8rem; padding: 0.75rem; background: var(--colour-bg); border-radius: var(--radius); }
.reading-notes p { margin: 0.35rem 0; }
.metadata-comparison { display: grid; gap: 0.75rem; margin: 1rem 0 0; padding: 0; list-style: none; }
.metadata-comparison li { padding: 0.8rem; border: 1px solid var(--colour-border); border-radius: var(--radius); }
.metadata-comparison p { margin: 0.35rem 0 0; overflow-wrap: anywhere; }
.comparison-heading { display: flex; gap: 0.75rem; align-items: center; justify-content: space-between; }
.comparison-state { padding: 0.15rem 0.45rem; border-radius: 999px; background: var(--colour-bg); font-size: 0.85rem; }
.comparison-state.match { background: var(--colour-accent); }
.comparison-state.different { border: 1px solid var(--colour-border); }
.popover-button { display: none; }
.source-help { max-width: 32rem; padding: 1rem; border: 1px solid var(--colour-border); border-radius: var(--radius); background: var(--colour-surface); color: var(--colour-text); }
.source-help h3 { margin-top: 0; }
@supports selector(:popover-open) {
  .popover-button { display: inline-block; }
  .source-help:popover-open { margin: auto; }
}
.result-card h3 { margin: 0 0 0.55rem; font-size: 1.15rem; }
.result-card h3 a { text-decoration-thickness: 0.08em; text-underline-offset: 0.16em; }
.result-meta, .result-source { margin: 0.35rem 0; color: var(--colour-muted); }
.result-tags { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 0.7rem; }
.tag { padding: 0.2rem 0.5rem; border-radius: 999px; background: var(--colour-accent); font-size: 0.85rem; }
.site-footer { padding-block: 1.5rem; border-top: 1px solid var(--colour-border); color: var(--colour-muted); font-size: 0.9rem; }

/* [C2]: mobile-first enhancement at a wider viewport. */
@media (min-width: 46rem) {
  .header-inner { display: flex; align-items: center; justify-content: space-between; }
  .menu-toggle { display: none; }
  .site-nav, .site-nav.is-open { display: block; clear: none; padding-top: 0; }
  .site-nav ul { display: flex; gap: 1.25rem; }
  .site-nav a { padding: 0.25rem 0; }
  .search-panel { padding: 1.5rem; }
  .search-grid { display: grid; grid-template-columns: 1fr 1.5fr; gap: 1rem; }
}


/* [C3]: result cards respond to their container width. */
@container (min-width: 42rem) {
  .results-section .result-card {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    column-gap: 1rem;
    align-items: start;
  }

  .results-section .result-card h3,
  .results-section .result-meta,
  .results-section .result-source { grid-column: 1; }

  .results-section .result-tags {
    grid-column: 2;
    grid-row: 1 / span 3;
    justify-content: flex-end;
    max-width: 14rem;
    margin-top: 0;
  }
}

/* [C4] [C5]: progressive MPA transitions with reduced-motion support below. */
@view-transition {
  navigation: auto;
}

@media (prefers-reduced-motion: reduce) {
  ::view-transition-old(root),
  ::view-transition-new(root),
  ::view-transition-old(site-name),
  ::view-transition-new(site-name),
  ::view-transition-old(page-content),
  ::view-transition-new(page-content) { animation: none; }
}