/* "What is this page?" popover — small ⓘ icon next to .page-title h1
 * elements; click reveals a one-paragraph explanation.
 *
 * Tokens: --text-tertiary / --surface / --border-* / --radius-md.
 * Dark mode falls through automatically.
 */

.nv-explain__trigger {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: none;
  border: 1px solid transparent;
  padding: 0;
  margin-left: var(--space-2, 8px);
  width: 22px;
  height: 22px;
  border-radius: 50%;
  color: var(--text-tertiary);
  cursor: pointer;
  vertical-align: middle;
  transition: background 0.12s ease, color 0.12s ease, border-color 0.12s ease;
  /* Heading-level vertical alignment without a magic number — translate
     a hair so the circle reads as part of the headline rather than a
     superscript. */
  transform: translateY(-1px);
}
.nv-explain__trigger:hover,
.nv-explain__trigger:focus-visible {
  color: var(--text-secondary);
  background: var(--interactive-ghost);
  border-color: var(--border-ghost, var(--border-subtle));
  outline: none;
}
.nv-explain__trigger[aria-expanded="true"] {
  color: var(--text-primary);
  background: var(--interactive-ghost);
  border-color: var(--border-ghost, var(--border-subtle));
}
.nv-explain__trigger svg {
  width: 14px;
  height: 14px;
  display: block;
}

.nv-explain__popover {
  position: absolute;
  background: var(--bg-float, var(--surface, var(--bg-surface)));
  border: 1px solid var(--border-default, var(--border-regular, var(--border)));
  border-radius: var(--radius-md, var(--radius));
  padding: var(--space-3, 12px) var(--space-4, 16px);
  max-width: 380px;
  z-index: 100;
  box-shadow: var(--shadow-lg, 0 8px 24px rgba(0, 0, 0, 0.15));
  font-size: 13.5px;
  color: var(--text-secondary);
  line-height: 1.55;
  /* Subtle entrance — matches the rest of gateway's micro-animations
     (~120ms, ease-out). */
  opacity: 0;
  transform: translateY(-2px);
  animation: nv-explain-in 120ms ease-out forwards;
}
@keyframes nv-explain-in {
  to { opacity: 1; transform: translateY(0); }
}

.nv-explain__popover h4 {
  margin: 0 0 var(--space-2, 8px);
  color: var(--text-primary);
  font-size: var(--text-base);
  font-weight: 500;
  letter-spacing: -0.005em;
}

.nv-explain__popover p {
  margin: 0;
  line-height: 1.55;
}

/* Optional secondary link — e.g. "Read the full methodology →".
   Rendered when an explanation entry includes a `link` field. */
.nv-explain__popover a {
  display: inline-block;
  margin-top: var(--space-2, 8px);
  color: var(--text-primary);
  font-size: 12.5px;
  font-weight: 500;
  text-decoration: none;
  border-bottom: 1px solid var(--border-subtle);
  transition: border-color 0.12s ease, color 0.12s ease;
}
.nv-explain__popover a:hover {
  color: var(--text-primary);
  border-color: var(--text-primary);
}

/* Print: hide entirely — popovers don't belong on paper. */
@media print {
  .nv-explain__trigger,
  .nv-explain__popover { display: none !important; }
}