/* riverb.co - base.css
   Reset, typography, layout primitives, nav, footer, links/buttons.
   Palette lives in tokens.css (do not redeclare colours here).
   Persona: Sarah, the Scholar rail - editorial authority, serif display at
   weight 400 only, hairline-only elevation, accent reserved for inline
   links / pull-quote marks / section numerals. See PITCH-PLAN.md.
*/

@import url("tokens.css");
@import url("https://fonts.googleapis.com/css2?family=Newsreader:ital,wght@0,400;1,400&family=Source+Sans+3:wght@400;600;700&display=swap");

/* ---------- reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body, h1, h2, h3, h4, p, figure, blockquote, dl, dd { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
input, textarea, select { font: inherit; color: inherit; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}

/* ---------- fonts + type scale ----------
   Sarah's pinned scale: hero 64 / H1 48 / H2 32 / H3 26 / body 18-19 / caption 12-13px.
   Negative tracking on display only, easing to 0 by 28px. Serif stays 400 everywhere. */
:root {
  --font-display: "Newsreader", Georgia, "Times New Roman", serif;
  --font-body: "Source Sans 3", "Segoe UI", Arial, sans-serif;

  --fs-h1: 3rem;        /* 48px */
  --fs-h1-mobile: 2.25rem;
  --fs-h2: 2rem;        /* 32px */
  --fs-h2-mobile: 1.625rem;
  --fs-h3: 1.625rem;    /* 26px */
  --fs-h3-mobile: 1.375rem;
  --fs-lead: 1.75rem;   /* thesis-paragraph scale, between H2 and H3 */
  --fs-lead-mobile: 1.375rem;
  --fs-body: 1.1875rem; /* 19px */
  --fs-body-sm: 1.125rem; /* 18px */
  --fs-small: 0.875rem; /* 14px */
  --fs-caption: 0.8125rem; /* 13px */

  --maxw: 71.25rem; /* 1140px */
  --gutter: 1.25rem;

  --space-1: 0.5rem;
  --space-2: 1rem;
  --space-3: 1.5rem;
  --space-4: 2.25rem;
  --space-5: 3.5rem;
  --space-6: 5rem;
  --space-7: 7rem;
}

html { background: var(--colour-bg); }
body {
  background: var(--colour-bg);
  color: var(--colour-text);
  font-family: var(--font-body);
  font-size: var(--fs-body-sm);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 { font-family: var(--font-display); font-weight: 400; color: var(--colour-grey-900); }

h1, .h1 {
  font-size: var(--fs-h1-mobile);
  line-height: 1.12;
  letter-spacing: -0.015em;
}
h2, .h2 {
  font-size: var(--fs-h2-mobile);
  line-height: 1.18;
  letter-spacing: -0.01em;
}
h3, .h3 {
  font-size: var(--fs-h3-mobile);
  line-height: 1.22;
  letter-spacing: -0.004em;
}
@media (min-width: 640px) {
  h1, .h1 { font-size: var(--fs-h1); line-height: 1.1; letter-spacing: -0.02em; }
  h2, .h2 { font-size: var(--fs-h2); line-height: 1.15; letter-spacing: -0.012em; }
  h3, .h3 { font-size: var(--fs-h3); line-height: 1.2; letter-spacing: -0.006em; }
}

p { max-width: 42rem; }
p.measure-wide { max-width: 48rem; }
.prose p + p, .history p + p { margin-top: 1.15em; }

/* Safety net: heading-styled elements that wrap must not inherit body line-height */
[class*="__title"], [class*="__name"], [class*="__label"], [class*="__role"], [class*="__num"] { line-height: 1.25; }

/* ---------- eyebrow / caption / small caps ---------- */
.eyebrow {
  font-family: var(--font-body);
  font-size: var(--fs-caption);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  /* --colour-text-muted measures 4.500:1 on --colour-bg (the only band .eyebrow sits on,
     inside .page-head.section--bg) - technically AA-passing but exactly at the floor, not
     comfortably above it. --colour-grey-600 measures 5.798:1 on the same background. See
     polish pass, 2026-09-11. */
  color: var(--colour-grey-600);
}
.caption {
  font-family: var(--font-body);
  font-size: var(--fs-caption);
  /* --colour-text-muted measures 4.05-4.3:1 on the surface/surface-alt bands this sits on -
     fails WCAG AA. --colour-grey-600 measures 5.15:1+ on both. See Fix 4, 2026-09-11. */
  color: var(--colour-grey-600);
  line-height: 1.5;
}

/* ---------- layout ---------- */
.wrap {
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
@media (min-width: 640px) {
  .wrap { --gutter: 2rem; }
}

.section { padding-block: var(--space-6); }
@media (min-width: 768px) {
  .section { padding-block: var(--space-7); }
}
.section--bg { background: var(--colour-bg); }
.section--surface { background: var(--colour-surface); }
.section--surface-alt { background: var(--colour-surface-alt); }

.visually-hidden {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}

.skip-link {
  position: absolute; left: 1rem; top: -3rem;
  background: var(--colour-grey-900); color: var(--colour-white);
  padding: 0.6rem 1rem; border-radius: 4px; z-index: 200;
  transition: top 0.15s ease;
}
.skip-link:focus { top: 1rem; }

/* ---------- inline links ----------
   Per the brief: inline links use --colour-primary, never --colour-link. */
.prose a,
.cf-form a,
p a {
  color: var(--colour-primary);
  text-decoration: underline;
  text-decoration-color: var(--colour-border);
  text-underline-offset: 0.15em;
  transition: text-decoration-color 0.15s ease;
}
.prose a:hover, .cf-form a:hover, p a:hover { text-decoration-color: currentColor; }
.prose a:focus-visible, p a:focus-visible, a:focus-visible {
  outline: 2px solid var(--colour-primary);
  outline-offset: 2px;
}
/* :active - a step deeper than the resting/hover indigo, so a press reads distinct
   from a hover; --colour-primary-active was already in tokens.css, unused until now. */
.prose a:active, .cf-form a:active, p a:active { color: var(--colour-primary-active); text-decoration-color: currentColor; }

/* ---------- quiet text-forward button / link ----------
   Never a filled accent per the accent-quarantine rule - text + arrow, hairline
   underline, hugs its own text, never wraps. */
a.btn,
a.quiet-link,
.btn,
.quiet-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4em;
  font-family: var(--font-body);
  font-size: var(--fs-small);
  font-weight: 600;
  color: var(--colour-grey-900);
  text-decoration: none;
  white-space: nowrap;
  border-bottom: 1px solid var(--colour-grey-900);
  padding-bottom: 0.2em;
  transition: color 0.15s ease, border-color 0.15s ease, gap 0.15s ease;
}
a.btn:hover, a.quiet-link:hover, .btn:hover, .quiet-link:hover {
  color: var(--colour-primary);
  border-color: var(--colour-primary);
  gap: 0.6em;
}
a.btn:focus-visible, a.quiet-link:focus-visible, .btn:focus-visible, .quiet-link:focus-visible {
  outline: 2px solid var(--colour-primary);
  outline-offset: 4px;
}
a.btn:active, a.quiet-link:active, .btn:active, .quiet-link:active {
  color: var(--colour-primary-active);
  border-color: var(--colour-primary-active);
}
.btn__arrow, .quiet-link__arrow { transition: transform 0.15s ease; }

/* ---------- hairline rule ---------- */
.hr {
  border: 0;
  border-top: 1px solid var(--colour-accent);
  opacity: 0.55;
  width: 4rem;
}
.hr--full { width: 100%; opacity: 1; border-top-color: var(--colour-border); }

/* ---------- header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--colour-bg);
  border-bottom: 1px solid var(--colour-border);
}
.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  min-height: 5rem; /* 80px headerHeight */
}
.brand {
  min-width: 0;
  display: inline-flex;
  align-items: center;
}
.brand img {
  height: 2.25rem; /* 36px mobile */
  width: auto;
  display: block;
}
@media (min-width: 640px) {
  .brand img { height: 3rem; } /* 48px desktop */
}

.nav-primary {
  display: none;
  align-items: center;
  gap: var(--space-4);
}
.nav-primary a {
  font-family: var(--font-body);
  font-size: var(--fs-small);
  font-weight: 600;
  color: var(--colour-grey-900);
  white-space: nowrap;
  padding-block: 0.4rem;
  border-bottom: 1px solid transparent;
  transition: color 0.15s ease, border-color 0.15s ease;
}
.nav-primary a:hover,
.nav-primary a[aria-current="page"] {
  color: var(--colour-primary);
  border-color: var(--colour-primary);
}
.nav-primary a:active {
  color: var(--colour-primary-active);
  border-color: var(--colour-primary-active);
}
@media (min-width: 900px) {
  .nav-primary { display: flex; }
  .nav-toggle { display: none; }
}

.nav-toggle {
  flex: 0 0 auto;
  width: 2.75rem;
  height: 2.75rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  transition: background-color 0.15s ease;
}
.nav-toggle:hover { background: var(--colour-surface); }
.nav-toggle:active { background: var(--colour-surface-alt); }
.nav-toggle:focus-visible {
  outline: 2px solid var(--colour-primary);
  outline-offset: 2px;
}
.nav-toggle__bars {
  display: flex;
  flex-direction: column;
  gap: 5px;
  width: 20px;
}
.nav-toggle__bars span {
  display: block;
  height: 2px;
  background: var(--colour-grey-900);
  border-radius: 1px;
}

.mobile-menu[open] {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  max-width: none;
  max-height: none;
  margin: 0;
  padding: 0;
  border: 0;
  background: var(--colour-bg);
  z-index: 100;
}
.mobile-menu__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2) var(--gutter);
  min-height: 5rem;
  border-bottom: 1px solid var(--colour-border);
}
.mobile-menu__close {
  width: 2.75rem;
  height: 2.75rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  transition: background-color 0.15s ease;
}
/* Conformance guard, 2026-09-11: with no explicit colour here, button{color:inherit}
   picked up Chromium's UA default dialog{color:black} rather than the site's ink
   token, so this one control rendered pure #000 while every sibling used the token. */
.mobile-menu__close { color: var(--colour-grey-900); }
.mobile-menu__close:hover { background: var(--colour-surface); }
.mobile-menu__close:active { background: var(--colour-surface-alt); }
.mobile-menu__close:focus-visible {
  outline: 2px solid var(--colour-primary);
  outline-offset: 2px;
}
.mobile-menu__nav {
  display: flex;
  flex-direction: column;
  padding: var(--space-3) var(--gutter);
  gap: var(--space-1);
}
.mobile-menu__nav a {
  font-family: var(--font-display);
  font-size: 1.5rem;
  padding-block: 0.6rem;
  border-bottom: 1px solid var(--colour-border);
  color: var(--colour-grey-900);
  transition: color 0.15s ease, border-color 0.15s ease;
}
.mobile-menu__nav a:hover { color: var(--colour-primary); border-color: var(--colour-primary); }
.mobile-menu__nav a:active { color: var(--colour-primary-active); border-color: var(--colour-primary-active); }
.mobile-menu__nav a:focus-visible {
  outline: 2px solid var(--colour-primary);
  outline-offset: 2px;
}
@media (min-width: 900px) {
  .mobile-menu, .nav-toggle { display: none; }
}

/* ---------- footer ---------- */
.site-footer {
  background: var(--colour-surface-alt);
  border-top: 1px solid var(--colour-accent);
}
.site-footer .wrap {
  padding-block: var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}
.site-footer__row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
}
/* Footer sits on --colour-surface-alt, where --colour-text-muted measures 4.05:1 (fails
   WCAG AA's 4.5:1). --colour-grey-600 measures 5.15:1 on the same background. See Fix 4,
   2026-09-11 - this held Lighthouse accessibility at 95/100 on both mobile and desktop. */
.site-footer__legal {
  font-size: var(--fs-caption);
  color: var(--colour-grey-600);
}
.site-footer__contacts {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  font-size: var(--fs-caption);
  color: var(--colour-grey-600);
}
.site-footer__contacts a { color: var(--colour-primary); text-decoration: underline; text-underline-offset: 0.15em; }
.site-footer__credit {
  font-size: var(--fs-caption);
  color: var(--colour-grey-600);
}
.site-footer__credit a {
  color: var(--colour-grey-600);
  text-decoration: underline;
  text-decoration-color: var(--colour-border);
  text-underline-offset: 0.15em;
}
.site-footer__credit a:hover { color: var(--colour-primary); text-decoration-color: currentColor; }