/* =====================================================================
   Shared by the homepage and the blog posts: colour tokens, base type,
   links, the theme toggle.
   ===================================================================== */

:root {
  --paper:    #fdfcf8;
  --ink:      #1b1b1b;
  --ink-2:    #2e2e2e;
  --muted:    #4f4f4f;
  --faint:    #6b6b6b;
  --rule:     #d6d2c7;
  --rule-2:   #e6e2d8;
  --box:      #f4f2ea;
  --box-rule: #dedad0;
  /* hyperref "colorlinks", toned down */
  --url:  #1f3a8a;   /* external links (urlcolor)  */
  --ref:  #8c1c1c;   /* internal links (linkcolor) */
  --cite: #17633a;   /* citations      (citecolor) */
  --mark: rgba(255, 214, 102, .32);
  --head-bg: rgba(253, 252, 248, .9);
  /* Paper figures are white-ground images: blend the white into the page */
  --fig-filter: none;
  --fig-blend: multiply;

  --serif: "STIX Two Text", "STIX Two", "Times New Roman", Times, serif;
  --mono:  "IBM Plex Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;

  --side: 15rem;
  --measure: 40rem;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper:    #1a1916;
    --ink:      #e8e3d8;
    --ink-2:    #d6d0c3;
    --muted:    #bdb6a8;
    --faint:    #a29b8c;
    --rule:     #3f3c35;
    --rule-2:   #302e29;
    --box:      #22211d;
    --box-rule: #36342e;
    --url:  #a8bcf2;
    --ref:  #f0a8a0;
    --cite: #92d2a7;
    --mark: rgba(240, 196, 90, .14);
    --head-bg: rgba(26, 25, 22, .9);
    --fig-filter: invert(1) hue-rotate(180deg) brightness(.92);   /* dark ground, hues kept */
  --fig-blend: screen;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper:    #1a1916;
  --ink:      #e8e3d8;
  --ink-2:    #d6d0c3;
  --muted:    #bdb6a8;
  --faint:    #a29b8c;
  --rule:     #3f3c35;
  --rule-2:   #302e29;
  --box:      #22211d;
  --box-rule: #36342e;
  --url:  #a8bcf2;
  --ref:  #f0a8a0;
  --cite: #92d2a7;
  --mark: rgba(240, 196, 90, .14);
  --head-bg: rgba(26, 25, 22, .9);
  --fig-filter: invert(1) hue-rotate(180deg) brightness(.92);   /* dark ground, hues kept */
  --fig-blend: screen;
  color-scheme: dark;
}

/* ---------------------------------------------------------------- base */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }
@media (prefers-reduced-motion: no-preference) {
  html { scroll-behavior: smooth; }
}
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: clamp(17px, 0.95rem + 0.2vw, 18.5px);
  line-height: 1.55;
  font-kerning: normal;
  font-variant-ligatures: common-ligatures;
  font-variant-numeric: oldstyle-nums proportional-nums;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}
[id] { scroll-margin-top: 4.25rem; }
p { margin: 0; }

a {
  color: var(--url);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: .16em;
  text-decoration-color: transparent;
  transition: text-decoration-color .18s ease, color .18s ease, background-color .18s ease, border-color .18s ease;
}
a:hover { text-decoration-color: currentColor; }
a[href^="#"] { color: var(--ref); }
a.cite { color: var(--cite); }

:focus { outline: none; }
:focus-visible {
  outline: 2px solid var(--url);
  outline-offset: 2px;
  border-radius: 2px;
}

.sc  { font-variant-caps: small-caps; letter-spacing: .04em; }
.tt  { font-family: var(--mono); font-size: .82em; letter-spacing: 0; }
.nowrap { white-space: nowrap; }
.visually-hidden {
  position: absolute !important; 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; z-index: 50;
  background: var(--paper); color: var(--ref); padding: .4rem .8rem;
  border: 1px solid var(--rule);
}
.skip-link:focus { top: .75rem; }

/* theme toggle */
.theme-toggle {
  font: inherit; font-size: .88rem; color: var(--muted);
  background: none; border: 0; padding: .3rem 0; cursor: pointer;
  display: inline-flex; align-items: baseline; gap: .45em;
  font-variant-caps: all-small-caps; letter-spacing: .08em;
}
.theme-toggle i { font-size: .82em; position: relative; top: .02em; }
.theme-toggle:hover { color: var(--ink); }
.theme-toggle .br { color: var(--faint); }
.theme-toggle:hover .lbl-t { text-decoration: underline; text-underline-offset: .16em; text-decoration-thickness: 1px; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
}