/* Light, dark and reading modes. With no choice saved, the page follows the
   system setting; a choice from the header menu is stored and set as
   data-theme on <html> before the first paint (see _includes/head.html).
   Every colour the site uses goes through these tokens, so a new rule only
   needs a var() to work in all three. */

:root {
  color-scheme: light;
  --bg: #fdfdfd;
  --text: #212529;
  --heading: #212529;
  --muted: #6c757d;
  --faint: #ced4da;
  --line: #e9ecef;
  --line-strong: #adb5bd;
  --link: #0b63c5;
  --code-bg: #f8f9fa;
  --img-filter: none;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #141618;
  --text: #d4d7da;
  --heading: #eceef0;
  --muted: #8a9198;
  --faint: #3a3f45;
  --line: #262a2e;
  --line-strong: #464c53;
  --link: #8ab4f0;
  --code-bg: #1b1e21;
  --img-filter: brightness(0.88);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    color-scheme: dark;
    --bg: #141618;
    --text: #d4d7da;
    --heading: #eceef0;
    --muted: #8a9198;
    --faint: #3a3f45;
    --line: #262a2e;
    --line-strong: #464c53;
    --link: #8ab4f0;
      --code-bg: #1b1e21;
    --img-filter: brightness(0.88);
  }
}

/* Reading: warm paper and softer ink for long posts. Only the colours
   change, so the layout is identical in every mode. */
:root[data-theme="reading"] {
  color-scheme: light;
  --bg: #f4eee1;
  --text: #3b3127;
  --heading: #2a221a;
  --muted: #7c6f5f;
  --faint: #d6cab4;
  --line: #e2d7c2;
  --line-strong: #c2b396;
  --link: #8c4a1c;
  --code-bg: #ece3d1;
  --img-filter: sepia(0.08);
}

body {
  background-color: var(--bg);
  color: var(--text);
}

h1, h2, h3, h4, h5, h6,
.h1, .h2, .h3, .h4, .h5, .h6,
.text-dark {
  color: var(--heading) !important;
}

.text-secondary {
  color: var(--muted) !important;
}

a {
  color: var(--link);
}

/* One hover colour for the whole site: the mode's accent. Text links are
   already that colour, so they underline instead; everything else (header,
   footer, the reading rail, the mode slider) turns accent on hover. */
a:hover,
a:focus-visible {
  color: var(--link);
}

a.text-dark:hover,
a.text-dark:focus-visible,
#site-footer a:hover,
#site-footer a:hover .text-secondary {
  color: var(--link) !important;
  text-decoration: none;
}

hr {
  border-top-color: var(--line);
}

#nav-header {
  border-top-color: var(--heading) !important;
  border-bottom-color: var(--line) !important;
}

@media (max-width: 767px) {
  #nav-menu-container {
    border-color: var(--line);
    background-color: var(--bg);
  }
}

#site-footer {
  border-top-color: var(--line);
}

#content blockquote {
  border-left-color: var(--line-strong);
  color: var(--muted);
}

.highlight pre,
pre,
code {
  color: inherit;
}

.highlight pre {
  background-color: var(--code-bg);
  border-color: var(--line);
}

:not(pre) > code {
  background-color: var(--code-bg);
  padding: 0.1em 0.3em;
  border-radius: 3px;
}

#content-container table {
  border-color: var(--line-strong);
}

#content-container th,
#content-container td {
  border-color: var(--line);
}

#content-container thead th {
  border-bottom-color: var(--line-strong);
}

#content img,
#content video {
  filter: var(--img-filter);
}

/* The reading rail. */
.reading-rail {
  color: var(--muted);
}

.rail-tree li::before {
  color: var(--faint);
}

.rail-tree a[aria-current] {
  color: var(--heading);
}

.rail-tree a:hover,
.rail-share a:hover,
.rail-copy:hover {
  color: var(--link);
}

.rail-bar {
  border-color: var(--line-strong);
}

.rail-fill {
  background: var(--muted);
}

/* Bootstrap draws the mobile menu icon as a dark SVG. */
:root[data-theme="dark"] .navbar-toggler-icon {
  filter: invert(1);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .navbar-toggler-icon {
    filter: invert(1);
  }
}

/* Syntax colours for code in dark mode; the theme's set is for a light page. */
:root[data-theme="dark"] .highlight .c,
:root[data-theme="dark"] .highlight .c1,
:root[data-theme="dark"] .highlight .cm { color: #7d858c; }
:root[data-theme="dark"] .highlight .k,
:root[data-theme="dark"] .highlight .kd,
:root[data-theme="dark"] .highlight .kn,
:root[data-theme="dark"] .highlight .o { color: #d4d7da; }
:root[data-theme="dark"] .highlight .s,
:root[data-theme="dark"] .highlight .s1,
:root[data-theme="dark"] .highlight .s2,
:root[data-theme="dark"] .highlight .sd { color: #e6a07c; }
:root[data-theme="dark"] .highlight .nf,
:root[data-theme="dark"] .highlight .nc,
:root[data-theme="dark"] .highlight .ne { color: #e8828a; }
:root[data-theme="dark"] .highlight .m,
:root[data-theme="dark"] .highlight .mi,
:root[data-theme="dark"] .highlight .mf { color: #7fd1c7; }
:root[data-theme="dark"] .highlight .nb,
:root[data-theme="dark"] .highlight .na,
:root[data-theme="dark"] .highlight .nv,
:root[data-theme="dark"] .highlight .no { color: #8ab4f0; }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .highlight .c,
  :root:not([data-theme]) .highlight .c1,
  :root:not([data-theme]) .highlight .cm { color: #7d858c; }
  :root:not([data-theme]) .highlight .k,
  :root:not([data-theme]) .highlight .kd,
  :root:not([data-theme]) .highlight .kn,
  :root:not([data-theme]) .highlight .o { color: #d4d7da; }
  :root:not([data-theme]) .highlight .s,
  :root:not([data-theme]) .highlight .s1,
  :root:not([data-theme]) .highlight .s2,
  :root:not([data-theme]) .highlight .sd { color: #e6a07c; }
  :root:not([data-theme]) .highlight .nf,
  :root:not([data-theme]) .highlight .nc,
  :root:not([data-theme]) .highlight .ne { color: #e8828a; }
  :root:not([data-theme]) .highlight .m,
  :root:not([data-theme]) .highlight .mi,
  :root:not([data-theme]) .highlight .mf { color: #7fd1c7; }
  :root:not([data-theme]) .highlight .nb,
  :root:not([data-theme]) .highlight .na,
  :root:not([data-theme]) .highlight .nv,
  :root:not([data-theme]) .highlight .no { color: #8ab4f0; }
}

/* The mode slider in the header: three stops, light, dark and reading, with
   a thumb that slides to the current one. With nothing saved, the thumb sits
   on whatever the system gives (light or dark) and nothing is stored. */
.theme-slider {
  position: relative;
  display: inline-grid;
  grid-template-columns: repeat(3, 1.75rem);
  height: 1.75rem;
  margin-left: 0.75rem;
  padding: 2px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  touch-action: none;
  user-select: none;
}

.theme-thumb {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 1.75rem;
  height: calc(100% - 4px);
  border-radius: 999px;
  background: var(--heading);
  transform: translateX(calc(var(--stop, 0) * 100%));
  transition: transform 0.18s ease;
}

.theme-slider[data-mode="light"] { --stop: 0; }
.theme-slider[data-mode="dark"] { --stop: 1; }
.theme-slider[data-mode="reading"] { --stop: 2; }

.theme-stop {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  color: var(--muted);
  background: none;
  border: 0;
  border-radius: 999px;
  cursor: pointer;
}

.theme-stop svg {
  width: 0.875rem;
  height: 0.875rem;
}

.theme-stop:hover {
  color: var(--link);
}

.theme-stop[aria-checked="true"],
.theme-stop[aria-checked="true"]:hover {
  color: var(--bg);
}

.theme-stop:focus-visible {
  outline: 1px solid var(--link);
  outline-offset: 1px;
}

@media (prefers-reduced-motion: reduce) {
  .theme-thumb {
    transition: none;
  }
}

@media (min-width: 768px) {
  #nav-menu-container {
    display: flex;
    align-items: center;
  }

  .theme-slider {
    order: 1;
  }
}

@media (max-width: 767px) {
  #nav-menu-container {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: flex-end;
  }

  .theme-slider {
    margin-left: 0.5rem;
  }

  #nav-menu {
    flex-basis: 100%;
  }
}