/* =======================================================================
   BASE
   Reset + element defaults + typography. No component classes here.
   ======================================================================= */

*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  /* Keeps hash-link targets clear of the sticky header (and, where
     present, the sticky .level-toc sub-nav) so the heading a user
     jumps to — or is already reading, when the browser re-flows the
     page on zoom — doesn't end up hidden underneath them. */
  scroll-padding-top: var(--sticky-offset);
  /* Reserves the scrollbar's own width permanently (on browsers that
     support it — no-op elsewhere, incl. iOS Safari's overlay
     scrollbars, which never needed this) instead of only when a
     scrollbar is actually present. Without it, anything that
     temporarily removes the page scrollbar (main.js's mobile-nav
     overflow:hidden, search.js's overlay) makes the page a scrollbar's
     width wider for as long as it's open, visibly nudging the header/
     content sideways and back — the "width jump" this avoids. */
  scrollbar-gutter: stable;
}

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

body {
  margin: 0;
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--step-0);
  line-height: var(--leading-normal);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color var(--duration-base) var(--ease-standard),
              color var(--duration-base) var(--ease-standard);
}

img, video { display: block; max-width: 100%; height: auto; }

/* Default icon size — components with a specific size class (e.g.
   .brand__mark, .card__icon svg) override this via higher specificity. */
svg { width: 20px; height: 20px; flex-shrink: 0; }

a { color: inherit; text-decoration: none; }

ul, ol { padding: 0; margin: 0; list-style: none; }

h1, h2, h3, h4 {
  font-family: var(--font-display);
  color: var(--color-text);
  line-height: var(--leading-tight);
  font-weight: 600;
  margin: 0;
}

h1 { font-size: var(--step-5); letter-spacing: -0.01em; }
h2 { font-size: var(--step-3); }
h3 { font-size: var(--step-1); }
h4 { font-size: var(--step-0); font-weight: 700; }

p { margin: 0 0 1em; }
p:last-child { margin-bottom: 0; }

small { font-size: var(--step--1); }

/* Small-caps "eyebrow" label used above headings throughout the site */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2xs);
  font-family: var(--font-body);
  font-size: var(--step--1);
  font-weight: 600;
  letter-spacing: var(--tracking-wider);
  text-transform: uppercase;
  color: var(--color-accent);
}

.eyebrow::before {
  content: "";
  display: inline-block;
  width: 1.5em;
  height: 1px;
  background: currentColor;
  opacity: 0.6;
}

/* Focus visibility — never suppressed, always legible on parchment or navy */
:focus-visible {
  outline: 3px solid var(--color-focus-ring);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* Skip link for keyboard users */
.skip-link {
  position: absolute;
  left: var(--space-sm);
  top: -60px;
  background: var(--color-primary-strong);
  color: var(--color-text-on-dark);
  padding: 0.7em 1.2em;
  border-radius: var(--radius-sm);
  z-index: 4000;
  transition: top var(--duration-fast) var(--ease-standard);
  font-weight: 600;
}
.skip-link:focus { top: var(--space-sm); }

/* Visually-hidden but screen-reader accessible */
.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;
}

hr.rule {
  border: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--color-border-strong) 20%, var(--color-border-strong) 80%, transparent);
  margin: var(--space-xl) auto;
  width: 100%;
  max-width: 320px;
  opacity: 0.7;
}

::selection {
  background: var(--gold-300);
  color: var(--ink-900);
}

/* ---------------------------------------------------------------------
   Native form controls — explicit theme-aware colors
   `color-scheme` (tokens.css / dark-mode.css) gets the browser's own
   dark chrome close, but isn't reliable enough on its own for a
   <select>'s dropdown popup across browsers — some keep rendering the
   open option list with a light/OS-default background regardless of
   theme, which is exactly what made dark-mode selects (e.g. the
   fill-blank/matching dropdowns in exercises.css) hard to read. Setting
   colors explicitly on both the closed control and its <option>s fixes
   that in every theme, using the same tokens as the rest of the page —
   a component-specific class (like .blank-input) can still override
   these, this is just the shared floor every select gets.
   --------------------------------------------------------------------- */
select {
  font: inherit;
  color: var(--color-text);
  background-color: var(--color-surface);
  border: var(--border-hairline);
  border-radius: var(--radius-sm);
}
select option {
  color: var(--color-text);
  background-color: var(--color-surface);
}