/* ==========================================================================
   digitalimagecorrelation.org
   Minimal, editorial, near-monochrome with one restrained blue accent.
   Adapted from the Archangel Research design language for a documentation
   guide layout (left section TOC + article). Light theme only.
   ========================================================================== */

/* Self-hosted variable font (no CDN at runtime) */
@font-face {
  font-family: 'Inter';
  src: url('/assets/fonts/inter-variable.woff2') format('woff2');
  font-weight: 100 900;
  font-style: normal;
  font-display: swap;
}

/* ---------- Design tokens ---------- */
:root {
  --paper: #ffffff;
  --paper-2: #f0f0f0;
  --ink: #111111;
  --ink-2: #565656;      /* secondary text — ~7:1 on paper */
  --line: #d9d9d9;
  --accent: #1a4f8b;     /* restrained blue — ~7:1 on paper */
  --accent-strong: #143c69;

  --font-sans:
    'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, monospace;

  --maxw: 80rem;
  --measure: 70ch;       /* readable line length for the article */
  --toc-w: 16rem;
  --gutter: clamp(1.25rem, 4vw, 3rem);
  --header-h: 4rem;

  --radius: 10px;
  --focus-ring: 3px solid var(--accent);
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 1rem); /* anchor offset under sticky header */
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 1.0625rem;
  line-height: 1.65;
  font-feature-settings: 'kern';
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 {
  line-height: 1.2;
  letter-spacing: -0.015em;
  font-weight: 650;
}

a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 0.15em;
  text-decoration-thickness: 1px;
}
a:hover { color: var(--accent-strong); text-decoration-thickness: 2px; }

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

/* ---------- Focus & accessibility helpers ---------- */
:focus-visible {
  outline: var(--focus-ring);
  outline-offset: 2px;
  border-radius: 2px;
}

.skip-link {
  position: absolute;
  left: 0.5rem;
  top: -3rem;
  z-index: 100;
  background: var(--ink);
  color: var(--paper);
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius) var(--radius);
  text-decoration: none;
  transition: top 0.15s ease;
}
.skip-link:focus { top: 0; color: var(--paper); }

/* ---------- Layout primitives ---------- */
.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(1.1) blur(8px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.25rem 1.25rem;
  min-height: var(--header-h);
  padding-block: 0.75rem;
}
.wordmark {
  font-weight: 700;
  font-size: 1.0625rem;
  letter-spacing: -0.01em;
  color: var(--ink);
  text-decoration: none;
}
.wordmark:hover { color: var(--ink); }
.tagline { margin: 0; color: var(--ink-2); font-size: 0.95rem; }

/* ---------- Two-column doc layout ---------- */
.layout {
  display: grid;
  grid-template-columns: var(--toc-w) minmax(0, 1fr);
  gap: clamp(1.5rem, 4vw, 3.5rem);
  align-items: start;
  padding-block: clamp(1.5rem, 4vw, 2.5rem);
}

/* ---------- TOC sidebar ---------- */
.toc {
  position: sticky;
  top: calc(var(--header-h) + 0.5rem);
  max-height: calc(100vh - var(--header-h) - 1.5rem);
  overflow-y: auto;
  font-size: 0.9375rem;
}
.toc-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-2);
  margin: 0 0 0.75rem;
}
.toc-list { list-style: none; margin: 0; padding: 0; }
.toc-list li { margin: 0; }
.toc-list a {
  display: block;
  padding: 0.3rem 0.6rem;
  color: var(--ink-2);
  text-decoration: none;
  border-left: 2px solid transparent;
  border-radius: 0 4px 4px 0;
  line-height: 1.35;
}
.toc-list a:hover { color: var(--ink); background: var(--paper-2); }
.toc-list a.is-active {
  color: var(--accent-strong);
  border-left-color: var(--accent);
  font-weight: 600;
}
/* nested (sub-section) entries */
.toc-list .toc-h3 a { padding-left: 1.4rem; font-size: 0.875rem; }

/* ---------- Article typography ---------- */
.doc-article { max-width: var(--measure); }
.doc-article > p:first-child {
  font-size: 1.15rem;
  color: var(--ink-2);
}
.doc-article h1 {
  font-size: clamp(1.6rem, 3.5vw, 2.1rem);
  margin: 2.75rem 0 1rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--line);
}
.doc-article h1:first-of-type { border-top: 0; padding-top: 0; }
.doc-article h2 { font-size: 1.4rem; margin: 2rem 0 0.75rem; }
.doc-article h3 { font-size: 1.15rem; margin: 1.75rem 0 0.5rem; }
.doc-article p,
.doc-article ul,
.doc-article ol { margin: 0 0 1.1rem; }
.doc-article ul, .doc-article ol { padding-left: 1.4rem; }
.doc-article li { margin-bottom: 0.35rem; }

/* anchored-heading affordance */
.doc-article :is(h1, h2, h3) { scroll-margin-top: calc(var(--header-h) + 1rem); }

/* figures / images */
.doc-article img {
  margin-inline: auto;
  border-radius: 6px;
}
.doc-article br + br { display: none; } /* tame the legacy <br/><br/> spacing */

/* code */
code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--paper-2);
  padding: 0.15em 0.35em;
  border-radius: 4px;
}
pre {
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
  overflow-x: auto;
}
pre code { background: none; padding: 0; }

/* blockquotes & tables */
blockquote {
  margin: 0 0 1.1rem;
  padding: 0.25rem 0 0.25rem 1rem;
  border-left: 3px solid var(--line);
  color: var(--ink-2);
}
table { border-collapse: collapse; width: 100%; margin: 0 0 1.1rem; }
th, td { border: 1px solid var(--line); padding: 0.5rem 0.7rem; text-align: left; }
th { background: var(--paper-2); }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--line);
  margin-top: 2rem;
}
.footer-inner {
  padding-block: 2.5rem;
  color: var(--ink-2);
  font-size: 0.9375rem;
  max-width: var(--measure);
}

/* ---------- Responsive: collapse TOC above the article ---------- */
@media (max-width: 60rem) {
  .layout { grid-template-columns: 1fr; }
  .toc {
    position: static;
    max-height: none;
    overflow: visible;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--line);
    margin-bottom: 0.5rem;
  }
  .doc-article { max-width: none; }
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}