/* ============================================================
   FW 536 — ACCESSIBLE stylesheet (screen-reader-first)
   Goals:
   - DOM reading order = visual order (single column)
   - High contrast, large, user-scalable text (rem units)
   - Strong, always-visible keyboard focus indicators
   - Nothing conveyed by color alone (type labels are real text)
   - Respects prefers-reduced-motion, prefers-contrast, forced-colors
   ============================================================ */

:root {
  --orange: #B33107;        /* darkened OSU orange for AA contrast on white */
  --orange-strong: #8F2705;
  --ink: #161616;           /* near-black body text on white = ~16:1 */
  --ink-soft: #2E2E2E;
  --bg: #FFFFFF;
  --panel: #FFFFFF;
  --panel-alt: #F4F2EC;
  --border: #6B6B6B;        /* high-contrast borders */
  --border-soft: #BDBDBD;
  --link: #0A4DA6;          /* AA-passing blue */
  --link-visited: #6B3FA0;
  --accent: #1F5B50;        /* dark teal, AA on white */
  --good: #1E5D1A;
  --warn: #7A4E00;
  --bad: #8E1B1B;
  --code-bg: #F3F1EA;
  --code-ink: #1A1A1A;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  /* allow the OS / browser font-size preference to scale everything */
  font-size: 100%;
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; animation: none !important; }
}

body {
  font-family: Georgia, 'Times New Roman', 'Charter', serif;
  font-size: 1.125rem;       /* 18px default, scales with user setting */
  line-height: 1.7;
  color: var(--ink);
  background: var(--bg);
  margin: 0;
  padding: 0;
}

/* ---- Skip link: visible when focused ---- */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--orange);
  color: #fff;
  padding: 12px 18px;
  z-index: 1000;
  font-family: Arial, Helvetica, sans-serif;
  font-weight: 700;
  border-radius: 0 0 6px 0;
  text-decoration: underline;
}
.skip-link:focus {
  left: 0;
}

/* ---- Single-column layout (no sticky sidebar) ---- */
.shell { display: block; }
.content, main {
  max-width: 75ch;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 5rem 1.25rem;
}

/* ---- In-page navigation rendered as a clear, bordered region ---- */
.sidebar {
  background: var(--panel-alt);
  border: 2px solid var(--border);
  border-radius: 8px;
  max-width: 75ch;
  margin: 1.25rem auto 0 auto;
  padding: 1rem 1.25rem;
}
.sidebar .brand {
  font-family: Arial, Helvetica, sans-serif;
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 0.25rem 0;
}
.sidebar .brand a { color: var(--orange-strong); }
.sidebar .subtitle {
  font-size: 0.95rem;
  color: var(--ink-soft);
  margin: 0 0 0.75rem 0;
}
.sidebar nav { margin-top: 0.5rem; }
.sidebar nav .section {
  font-family: Arial, Helvetica, sans-serif;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--ink-soft);
  margin: 0.75rem 0 0.25rem 0;
}
.sidebar nav ul {
  list-style: disc;
  margin: 0.25rem 0 0.5rem 1.25rem;
  padding: 0;
}
.sidebar nav li { margin: 0.2rem 0; }
.sidebar nav a { font-size: 1rem; }
.sidebar nav a.featured { font-weight: 700; }

/* ---- Links: always underlined, high contrast ---- */
a { color: var(--link); text-decoration: underline; text-underline-offset: 2px; }
a:visited { color: var(--link-visited); }
a:hover { color: var(--orange-strong); }

/* ---- Focus: strong, never removed ---- */
:focus { outline: 3px solid #0A4DA6; outline-offset: 2px; }
:focus:not(:focus-visible) { outline: 3px solid #0A4DA6; } /* keep for older browsers */
a:focus, button:focus, summary:focus, input:focus, [tabindex]:focus {
  outline: 3px solid #0A4DA6;
  outline-offset: 2px;
  background: #FFF6CC;
}
main:focus { outline: none; }   /* focus target for skip link, no visible box */

/* ---- Headings ---- */
h1, h2, h3, h4 { font-family: Arial, Helvetica, sans-serif; line-height: 1.25; color: var(--ink); }
h1 { font-size: 1.9rem; margin: 0.4rem 0 0.6rem; }
h2 { font-size: 1.5rem; margin: 2rem 0 0.5rem; border-bottom: 2px solid var(--border-soft); padding-bottom: 0.25rem; }
h3 { font-size: 1.25rem; margin: 1.5rem 0 0.4rem; color: var(--orange-strong); }
h4 { font-size: 1.05rem; margin: 1.2rem 0 0.3rem; text-transform: uppercase; letter-spacing: 0.03em; color: var(--ink-soft); }

.lab-header { border-bottom: 3px solid var(--orange); padding-bottom: 0.75rem; margin-bottom: 1.5rem; }
.lab-header .eyebrow {
  font-family: Arial, Helvetica, sans-serif; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.08em; font-size: 0.85rem; color: var(--orange-strong);
}
.lab-header h1 { font-size: 2rem; }
.lab-header .lede { font-size: 1.15rem; color: var(--ink-soft); font-style: italic; }

p, li { max-width: 75ch; }

/* ---- Accessibility info bar at the very top of body content ---- */
.a11y-bar {
  background: #11304A;
  color: #fff;
  padding: 0.6rem 1rem;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 0.95rem;
  text-align: center;
}
.a11y-bar a { color: #FFE08A; }
.a11y-bar a:hover { color: #fff; }

/* ---- Callouts: real text label injected by transform; hide ::before ---- */
.callout { border-left: 6px solid var(--accent); background: var(--panel-alt); padding: 0.8rem 1.1rem; margin: 1.25rem 0; border-radius: 0 6px 6px 0; }
.callout::before { content: none !important; }     /* we use real <p class="callout-label"> instead */
.callout-label {
  font-family: Arial, Helvetica, sans-serif;
  font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em;
  font-size: 0.8rem; margin: 0 0 0.35rem 0;
}
.callout.plain { border-left-color: var(--orange); } .callout.plain .callout-label { color: var(--orange-strong); }
.callout.bio   { border-left-color: var(--good); }   .callout.bio .callout-label   { color: var(--good); }
.callout.warn  { border-left-color: var(--warn); background: #FCF4E0; } .callout.warn .callout-label { color: var(--warn); }
.callout.key   { border-left-color: var(--orange); background: #F7F1E2; } .callout.key .callout-label { color: var(--orange-strong); }
.callout.try   { border-left-color: var(--accent); } .callout.try .callout-label { color: var(--accent); }

/* ---- Exercises ---- */
.exercise { border: 2px solid var(--border); border-radius: 8px; padding: 1rem 1.25rem; margin: 1.5rem 0; background: var(--panel); }
.exercise .ex-tag {
  display: inline-block; background: var(--orange-strong); color: #fff;
  font-family: Arial, Helvetica, sans-serif; font-weight: 700; font-size: 0.8rem;
  padding: 0.2rem 0.5rem; border-radius: 4px; text-transform: uppercase; letter-spacing: 0.04em;
}
.exercise .difficulty { font-family: Arial, Helvetica, sans-serif; font-size: 0.85rem; color: var(--ink-soft); }
.exercise h3 { margin-top: 0.5rem; color: var(--ink); }

/* ---- Reveal-able answers ---- */
details.answer { border: 2px dashed var(--border); border-radius: 6px; margin: 1rem 0 0; background: var(--panel-alt); }
details.answer > summary {
  cursor: pointer; font-family: Arial, Helvetica, sans-serif; font-weight: 700;
  color: var(--orange-strong); padding: 0.7rem 1rem; font-size: 1rem;
}
details.answer > summary:hover { background: #ECE7D8; }
details.answer .answer-body { padding: 0.25rem 1.1rem 1rem; }
details.answer[open] > summary { border-bottom: 1px solid var(--border-soft); }

/* ---- Code ---- */
pre, code { font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace; }
code { background: var(--code-bg); color: var(--code-ink); padding: 0.05rem 0.3rem; border-radius: 3px; font-size: 0.95em; }
pre {
  background: var(--code-bg); color: var(--code-ink);
  padding: 1rem 1.1rem; border: 1px solid var(--border-soft); border-left: 4px solid var(--accent);
  border-radius: 6px; overflow-x: auto; font-size: 1rem; line-height: 1.55;
}
pre code { background: transparent; padding: 0; }
/* In the accessible build, syntax-color spans are flattened to one ink color
   so screen readers and low-contrast detection stay simple. */
pre .cm, pre .kw, pre .st, pre .nu, pre .fn, pre .op { color: var(--code-ink); }
pre .cm { font-style: italic; }
.code-label {
  display: inline-block; background: #2c2c2c; color: #fff;
  font-family: Arial, Helvetica, sans-serif; font-size: 0.8rem; text-transform: uppercase;
  letter-spacing: 0.04em; padding: 0.25rem 0.6rem; border-radius: 4px 4px 0 0;
}
.code-label + pre { border-top-left-radius: 0; margin-top: 0; }

/* ---- Tables ---- */
table { border-collapse: collapse; width: 100%; margin: 1.25rem 0; }
caption { text-align: left; font-weight: 700; font-family: Arial, Helvetica, sans-serif; padding: 0.3rem 0; color: var(--ink); }
th, td { border: 1px solid var(--border); padding: 0.5rem 0.7rem; text-align: left; vertical-align: top; }
th { background: #E9E5DA; font-family: Arial, Helvetica, sans-serif; }
thead th { border-bottom: 2px solid var(--ink); }

/* ---- Math: keep MathJax output legible; assistive MathML is visually hidden ---- */
.eq, .eq-block { margin: 1rem 0; font-size: 1.05rem; }
.eq-block { background: var(--panel-alt); border-left: 4px solid var(--orange); padding: 0.6rem 1rem; border-radius: 0 6px 6px 0; overflow-x: auto; }
mjx-container { outline: none; }
mjx-container:focus { outline: 3px solid #0A4DA6; }

/* ---- Pills / tags (already real text) ---- */
.pill, .tag {
  display: inline-block; font-family: Arial, Helvetica, sans-serif; font-weight: 700;
  font-size: 0.78rem; padding: 0.15rem 0.5rem; border-radius: 4px; border: 1px solid var(--border);
  text-transform: uppercase; letter-spacing: 0.03em; background: #ECE9DF; color: var(--ink);
}

/* ---- Lab table-of-contents card ---- */
.lab-toc { border: 2px solid var(--orange); border-radius: 8px; padding: 1rem 1.25rem; margin: 1.5rem 0; background: var(--panel); }
.lab-toc h2 { border: none; margin-top: 0; }
.lab-toc .session { border-top: 1px solid var(--border-soft); padding: 0.75rem 0; }
.lab-toc .session:first-of-type { border-top: none; }
.lab-toc .session-label { font-family: Arial, Helvetica, sans-serif; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; font-size: 0.85rem; color: var(--orange-strong); }
.lab-toc .session-title { font-family: Arial, Helvetica, sans-serif; font-weight: 700; font-size: 1.05rem; margin: 0.2rem 0 0.4rem; }
.lab-toc .row { padding: 0.3rem 0; }
.lab-toc .row .tag { margin-right: 0.4rem; }
.lab-toc .note { color: var(--ink-soft); font-size: 0.92rem; }

/* ---- Practice banner ---- */
.practice-banner { border: 2px solid var(--good); border-left-width: 6px; background: #F1F8EC; padding: 0.9rem 1.1rem; border-radius: 0 6px 6px 0; margin: 1.5rem 0; }
.practice-banner .label { font-family: Arial, Helvetica, sans-serif; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; font-size: 0.8rem; color: var(--good); }
.practice-banner h3 { margin: 0.2rem 0 0.4rem; }
.practice-banner .hand-in { display: inline-block; margin-top: 0.4rem; padding: 0.35rem 0.7rem; border: 2px solid var(--orange-strong); border-radius: 4px; color: var(--orange-strong); font-family: Arial, Helvetica, sans-serif; font-weight: 700; text-decoration: underline; }
.practice-banner .hand-in:hover { background: var(--orange-strong); color: #fff; }

/* ---- Data files card ---- */
.data-card { border: 2px solid var(--accent); border-left-width: 6px; border-radius: 8px; padding: 1rem 1.25rem; margin: 1.5rem 0; background: var(--panel); }
.data-card h2 { border: none; margin-top: 0; }
.data-card .data-h { font-family: Arial, Helvetica, sans-serif; text-transform: uppercase; letter-spacing: 0.04em; font-size: 0.85rem; color: var(--accent); margin: 0.75rem 0 0.25rem; }
.data-card .data-row { padding: 0.35rem 0; border-bottom: 1px solid var(--border-soft); }
.data-card .data-row:last-child { border-bottom: none; }
.data-card .data-desc { display: block; color: var(--ink-soft); font-size: 0.95rem; }

/* ---- Tabs (ARIA wired in JS) ---- */
.tab-buttons { display: flex; flex-wrap: wrap; gap: 0.25rem; border-bottom: 2px solid var(--border); margin: 1rem 0 0; padding: 0; }
.tab-buttons button {
  font-family: Arial, Helvetica, sans-serif; font-size: 1rem; font-weight: 700;
  background: var(--panel-alt); color: var(--ink); border: 2px solid var(--border);
  border-bottom: none; padding: 0.5rem 1rem; cursor: pointer; border-radius: 6px 6px 0 0;
}
.tab-buttons button[aria-selected="true"] { background: var(--orange-strong); color: #fff; }
.tab-panel { border: 2px solid var(--border); border-top: none; padding: 1rem; }
.tab-panel[hidden] { display: none; }

/* ---- Quiz ---- */
.quiz { border: 2px solid var(--accent); border-radius: 8px; padding: 1rem 1.25rem; margin: 1.5rem 0; }
.quiz h4 { margin-top: 0; color: var(--accent); }
.quiz .choices { list-style: none; padding: 0; }
.quiz .choices li { padding: 0.3rem 0; }
.quiz .choices label { display: flex; gap: 0.6rem; align-items: flex-start; cursor: pointer; }
.quiz button { font-family: Arial, Helvetica, sans-serif; font-weight: 700; background: var(--accent); color: #fff; border: none; padding: 0.5rem 1.1rem; border-radius: 4px; cursor: pointer; font-size: 1rem; }
.quiz .feedback { margin-top: 0.8rem; padding: 0.7rem 0.9rem; border-radius: 6px; border: 2px solid var(--border); }
.quiz .feedback.correct { background: #E7F4E0; border-color: var(--good); color: var(--good); }
.quiz .feedback.wrong { background: #FBE9E6; border-color: var(--bad); color: var(--bad); }

/* ---- Footer ---- */
footer { border-top: 2px solid var(--border-soft); padding: 1.5rem 1.25rem; color: var(--ink-soft); font-size: 0.95rem; max-width: 75ch; margin: 2rem auto 0; }

/* ---- Visually-hidden helper for SR-only text ---- */
.sr-only {
  position: absolute !important; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

/* ---- High-contrast / forced-colors mode ---- */
@media (prefers-contrast: more) {
  :root { --ink: #000; --border: #000; --border-soft: #000; }
  a { text-decoration-thickness: 2px; }
}
@media (forced-colors: active) {
  .callout, .exercise, .lab-toc, .data-card, .practice-banner, .primer-banner, .quiz, details.answer, pre, th, td {
    border: 1px solid CanvasText;
  }
  .exercise .ex-tag, .practice-banner .hand-in, .tab-buttons button[aria-selected="true"] {
    forced-color-adjust: none;
  }
}

/* ---- Landing page (index) helpers ---- */
.day-list { list-style: none; padding: 0; max-width: 75ch; margin: 0 auto; }
.day-list > li { border: 2px solid var(--border); border-radius: 8px; padding: 1rem 1.25rem; margin: 1rem 0; }
.day-list h2 { margin-top: 0; }

/* ---- Plain-language primer banner (prominent "read first" link) ---- */
.primer-banner {
  display: block;
  border: 2px solid var(--orange);
  border-left: 8px solid var(--orange);
  background: #FFF6EC;
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  border-radius: 0 6px 6px 0;
  text-decoration: none;
  color: inherit;
}
.primer-banner:hover { background: #FDEBD9; }
.primer-banner .label {
  display: block;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--orange-strong);
}
.primer-banner .pb-title {
  display: block;
  font-size: 1.15rem;
  font-weight: 700;
  margin: 0.25rem 0 0.35rem;
  color: var(--link);
  text-decoration: underline;
  text-underline-offset: 2px;
}
.primer-banner .pb-desc { display: block; }
.primer-banner .pb-cta {
  display: inline-block;
  margin-top: 0.5rem;
  font-weight: 700;
  color: var(--link);
  text-decoration: underline;
}

/* ============================================================
   Interactive explorers (explore_*.html)
   These pages carry their own inline <style> written against the
   standard site's --osu-* custom properties. Alias them onto the
   accessible palette so the widgets keep their meaning (e.g. the
   selected mode button stays legible) instead of losing colour.
   ============================================================ */
:root {
  --osu-orange: #B33107;
  --osu-orange-dark: #8F2705;
  --osu-stone: #2E2E2E;
  --text: #161616;
  --muted: #4A4A4A;
}

/* .sr-readout is announced by screen readers (role=status / aria-live=polite)
 * AND kept visible: low-vision and sighted users benefit from the same
 * plain-text statement of the current parameters and derived quantities. */
.sr-readout {
  font-family: inherit;
  font-size: 1.05rem;
  line-height: 1.6;
  background: var(--panel-alt);
  border: 2px solid var(--border);
  border-left: 6px solid var(--orange);
  border-radius: 0 8px 8px 0;
  padding: 0.6rem 0.9rem;
  margin: 0.9rem 0;
  color: var(--ink);
}
.data-table-details { margin: 0.9rem 0; }
.data-table-details > summary {
  font-weight: 700;
  color: var(--link);
  text-decoration: underline;
  text-underline-offset: 2px;
  cursor: pointer;
  padding: 0.3rem 0;
}
.data-table-wrap { max-height: 24em; overflow: auto; border: 2px solid var(--border); }
.data-table-wrap table { border-collapse: collapse; width: 100%; font-size: 0.95rem; }
.data-table-wrap caption {
  caption-side: top;
  text-align: left;
  padding: 0.4rem 0.5rem;
  color: var(--ink-soft);
  font-size: 0.95rem;
}
.data-table-wrap th, .data-table-wrap td {
  border: 1px solid var(--border-soft);
  padding: 0.2rem 0.5rem;
  text-align: right;
  font-variant-numeric: tabular-nums;
}
.data-table-wrap th { background: var(--panel-alt); }