/* course.css — shared stylesheet for every lesson and reference sheet.
   Tufte-adjacent: generous measure, sidenotes, restrained colour, prints well. */

:root {
  --bg: #fffef9;
  --bg-sunk: #f6f4ec;
  --ink: #1a1a18;
  --ink-soft: #5c594f;
  --ink-faint: #8b877a;
  --rule: #ddd8c8;
  --accent: #8a4f1e;
  --accent-soft: #f2e6d8;
  --good: #2e6b3e;
  --bad: #9b2c2c;
  --code-bg: #f4f1e8;
  --measure: 38rem;
  --font-text: "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua",
    Georgia, "Times New Roman", serif;
  --font-mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas,
    monospace;
  --font-sans: ui-sans-serif, -apple-system, "Segoe UI", Roboto, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15161a;
    --bg-sunk: #1d1f24;
    --ink: #e6e3da;
    --ink-soft: #a9a496;
    --ink-faint: #77736a;
    --rule: #33353c;
    --accent: #d99a5e;
    --accent-soft: #2b2419;
    --good: #7fbf8f;
    --bad: #e08585;
    --code-bg: #1e2026;
  }
}

:root[data-theme="dark"] {
  --bg: #15161a;
  --bg-sunk: #1d1f24;
  --ink: #e6e3da;
  --ink-soft: #a9a496;
  --ink-faint: #77736a;
  --rule: #33353c;
  --accent: #d99a5e;
  --accent-soft: #2b2419;
  --good: #7fbf8f;
  --bad: #e08585;
  --code-bg: #1e2026;
}

:root[data-theme="light"] {
  --bg: #fffef9;
  --bg-sunk: #f6f4ec;
  --ink: #1a1a18;
  --ink-soft: #5c594f;
  --ink-faint: #8b877a;
  --rule: #ddd8c8;
  --accent: #8a4f1e;
  --accent-soft: #f2e6d8;
  --good: #2e6b3e;
  --bad: #9b2c2c;
  --code-bg: #f4f1e8;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-text);
  font-size: 1.0625rem;
  line-height: 1.62;
  -webkit-text-size-adjust: 100%;
  text-rendering: optimizeLegibility;
}

.wrap {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 3rem 1.25rem 6rem;
}

/* ---------- masthead ---------- */

.masthead {
  border-bottom: 1px solid var(--rule);
  padding-bottom: 1.25rem;
  margin-bottom: 2.5rem;
}

.crumb {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 0.75rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: baseline;
}
.crumb a { color: var(--ink-faint); text-decoration: none; border-bottom: 1px solid var(--rule); }
.crumb a:hover { color: var(--accent); }
.crumb .sep { opacity: 0.5; }

h1 {
  font-size: 2rem;
  line-height: 1.15;
  margin: 0 0 0.5rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.standfirst {
  font-size: 1.1rem;
  color: var(--ink-soft);
  font-style: italic;
  margin: 0;
}

.meta {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  color: var(--ink-faint);
  margin-top: 1rem;
  letter-spacing: 0.03em;
}

/* ---------- headings ---------- */

h2 {
  font-size: 1.3rem;
  font-weight: 600;
  margin: 3rem 0 0.75rem;
  line-height: 1.25;
}

h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 2rem 0 0.5rem;
}

h2 + p, h3 + p { margin-top: 0; }

p { margin: 0 0 1.1rem; }

a { color: var(--accent); text-underline-offset: 2px; }

strong { font-weight: 600; }

/* ---------- code ---------- */

code {
  font-family: var(--font-mono);
  font-size: 0.86em;
  background: var(--code-bg);
  padding: 0.1em 0.34em;
  border-radius: 3px;
  word-break: break-word;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-radius: 5px;
  padding: 0.9rem 1rem;
  overflow-x: auto;
  font-size: 0.82rem;
  line-height: 1.55;
  margin: 0 0 1.3rem;
}
pre code { background: none; padding: 0; font-size: 1em; }

.cmt { color: var(--ink-faint); font-style: italic; }
.ok  { color: var(--good); }
.err { color: var(--bad); }

/* ---------- tables ---------- */

.tablewrap { overflow-x: auto; margin: 0 0 1.5rem; }

table {
  border-collapse: collapse;
  width: 100%;
  font-family: var(--font-sans);
  font-size: 0.83rem;
  line-height: 1.45;
}

th {
  text-align: left;
  font-weight: 600;
  border-bottom: 2px solid var(--rule);
  padding: 0.5rem 0.7rem 0.5rem 0;
  vertical-align: bottom;
}

td {
  border-bottom: 1px solid var(--rule);
  padding: 0.55rem 0.7rem 0.55rem 0;
  vertical-align: top;
}

td code, th code { font-size: 0.92em; }

/* ---------- callouts ---------- */

.note {
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  padding: 0.85rem 1rem;
  margin: 0 0 1.4rem;
  font-size: 0.95rem;
  border-radius: 0 4px 4px 0;
}
.note > :last-child { margin-bottom: 0; }
.note .label {
  display: block;
  font-family: var(--font-sans);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.3rem;
  font-weight: 600;
}

.note.trap { border-left-color: var(--bad); background: none; }
.note.trap .label { color: var(--bad); }
.note.trap { border: 1px solid var(--rule); border-left: 3px solid var(--bad); }

/* ---------- layer diagram ---------- */

.layers { margin: 0 0 1.6rem; }

.layer {
  display: grid;
  grid-template-columns: 2.2rem 1fr;
  gap: 0 0.9rem;
  border: 1px solid var(--rule);
  border-radius: 5px;
  padding: 0.8rem 1rem;
  margin-bottom: 0.5rem;
  background: var(--bg-sunk);
}

.layer .n {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--accent);
  grid-row: span 2;
  align-self: start;
  line-height: 1.3;
}

.layer .t {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.92rem;
}

.layer .d {
  font-size: 0.88rem;
  color: var(--ink-soft);
}
.layer .d code { font-size: 0.86em; }

/* ---------- flow ---------- */

.flow {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  line-height: 1.7;
  background: var(--bg-sunk);
  border: 1px solid var(--rule);
  border-radius: 5px;
  padding: 1rem;
  overflow-x: auto;
  margin: 0 0 1.5rem;
  white-space: pre;
  color: var(--ink-soft);
}

/* ---------- quiz ---------- */

.quiz {
  border: 1px solid var(--rule);
  border-radius: 6px;
  padding: 1.1rem 1.2rem;
  margin: 0 0 1.2rem;
  background: var(--bg-sunk);
}

.quiz .q {
  font-weight: 600;
  margin: 0 0 0.85rem;
  font-size: 1rem;
}

.quiz .opts { display: grid; gap: 0.4rem; }

.quiz button.opt {
  font-family: var(--font-sans);
  font-size: 0.86rem;
  text-align: left;
  padding: 0.55rem 0.8rem;
  border: 1px solid var(--rule);
  border-radius: 4px;
  background: var(--bg);
  color: var(--ink);
  cursor: pointer;
  line-height: 1.4;
  transition: border-color 0.12s, background 0.12s;
}
.quiz button.opt:hover:not([disabled]) { border-color: var(--accent); }
.quiz button.opt[disabled] { cursor: default; opacity: 0.55; }
.quiz button.opt.right {
  border-color: var(--good);
  box-shadow: inset 3px 0 0 var(--good);
  opacity: 1;
  font-weight: 600;
}
.quiz button.opt.wrong {
  border-color: var(--bad);
  box-shadow: inset 3px 0 0 var(--bad);
  opacity: 1;
}

.quiz .why {
  margin-top: 0.85rem;
  font-size: 0.9rem;
  color: var(--ink-soft);
  border-top: 1px solid var(--rule);
  padding-top: 0.75rem;
  display: none;
}
.quiz .why.show { display: block; }
.quiz .why > :last-child { margin-bottom: 0; }

.recall {
  border: 1px dashed var(--rule);
  border-radius: 6px;
  padding: 1.1rem 1.2rem;
  margin: 0 0 1.2rem;
}
.recall .q { font-weight: 600; margin: 0 0 0.6rem; }
.recall .peek {
  font-family: var(--font-sans);
  font-size: 0.78rem;
  padding: 0.35rem 0.75rem;
  border: 1px solid var(--rule);
  border-radius: 4px;
  background: var(--bg);
  color: var(--ink-soft);
  cursor: pointer;
}
.recall .a { display: none; margin-top: 0.8rem; font-size: 0.93rem; color: var(--ink-soft); }
.recall .a.show { display: block; }
.recall .a > :last-child { margin-bottom: 0; }

/* ---------- checklist ---------- */

.check { list-style: none; padding: 0; margin: 0 0 1.5rem; }
.check li {
  display: flex;
  gap: 0.7rem;
  align-items: flex-start;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--rule);
  font-size: 0.95rem;
}
.check input { margin-top: 0.42rem; flex: none; accent-color: var(--accent); }

/* ---------- footer ---------- */

.foot {
  margin-top: 4rem;
  border-top: 1px solid var(--rule);
  padding-top: 1.5rem;
  font-size: 0.9rem;
  color: var(--ink-soft);
}

.foot h2 { font-size: 0.72rem; letter-spacing: 0.1em; text-transform: uppercase;
  color: var(--ink-faint); margin: 0 0 0.6rem; font-family: var(--font-sans); }

.source {
  border-left: 3px solid var(--rule);
  padding-left: 0.9rem;
  margin: 0 0 1.6rem;
}
.source .label {
  font-family: var(--font-sans);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  display: block;
  margin-bottom: 0.3rem;
}

.nextprev {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  margin-top: 1.6rem;
}

.ask {
  font-size: 0.9rem;
  color: var(--ink-soft);
  background: var(--bg-sunk);
  border-radius: 5px;
  padding: 0.85rem 1rem;
  margin-top: 1.6rem;
}
.ask > :last-child { margin-bottom: 0; }

/* ---------- index page ---------- */

.toc { list-style: none; padding: 0; margin: 0 0 2rem; counter-reset: l; }
.toc li { border-bottom: 1px solid var(--rule); }
.toc a {
  display: grid;
  grid-template-columns: 2.6rem 1fr;
  gap: 0.6rem;
  padding: 0.85rem 0;
  text-decoration: none;
  color: inherit;
}
.toc a:hover .tt { color: var(--accent); }
.toc .num {
  font-family: var(--font-sans);
  font-size: 0.78rem;
  color: var(--ink-faint);
  padding-top: 0.15rem;
  letter-spacing: 0.05em;
}
.toc .tt { display: block; font-weight: 600; font-size: 1rem; line-height: 1.3;
  font-family: var(--font-sans); }
.toc .td { display: block; font-size: 0.88rem; color: var(--ink-soft);
  line-height: 1.45; margin-top: 0.25rem; }

.pill {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.64rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  border: 1px solid var(--rule);
  border-radius: 999px;
  padding: 0.1rem 0.5rem;
  color: var(--ink-faint);
  vertical-align: 0.15em;
  margin-left: 0.4rem;
}

/* ---------- print ---------- */

@media print {
  :root {
    --bg: #fff; --bg-sunk: #fff; --ink: #000; --ink-soft: #333;
    --ink-faint: #666; --rule: #bbb; --accent: #000; --accent-soft: #fff;
    --code-bg: #f4f4f4;
  }
  body { font-size: 10.5pt; }
  .wrap { max-width: none; padding: 0; }
  .nextprev, .ask, .quiz .opts, .recall .peek { display: none; }
  .quiz .why, .recall .a { display: block; }
  h2 { page-break-after: avoid; margin-top: 1.6rem; }
  table, pre, .layer, .note { page-break-inside: avoid; }
  a { color: #000; text-decoration: none; }
  a[href^="http"]::after { content: " (" attr(href) ")"; font-size: 8pt; color: #666; }
  .crumb a::after { content: none; }
}

@media (max-width: 480px) {
  .wrap { padding: 2rem 1rem 4rem; }
  h1 { font-size: 1.6rem; }
}