/* Shared lesson stylesheet — Tufte-inspired.
   Linked by every lesson and reference doc so the course looks consistent. */

:root {
  --ink: #1a1a1a;
  --paper: #fdfcf9;
  --muted: #6b6b6b;
  --rule: #e2ddd2;
  --accent: #8a1c1c;      /* deep red, used sparingly */
  --code-bg: #f4f1ea;
  --good: #1f6b3b;
  --warn: #9a6b00;
  --link: #2a4b8d;
  --mono: "SF Mono", "JetBrains Mono", "Fira Code", Consolas, monospace;
  --serif: Georgia, "Iowan Old Style", "Palatino Linotype", serif;
}

* { box-sizing: border-box; }

html { font-size: 18px; }

body {
  font-family: var(--serif);
  color: var(--ink);
  background: var(--paper);
  line-height: 1.55;
  max-width: 46rem;
  margin: 3rem auto 6rem;
  padding: 0 1.5rem;
  -webkit-font-smoothing: antialiased;
}

.eyebrow {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 0.4rem;
}

h1 { font-size: 1.9rem; line-height: 1.15; margin: 0 0 0.6rem; }
h2 { font-size: 1.3rem; margin: 2.4rem 0 0.6rem; border-bottom: 1px solid var(--rule); padding-bottom: 0.3rem; }
h3 { font-size: 1.05rem; margin: 1.6rem 0 0.4rem; }

p, li { font-size: 1.02rem; }
.lede { font-size: 1.12rem; color: #333; }

a { color: var(--link); text-decoration: none; border-bottom: 1px solid #c9d2e6; }
a:hover { border-bottom-color: var(--link); }

code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--code-bg);
  padding: 0.1em 0.35em;
  border-radius: 3px;
}

pre {
  font-family: var(--mono);
  font-size: 0.82rem;
  line-height: 1.5;
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--accent);
  border-radius: 4px;
  padding: 0.9rem 1.1rem;
  overflow-x: auto;
}
pre code { background: none; padding: 0; font-size: 1em; }

.cmt { color: var(--muted); font-style: italic; }
.kw  { color: var(--accent); }
.lit { color: var(--good); font-weight: 600; }

blockquote {
  margin: 1.2rem 0;
  padding: 0.2rem 0 0.2rem 1.1rem;
  border-left: 3px solid var(--rule);
  color: #444;
}

.callout {
  border: 1px solid var(--rule);
  border-radius: 6px;
  padding: 0.9rem 1.1rem;
  margin: 1.4rem 0;
  background: #fffef9;
}
.callout.tip   { border-left: 4px solid var(--good); }
.callout.warn  { border-left: 4px solid var(--warn); background: #fffdf3; }
.callout .label {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  display: block;
  margin-bottom: 0.35rem;
}
.callout.tip  .label { color: var(--good); }
.callout.warn .label { color: var(--warn); }

table { border-collapse: collapse; width: 100%; margin: 1.2rem 0; font-size: 0.92rem; }
th, td { text-align: left; padding: 0.45rem 0.7rem; border-bottom: 1px solid var(--rule); vertical-align: top; }
th { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); }
td.mono, th.mono { font-family: var(--mono); font-size: 0.82rem; }

hr { border: none; border-top: 1px solid var(--rule); margin: 2.5rem 0; }

.step { font-family: var(--mono); color: var(--accent); font-weight: 700; }

/* Quiz widget */
.quiz { margin: 1.1rem 0; }
.quiz .q { font-weight: 600; margin-bottom: 0.5rem; }
.quiz button {
  display: block; width: 100%; text-align: left;
  font-family: var(--serif); font-size: 0.96rem;
  background: #fff; border: 1px solid var(--rule); border-radius: 5px;
  padding: 0.55rem 0.8rem; margin: 0.35rem 0; cursor: pointer;
  transition: background 0.12s, border-color 0.12s;
}
.quiz button:hover { background: #faf8f2; }
.quiz button.correct { border-color: var(--good); background: #eef7f0; }
.quiz button.wrong   { border-color: var(--accent); background: #fbeeee; }
.quiz .fb { font-size: 0.9rem; margin-top: 0.4rem; min-height: 1.2rem; color: #444; }
.quiz .fb.show-correct { color: var(--good); }
.quiz .fb.show-wrong   { color: var(--accent); }

/* Prev / next lesson navigation — sits above the footer note */
.lesson-nav {
  display: flex; flex-wrap: wrap; align-items: stretch; gap: 0.6rem;
  margin-top: 3rem; padding-top: 1.4rem; border-top: 1px solid var(--rule);
}
.lesson-nav a {
  flex: 1 1 0; min-width: 0;
  border: 1px solid var(--rule); border-radius: 6px;
  padding: 0.5rem 0.8rem; background: #fff;
  font-family: var(--mono); font-size: 0.78rem; line-height: 1.35;
  color: var(--link); border-bottom: 1px solid var(--rule);
  transition: border-color 0.12s, background 0.12s;
}
.lesson-nav a:hover { border-color: var(--link); background: #faf8f2; }
.lesson-nav a.prev { text-align: left; }
.lesson-nav a.next { text-align: right; }
.lesson-nav a.up {
  flex: 0 0 auto; align-self: center; text-align: center;
  color: var(--muted); border-style: dashed;
}
.lesson-nav .nav-label {
  display: block; font-size: 0.62rem; letter-spacing: 0.1em;
  text-transform: uppercase; color: var(--muted); margin-bottom: 0.15rem;
}
.lesson-nav .spacer { flex: 1 1 0; }
@media (max-width: 34rem) {
  .lesson-nav { flex-direction: column; }
  .lesson-nav a.up { order: -1; }
}

.footer-note {
  margin-top: 1.6rem; padding-top: 1rem; border-top: 1px solid var(--rule);
  font-size: 0.9rem; color: var(--muted);
}

@media print {
  .lesson-nav { display: none; }
  body { max-width: none; margin: 0; font-size: 11pt; }
  .quiz button { break-inside: avoid; }
  a { color: var(--ink); border: none; }
}