/* ============================================================
   Shared lesson stylesheet.
   Every lesson and reference document links this file.
   Tufte-adjacent: generous measure, sidenotes, restrained palette,
   and it must print cleanly.
   ============================================================ */

:root {
  --ink: #16150f;
  --ink-soft: #55524a;
  --ink-faint: #8b877c;
  --paper: #fffdf8;
  --rule: #e2ddd0;
  --accent: #8a3324;      /* burnt sienna — links, marks */
  --accent-soft: #f6ece7;
  --code-bg: #f4f1e8;
  --ok: #2d6a4f;
  --no: #9b2226;

  --measure: 34rem;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Charter, Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Inter", "Helvetica Neue", sans-serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0 auto;
  padding: 4rem 2rem 8rem;
  max-width: 66rem;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.0625rem;
  line-height: 1.6;
  font-kerning: normal;
  text-rendering: optimizeLegibility;
}

/* ---------- Masthead ---------- */

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

.eyebrow {
  font-family: var(--sans);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 0.6rem;
}

h1 {
  font-size: 2.1rem;
  line-height: 1.15;
  font-weight: 600;
  margin: 0 0 0.5rem;
  letter-spacing: -0.015em;
}

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

h2 {
  font-size: 1.4rem;
  font-weight: 600;
  margin: 3rem 0 0.75rem;
  max-width: var(--measure);
  letter-spacing: -0.01em;
}

h3 {
  font-family: var(--sans);
  font-size: 0.95rem;
  font-weight: 650;
  margin: 2rem 0 0.5rem;
  max-width: var(--measure);
}

p, ul, ol, blockquote, .block { max-width: var(--measure); }

p { margin: 0 0 1.1rem; }

ul, ol { padding-left: 1.2rem; margin: 0 0 1.1rem; }
li { margin-bottom: 0.4rem; }

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

strong { font-weight: 650; }

code {
  font-family: var(--mono);
  font-size: 0.855em;
  background: var(--code-bg);
  padding: 0.1em 0.32em;
  border-radius: 3px;
}

/* ---------- Code blocks ---------- */

pre {
  font-family: var(--mono);
  font-size: 0.8rem;
  line-height: 1.55;
  background: var(--code-bg);
  border-left: 3px solid var(--rule);
  padding: 1rem 1.1rem;
  overflow-x: auto;
  max-width: var(--measure);
  margin: 0 0 1.3rem;
}
pre code { background: none; padding: 0; font-size: inherit; }

.filename {
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--ink-faint);
  max-width: var(--measure);
  margin: 0 0 0.3rem;
  letter-spacing: 0.02em;
}

/* Terminal-flavoured block */
pre.shell {
  background: #1c1b16;
  color: #ece7d9;
  border-left-color: var(--accent);
}
pre.shell code { color: inherit; }
pre.shell .c { color: #8b877c; }   /* comment */

/* ---------- Sidenotes ---------- */

.sidenote {
  float: right;
  clear: right;
  width: 16rem;
  margin-right: -19rem;
  margin-bottom: 1rem;
  font-family: var(--sans);
  font-size: 0.78rem;
  line-height: 1.5;
  color: var(--ink-soft);
}
.sidenote .label {
  display: block;
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: 0.2rem;
}

@media (max-width: 1080px) {
  .sidenote {
    float: none;
    width: auto;
    margin: 0 0 1.2rem;
    max-width: var(--measure);
    border-left: 2px solid var(--rule);
    padding-left: 0.9rem;
  }
}

/* ---------- Callouts ---------- */

.callout {
  max-width: var(--measure);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--accent);
  background: #fffefb;
  padding: 1rem 1.2rem;
  margin: 0 0 1.4rem;
}
.callout > :last-child { margin-bottom: 0; }
.callout .label {
  font-family: var(--sans);
  font-size: 0.65rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  display: block;
  margin-bottom: 0.4rem;
}

/* The recurring "you already know this from Python" device */
.callout.python { border-left-color: #2d5f8a; }
.callout.python .label { color: #2d5f8a; }

.callout.warn { border-left-color: var(--no); }
.callout.warn .label { color: var(--no); }

/* ---------- Tables ---------- */

table {
  border-collapse: collapse;
  width: 100%;
  max-width: 46rem;
  font-family: var(--sans);
  font-size: 0.82rem;
  margin: 0 0 1.5rem;
}
th, td {
  text-align: left;
  padding: 0.5rem 0.7rem;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
}
th {
  font-weight: 600;
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  border-bottom-color: var(--ink-faint);
}

/* ---------- Steps ---------- */

.steps { counter-reset: step; list-style: none; padding: 0; max-width: var(--measure); }
.steps > li {
  counter-increment: step;
  position: relative;
  padding-left: 2.2rem;
  margin-bottom: 1.6rem;
}
.steps > li::before {
  content: counter(step);
  position: absolute;
  left: 0; top: 0.05rem;
  width: 1.5rem; height: 1.5rem;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-family: var(--sans);
  font-size: 0.75rem;
  font-weight: 600;
  display: grid;
  place-items: center;
}
.steps pre, .steps p, .steps ul { max-width: 100%; }

/* ---------- Footer / nav ---------- */

.lesson-footer {
  margin-top: 4rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--rule);
  max-width: var(--measure);
  font-family: var(--sans);
  font-size: 0.82rem;
  color: var(--ink-soft);
}
.lesson-footer h3 { margin-top: 0; }

.ask-teacher {
  background: var(--accent-soft);
  border: none;
  padding: 0.9rem 1.1rem;
  font-family: var(--sans);
  font-size: 0.82rem;
  max-width: var(--measure);
  margin: 2rem 0 0;
}

nav.lesson-nav { display: flex; gap: 1.5rem; flex-wrap: wrap; margin-top: 1.5rem; }

/* ---------- Print ---------- */

@media print {
  :root { --paper: #fff; }
  body { padding: 0; font-size: 10.5pt; max-width: none; }
  .sidenote { float: none; width: auto; margin: 0 0 1rem; border-left: 2px solid #ccc; padding-left: 0.8rem; }
  pre, .callout, table, .quiz { break-inside: avoid; }
  pre.shell { background: #f4f1e8; color: #16150f; }
  .quiz-controls, .ask-teacher, nav.lesson-nav { display: none; }
  a { color: var(--ink); text-decoration: none; }
  a[href^="http"]::after { content: " (" attr(href) ")"; font-size: 8pt; color: #666; }
}

/* ---------- Dark mode (screen only) ---------- */

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e8e3d6;
    --ink-soft: #a8a396;
    --ink-faint: #7d7970;
    --paper: #14130f;
    --rule: #33302a;
    --accent: #d98b6f;
    --accent-soft: #2a211c;
    --code-bg: #1d1c17;
  }
  .callout { background: #191811; }
  pre.shell { background: #0c0b08; }
  .callout.python { border-left-color: #6fa3d9; }
  .callout.python .label { color: #6fa3d9; }
  .callout.warn { border-left-color: #e0796f; }
  .callout.warn .label { color: #e0796f; }
}