/* ============================================================================
   course site — one stylesheet for lecture notes and class activities.
   Light and dark are both first-class: the palette is defined once as tokens
   and re-pointed under prefers-color-scheme.
   ==========================================================================*/

:root {
  --bg:        #fbfaf8;
  --surface:   #ffffff;
  --surface-2: #f3f1ed;
  --border:    #ddd8d0;
  --text:      #1f1d1a;
  --muted:     #6b655c;
  --accent:    #7a4b1e;
  --accent-2:  #a8641f;
  --ok:        #2f6b3f;
  --warn:      #8a5a00;
  --err:       #9b2f2f;
  --code-bg:   #f5f2ec;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --serif: ui-serif, Georgia, "Iowan Old Style", "Times New Roman", serif;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:        #171614;
    --surface:   #1f1e1b;
    --surface-2: #272521;
    --border:    #3a3733;
    --text:      #ece8e1;
    --muted:     #a49c90;
    --accent:    #e0a86a;
    --accent-2:  #c88c4a;
    --ok:        #7fc48f;
    --warn:      #e0b25f;
    --err:       #e08b8b;
    --code-bg:   #201f1c;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.65;
}

.wrap { max-width: 60rem; margin: 0 auto; padding: 0 1.25rem 6rem; }

/* ── masthead ───────────────────────────────────────────────────────────── */
header.masthead {
  border-bottom: 1px solid var(--border);
  background: var(--surface);
  padding: 1.6rem 0 1.3rem;
  margin-bottom: 2.5rem;
}
header.masthead .wrap { padding-bottom: 0; }
.eyebrow {
  font-family: var(--mono);
  font-size: .74rem;
  letter-spacing: .13em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 .45rem;
}
h1 { font-family: var(--serif); font-size: 2.05rem; line-height: 1.2; margin: 0 0 .5rem; font-weight: 600; }
.lede { color: var(--muted); margin: 0; max-width: 46rem; }
nav.crumbs { font-size: .85rem; margin-top: .9rem; }
nav.crumbs a { color: var(--muted); text-decoration: none; border-bottom: 1px solid var(--border); }
nav.crumbs a:hover { color: var(--accent); }

/* ── structure ──────────────────────────────────────────────────────────── */
h2 {
  font-family: var(--serif);
  font-size: 1.45rem;
  margin: 3rem 0 .8rem;
  padding-bottom: .35rem;
  border-bottom: 1px solid var(--border);
  font-weight: 600;
}
h3 { font-size: 1.08rem; margin: 2rem 0 .5rem; font-weight: 650; }
h4 { font-size: .95rem; margin: 1.4rem 0 .35rem; font-weight: 650; color: var(--muted); }
p  { margin: 0 0 1rem; }
ul, ol { margin: 0 0 1rem; padding-left: 1.4rem; }
li { margin-bottom: .35rem; }
a { color: var(--accent); }

/* ── code ───────────────────────────────────────────────────────────────── */
code { font-family: var(--mono); font-size: .875em; background: var(--code-bg);
       padding: .1em .35em; border-radius: 3px; }
pre {
  font-family: var(--mono);
  font-size: .82rem;
  line-height: 1.55;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: .85rem 1rem;
  overflow-x: auto;
  margin: 0 0 1rem;
}
pre code { background: none; padding: 0; font-size: inherit; }
pre .cm { color: var(--muted); font-style: italic; }
pre .kw { color: var(--accent); font-weight: 600; }
pre .hi { background: color-mix(in srgb, var(--accent) 18%, transparent); border-radius: 2px; }

/* ── callouts ───────────────────────────────────────────────────────────── */
.note, .warn, .key {
  border-left: 3px solid var(--accent);
  background: var(--surface);
  padding: .8rem 1rem;
  margin: 0 0 1.2rem;
  border-radius: 0 5px 5px 0;
}
.warn { border-left-color: var(--warn); }
.key  { border-left-color: var(--ok); }
.note > :last-child, .warn > :last-child, .key > :last-child { margin-bottom: 0; }
.note b, .warn b, .key b { display: block; font-size: .74rem; letter-spacing: .1em;
  text-transform: uppercase; font-family: var(--mono); margin-bottom: .3rem; color: var(--muted); }

/* ── cards / grid ───────────────────────────────────────────────────────── */
.grid { display: grid; gap: 1rem; grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); margin-bottom: 1.5rem; }
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 8px; padding: 1rem 1.1rem;
}
.card h3 { margin-top: 0; }
.card p:last-child { margin-bottom: 0; }
.card a.title { text-decoration: none; font-weight: 650; }

/* ── tables ─────────────────────────────────────────────────────────────── */
.tablewrap { overflow-x: auto; margin-bottom: 1.4rem; }
table { border-collapse: collapse; width: 100%; font-size: .9rem; }
th, td { text-align: left; padding: .45rem .7rem; border-bottom: 1px solid var(--border); vertical-align: top; }
th { font-size: .76rem; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); font-weight: 600; }
tbody tr:hover { background: var(--surface); }
td code { white-space: nowrap; }

/* ── pipeline diagram ───────────────────────────────────────────────────── */
.pipeline { margin: 0 0 1.6rem; }
.pipeline svg { width: 100%; height: auto; display: block; }
.pipeline .ph-box { fill: var(--surface); stroke: var(--border); }
.pipeline .ph-box.on { fill: color-mix(in srgb, var(--accent) 16%, var(--surface)); stroke: var(--accent); }
.pipeline .ph-box.done { fill: var(--surface-2); }
.pipeline .ph-t { fill: var(--text); font: 600 10px var(--sans); }
.pipeline .ph-s { fill: var(--muted); font: 9px var(--mono); }
.pipeline .ph-arrow { stroke: var(--border); fill: none; }
.pipeline .ph-lbl { fill: var(--muted); font: 8.5px var(--mono); }

/* ── interactive: tabs ──────────────────────────────────────────────────── */
.tabs { border: 1px solid var(--border); border-radius: 8px; overflow: hidden; margin-bottom: 1.5rem; background: var(--surface); }
.tabs .tabbar { display: flex; flex-wrap: wrap; gap: 0; border-bottom: 1px solid var(--border); background: var(--surface-2); }
.tabs button {
  appearance: none; border: 0; background: none; cursor: pointer;
  font: 600 .78rem var(--mono); letter-spacing: .04em;
  padding: .55rem .9rem; color: var(--muted); border-bottom: 2px solid transparent;
}
.tabs button[aria-selected="true"] { color: var(--accent); border-bottom-color: var(--accent); background: var(--surface); }
.tabs .panel { padding: .9rem 1rem 0; }
.tabs .panel pre { margin-bottom: .9rem; }

/* ── interactive: stepper ───────────────────────────────────────────────── */
.stepper { border: 1px solid var(--border); border-radius: 8px; background: var(--surface); margin-bottom: 1.5rem; }
.stepper .bar { display: flex; align-items: center; gap: .6rem; padding: .55rem .8rem;
  border-bottom: 1px solid var(--border); background: var(--surface-2); }
.stepper .bar button {
  appearance: none; cursor: pointer; font: 600 .78rem var(--mono);
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  border-radius: 5px; padding: .28rem .7rem;
}
.stepper .bar button:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
.stepper .bar button:disabled { opacity: .4; cursor: default; }
.stepper .count { font: .78rem var(--mono); color: var(--muted); margin-left: auto; }
.stepper .body { padding: .9rem 1rem; }
.stepper .body .caption { font-size: .9rem; color: var(--muted); margin: 0 0 .6rem; }
.stepper .body pre { margin-bottom: 0; }

/* ── interactive: reveal ────────────────────────────────────────────────── */
details.reveal {
  border: 1px solid var(--border); border-radius: 6px; background: var(--surface);
  padding: .55rem .85rem; margin-bottom: 1rem;
}
details.reveal summary {
  cursor: pointer; font: 600 .8rem var(--mono); color: var(--accent);
  letter-spacing: .03em; list-style: none;
}
details.reveal summary::-webkit-details-marker { display: none; }
details.reveal summary::before { content: "▸ "; }
details.reveal[open] summary::before { content: "▾ "; }
details.reveal[open] summary { margin-bottom: .6rem; }
details.reveal > :last-child { margin-bottom: 0; }

/* ── interactive: quiz ──────────────────────────────────────────────────── */
.quiz { border: 1px solid var(--border); border-radius: 8px; background: var(--surface);
        padding: 1rem 1.1rem; margin-bottom: 1.5rem; }
.quiz .q { font-weight: 600; margin-bottom: .7rem; }
.quiz .opt { display: block; width: 100%; text-align: left; cursor: pointer;
  border: 1px solid var(--border); background: var(--bg); color: var(--text);
  border-radius: 5px; padding: .45rem .7rem; margin-bottom: .4rem; font: inherit; font-size: .92rem; }
.quiz .opt:hover { border-color: var(--accent); }
.quiz .opt.right { border-color: var(--ok); background: color-mix(in srgb, var(--ok) 12%, var(--bg)); }
.quiz .opt.wrong { border-color: var(--err); background: color-mix(in srgb, var(--err) 12%, var(--bg)); }
.quiz .fb { font-size: .9rem; margin-top: .6rem; color: var(--muted); min-height: 1.2em; }
.quiz .fb.shown { color: var(--text); }

/* ── activity blocks ────────────────────────────────────────────────────── */
.meta {
  display: flex; flex-wrap: wrap; gap: .5rem 1.4rem;
  font: .8rem var(--mono); color: var(--muted);
  border: 1px solid var(--border); border-radius: 8px;
  padding: .7rem .9rem; margin-bottom: 1.8rem; background: var(--surface);
}
.meta b { color: var(--text); font-weight: 600; }
ol.steps { counter-reset: st; list-style: none; padding-left: 0; }
ol.steps > li {
  counter-increment: st; position: relative; padding-left: 2.2rem; margin-bottom: 1.1rem;
}
ol.steps > li::before {
  content: counter(st); position: absolute; left: 0; top: .1rem;
  width: 1.55rem; height: 1.55rem; border-radius: 50%;
  background: var(--surface-2); border: 1px solid var(--border);
  font: 600 .78rem var(--mono); color: var(--accent);
  display: grid; place-items: center;
}
.deliverable { border: 2px solid var(--accent); border-radius: 8px; padding: 1rem 1.1rem;
  background: var(--surface); margin: 1.5rem 0; }
.deliverable h3 { margin-top: 0; color: var(--accent); }
.deliverable > :last-child { margin-bottom: 0; }

/* ── footer ─────────────────────────────────────────────────────────────── */
footer.pagefoot { border-top: 1px solid var(--border); margin-top: 4rem; padding-top: 1.2rem;
  font-size: .85rem; color: var(--muted); display: flex; flex-wrap: wrap; gap: 1rem; justify-content: space-between; }
footer.pagefoot a { color: var(--muted); }

@media print {
  body { background: #fff; color: #000; font-size: 11pt; }
  .stepper .bar, .quiz .opt { display: none; }
  details.reveal[open] summary { color: #000; }
  details.reveal { break-inside: avoid; }
}

/* ── figures and diagrams ───────────────────────────────────────────────── */
figure.dia {
  margin: 0 0 1.6rem; padding: 1rem 1rem .6rem;
  border: 1px solid var(--border); border-radius: 8px; background: var(--surface);
}
figure.dia svg { width: 100%; height: auto; display: block; margin: 0 auto; }
figure.dia figcaption {
  margin-top: .7rem; padding-top: .6rem; border-top: 1px solid var(--border);
  font-size: .85rem; color: var(--muted);
}
figure.dia figcaption b { color: var(--text); font-weight: 600; }

/* shared diagram primitives */
.d-box   { fill: var(--surface-2); stroke: var(--border); }
.d-box.on{ fill: color-mix(in srgb, var(--accent) 16%, var(--surface)); stroke: var(--accent); }
.d-box.alt{ fill: color-mix(in srgb, var(--ok) 13%, var(--surface)); stroke: color-mix(in srgb, var(--ok) 55%, var(--border)); }
.d-t     { fill: var(--text); font: 600 12px var(--sans); }
.d-s     { fill: var(--muted); font: 11px var(--mono); }
.d-s2    { fill: var(--muted); font: 10px var(--sans); font-style: italic; }
.d-line  { stroke: var(--border); fill: none; stroke-width: 1.2; }
.d-line.hot { stroke: var(--accent); stroke-width: 1.6; }
.d-dash  { stroke: var(--muted); fill: none; stroke-dasharray: 4 3; stroke-width: 1; }
.d-state { fill: var(--surface); stroke: var(--text); stroke-width: 1.4; }
.d-state.acc { stroke: var(--ok); stroke-width: 2; }
.d-state.start { fill: color-mix(in srgb, var(--accent) 14%, var(--surface)); }
.d-lbl   { fill: var(--text); font: 600 11px var(--mono); }
.d-edge  { fill: var(--muted); font: 10px var(--mono); }

/* readings box */
.readings {
  border: 1px solid var(--border); border-left: 3px solid var(--ok);
  border-radius: 0 6px 6px 0; background: var(--surface);
  padding: .85rem 1rem; margin: 0 0 1.4rem;
}
.readings > b { display: block; font: 600 .74rem var(--mono); letter-spacing: .1em;
  text-transform: uppercase; color: var(--muted); margin-bottom: .45rem; }
.readings ul { margin-bottom: 0; }
.readings cite { font-style: normal; font-weight: 600; }

/* numbered section headings */
h2 .secnum { font-family: var(--mono); font-size: .78em; color: var(--accent);
  margin-right: .5rem; font-weight: 700; }

/* Comments inside a code block, dimmed so the code itself reads first.
   Written in the source as «…» — see code() in docgen.py. */
pre code .cm { color: var(--muted); font-style: italic; }

/* ── two-table color coding ────────────────────────────────────────────────
   The Topic 2 reference handout contrasts two symbol tables, and the reader
   has to keep them apart across three figures, two tables and a worked
   example.  So the two get one color each, reused everywhere without
   exception: the scope stack is --ok, the storage map is --accent.  Both
   tokens are already theme-aware, which is the reason for reusing them rather
   than introducing a third and a fourth hue. */
.t-scope { color: var(--ok);     font-weight: 650; }
.t-store { color: var(--accent); font-weight: 650; }

/* A frame slot the optimizer deleted: present in the drawing so the reader can
   see what went missing, but clearly not part of the final frame. */
.d-box.gone { fill: none; stroke: var(--muted); stroke-dasharray: 4 3; }