/* Copied from peiyuUniversity/aie1001/site/assets/style.css via peiyuAIForAll (no Google Fonts @import, so it
   works offline and in mainland China). Colours follow kit/style.py, so the site matches the videos. */
:root {
  --paper: #f6f5f1;
  --paper-2: #efede6;
  --card: #ffffff;
  --card-2: #e7ebe8;
  --ink: #1d232b;
  --ink-2: #4a525b;
  --stone: #7d847f;
  --line: #d9dbd4;
  --grid: rgba(29, 35, 43, 0.045);
  --teal: #0f6e73;
  --teal-soft: #d5e8e6;
  --sea: #3e8e8a;
  --amber: #c27a1a;
  --mark: #f6e3be;
  --red: #b03a2e;
  --red-soft: #f4dcd8;
  --green: #2f7d4f;
  --green-soft: #d8ecdf;
  --code-bg: #ffffff;
  --code-line: #fbf1dc;
  --kw: #0f6e73;
  --fn: #8a4f0f;
  --str: #2f7d4f;
  --num: #b03a2e;
  --com: #8b918c;
  --shadow: 0 1px 2px rgba(29, 35, 43, 0.06), 0 6px 24px rgba(29, 35, 43, 0.06);
  --sans: "IBM Plex Sans", system-ui, -apple-system, sans-serif;
  --display: "Space Grotesk", "IBM Plex Sans", system-ui, sans-serif;
  --mono: "Source Code Pro", ui-monospace, Menlo, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #14181d;
    --paper-2: #1a1f25;
    --card: #1e242b;
    --card-2: #252c34;
    --ink: #e8e6df;
    --ink-2: #b4b8b3;
    --stone: #8d948f;
    --line: #333b44;
    --grid: rgba(232, 230, 223, 0.035);
    --teal: #4fb3b0;
    --teal-soft: #173a3b;
    --sea: #6bb3ad;
    --amber: #e3a54b;
    --mark: #4a3818;
    --red: #e07a6c;
    --red-soft: #45231f;
    --green: #6cc08c;
    --green-soft: #1d3b29;
    --code-bg: #181d23;
    --code-line: #3a3020;
    --kw: #5fc4c0;
    --fn: #e9b066;
    --str: #8fd0a4;
    --num: #ec9283;
    --com: #7a817c;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 6px 24px rgba(0, 0, 0, 0.25);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --paper: #14181d;
  --paper-2: #1a1f25;
  --card: #1e242b;
  --card-2: #252c34;
  --ink: #e8e6df;
  --ink-2: #b4b8b3;
  --stone: #8d948f;
  --line: #333b44;
  --grid: rgba(232, 230, 223, 0.035);
  --teal: #4fb3b0;
  --teal-soft: #173a3b;
  --sea: #6bb3ad;
  --amber: #e3a54b;
  --mark: #4a3818;
  --red: #e07a6c;
  --red-soft: #45231f;
  --green: #6cc08c;
  --green-soft: #1d3b29;
  --code-bg: #181d23;
  --code-line: #3a3020;
  --kw: #5fc4c0;
  --fn: #e9b066;
  --str: #8fd0a4;
  --num: #ec9283;
  --com: #7a817c;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 6px 24px rgba(0, 0, 0, 0.25);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 76px; }
body {
  margin: 0;
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 24px 24px;
  color: var(--ink);
  font: 16px/1.65 var(--sans);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--teal); }
code, .mono { font-family: var(--mono); font-size: 0.92em; }
p code, li code, td code, .callout code {
  background: var(--card-2);
  padding: 0.08em 0.35em;
  border-radius: 4px;
}
button { font: inherit; color: inherit; }
h1, h2, h3 { font-family: var(--display); letter-spacing: -0.01em; line-height: 1.2; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: 20px;
  padding: 10px 24px;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); flex: none; }
.brand-mark {
  width: 32px; height: 32px; border-radius: 8px;
  display: grid; place-items: center;
  background: var(--teal); color: var(--paper);
  font: 700 15px var(--mono);
}
.brand-text b { display: block; font: 700 15px/1.1 var(--display); }
.brand-text span { font-size: 11px; color: var(--stone); }
.chapnav { display: flex; gap: 2px; overflow-x: auto; flex: 1; scrollbar-width: none; }
.chapnav::-webkit-scrollbar { display: none; }
.chapnav a {
  white-space: nowrap; text-decoration: none; color: var(--ink-2);
  font-size: 13px; padding: 6px 10px; border-radius: 6px;
}
.chapnav a:hover { background: var(--card-2); }
.chapnav a.active { color: var(--teal); background: var(--teal-soft); font-weight: 600; }
.chapnav a span { font-family: var(--mono); opacity: 0.7; margin-right: 4px; }
.iconbtn {
  flex: none; width: 34px; height: 34px; border-radius: 8px;
  border: 1px solid var(--line); background: var(--card); cursor: pointer;
  display: grid; place-items: center;
}
.iconbtn:hover { border-color: var(--teal); }
.progress { position: absolute; left: 0; bottom: -1px; height: 2px; background: var(--teal); width: 0; }

/* ---------- layout ---------- */
.wrap { max-width: 1180px; margin: 0 auto; padding: 0 24px; }
main { min-height: 70vh; }

/* ---------- home ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); gap: 48px; align-items: center; padding: 64px 0 40px; }
.pill {
  display: inline-block; font: 500 12px var(--mono);
  color: var(--teal); background: var(--teal-soft);
  border: 1px solid color-mix(in srgb, var(--teal) 30%, transparent);
  padding: 4px 10px; border-radius: 999px;
}
.hero h1 { font-size: clamp(40px, 6vw, 64px); margin: 18px 0 6px; }
.hero h1 small { display: block; font-size: 0.42em; color: var(--ink-2); font-weight: 500; margin-top: 10px; }
.hero p.lead { font-size: 18px; color: var(--ink-2); max-width: 34em; }
.btnrow { display: flex; flex-wrap: wrap; gap: 12px; margin: 26px 0 18px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 18px; border-radius: 10px; text-decoration: none;
  font-weight: 600; font-size: 15px; cursor: pointer;
  border: 1px solid var(--line); background: var(--card); color: var(--ink);
}
.btn.primary { background: var(--teal); border-color: var(--teal); color: var(--paper); }
.btn:hover { filter: brightness(1.05); border-color: var(--teal); }
.meta { font-size: 13px; color: var(--stone); }

.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: 14px; box-shadow: var(--shadow);
}
.hero-demo { padding: 16px; }
.hero-demo .head, .demo .head {
  display: flex; justify-content: space-between; align-items: center; gap: 12px;
  font: 500 12px var(--mono); color: var(--stone); margin-bottom: 10px;
}
.hero-demo .caption { font-size: 13px; color: var(--ink-2); text-align: center; margin-top: 10px; }

.section-title { text-align: center; margin: 56px 0 8px; font-size: 30px; }
.section-sub { text-align: center; color: var(--stone); margin: 0 0 28px; }
.why { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.why .card { padding: 20px; }
.why h3 { margin: 0 0 6px; font-size: 17px; color: var(--teal); }
.why p { margin: 0; color: var(--ink-2); font-size: 15px; }

.chapters { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 18px; }
.chapcard {
  padding: 20px; text-decoration: none; color: var(--ink);
  display: flex; flex-direction: column; gap: 8px;
  transition: transform 0.15s, border-color 0.15s;
}
.chapcard:hover { transform: translateY(-2px); border-color: var(--teal); }
.chapcard .num { font: 700 28px var(--display); color: var(--amber); }
.chapcard h3 { margin: 0; font-size: 19px; }
.chapcard p { margin: 0; color: var(--ink-2); font-size: 14px; flex: 1; }
.tags { display: flex; flex-wrap: wrap; gap: 6px; }
.tag { font: 500 11px var(--mono); padding: 3px 8px; border-radius: 6px; background: var(--card-2); color: var(--ink-2); }
.chapcard .go { font-size: 13px; color: var(--teal); font-weight: 600; }

.steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
.steps .card { padding: 18px; }
.steps b { font: 600 11px var(--mono); color: var(--amber); letter-spacing: 0.06em; }
.steps h3 { margin: 4px 0 6px; font-size: 17px; }
.steps p { margin: 0; font-size: 14px; color: var(--ink-2); }
.cta { text-align: center; padding: 56px 0 72px; }
.cta h2 { font-size: 26px; margin: 0 0 18px; }

/* ---------- chapter ---------- */
.chap-hero { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr); gap: 40px; align-items: center; padding: 48px 0 32px; }
.chap-hero h1 { font-size: clamp(34px, 5vw, 52px); margin: 14px 0 8px; }
.chap-hero .subtitle { font-size: 19px; color: var(--ink-2); margin: 0 0 14px; }
.chap-hero .abstract { border-left: 3px solid var(--amber); padding-left: 14px; color: var(--ink-2); }
.chap-body { display: grid; grid-template-columns: 200px minmax(0, 1fr); gap: 40px; padding-bottom: 40px; }
.toc { position: sticky; top: 80px; align-self: start; font-size: 13px; }
.toc b { display: block; font: 600 11px var(--mono); color: var(--stone); margin-bottom: 8px; letter-spacing: 0.06em; }
.toc a { display: block; padding: 5px 10px; color: var(--ink-2); text-decoration: none; border-left: 2px solid var(--line); }
.toc a.active { color: var(--teal); border-left-color: var(--teal); background: var(--teal-soft); }
article { max-width: 800px; }
article section { margin-bottom: 48px; }
article h2 { font-size: 27px; margin: 0 0 14px; }
article h2 .sec { display: block; font: 500 13px var(--mono); color: var(--amber); margin-bottom: 6px; }
article h3 { font-size: 19px; margin: 28px 0 10px; }
article p, article li { color: var(--ink); }
article table { border-collapse: collapse; width: 100%; font-size: 14px; margin: 14px 0; }
article th, article td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
article th { background: var(--card-2); font-weight: 600; }
.math { font-family: "Cambria Math", "STIX Two Math", Georgia, serif; font-style: italic; }
.math-block {
  text-align: center; font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: 19px; margin: 16px 0; padding: 14px; background: var(--card);
  border: 1px solid var(--line); border-radius: 10px;
}

/* callouts */
.callout { border-radius: 12px; padding: 14px 18px; margin: 18px 0; border: 1px solid var(--line); background: var(--card); }
.callout > b:first-child { display: block; font: 600 12px var(--mono); letter-spacing: 0.05em; margin-bottom: 6px; }
.callout p:first-of-type { margin-top: 0; }
.callout p:last-child, .callout ol:last-child, .callout ul:last-child { margin-bottom: 0; }
.callout.pattern { border-color: color-mix(in srgb, var(--teal) 40%, transparent); background: var(--teal-soft); }
.callout.pattern > b:first-child { color: var(--teal); }
.callout.pitfall { border-color: color-mix(in srgb, var(--red) 40%, transparent); background: var(--red-soft); }
.callout.pitfall > b:first-child { color: var(--red); }
.callout.note > b:first-child { color: var(--stone); }
.callout.predict { border-color: color-mix(in srgb, var(--amber) 45%, transparent); background: var(--mark); }
.callout.predict > b:first-child { color: var(--amber); }
.reveal { margin-top: 10px; }
.reveal summary { cursor: pointer; font-weight: 600; font-size: 14px; color: var(--teal); }
.reveal[open] summary { margin-bottom: 8px; }

/* code */
pre.code {
  margin: 14px 0; padding: 12px 0; background: var(--code-bg);
  border: 1px solid var(--line); border-radius: 10px; overflow-x: auto;
  font: 14px/1.6 var(--mono);
}
pre.code .ln { display: block; padding: 0 16px 0 0; white-space: pre; }
pre.code .ln::before {
  content: attr(data-n); display: inline-block; width: 2.6em; padding-right: 12px;
  text-align: right; color: var(--com); user-select: none;
}
pre.code.nonum .ln::before { content: none; }
pre.code.nonum .ln { padding-left: 16px; }
pre.code .ln.hl { background: var(--code-line); box-shadow: inset 3px 0 0 var(--amber); }
pre.code.out { background: var(--card-2); }
.tk-kw { color: var(--kw); font-weight: 600; }
.tk-fn { color: var(--fn); }
.tk-str { color: var(--str); }
.tk-num { color: var(--num); }
.tk-com { color: var(--com); font-style: italic; }
.tk-prompt { color: var(--stone); }
.tk-err { color: var(--red); }

/* ---------- demos ---------- */
.demo { padding: 16px; margin: 22px 0; }
.demo .head .title { color: var(--teal); font-weight: 600; }
.demo .hint { font-size: 13px; color: var(--ink-2); margin: 10px 0 0; }
.controls { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin-top: 12px; }
.controls label { font-size: 13px; color: var(--ink-2); display: inline-flex; align-items: center; gap: 6px; }
.controls input[type="range"] { accent-color: var(--teal); width: 130px; }
.controls input[type="text"], .controls input[type="number"], .controls select {
  font: 13px var(--mono); padding: 6px 8px; border-radius: 7px;
  border: 1px solid var(--line); background: var(--paper); color: var(--ink);
}
.controls input[type="number"] { width: 72px; }
.controls select, .controls input[type="text"] { max-width: 100%; }
.cbtn {
  padding: 6px 12px; border-radius: 7px; border: 1px solid var(--line);
  background: var(--paper); cursor: pointer; font-size: 13px; font-weight: 500;
}
.cbtn:hover:not(:disabled) { border-color: var(--teal); color: var(--teal); }
.cbtn:disabled { opacity: 0.4; cursor: default; }
.cbtn.on { background: var(--teal); color: var(--paper); border-color: var(--teal); }
.spacer { flex: 1; }
.counter { font: 500 12px var(--mono); color: var(--stone); }
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); gap: 8px; margin-top: 12px; }
.stat { background: var(--paper-2); border-radius: 8px; padding: 8px 10px; }
.stat small { display: block; font: 500 10px var(--mono); color: var(--stone); text-transform: uppercase; letter-spacing: 0.05em; }
.stat b { font: 600 18px var(--mono); }
.stat.bad b { color: var(--red); }
.stat.good b { color: var(--green); }
.msg {
  margin-top: 10px; padding: 8px 12px; border-radius: 8px; font-size: 14px;
  background: var(--paper-2); min-height: 2.4em; overflow-wrap: anywhere;
}
.msg.bad { background: var(--red-soft); color: var(--red); }
.msg.good { background: var(--green-soft); color: var(--green); }

/* stepper */
.stepper { display: grid; grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr); gap: 14px; }
.stepper pre.code { margin: 0; font-size: 13px; }
.stepper.mini { grid-template-columns: minmax(0, 1fr) minmax(0, 0.85fr); }
.stepper.mini pre.code { font-size: 12px; }
.stack { display: flex; flex-direction: column-reverse; gap: 6px; justify-content: flex-start; min-height: 240px; }
.stack-wrap { background: var(--paper-2); border-radius: 10px; padding: 10px; display: flex; flex-direction: column; }
.stack-wrap > small { font: 500 11px var(--mono); color: var(--stone); margin-bottom: 8px; display: flex; justify-content: space-between; }
.frame {
  border: 1px solid var(--line); background: var(--card); border-radius: 8px;
  padding: 6px 10px; font: 13px/1.45 var(--mono);
}
.frame.new { animation: pushin 0.25s ease-out; }
.frame .fname { font-weight: 600; }
.frame .vars { color: var(--ink-2); }
.frame .status { font-size: 12px; color: var(--stone); }
.frame.top { border-color: var(--teal); box-shadow: inset 3px 0 0 var(--teal); }
.frame.ret { border-color: var(--green); box-shadow: inset 3px 0 0 var(--green); }
.frame.ret .status { color: var(--green); font-weight: 600; }
.frame.err { border-color: var(--red); box-shadow: inset 3px 0 0 var(--red); }
.frame.err .status { color: var(--red); }
.frame.more { text-align: center; color: var(--stone); border-style: dashed; animation: none; }
@keyframes pushin { from { transform: translateY(-6px); opacity: 0; } to { transform: none; opacity: 1; } }
.console {
  margin-top: 10px; background: var(--code-bg); border: 1px solid var(--line); border-radius: 8px;
  font: 12.5px/1.5 var(--mono); padding: 8px 12px; min-height: 3em; max-height: 200px; overflow: auto; white-space: pre;
}
.console:empty::before { content: "(no output yet)"; color: var(--stone); }

/* svg demos */
svg { display: block; max-width: 100%; height: auto; }
svg text { font-family: var(--mono); }
.svgbox { background: var(--paper-2); border-radius: 10px; padding: 8px; }

/* binary search cells */
.cells { display: flex; gap: 4px; flex-wrap: wrap; justify-content: center; margin: 8px 0; }
.cellcol { display: flex; flex-direction: column; align-items: center; gap: 2px; }
.cell {
  width: 52px; height: 44px; display: grid; place-items: center;
  border: 1px solid var(--line); border-radius: 7px; background: var(--card);
  font: 600 15px var(--mono); transition: all 0.2s;
}
.cell.out { opacity: 0.3; background: var(--paper-2); }
.cell.mid { background: var(--mark); border-color: var(--amber); }
.cell.found { background: var(--green-soft); border-color: var(--green); color: var(--green); }
.cellidx { font: 11px var(--mono); color: var(--stone); }
.ptr { font: 600 11px var(--mono); height: 16px; color: var(--teal); }
.ptr .m { color: var(--amber); }

/* bars */
.bars { display: grid; gap: 8px; margin-top: 8px; }
.bar { display: grid; grid-template-columns: 150px 1fr 90px; align-items: center; gap: 10px; font-size: 13px; }
.bar .track { height: 18px; background: var(--paper-2); border-radius: 5px; overflow: hidden; }
.bar .fill { height: 100%; background: var(--teal); border-radius: 5px; transition: width 0.3s; }
.bar .fill.amber { background: var(--amber); }
.bar .fill.red { background: var(--red); }
.bar .v { font: 600 13px var(--mono); text-align: right; }

/* quiz */
.quiz .q { padding: 16px; margin-bottom: 14px; }
.quiz .q p { margin-top: 0; }
.opts { display: grid; gap: 8px; }
.opt {
  text-align: left; padding: 9px 12px; border-radius: 8px; border: 1px solid var(--line);
  background: var(--paper); cursor: pointer; font-size: 14px;
}
.opt:hover:not(:disabled) { border-color: var(--teal); }
.opt.right { background: var(--green-soft); border-color: var(--green); }
.opt.wrong { background: var(--red-soft); border-color: var(--red); }
.opt:disabled { cursor: default; }
.explain { margin-top: 10px; font-size: 14px; color: var(--ink-2); display: none; }
.q.done .explain { display: block; }
.score { font: 600 14px var(--mono); color: var(--teal); }

/* map */
.map { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.map .card { padding: 16px; }
.map h3 { margin: 0 0 8px; font-size: 15px; color: var(--teal); }
.map ul { margin: 0; padding-left: 18px; font-size: 14px; }
.map li { margin: 3px 0; }

/* video */
.video { margin: 18px 0; overflow: hidden; }
.video video { display: block; width: 100%; background: #000; }
.video .missing { padding: 28px; text-align: center; color: var(--stone); font-size: 14px; }
.video .vcap { padding: 10px 14px; font-size: 13px; color: var(--ink-2); }

/* pager */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 20px 0 60px; }
.pager a { padding: 16px 18px; text-decoration: none; color: var(--ink); }
.pager a:hover { border-color: var(--teal); }
.pager small { display: block; font: 500 11px var(--mono); color: var(--stone); }
.pager b { font-family: var(--display); font-size: 17px; }
.pager .next { text-align: right; }
.takeaways { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.takeaways .card { padding: 14px; font-size: 14px; }
.takeaways .card b { display: block; font: 600 11px var(--mono); color: var(--amber); margin-bottom: 4px; }

footer { border-top: 1px solid var(--line); padding: 22px 0 36px; font-size: 13px; color: var(--stone); }

/* ---------- small screens ---------- */
@media (max-width: 900px) {
  .hero, .chap-hero { grid-template-columns: minmax(0, 1fr); gap: 24px; padding-top: 32px; }
  .chap-body { grid-template-columns: minmax(0, 1fr); }
  .toc { display: none; }
  .why, .steps, .map, .takeaways { grid-template-columns: 1fr 1fr; }
  .stepper, .stepper.mini { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 600px) {
  .wrap { padding: 0 16px; }
  .topbar { padding: 8px 16px; gap: 10px; }
  .brand-text { display: none; }
  .why, .steps, .map, .takeaways, .pager { grid-template-columns: minmax(0, 1fr); }
  .chapters { grid-template-columns: minmax(0, 1fr); }
  .bar { grid-template-columns: 90px minmax(0, 1fr) auto; gap: 8px; }
  .bar .v { font-size: 11px; }
  article table { display: block; overflow-x: auto; }
  .cell { width: 38px; height: 36px; font-size: 13px; }
  .stack { min-height: 160px; }
}
@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}

/* Footer credit (same as CSC4801): course line first, then one small 培玉 line. */
footer p { margin: 4px 0; }
footer .credit { display: flex; align-items: center; gap: 8px; margin-top: 10px; }
footer .credit img { flex: none; }
footer .credit b { font-weight: 600; color: var(--ink-2); }
.logo-dark { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .logo-light { display: none; }
  :root:not([data-theme="light"]) .logo-dark { display: inline; }
}
:root[data-theme="dark"] .logo-light { display: none; }
:root[data-theme="dark"] .logo-dark { display: inline; }

/* "← All lectures" link at the left of the top bar (lecture pages). */
.homelink {
  flex: none; display: flex; align-items: center; gap: 6px;
  font-size: 13px; color: var(--ink-2); text-decoration: none;
  padding: 6px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--card);
}
.homelink:hover { border-color: var(--teal); color: var(--teal); }
@media (max-width: 600px) { .homelink-text { display: none; } }

/* ---------- LA101 additions: maths, SVG planes, sliders ---------- */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.callout.solution > b:first-child, .callout.ml > b:first-child, .callout.ai > b:first-child { color: var(--teal); }
.video { padding: 0; overflow: hidden; margin: 18px 0; }
.video video { display: block; width: 100%; }
.video .vcap { font-size: 13px; color: var(--ink-2); padding: 8px 14px; }
.video .missing { padding: 18px; font-size: 14px; color: var(--ink-2); }
.la-plane { display: block; margin: 6px auto; font-family: var(--mono); }
.la-plane .grid { stroke: var(--line); stroke-width: 1; }
.la-plane .axis { stroke: var(--ink-2); stroke-width: 1.4; }
.la-plane .tick { font-size: 10px; fill: var(--stone); text-anchor: middle; }
.la-plane .tick.r { text-anchor: end; }
.la-plane .albl { font-size: 11px; fill: var(--ink-2); }
.la-plane .ln { stroke-width: 2.4; }
.la-plane .vec { stroke-width: 3; }
.la-plane .vlbl, .la-plane .plbl { font-size: 12px; font-weight: 600; }
.la-plane .A { stroke: var(--teal); fill: var(--teal); }
.la-plane .C { stroke: var(--amber); fill: var(--amber); }
.la-plane .HL { stroke: var(--red); fill: var(--red); }
.la-plane .NO { stroke: var(--stone); fill: var(--stone); }
.la-plane .DIM { stroke: var(--line); stroke-dasharray: 5 4; }
.la-plane text.A, .la-plane text.C, .la-plane text.HL, .la-plane text.NO { stroke: none; }
.la-ctrl { display: flex; flex-wrap: wrap; gap: 10px 22px; margin-top: 8px; }
.la-slider { display: flex; align-items: center; gap: 8px; font-size: 13px; }
.la-slider output { font: 600 13px var(--mono); min-width: 2.5em; }
.la-in { font: 14px var(--mono); padding: 4px 8px; border: 1px solid var(--line); border-radius: 8px; background: var(--paper); color: var(--ink); width: 11em; }
.la-read { font-size: 14px; margin: 10px 0 0; }
.la-read .A { color: var(--teal); } .la-read .C { color: var(--amber); } .la-read .NO { color: var(--red); }
.la-two { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 640px) { .la-two { grid-template-columns: 1fr; } }

/* ---------- LA101: exercises with Hint / Full solution (from the notes; la101/tools/site_build.py) ---------- */
.exlist { list-style: none; padding: 0; margin: 14px 0; display: grid; gap: 12px; }
.exo { padding: 14px 18px; min-width: 0; }
.exo-head { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin-bottom: 6px; }
.exo-head b { font: 600 13px var(--mono); color: var(--ink-2); }
.exo-head .stars { color: var(--amber); letter-spacing: 0.08em; }
.exo-q > :first-child { margin-top: 0; }
.exo-q > :last-child { margin-bottom: 0; }
.exo .reveal { margin-top: 10px; border-top: 1px solid var(--line); padding-top: 8px; }
.exo .exo-sol summary { color: var(--amber); }
.exo-body { min-width: 0; overflow-wrap: anywhere; }
.exo-body > :first-child { margin-top: 0; }
.exo .math.display { display: block; }
.exo pre.code { font-size: 13px; }

/* ---------- transcript under each video ---------- */
.transcript { border-top: 1px solid var(--line); }
.transcript summary { cursor: pointer; padding: 8px 14px; font-size: 13px; font-weight: 600; color: var(--teal); }
.transcript .tx { max-height: 320px; overflow-y: auto; padding: 0 8px 10px; }
.tx-line { display: block; width: 100%; text-align: left; border: 0; background: none; color: var(--ink); font: 14px/1.5 var(--sans); padding: 4px 6px; border-radius: 6px; cursor: pointer; }
.tx-line:hover { background: var(--paper-2); }
.tx-line.on { background: var(--mark); }
.tx-time { display: inline-block; min-width: 3.2em; margin-right: 6px; font: 12px var(--mono); color: var(--stone); }
.transcript .missing { font-size: 13px; color: var(--ink-2); margin: 4px 6px; }

/* ---------- links between lectures, whole-lecture view ---------- */
a.lec-link { color: var(--teal); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 2px; }
.toc a.toc-all { margin-top: 12px; border-left-color: transparent; color: var(--teal); }
.all-chapter { max-width: 48em; margin: 0 auto 40px; }
.all-chapter .all-title { font-size: 28px; margin: 48px 0 4px; border-top: 1px solid var(--line); padding-top: 28px; }
.all-chapter .all-title .sec { display: block; font: 600 12px var(--mono); color: var(--amber); letter-spacing: 0.06em; margin-bottom: 6px; }
.all-chapter section h2 { font-size: 21px; }

/* ---------- print: light theme, no controls; every hidden answer is opened by app.js on beforeprint ---------- */
@media print {
  html:root, html:root:not([data-theme="light"]), html:root[data-theme="dark"] {
    --paper: #ffffff; --paper-2: #f4f3ee; --card: #ffffff; --card-2: #f1f1ec; --ink: #111111; --ink-2: #3a3f45;
    --stone: #5f6661; --line: #cfd2ca; --grid: transparent; --teal: #0f6e73; --teal-soft: #e6f1f0; --sea: #3e8e8a;
    --amber: #9a5f10; --mark: #fbefd6; --red: #a3352a; --red-soft: #f8e6e3; --green: #2f7d4f; --green-soft: #e3f1e7;
    --code-bg: #ffffff; --code-line: #fbf1dc; --kw: #0f6e73; --fn: #8a4f0f; --str: #2f7d4f; --num: #b03a2e; --com: #6b716c;
    --shadow: none; color-scheme: light;
  }
  html, body { background: #fff !important; color: var(--ink); }
  .topbar, .toc, .pager, .btnrow, .noprint, .hero-demo, .cta, .progress, .homelink, .iconbtn, .transcript,
  .chapnav, .cbtn, .la-ctrl, .steps { display: none !important; }
  .chap-body { display: block !important; }
  .video { border: 1px solid var(--line); }
  .video video, .video .missing { display: none !important; }
  .video .vcap::before { content: "Video: "; font-weight: 600; }
  .card, .callout, pre.code, .exo, .demo { box-shadow: none !important; break-inside: avoid; }
  .exo { break-inside: auto; }
  details > summary { list-style: none; font-size: 12px; }
  details > summary::-webkit-details-marker { display: none; }
  a { color: inherit; }
  a.lec-link { text-decoration: none; }
  h1, h2, h3 { break-after: avoid; }
  .all-chapter { break-before: page; }
  .all-chapter:first-of-type { break-before: auto; }
  pre.code .ln { white-space: pre-wrap; }
  footer { font-size: 10px; }
}

/* Whole-lecture page title: the tagline on its own line, as on the lecture home. */
.all-view h1 small { display: block; font-size: 0.42em; color: var(--ink-2); font-weight: 500; margin-top: 10px; }