/* Layout: study notebook. A sticky outline on wide screens, one reading column, and lab-bench panels for demos. */
:root {
  --paper: #f6f7f9;
  --surface: #ffffff;
  --ink: #18202c;
  --muted: #5a6577;
  --rule: #d9dee6;
  --accent: #2346a8;
  --accent-soft: #e4eafb;
  --note: #9a5b00;
  --note-soft: #fbf1e1;
  --warn: #b3261e;
  --warn-soft: #fbe7e5;
  --ok: #1f7a4d;
  --c1: #2f5fd0; --c2: #d0622f; --c3: #2a9a6a; --c4: #9a3fc0;
  --f-display: "Noto Serif TC", "Songti TC", serif;
  --f-body: "IBM Plex Sans", "Noto Sans TC", "PingFang TC", system-ui, sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, Menlo, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #12161d; --surface: #1a2029; --ink: #e6e9ef; --muted: #9aa5b5; --rule: #2c3442;
    --accent: #8fb0ff; --accent-soft: #1f2a44; --note: #f0b45c; --note-soft: #2c2416;
    --warn: #ff8a80; --warn-soft: #3a1f1d; --ok: #6fd3a0;
    --c1: #7aa2ff; --c2: #ff9a66; --c3: #5fd3a0; --c4: #d08bff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #12161d; --surface: #1a2029; --ink: #e6e9ef; --muted: #9aa5b5; --rule: #2c3442;
  --accent: #8fb0ff; --accent-soft: #1f2a44; --note: #f0b45c; --note-soft: #2c2416;
  --warn: #ff8a80; --warn-soft: #3a1f1d; --ok: #6fd3a0;
  --c1: #7aa2ff; --c2: #ff9a66; --c3: #5fd3a0; --c4: #d08bff;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  background: var(--paper); color: var(--ink);
  font-family: var(--f-body); font-size: 16.5px; line-height: 1.85;
  padding-left: max(16px, env(safe-area-inset-left, 0px));
  padding-right: max(16px, env(safe-area-inset-right, 0px));
  padding-block: 0 64px;
}
a { color: var(--accent); text-underline-offset: 3px; }
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, summary:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.shell { max-width: 1120px; margin: 0 auto; display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 48px; }
@media (max-width: 900px) { .shell { grid-template-columns: minmax(0, 1fr); gap: 0; } nav.toc { display: none; } }
nav.toc { position: sticky; top: env(safe-area-inset-top, 0px); align-self: start; padding-top: 40px; font-size: 13.5px; line-height: 1.6; max-height: 100vh; overflow-y: auto; }
nav.toc .label { font-family: var(--f-mono); font-size: 11px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); margin-bottom: 8px; }
nav.toc ol { list-style: none; padding: 0; margin: 0; display: grid; gap: 4px; }
nav.toc a { color: var(--muted); text-decoration: none; display: block; padding: 2px 0 2px 10px; border-left: 2px solid transparent; }
nav.toc a:hover { color: var(--ink); border-left-color: var(--rule); }
main { min-width: 0; max-width: 760px; overflow-wrap: break-word; }
h1, h2, h3, summary { overflow-wrap: anywhere; }

header.lec { padding-block: 44px 28px; border-bottom: 1px solid var(--rule); margin-bottom: 8px; }
.eyebrow { font-family: var(--f-mono); font-size: 12px; letter-spacing: .14em; text-transform: uppercase; color: var(--accent); }
h1 { font-family: var(--f-display); font-weight: 900; font-size: clamp(30px, 5vw, 44px); line-height: 1.2; margin: 8px 0 12px; text-wrap: balance; }
.lede { font-size: 18px; color: var(--muted); margin: 0 0 18px; max-width: 62ch; }
.meta { display: flex; flex-wrap: wrap; gap: 8px 18px; font-size: 14px; font-family: var(--f-mono); }
.meta span { color: var(--muted); }

section { padding-top: 36px; }
h2 { font-family: var(--f-display); font-weight: 900; font-size: 26px; line-height: 1.35; margin: 0 0 14px; text-wrap: balance; display: flex; gap: 12px; align-items: baseline; }
h2 .n { font-family: var(--f-mono); font-weight: 500; font-size: 14px; color: var(--accent); }
h3 { font-family: var(--f-body); font-weight: 700; font-size: 18.5px; margin: 28px 0 8px; }
p { margin: 0 0 14px; }
ul, ol { margin: 0 0 14px; padding-left: 1.4em; }
li { margin-bottom: 4px; }
strong { font-weight: 700; }
.term { color: var(--accent); font-weight: 600; }
code { font-family: var(--f-mono); font-size: .9em; background: var(--accent-soft); padding: 1px 5px; border-radius: 4px; }
.math-block { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

.goals { background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; padding: 18px 22px; }
.goals h3 { margin-top: 0; font-size: 15px; font-family: var(--f-mono); letter-spacing: .08em; text-transform: uppercase; color: var(--muted); font-weight: 500; }
.goals ol { margin-bottom: 0; }

.ts { font-family: var(--f-mono); font-size: 12.5px; white-space: nowrap; text-decoration: none; background: var(--accent-soft); color: var(--accent); padding: 1px 7px; border-radius: 999px; margin-left: 4px; }
.ts:hover { text-decoration: underline; }

.prof { border-left: 3px solid var(--accent); padding: 4px 0 4px 16px; margin: 16px 0; }
.prof .who { font-family: var(--f-mono); font-size: 11.5px; letter-spacing: .1em; text-transform: uppercase; color: var(--accent); display: block; margin-bottom: 2px; }

details.bg { background: var(--note-soft); border-radius: 10px; margin: 18px 0; padding: 0 18px; }
details.bg > summary { cursor: pointer; padding: 12px 0; font-weight: 600; color: var(--note); list-style: none; display: flex; gap: 10px; align-items: baseline; }
details.bg > summary::-webkit-details-marker { display: none; }
details.bg > summary::before { content: "背景補充"; font-family: var(--f-mono); font-size: 11px; letter-spacing: .08em; border: 1px solid var(--note); border-radius: 4px; padding: 0 6px; flex: none; }
details.bg[open] > summary { border-bottom: 1px solid color-mix(in srgb, var(--note) 30%, transparent); margin-bottom: 12px; }
details.bg > div { padding-bottom: 6px; }

.keybox { background: var(--accent-soft); border-radius: 10px; padding: 14px 18px; margin: 16px 0; }
.keybox .k { font-family: var(--f-mono); font-size: 11.5px; letter-spacing: .1em; color: var(--accent); display: block; margin-bottom: 2px; }

.supp { font-size: 14px; margin: 14px 0 4px; padding: 6px 12px; border-left: 3px solid var(--accent); background: var(--accent-soft); border-radius: 0 6px 6px 0; color: var(--muted); }
.supp b { color: var(--accent); font-weight: 600; }
.pitfall { background: var(--warn-soft); border-radius: 10px; padding: 14px 18px; margin: 12px 0; }
.pitfall b { color: var(--warn); }

table { border-collapse: collapse; width: 100%; font-size: 14.5px; line-height: 1.6; }
.tablewrap { overflow-x: auto; margin: 12px 0 18px; border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--rule); vertical-align: top; }
th { font-weight: 600; color: var(--muted); font-size: 13px; background: color-mix(in srgb, var(--rule) 30%, var(--surface)); }
tr:last-child td { border-bottom: 0; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; font-family: var(--f-mono); font-size: 13.5px; white-space: nowrap; }

.bench { background: var(--surface); border: 1px solid var(--rule); border-radius: 12px; padding: 18px; margin: 16px 0; }
.bench h4 { margin: 0 0 10px; font-size: 13px; font-family: var(--f-mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); font-weight: 500; }
.row { display: flex; flex-wrap: wrap; gap: 8px 14px; align-items: center; }
.controls { display: grid; gap: 12px; font-size: 14px; }
.ctl { display: grid; gap: 4px; color: var(--muted); font-size: 13px; min-width: 0; }
.ctl input[type=range] { width: 100%; }
select { font: inherit; font-size: 14px; padding: 6px 8px; border-radius: 6px; border: 1px solid var(--rule); background: var(--paper); color: var(--ink); max-width: 100%; }
button { font: inherit; font-size: 14px; padding: 7px 12px; border-radius: 7px; border: 1px solid var(--accent); background: var(--accent); color: var(--surface); cursor: pointer; font-weight: 600; }
button.ghost { background: transparent; color: var(--accent); }
button:disabled { opacity: .5; cursor: default; }
.readout { font-family: var(--f-mono); font-size: 12.5px; line-height: 1.7; background: var(--paper); border-radius: 8px; padding: 10px 12px; font-variant-numeric: tabular-nums; overflow-x: auto; }
.readout b { color: var(--accent); }
details.q { border-top: 1px solid var(--rule); padding: 12px 0; }
details.q:last-of-type { border-bottom: 1px solid var(--rule); }
details.q > summary { cursor: pointer; font-weight: 600; }
details.q > div { padding-top: 10px; }
details.q > div::before { content: "參考答案"; display: block; font-family: var(--f-mono); font-size: 11px; letter-spacing: .1em; color: var(--ok); margin-bottom: 4px; }
footer { margin-top: 48px; font-size: 13px; color: var(--muted); border-top: 1px solid var(--rule); padding-top: 16px; }
mjx-container[jax="SVG"][display="true"] { overflow-x: auto; overflow-y: hidden; max-width: 100%; padding-block: 2px; }