/* ==========================================================================
   AI Engineering for FDEs — site styles
   - 顏色全部用 CSS 變數；深色模式由 prefers-color-scheme 或 data-theme 控制
   - 雙語：html[data-lang] 決定顯示 [lang="zh-Hant"] 或 [lang="en"] 的元素
   ========================================================================== */

:root {
  --bg: #faf9f6;
  --bg-elev: #ffffff;
  --bg-sunk: #f2f0eb;
  --fg: #1d1f23;
  --fg-muted: #5c606a;
  --fg-faint: #8a8e97;
  --border: #e3e0d8;
  --border-strong: #cdc9be;
  --accent: #0f6e6a;
  --accent-fg: #ffffff;
  --accent-soft: #e2f1ef;
  --link: #0b5f8a;
  --note: #2f6db5;   --note-soft: #e8f0fb;
  --tip: #1f7a4d;    --tip-soft: #e5f4ec;
  --warn: #a35a00;   --warn-soft: #fbf0df;
  --bad: #b3261e;    --bad-soft: #fbe9e7;
  --code-bg: #f4f2ed;
  --code-fg: #24292f;
  --hl-keyword: #8a3ffc; --hl-string: #1a7f37; --hl-comment: #6e7781; --hl-number: #b35900;
  --hl-title: #0b5f8a;   --hl-attr: #953800;   --hl-meta: #6639ba;
  --shadow: 0 1px 2px rgba(20, 20, 20, .04), 0 4px 16px rgba(20, 20, 20, .05);
  --radius: 10px;
  --sidebar-w: 264px;
  --content-w: 760px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "JetBrains Mono", Menlo, Consolas, "Noto Sans Mono CJK TC", monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14161a; --bg-elev: #1b1e23; --bg-sunk: #101215;
    --fg: #e6e7ea; --fg-muted: #a5a9b2; --fg-faint: #7c818b;
    --border: #2a2e35; --border-strong: #3a3f48;
    --accent: #4fc1b8; --accent-fg: #0d1f1d; --accent-soft: #15302d;
    --link: #7cc4f0;
    --note: #7fb0ec; --note-soft: #18243a;
    --tip: #6fcf9b;  --tip-soft: #15291f;
    --warn: #f0b35a; --warn-soft: #2d2313;
    --bad: #f28b82;  --bad-soft: #2f1a19;
    --code-bg: #101215; --code-fg: #d7dae0;
    --hl-keyword: #c49bff; --hl-string: #8ccf7e; --hl-comment: #7c818b; --hl-number: #f0a35a;
    --hl-title: #7cc4f0;   --hl-attr: #e7a26b;   --hl-meta: #b392f0;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 16px rgba(0, 0, 0, .25);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #14161a; --bg-elev: #1b1e23; --bg-sunk: #101215;
  --fg: #e6e7ea; --fg-muted: #a5a9b2; --fg-faint: #7c818b;
  --border: #2a2e35; --border-strong: #3a3f48;
  --accent: #4fc1b8; --accent-fg: #0d1f1d; --accent-soft: #15302d;
  --link: #7cc4f0;
  --note: #7fb0ec; --note-soft: #18243a;
  --tip: #6fcf9b;  --tip-soft: #15291f;
  --warn: #f0b35a; --warn-soft: #2d2313;
  --bad: #f28b82;  --bad-soft: #2f1a19;
  --code-bg: #101215; --code-fg: #d7dae0;
  --hl-keyword: #c49bff; --hl-string: #8ccf7e; --hl-comment: #7c818b; --hl-number: #f0a35a;
  --hl-title: #7cc4f0;   --hl-attr: #e7a26b;   --hl-meta: #b392f0;
  --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 16px rgba(0, 0, 0, .25);
  color-scheme: dark;
}

/* ------------------------------------------------------------ bilingual */
html[data-lang="zh"] body [lang="en"]:not(.both),
html[data-lang="en"] body [lang="zh-Hant"]:not(.both) { display: none !important; }

/* ------------------------------------------------------------ base */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 72px; }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font: 16.5px/1.75 var(--font-sans);
  text-rendering: optimizeLegibility;
}
html[data-lang="en"] body { line-height: 1.65; }
a { color: var(--link); text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }
img, svg { max-width: 100%; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2.5rem 0; }
::selection { background: var(--accent-soft); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }

h1, h2, h3, h4 { line-height: 1.3; letter-spacing: -.01em; margin: 2.2em 0 .6em; }
h1 { font-size: clamp(1.8rem, 1.2rem + 2vw, 2.4rem); margin-top: .3em; letter-spacing: -.02em; }
h2 { font-size: 1.5rem; padding-top: .4rem; border-top: 1px solid var(--border); margin-top: 3rem; padding-top: 1.6rem; }
h3 { font-size: 1.18rem; }
h4 { font-size: 1rem; }
p, ul, ol { margin: 0 0 1.05em; }
li + li { margin-top: .3em; }
strong { font-weight: 650; }

code, kbd, pre { font-family: var(--font-mono); font-size: .88em; }
:not(pre) > code {
  background: var(--code-bg); border: 1px solid var(--border);
  padding: .08em .38em; border-radius: 5px; white-space: break-spaces; overflow-wrap: anywhere;
}

/* ------------------------------------------------------------ layout */
.topbar {
  position: sticky; top: 0; z-index: 30; height: 56px;
  display: flex; align-items: center; gap: .75rem; padding: 0 16px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px); -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: .55rem; font-weight: 700; color: var(--fg); text-decoration: none; min-width: 0; }
.brand-mark {
  width: 28px; height: 28px; border-radius: 7px; flex: none; display: grid; place-items: center;
  background: var(--accent); color: var(--accent-fg); font: 700 13px/1 var(--font-mono);
}
.brand-name { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar .spacer { flex: 1; }
.btn {
  appearance: none; border: 1px solid var(--border-strong); background: var(--bg-elev); color: var(--fg);
  font: 500 .86rem/1 var(--font-sans); padding: .55rem .8rem; border-radius: 8px; cursor: pointer;
  display: inline-flex; align-items: center; gap: .4rem; text-decoration: none; white-space: nowrap;
}
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); color: var(--accent-fg); border-color: var(--accent); }
.btn.ghost { background: transparent; }
.icon-btn { padding: .5rem .6rem; }
#menuBtn { display: none; }

.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0, 1fr); min-height: calc(100vh - 56px); }
.sidebar {
  position: sticky; top: 56px; height: calc(100vh - 56px); overflow-y: auto;
  border-right: 1px solid var(--border); padding: 1.2rem .8rem 2rem; background: var(--bg);
}
.sidebar h2 { font-size: .74rem; text-transform: uppercase; letter-spacing: .08em; color: var(--fg-faint); border: 0; margin: 1.2rem .6rem .4rem; padding: 0; }
.sidebar ol { list-style: none; margin: 0; padding: 0; }
.sidebar li { margin: 0; }
.sidebar a {
  display: grid; grid-template-columns: 1.9rem 1fr auto; align-items: baseline; gap: .1rem;
  padding: .42rem .6rem; border-radius: 7px; color: var(--fg-muted); text-decoration: none; font-size: .92rem; line-height: 1.4;
}
.sidebar a:hover { background: var(--bg-sunk); color: var(--fg); }
.sidebar a[aria-current="page"] { background: var(--accent-soft); color: var(--fg); font-weight: 600; }
.sidebar .num { font: 500 .78rem var(--font-mono); color: var(--fg-faint); }
.sidebar .done { color: var(--tip); font-size: .8rem; }
.sidebar .progress { margin: 1.4rem .6rem 0; font-size: .82rem; color: var(--fg-muted); }
.bar { height: 6px; background: var(--bg-sunk); border-radius: 99px; overflow: hidden; margin-top: .4rem; border: 1px solid var(--border); }
.bar > span { display: block; height: 100%; background: var(--accent); width: 0; transition: width .3s; }

.main { display: grid; grid-template-columns: minmax(0, var(--content-w)) 220px; justify-content: center; gap: 48px; padding: 2.2rem 32px 5rem; }
.content { min-width: 0; }
.toc { position: sticky; top: 80px; align-self: start; font-size: .84rem; max-height: calc(100vh - 100px); overflow-y: auto; }
.toc h2 { font-size: .74rem; text-transform: uppercase; letter-spacing: .08em; color: var(--fg-faint); border: 0; margin: 0 0 .6rem; padding: 0; }
.toc ol { list-style: none; padding: 0; margin: 0; border-left: 1px solid var(--border); }
.toc li { margin: 0; }
.toc a { display: block; padding: .25rem 0 .25rem .9rem; margin-left: -1px; border-left: 2px solid transparent; color: var(--fg-muted); text-decoration: none; line-height: 1.45; }
.toc a:hover { color: var(--fg); }
.toc a.active { border-left-color: var(--accent); color: var(--fg); }

@media (max-width: 1180px) {
  .main { grid-template-columns: minmax(0, var(--content-w)); }
  .toc { display: none; }
}
@media (max-width: 900px) {
  #menuBtn { display: inline-flex; }
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; top: 56px; left: 0; z-index: 25; width: min(86vw, 320px);
    transform: translateX(-102%); transition: transform .22s ease; box-shadow: var(--shadow); background: var(--bg-elev);
  }
  body.nav-open .sidebar { transform: none; }
  body.nav-open::after { content: ""; position: fixed; inset: 56px 0 0; background: rgba(0,0,0,.3); z-index: 20; }
  .main { padding: 1.4rem 16px 4rem; }
}
@media (max-width: 520px) {
  body { font-size: 16px; }
  .brand-name { display: none; }
  .btn .label-long { display: none; }
}

/* ------------------------------------------------------------ chapter header */
.eyebrow { font: 600 .8rem var(--font-mono); color: var(--accent); letter-spacing: .04em; text-transform: uppercase; margin-bottom: .3rem; }
.lede { font-size: 1.12rem; color: var(--fg-muted); margin-bottom: 1.4rem; }
.meta { display: flex; flex-wrap: wrap; gap: .4rem 1.2rem; font-size: .86rem; color: var(--fg-faint); margin-bottom: 1.8rem; }

.objectives {
  border: 1px solid var(--border); background: var(--bg-elev); border-radius: var(--radius);
  padding: 1.1rem 1.3rem .5rem; margin: 0 0 2rem; box-shadow: var(--shadow);
}
.objectives h2 { font-size: .8rem; text-transform: uppercase; letter-spacing: .08em; color: var(--fg-faint); border: 0; margin: 0 0 .5rem; padding: 0; }
.objectives ul { padding-left: 1.2rem; }

/* ------------------------------------------------------------ callouts */
.callout { border: 1px solid var(--border); border-left: 4px solid var(--note); background: var(--note-soft); border-radius: 8px; padding: .9rem 1.1rem .1rem; margin: 1.4rem 0; }
.callout > .label { display: block; font: 700 .76rem var(--font-sans); text-transform: uppercase; letter-spacing: .08em; color: var(--note); margin-bottom: .3rem; }
.callout.tip { border-left-color: var(--tip); background: var(--tip-soft); }
.callout.tip > .label { color: var(--tip); }
.callout.warn { border-left-color: var(--warn); background: var(--warn-soft); }
.callout.warn > .label { color: var(--warn); }
.callout.bad { border-left-color: var(--bad); background: var(--bad-soft); }
.callout.bad > .label { color: var(--bad); }

/* ------------------------------------------------------------ code */
figure.code { margin: 1.4rem 0; border: 1px solid var(--border); border-radius: var(--radius); background: var(--code-bg); overflow: hidden; }
figure.code figcaption {
  display: flex; align-items: center; justify-content: space-between; gap: .6rem;
  padding: .45rem .5rem .45rem .9rem; border-bottom: 1px solid var(--border);
  font: .8rem var(--font-mono); color: var(--fg-muted); background: var(--bg-sunk);
}
figure.code pre { margin: 0; padding: .95rem 1.1rem; overflow-x: auto; line-height: 1.6; color: var(--code-fg); tab-size: 4; }
.copy-btn { font: 500 .74rem var(--font-sans); padding: .3rem .55rem; border-radius: 6px; border: 1px solid var(--border-strong); background: var(--bg-elev); color: var(--fg-muted); cursor: pointer; }
.copy-btn:hover { color: var(--fg); border-color: var(--accent); }
.hljs-keyword, .hljs-selector-tag, .hljs-built_in.hljs-keyword { color: var(--hl-keyword); }
.hljs-string, .hljs-regexp, .hljs-addition { color: var(--hl-string); }
.hljs-comment, .hljs-quote { color: var(--hl-comment); font-style: italic; }
.hljs-number, .hljs-literal { color: var(--hl-number); }
.hljs-title, .hljs-title.function_, .hljs-title.class_, .hljs-section { color: var(--hl-title); }
.hljs-attr, .hljs-attribute, .hljs-variable, .hljs-template-variable, .hljs-property { color: var(--hl-attr); }
.hljs-meta, .hljs-built_in, .hljs-type, .hljs-symbol { color: var(--hl-meta); }
.hljs-deletion { color: var(--bad); }

/* ------------------------------------------------------------ tables */
.table-wrap { overflow-x: auto; margin: 1.4rem 0; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-elev); }
table { border-collapse: collapse; width: 100%; font-size: .92rem; line-height: 1.55; }
th, td { text-align: left; vertical-align: top; padding: .65rem .85rem; border-bottom: 1px solid var(--border); }
th { background: var(--bg-sunk); font-weight: 650; font-size: .84rem; white-space: nowrap; }
tr:last-child td { border-bottom: 0; }
td:first-child { font-weight: 600; }
table.plain td:first-child { font-weight: 400; }

/* ------------------------------------------------------------ cards & grids */
.grid { display: grid; gap: 1rem; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); margin: 1.4rem 0; }
.card { border: 1px solid var(--border); background: var(--bg-elev); border-radius: var(--radius); padding: 1rem 1.15rem; box-shadow: var(--shadow); }
.card h3 { margin: 0 0 .35rem; font-size: 1.02rem; }
.card p { margin: 0; color: var(--fg-muted); font-size: .93rem; line-height: 1.6; }
a.card { text-decoration: none; color: inherit; display: block; transition: border-color .15s, transform .15s; }
a.card:hover { border-color: var(--accent); transform: translateY(-1px); }
.card .kicker { font: 600 .74rem var(--font-mono); color: var(--accent); margin-bottom: .25rem; display: block; }

.steps { counter-reset: step; list-style: none; padding: 0; margin: 1.4rem 0; }
.steps > li { position: relative; padding: 0 0 1.1rem 2.8rem; margin: 0; border-left: 2px solid var(--border); margin-left: .95rem; }
.steps > li:last-child { border-left-color: transparent; }
.steps > li::before {
  counter-increment: step; content: counter(step);
  position: absolute; left: -1rem; top: -.1rem; width: 1.9rem; height: 1.9rem; border-radius: 50%;
  display: grid; place-items: center; background: var(--bg-elev); border: 2px solid var(--accent); color: var(--accent);
  font: 700 .85rem var(--font-mono);
}
.steps > li > strong:first-child { display: block; }

/* ------------------------------------------------------------ diagrams */
.diagram { margin: 1.6rem 0; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-elev); padding: 1rem; overflow-x: auto; }
.diagram svg { display: block; margin: 0 auto; min-width: 560px; height: auto; }
.diagram .caption { font-size: .85rem; color: var(--fg-muted); margin: .6rem 0 0; text-align: center; }
.diagram text { fill: var(--fg); font: 13px var(--font-sans); }
.diagram .muted { fill: var(--fg-muted); font-size: 11.5px; }
.diagram .box { fill: var(--bg-sunk); stroke: var(--border-strong); stroke-width: 1.2; }
.diagram .box.accent { fill: var(--accent-soft); stroke: var(--accent); }
.diagram .box.warn { fill: var(--warn-soft); stroke: var(--warn); }
.diagram .edge { stroke: var(--fg-faint); stroke-width: 1.4; fill: none; }
.diagram .edge.accent { stroke: var(--accent); }
.diagram .edge.dashed { stroke-dasharray: 4 4; }
.diagram .arrowhead { fill: var(--fg-faint); }

/* ------------------------------------------------------------ interactive demo */
.demo { border: 1px solid var(--border-strong); border-radius: var(--radius); background: var(--bg-elev); margin: 1.8rem 0; box-shadow: var(--shadow); overflow: hidden; }
.demo-head { padding: .8rem 1.1rem; border-bottom: 1px solid var(--border); background: var(--bg-sunk); display: flex; align-items: baseline; gap: .7rem; flex-wrap: wrap; }
.demo-head .tag { font: 700 .7rem var(--font-mono); text-transform: uppercase; letter-spacing: .08em; color: var(--accent-fg); background: var(--accent); padding: .15rem .45rem; border-radius: 4px; }
.demo-head h3 { margin: 0; font-size: 1rem; }
.demo-body { padding: 1rem 1.1rem 1.2rem; }
.demo-body p.hint { color: var(--fg-muted); font-size: .9rem; }
.row { display: flex; gap: .5rem; flex-wrap: wrap; align-items: center; margin: .6rem 0; }
input[type="text"], input[type="number"], textarea, select {
  font: inherit; font-size: .92rem; color: var(--fg); background: var(--bg); border: 1px solid var(--border-strong);
  border-radius: 8px; padding: .5rem .7rem; min-width: 0;
}
textarea { font-family: var(--font-mono); font-size: .84rem; width: 100%; min-height: 220px; line-height: 1.55; resize: vertical; }
input[type="text"] { flex: 1 1 260px; }
input[type="range"] { accent-color: var(--accent); }
.chip { font: 500 .8rem var(--font-sans); padding: .32rem .65rem; border-radius: 99px; border: 1px solid var(--border-strong); background: var(--bg); color: var(--fg-muted); cursor: pointer; }
.chip:hover, .chip[aria-pressed="true"] { border-color: var(--accent); color: var(--fg); background: var(--accent-soft); }
.output { font: .84rem/1.6 var(--font-mono); background: var(--code-bg); border: 1px solid var(--border); border-radius: 8px; padding: .8rem 1rem; white-space: pre-wrap; overflow-x: auto; margin-top: .8rem; min-height: 3rem; }
.output .ok { color: var(--tip); } .output .err { color: var(--bad); } .output .dim { color: var(--fg-faint); } .output .warn { color: var(--warn); }
.cols { display: grid; gap: .9rem; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); margin-top: .9rem; }
.col { border: 1px solid var(--border); border-radius: 8px; padding: .7rem .8rem; background: var(--bg); }
.col h4 { margin: 0 0 .5rem; font-size: .82rem; text-transform: uppercase; letter-spacing: .06em; color: var(--fg-muted); }
.col ol { margin: 0; padding-left: 1.2rem; font-size: .86rem; }
.col li { margin: .25rem 0; }
.col .score { font-family: var(--font-mono); color: var(--fg-faint); font-size: .78rem; }
.col.fused { border-color: var(--accent); }
.hit { background: var(--accent-soft); border-radius: 3px; box-shadow: 0 0 0 2px var(--accent-soft); }
.empty { color: var(--fg-faint); font-style: italic; font-size: .86rem; }

/* state machine demo */
.sm { display: flex; flex-wrap: wrap; gap: .4rem; align-items: center; margin: .6rem 0 .2rem; }
.sm .node { font: 600 .8rem var(--font-mono); padding: .4rem .65rem; border: 1.5px solid var(--border-strong); border-radius: 7px; background: var(--bg); color: var(--fg-muted); transition: all .2s; }
.sm .node.active { border-color: var(--accent); background: var(--accent-soft); color: var(--fg); }
.sm .node.paused { border-color: var(--warn); background: var(--warn-soft); color: var(--fg); }
.sm .node.done { border-color: var(--tip); color: var(--tip); }
.sm .node.stopped { border-color: var(--bad); color: var(--bad); }
.sm .arrow { color: var(--fg-faint); }
.approval { border: 1px solid var(--warn); background: var(--warn-soft); border-radius: 8px; padding: .8rem 1rem; margin-top: .8rem; }

/* ------------------------------------------------------------ quiz */
.quiz { margin: 2.2rem 0; }
.quiz fieldset { border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-elev); padding: 1rem 1.2rem .6rem; margin: 0 0 1rem; }
.quiz legend { font-weight: 650; padding: 0 .3rem; margin-left: -.3rem; line-height: 1.5; }
.quiz label { display: flex; gap: .6rem; align-items: flex-start; padding: .45rem .6rem; border-radius: 7px; cursor: pointer; margin: .15rem 0; line-height: 1.55; }
.quiz label:hover { background: var(--bg-sunk); }
.quiz input[type="radio"] { margin-top: .35rem; accent-color: var(--accent); flex: none; }
.quiz label.correct { background: var(--tip-soft); outline: 1px solid var(--tip); }
.quiz label.wrong { background: var(--bad-soft); outline: 1px solid var(--bad); }
.quiz .explain { display: none; font-size: .92rem; color: var(--fg-muted); border-top: 1px dashed var(--border); margin-top: .6rem; padding-top: .7rem; }
.quiz fieldset.answered .explain { display: block; }
.quiz .result { font-weight: 600; margin-top: .4rem; }

/* ------------------------------------------------------------ chapter footer */
.chapter-end { margin-top: 3.5rem; padding-top: 1.6rem; border-top: 1px solid var(--border); }
.complete-row { display: flex; align-items: center; gap: .8rem; flex-wrap: wrap; margin-bottom: 1.6rem; }
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.pager a { border: 1px solid var(--border); border-radius: var(--radius); padding: .8rem 1rem; text-decoration: none; color: var(--fg); background: var(--bg-elev); }
.pager a:hover { border-color: var(--accent); }
.pager small { display: block; color: var(--fg-faint); font-size: .78rem; }
.pager .next { text-align: right; grid-column: 2; }
@media (max-width: 520px) { .pager { grid-template-columns: 1fr; } .pager .next { grid-column: 1; } }

/* ------------------------------------------------------------ home */
.hero { padding: 1rem 0 1.2rem; }
.hero h1 { font-size: clamp(2rem, 1.3rem + 2.6vw, 2.9rem); margin-bottom: .6rem; }
.hero .lede { font-size: 1.18rem; max-width: 40em; }
.cta { display: flex; gap: .6rem; flex-wrap: wrap; margin: 1.4rem 0 .4rem; }
.chapter-list { list-style: none; padding: 0; margin: 1.2rem 0; display: grid; gap: .7rem; }
.chapter-list li { margin: 0; }
.chapter-list a { display: grid; grid-template-columns: 3rem 1fr auto; gap: .2rem .8rem; align-items: baseline; padding: .9rem 1rem; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-elev); text-decoration: none; color: var(--fg); }
.chapter-list a:hover { border-color: var(--accent); }
.chapter-list .n { font: 700 1rem var(--font-mono); color: var(--accent); grid-row: span 2; }
.chapter-list .t { font-weight: 650; }
.chapter-list .d { grid-column: 2 / 4; color: var(--fg-muted); font-size: .92rem; line-height: 1.55; }
.chapter-list .s { font-size: .8rem; color: var(--tip); }

.assess fieldset { border: 1px solid var(--border); border-radius: var(--radius); padding: .9rem 1.1rem .5rem; margin: 0 0 .8rem; background: var(--bg-elev); }
.assess legend { font-weight: 650; padding: 0 .3rem; }
.assess label { display: flex; gap: .55rem; align-items: flex-start; padding: .3rem .4rem; border-radius: 6px; cursor: pointer; font-size: .94rem; line-height: 1.55; }
.assess label:hover { background: var(--bg-sunk); }
.assess input { accent-color: var(--accent); margin-top: .35rem; }
.recommend { border: 1px solid var(--accent); background: var(--accent-soft); border-radius: var(--radius); padding: 1rem 1.2rem .3rem; margin-top: 1rem; }

.site-footer { border-top: 1px solid var(--border); padding: 1.6rem 16px; text-align: center; color: var(--fg-faint); font-size: .84rem; }

@media print {
  .topbar, .sidebar, .toc, .chapter-end .pager, .copy-btn, #menuBtn { display: none !important; }
  .layout, .main { display: block; padding: 0; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; scroll-behavior: auto !important; } }