/* 機器學習筆記 — shared styles for /element/ pages. Palette and type follow the home page. */
:root{
  --paper:#F6F2EC; --sand:#E9E1D6; --panel:#EFE8DF;
  --ink:#2B2420; --ink-2:#4A3D33; --muted:#5A4C42; --faint:#7D6F64;
  --rule:#C9C2B9; --rule-soft:#DDD5CB;
  --accent:#7A4E33; --terracotta:#9A5B3B;
  --marble:#1D1B19; --on-marble:#F3EFE9; --on-marble-2:#D8D3CC; --on-marble-muted:#B9B3AB; --marble-rule:#5C5853;
  --serif-en:'Cormorant Garamond','Noto Serif TC',serif;
  --serif-zh:'Noto Serif TC','Songti TC',serif;
  --sans:'Noto Sans TC','PingFang TC','Microsoft JhengHei',sans-serif;
  --mono:'SFMono-Regular',Menlo,Consolas,'Liberation Mono',monospace;
  --gutter:clamp(20px,5.56vw,80px);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{margin:0;font-variant-numeric:lining-nums;background:var(--paper);color:var(--ink);font-family:var(--sans);font-weight:300;font-size:17px;line-height:1.95}
a{color:inherit;text-decoration-thickness:1px;text-underline-offset:.3em}
a:hover{opacity:.65}
a:focus-visible,button:focus-visible,summary:focus-visible{outline:1px solid currentColor;outline-offset:4px}
strong{font-weight:500}
img{max-width:100%}
@media (prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}
.wrap{width:100%;max-width:1440px;margin:0 auto;padding:0 var(--gutter)}

/* ---------- marble band (hero + footer) ---------- */
.marble{color:var(--on-marble);background-color:var(--marble);
  background-image:radial-gradient(ellipse 60% 50% at 12% 0%,rgba(255,255,255,.07),transparent 70%),
  linear-gradient(118deg,transparent 0 37%,rgba(255,255,255,.045) 38.5%,transparent 41% 63%,rgba(255,255,255,.03) 64.5%,transparent 67%),
  linear-gradient(64deg,transparent 0 71%,rgba(255,255,255,.03) 72%,transparent 74%)}
.site-header{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 32px;padding:26px 0}
.wordmark{display:inline-flex;align-items:center;min-height:44px;font-family:var(--serif-en);font-weight:600;font-size:24px;letter-spacing:.24em;text-decoration:none}
.site-nav{display:flex;flex-wrap:wrap;gap:0 36px}
.site-nav a{display:inline-flex;align-items:center;min-height:44px;font-size:15px;font-weight:400;letter-spacing:.16em;text-decoration:none}
.site-nav a[aria-current="page"]{text-decoration:underline}

.crumbs{margin:0;font-size:13px;font-weight:400;letter-spacing:.2em;color:var(--on-marble-muted)}
.crumbs a{text-decoration:none}
.crumbs span[aria-hidden]{margin:0 .6em}

.hero{padding:40px 0 88px}
.hero-num{margin:28px 0 0;font-family:var(--serif-en);font-weight:500;font-size:clamp(64px,8vw,120px);line-height:.9;color:var(--on-marble-muted);letter-spacing:.02em}
.hero h1{margin:18px 0 0;font-family:var(--serif-zh);font-weight:500;font-size:clamp(34px,4.2vw,52px);line-height:1.3;letter-spacing:.1em}
.hero .en{display:block;margin-top:6px;font-family:var(--serif-en);font-style:italic;font-weight:500;font-size:clamp(22px,2.4vw,30px);letter-spacing:.02em;color:var(--on-marble-muted)}
.hero .summary{margin:28px 0 0;max-width:34em;color:var(--on-marble-2);text-wrap:pretty}
.hero .meta{margin:28px 0 0;font-size:13px;letter-spacing:.14em;color:var(--on-marble-muted)}
.hero-rule{width:64px;height:1px;margin-top:32px;background:var(--on-marble-muted)}

/* ---------- chapter layout ---------- */
.layout{display:grid;grid-template-columns:220px minmax(0,740px);gap:80px;justify-content:center;padding:88px 0 40px}
.toc{position:sticky;top:32px;align-self:start;max-height:calc(100vh - 64px);overflow:auto;font-size:14px;line-height:1.6}
.toc-title{margin:0 0 14px;font-size:12px;font-weight:400;letter-spacing:.24em;color:var(--muted)}
.toc ol{list-style:none;margin:0;padding:0;border-left:1px solid var(--rule)}
.toc li a{display:block;padding:7px 0 7px 16px;margin-left:-1px;border-left:1px solid transparent;text-decoration:none;color:var(--muted)}
.toc li a .n{font-family:var(--serif-en);font-weight:600;margin-right:.6em}
.toc li a.active{color:var(--ink);border-left-color:var(--ink)}
.toc-mobile{display:none}

.prose{min-width:0}
.prose>p:first-child,.prose>.lead{font-size:19px;line-height:1.9;color:var(--ink-2)}
.prose p{margin:0 0 1.15em;text-wrap:pretty}
.prose h2{margin:88px 0 26px;padding-top:26px;border-top:1px solid var(--ink);font-family:var(--serif-zh);font-weight:500;font-size:clamp(25px,2.6vw,31px);line-height:1.45;letter-spacing:.08em;scroll-margin-top:24px}
.prose h2:first-child{margin-top:0}
.prose h2 .n{display:block;margin-bottom:6px;font-family:var(--serif-en);font-weight:600;font-size:16px;letter-spacing:.14em;color:var(--faint)}
.prose h2 .en{display:block;font-family:var(--serif-en);font-style:italic;font-weight:500;font-size:.82em;letter-spacing:.01em;color:#6B5C50}
.prose h3{margin:48px 0 14px;font-family:var(--serif-zh);font-weight:500;font-size:20px;line-height:1.6;letter-spacing:.08em}
.prose ul,.prose ol{margin:0 0 1.2em;padding-left:1.4em}
.prose li{margin:.25em 0;padding-left:.2em}
.prose li::marker{color:var(--faint)}
.prose ol>li::marker{font-family:var(--serif-en);font-weight:600}
.prose a{color:var(--accent)}
.prose code{font-family:var(--mono);font-size:.86em;background:var(--panel);padding:.12em .4em;border-radius:3px}
.prose pre{margin:0 0 1.6em;padding:20px 24px;background:var(--marble);color:var(--on-marble);overflow-x:auto;font-size:14px;line-height:1.7;border-radius:2px}
.prose pre code{background:none;padding:0;font-size:inherit;color:inherit}
.prose hr{border:0;border-top:1px solid var(--rule);margin:48px 0}

/* math */
.prose .katex{font-size:1.06em}
.prose eq{display:inline}
.prose eqn,.prose section.eqno{display:block;margin:1.4em 0 1.6em;padding:18px 0;overflow-x:auto;overflow-y:hidden;text-align:center}
.prose .katex-display{margin:0}
.prose .katex .katex-mathml{width:1px;height:1px;overflow:hidden}

/* tables */
.table-wrap{margin:8px 0 1.8em;overflow-x:auto;-webkit-overflow-scrolling:touch}
.prose table{width:100%;border-collapse:collapse;font-size:15px;line-height:1.75}
.prose th{text-align:left;font-weight:500;letter-spacing:.06em;padding:10px 14px 10px 0;border-bottom:1px solid var(--ink);vertical-align:bottom}
.prose td{padding:12px 14px 12px 0;border-bottom:1px solid var(--rule-soft);vertical-align:top}
.prose tr:last-child td{border-bottom-color:var(--rule)}

/* callouts */
.callout{margin:1.8em 0;padding:20px 24px 6px;background:var(--panel);border-left:2px solid var(--ink)}
.callout-label{margin:0 0 8px!important;font-size:12px;font-weight:500;letter-spacing:.28em;color:var(--muted)}
.callout-label .en{margin-left:.8em;font-family:var(--serif-en);font-style:italic;font-weight:500;font-size:15px;letter-spacing:.04em}
.callout.caution{background:#F3E7DD;border-left-color:var(--terracotta)}
.callout.caution .callout-label{color:var(--terracotta)}
.callout.note{background:transparent;border:1px solid var(--rule);border-left:2px solid var(--faint)}

/* figures */
figure.fig{margin:2.2em 0 2.4em}
figure.fig figcaption{margin-top:14px;font-size:13px;letter-spacing:.08em;color:var(--muted);line-height:1.7}
.flow{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:0;border-top:1px solid var(--ink)}
.flow-step{position:relative;padding:18px 18px 18px 0}
.flow-step+.flow-step{padding-left:18px;border-left:1px solid var(--rule)}
.flow-k{margin:0!important;font-family:var(--serif-en);font-weight:600;font-size:14px;letter-spacing:.14em;color:var(--faint)}
.flow-t{margin:4px 0 0!important;font-family:var(--serif-zh);font-weight:500;font-size:18px;letter-spacing:.08em;line-height:1.5}
.flow-band{display:inline-block;margin-top:10px;padding:1px 10px;font-size:12px;letter-spacing:.14em;background:var(--sand);color:var(--ink-2)}
.flow-fix{margin:12px 0 0!important;font-size:14px;line-height:1.75;color:var(--muted)}
.flow-fix b{display:block;font-weight:500;font-size:12px;letter-spacing:.2em;color:var(--terracotta)}
.split-bar{display:flex;height:44px;margin-top:34px}
.split-bar>div{display:flex;align-items:center;justify-content:center;font-size:13px;letter-spacing:.08em;white-space:nowrap;overflow:hidden}
.split-legend{display:flex;margin-top:10px;font-size:13px;line-height:1.5;color:var(--muted)}
.split-legend>div{padding-top:8px;border-top:1px solid var(--ink)}
.split-legend>div+div{margin-left:8px}
.cm{width:100%;border-collapse:collapse;font-size:14px;line-height:1.55;text-align:center}
.cm th,.cm td{padding:12px 10px;border:1px solid var(--rule)!important;vertical-align:middle!important;text-align:center!important}
.cm thead th{font-weight:500;background:var(--sand)}
.cm .rh{font-weight:500;background:var(--sand)}
.cm .hit{background:#E3D6C6}
.cm .miss{background:var(--paper)}
.cm .ratio{background:var(--panel);color:var(--ink-2)}
.cm .corner{background:transparent;border-color:transparent!important}
.cm small{display:block;font-size:12px;color:var(--muted);letter-spacing:.04em}
.cm .t{font-family:var(--serif-zh);font-weight:500;font-size:15px}

/* prev / next */
.pager{display:grid;grid-template-columns:1fr 1fr;gap:24px;max-width:1040px;margin:0 auto;padding:40px 0 112px}
.pager a{display:block;padding:24px 0 6px;border-top:1px solid var(--ink);text-decoration:none}
.pager a.next{text-align:right;grid-column:2}
.pager .dir{display:block;font-size:12px;letter-spacing:.24em;color:var(--muted)}
.pager .num{font-family:var(--serif-en);font-weight:600;font-size:22px;margin-right:.5em}
.pager .t{font-family:var(--serif-zh);font-weight:500;font-size:20px;letter-spacing:.06em}

/* footer */
.site-footer .row{display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;gap:24px 48px;padding:48px 0 56px;border-top:1px solid var(--marble-rule)}
.site-footer .credit{margin:0;padding:0 0 40px;font-size:13px;line-height:1.8;letter-spacing:.06em;color:var(--on-marble-muted)}
.site-footer a{display:inline-flex;align-items:center;min-height:44px;font-size:14px;font-weight:400;letter-spacing:.2em}

/* ---------- handbook index ---------- */
.idx-hero{display:flex;flex-wrap:wrap;align-items:center;gap:24px 72px;padding:24px 0 96px}
.idx-hero .text{flex:1.3 1 480px;min-width:0}
.idx-hero h1{margin:16px 0 0;display:flex;flex-wrap:wrap;align-items:baseline;gap:4px 18px;font-family:var(--serif-zh);font-weight:500;font-size:clamp(40px,4.6vw,60px);line-height:1.25;letter-spacing:.12em}
.idx-hero h1 .en{font-family:var(--serif-en);font-style:italic;font-weight:500;font-size:.66em;letter-spacing:.02em;color:var(--on-marble-muted)}
.idx-hero .sub{margin:10px 0 0;font-family:var(--serif-zh);font-weight:500;font-size:20px;letter-spacing:.24em;color:var(--on-marble-2)}
.idx-hero .intro{margin:28px 0 0;max-width:32em;color:var(--on-marble-2);text-wrap:pretty}
.idx-hero img{flex:1 1 320px;max-width:460px;min-width:0;aspect-ratio:4/3;object-fit:cover;-webkit-mask-image:radial-gradient(closest-side,#000 26%,rgba(0,0,0,.5) 58%,transparent 90%);mask-image:radial-gradient(closest-side,#000 26%,rgba(0,0,0,.5) 58%,transparent 90%)}
.stats{display:flex;flex-wrap:wrap;gap:12px 40px;margin:36px 0 0;padding:0;list-style:none}
.stats li{font-size:13px;letter-spacing:.16em;color:var(--on-marble-muted)}
.stats b{display:block;font-family:var(--serif-en);font-weight:500;font-size:40px;line-height:1.1;letter-spacing:0;color:var(--on-marble)}
.parts{padding:96px 0 120px}
.part{display:grid;grid-template-columns:minmax(0,280px) minmax(0,1fr);gap:24px 72px;padding:40px 0 48px;border-top:1px solid var(--ink)}
.part+.part{margin-top:24px}
.part-head .k{margin:0;font-family:var(--serif-en);font-weight:600;font-size:14px;letter-spacing:.24em;color:var(--faint)}
.part-head h2{margin:6px 0 0;font-family:var(--serif-zh);font-weight:500;font-size:30px;letter-spacing:.14em;line-height:1.4}
.part-head h2 .en{display:block;font-family:var(--serif-en);font-style:italic;font-size:22px;letter-spacing:.02em;color:#6B5C50}
.part-head p{margin:14px 0 0;font-size:15px;color:var(--muted);text-wrap:pretty}
.ch-list{list-style:none;margin:0;padding:0}
.ch-list li+li{border-top:1px solid var(--rule-soft)}
.ch-list a{display:grid;grid-template-columns:64px minmax(0,1fr);gap:4px 16px;padding:22px 0;text-decoration:none}
.ch-list .num{font-family:var(--serif-en);font-weight:500;font-size:34px;line-height:1.1;color:var(--faint)}
.ch-list .t{font-family:var(--serif-zh);font-weight:500;font-size:22px;letter-spacing:.08em;line-height:1.5}
.ch-list .t .en{margin-left:12px;font-family:var(--serif-en);font-style:italic;font-weight:500;font-size:18px;letter-spacing:.01em;color:#6B5C50}
.ch-list .s{grid-column:2;margin:2px 0 0;font-size:15px;line-height:1.85;color:var(--muted);text-wrap:pretty}
.colophon{max-width:46em;margin:0;padding:0 0 112px;font-size:14px;line-height:1.9;color:var(--muted)}

/* ---------- responsive ---------- */
@media (max-width:1000px){
  .layout{grid-template-columns:minmax(0,1fr);gap:0;padding-top:48px}
  .toc{display:none}
  .toc-mobile{display:block;margin:0 0 40px;border-top:1px solid var(--ink);border-bottom:1px solid var(--rule)}
  .toc-mobile summary{cursor:pointer;min-height:48px;display:flex;align-items:center;font-size:14px;font-weight:400;letter-spacing:.2em}
  .toc-mobile ol{list-style:none;margin:0 0 12px;padding:0;font-size:15px;line-height:1.6}
  .toc-mobile li a{display:block;padding:8px 0;text-decoration:none;color:var(--muted)}
  .toc-mobile .n{font-family:var(--serif-en);font-weight:600;margin-right:.6em}
  .part{grid-template-columns:minmax(0,1fr)}
}
@media (max-width:640px){
  body{font-size:16px}
  .prose>p:first-child{font-size:17px}
  .flow{grid-template-columns:minmax(0,1fr)}
  .flow-step,.flow-step+.flow-step{padding:16px 0;border-left:0;border-bottom:1px solid var(--rule)}
  .pager{grid-template-columns:minmax(0,1fr)}
  .pager a.next{grid-column:1}
  .ch-list a{grid-template-columns:48px minmax(0,1fr)}
  .ch-list .num{font-size:28px}
  .ch-list .t .en{display:block;margin-left:0}
  .site-nav{gap:0 22px}
  .cm{font-size:13px;min-width:560px}
  .callout{padding:16px 18px 4px}
  .cm th,.cm td{padding:9px 5px}
}