:root{
  --bg:#ffffff; --surface:#f7f8fa; --surface2:#eef1f5; --text:#1a1d21; --muted:#5b6470;
  --border:#e2e6ea; --accent:#1f6feb; --accent-soft:rgba(31,111,235,.10);
  --mark:rgba(35,150,70,.16); --shadow:0 6px 24px rgba(20,30,50,.10);
  --serif:Charter,"Iowan Old Style","Palatino Linotype",Palatino,Georgia,"Times New Roman",serif;
  --sans:system-ui,-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  --measure:38rem; --side:19rem; --otp:15rem;
}
:root[data-theme="dark"]{
  --bg:#0f1419; --surface:#161b22; --surface2:#1c232c; --text:#e6e8eb; --muted:#9aa4af;
  --border:#262d36; --accent:#589bff; --accent-soft:rgba(88,155,255,.14);
  --mark:rgba(70,180,110,.20); --shadow:0 8px 30px rgba(0,0,0,.45);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font-family:var(--sans);
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;line-height:1.6}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%;height:auto}

/* progress + topbar */
.progress{position:fixed;top:0;left:0;height:3px;width:0;background:var(--accent);z-index:60;transition:width .1s linear}
.topbar{position:sticky;top:0;z-index:50;display:flex;align-items:center;gap:.6rem;
  height:56px;padding:0 clamp(.7rem,3vw,1.4rem);background:color-mix(in srgb,var(--bg) 88%,transparent);
  backdrop-filter:saturate(1.4) blur(8px);border-bottom:1px solid var(--border)}
.brand{font-family:var(--serif);font-weight:700;font-size:1.05rem;color:var(--text);
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.top-actions{margin-left:auto;display:flex;gap:.25rem}
.icon-btn{display:inline-flex;align-items:center;justify-content:center;min-width:38px;height:38px;
  padding:0 .5rem;border:0;background:transparent;color:var(--text);cursor:pointer;border-radius:9px;
  font:inherit;font-size:.8rem}
.icon-btn:hover{background:var(--surface2)}
.menu-btn{display:none}
.ico-moon{display:none}
:root[data-theme="dark"] .ico-sun{display:none}
:root[data-theme="dark"] .ico-moon{display:inline}

/* download menu */
.dl-wrap{position:relative}
.dl-btn{gap:.35rem}
.dl-label{font-size:.85rem}
.dl-menu{position:absolute;right:0;top:calc(100% + 6px);min-width:9rem;background:var(--bg);
  border:1px solid var(--border);border-radius:11px;box-shadow:var(--shadow);padding:.3rem;display:none;z-index:55}
.dl-menu.open{display:block}
.dl-menu a{display:block;padding:.5rem .7rem;border-radius:8px;color:var(--text);font-size:.92rem}
.dl-menu a:hover{background:var(--surface2);text-decoration:none}
@media (max-width:520px){.dl-label{display:none}}

/* layout */
.layout{display:grid;grid-template-columns:var(--side) minmax(0,1fr) var(--otp);
  max-width:96rem;margin:0 auto;align-items:start}
.sidebar{position:sticky;top:56px;height:calc(100vh - 56px);overflow-y:auto;
  border-right:1px solid var(--border);background:var(--bg)}
.sidebar-inner{padding:1.2rem 1rem 3rem}
.side-brand{display:none;font-family:var(--serif);font-weight:700}
.toc ul{list-style:none;margin:0;padding:0}
.toc li{margin:.1rem 0}
.toc a{display:block;padding:.42rem .6rem;border-radius:8px;color:var(--muted);font-size:.9rem;line-height:1.35}
.toc a:hover{background:var(--surface2);color:var(--text);text-decoration:none}
.toc a.active{background:var(--accent-soft);color:var(--accent);font-weight:600}

/* content */
.content{min-width:0;padding:clamp(1.2rem,3vw,2.6rem) clamp(1rem,4vw,3rem) 4rem}
.prose{max-width:var(--measure);margin:0 auto;font-family:var(--serif);font-size:1.16rem;line-height:1.72;overflow-wrap:break-word}
.prose img{max-width:100%;height:auto}
.prose>*:first-child{margin-top:0}
.prose h1{font-size:2.05rem;line-height:1.2;margin:.2em 0 .6em;letter-spacing:-.01em}
.prose h2{font-size:1.5rem;margin:2.2em 0 .5em;letter-spacing:-.005em}
.prose h3{font-size:1.2rem;margin:1.8em 0 .4em}
.prose h4{font-size:1.05rem;margin:1.5em 0 .3em}
.prose h1,.prose h2,.prose h3,.prose h4{font-weight:700;scroll-margin-top:74px;position:relative}
.prose p{margin:0 0 1.05em}
.prose ul,.prose ol{margin:0 0 1.1em;padding-left:1.4em}
.prose li{margin:.3em 0}
.prose blockquote{margin:1.4em 0;padding:.2em 1.2em;border-left:3px solid var(--accent);
  color:var(--muted);font-style:italic}
.prose blockquote p:last-child{margin-bottom:0}
.prose hr{border:0;border-top:1px solid var(--border);margin:2.2em 0}
.prose a{text-decoration:underline;text-underline-offset:2px;text-decoration-thickness:1px;
  text-decoration-color:color-mix(in srgb,var(--accent) 45%,transparent)}
.prose strong{font-weight:700}
.prose code{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.9em;
  background:var(--surface2);padding:.1em .35em;border-radius:5px}

/* highlights / definitions / epigraphs */
mark{background:var(--mark)!important;color:inherit!important;padding:.02em .18em;border-radius:4px}
.definition{margin:1.8em 0;padding:1.1em 1.3em;background:var(--surface);border:1px solid var(--border);
  border-left:4px solid #23a05a;border-radius:12px;box-shadow:var(--shadow)}
.definition>*:first-child{margin-top:0}
.definition>*:last-child{margin-bottom:0}
.definition h4{color:#23a05a;font-variant:normal}
.definition mark{background:transparent!important}
.epigraph{margin:1.6em 0 2.2em;padding:.2em 0 .2em 1.2em;border-left:3px solid var(--border);color:var(--muted)}
.epigraph em{font-style:italic}
.epigraph strong{display:inline-block;margin-top:.2em;color:var(--text);font-weight:600;font-style:normal}
.epigraph p{margin:.3em 0}

/* figures & tables */
.prose figure{margin:1.8em auto;text-align:center}
.prose figure img{border-radius:10px;border:1px solid var(--border);background:#fff}
.prose figcaption{margin-top:.6em;font-family:var(--sans);font-size:.86rem;color:var(--muted)}
.prose figcaption p{margin:0}
.table-wrap{overflow-x:auto;margin:1.6em 0;border:1px solid var(--border);border-radius:12px}
.prose table{border-collapse:collapse;width:100%;font-family:var(--sans);font-size:.92rem}
.prose th,.prose td{padding:.6em .8em;border-bottom:1px solid var(--border);text-align:left;vertical-align:top}
.prose thead th{background:var(--surface);font-weight:700}
.prose tbody tr:last-child td{border-bottom:0}

/* heading anchor links */
.headlink{position:absolute;left:-1.1em;top:.12em;opacity:0;color:var(--muted);font-weight:400;
  text-decoration:none;font-size:.8em;padding:0 .2em}
.prose h2:hover .headlink,.prose h3:hover .headlink{opacity:1}

/* pager */
.pager{max-width:var(--measure);margin:3rem auto 0;display:flex;gap:1rem;flex-wrap:wrap}
.pager-link{flex:1 1 40%;min-width:0;display:flex;flex-direction:column;gap:.2rem;padding:1rem 1.1rem;
  border:1px solid var(--border);border-radius:12px;background:var(--surface);color:var(--text)}
.pager-link:hover{border-color:var(--accent);background:var(--accent-soft);text-decoration:none}
.pager-link.next{text-align:right;margin-left:auto}
.pager-dir{font-family:var(--sans);font-size:.78rem;color:var(--muted)}
.pager-title{font-family:var(--serif);font-weight:600;line-height:1.3;overflow:hidden;
  display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical}
.page-footer{max-width:var(--measure);margin:2.5rem auto 0;padding-top:1.4rem;border-top:1px solid var(--border);
  font-family:var(--sans);font-size:.85rem;color:var(--muted);display:flex;gap:.6rem}
.page-footer a{color:var(--muted)}

/* on this page */
.onthispage{position:sticky;top:56px;height:calc(100vh - 56px);overflow-y:auto;padding:1.6rem 1rem}
.otp-title{font-family:var(--sans);font-size:.72rem;text-transform:uppercase;letter-spacing:.06em;
  color:var(--muted);margin:0 0 .6rem}
.otp-inner ul{list-style:none;margin:0;padding:0;border-left:1px solid var(--border)}
.otp-inner li{margin:0}
.otp-inner a{display:block;padding:.28rem .8rem;margin-left:-1px;border-left:2px solid transparent;
  color:var(--muted);font-size:.83rem;line-height:1.3;font-family:var(--sans)}
.otp-inner a:hover{color:var(--text);text-decoration:none}
.otp-inner a.active{color:var(--accent);border-left-color:var(--accent);font-weight:600}
.otp-h3 a{padding-left:1.5rem;font-size:.8rem}

/* search */
.search-modal{position:fixed;inset:0;z-index:80;display:none;padding:10vh 1rem 1rem;
  background:rgba(10,15,25,.5);backdrop-filter:blur(3px)}
.search-modal.open{display:block}
.search-box{max-width:40rem;margin:0 auto;background:var(--bg);border:1px solid var(--border);
  border-radius:16px;box-shadow:var(--shadow);overflow:hidden}
.search-inputrow{display:flex;align-items:center;gap:.6rem;padding:.7rem 1rem;border-bottom:1px solid var(--border);color:var(--muted)}
.search-inputrow input{flex:1;border:0;background:transparent;color:var(--text);font:inherit;font-size:1.05rem;outline:none}
.search-inputrow .icon-btn{border:1px solid var(--border);border-radius:7px;min-width:auto;height:26px;font-size:.72rem;text-transform:uppercase}
.search-results{max-height:60vh;overflow-y:auto}
.search-results a{display:block;padding:.7rem 1rem;border-bottom:1px solid var(--border);color:var(--text)}
.search-results a:hover,.search-results a.sel{background:var(--surface2);text-decoration:none}
.sr-title{font-weight:600;font-size:.95rem}
.sr-crumb{font-size:.78rem;color:var(--accent);margin-bottom:.15rem}
.sr-snippet{font-size:.85rem;color:var(--muted);margin-top:.15rem;line-height:1.4}
.sr-snippet mark{background:var(--mark)!important;font-weight:600}
.sr-empty{padding:1.4rem 1rem;color:var(--muted);text-align:center}

/* home / landing */
.home-main{max-width:60rem;margin:0 auto;padding:clamp(1.4rem,4vw,3rem) clamp(1rem,4vw,2rem) 4rem}
.hero{display:grid;grid-template-columns:minmax(180px,280px) 1fr;gap:clamp(1.4rem,4vw,3rem);align-items:center;margin-bottom:3rem}
.hero-cover{border-radius:14px;box-shadow:var(--shadow);width:100%}
.hero-text h1{font-family:var(--serif);font-size:clamp(1.8rem,4vw,2.6rem);line-height:1.15;margin:0 0 .3em;letter-spacing:-.015em}
.hero-sub{font-family:var(--serif);font-size:1.15rem;color:var(--muted);margin:0 0 1.2em;line-height:1.4}
.hero-blurb{font-size:1rem;color:var(--text);margin:0 0 1.6em}
.hero-blurb a{color:var(--accent)}
.cta{display:inline-block;background:var(--accent);color:#fff;font-weight:600;padding:.8em 1.5em;
  border-radius:11px;font-size:1.05rem}
.cta:hover{filter:brightness(1.08);text-decoration:none}
.toc-section h2{font-family:var(--serif);font-size:1.5rem;border-bottom:1px solid var(--border);padding-bottom:.4rem}
.home-toc{margin:1.2rem 0;padding:0;list-style:none;counter-reset:toc}
.home-toc li{margin:.15rem 0}
.home-toc a{display:block;padding:.6rem .9rem;border-radius:10px;color:var(--text);font-family:var(--serif);font-size:1.05rem}
.home-toc a:hover{background:var(--surface2);text-decoration:none}
.home-footer{margin-top:2.5rem;padding-top:1.4rem;border-top:1px solid var(--border);color:var(--muted);font-size:.85rem}

/* responsive */
@media (max-width:1100px){
  .layout{grid-template-columns:var(--side) minmax(0,1fr)}
  .onthispage{display:none}
}
@media (max-width:820px){
  .menu-btn{display:inline-flex}
  .layout{grid-template-columns:minmax(0,1fr)}
  .sidebar{position:fixed;top:0;left:0;height:100vh;width:min(84vw,var(--side));z-index:70;
    transform:translateX(-100%);transition:transform .25s ease;box-shadow:var(--shadow);border-right:1px solid var(--border)}
  .sidebar.open{transform:translateX(0)}
  .sidebar-inner{padding-top:1rem}
  .side-brand{display:block;margin:0 .6rem 1rem;padding-bottom:.8rem;border-bottom:1px solid var(--border);color:var(--text)}
  .scrim{position:fixed;inset:0;background:rgba(10,15,25,.45);z-index:65;opacity:0;visibility:hidden;transition:opacity .25s}
  .scrim.show{opacity:1;visibility:visible}
  .hero{grid-template-columns:1fr;text-align:center}
  .hero-cover{max-width:230px;margin:0 auto}
  .cta{width:100%}
  .pager-link{flex:1 1 100%}
}
@media (min-width:821px){.scrim{display:none}}