:root{
  --bg:#14101b; --bg2:#1a1524; --surface:#201a2c; --surface2:#2a2238; --line:#352c47;
  --text:#efeaf7; --muted:#a99fbd; --faint:#7d7392;
  --accent:#b9a2ff; --accent-ink:#14101b;
  --vl:#ff8f7f; --vl-bg:rgba(255,143,127,.14);
  --l:#f3c56b;  --l-bg:rgba(243,197,107,.14);
  --p:#7fd3c3;  --p-bg:rgba(127,211,195,.14);
  --fin:#b9a2ff; --fin-bg:rgba(185,162,255,.14);
  --good:#6fdc9a; --good-bg:rgba(111,220,154,.14);
  --warn:#ffb86b; --warn-bg:rgba(255,184,107,.14);
  --shadow:0 1px 0 rgba(255,255,255,.03), 0 8px 24px rgba(0,0,0,.25);
  --radius:14px; --course:var(--accent);
  color-scheme:dark;
}
:root[data-theme="light"]{
  --bg:#f7f5fb; --bg2:#f0edf6; --surface:#ffffff; --surface2:#f3f0f8; --line:#e2dcec;
  --text:#1c1726; --muted:#5f566f; --faint:#8a819b;
  --accent:#6b4fd8; --accent-ink:#ffffff;
  --vl:#c8452f; --vl-bg:rgba(200,69,47,.10);
  --l:#9a6a00;  --l-bg:rgba(154,106,0,.10);
  --p:#1f7f6e;  --p-bg:rgba(31,127,110,.10);
  --fin:#6a4fc4; --fin-bg:rgba(106,79,196,.10);
  --good:#1d8a4c; --good-bg:rgba(29,138,76,.10);
  --warn:#a85d00; --warn-bg:rgba(168,93,0,.10);
  --shadow:0 1px 2px rgba(30,20,50,.06), 0 6px 18px rgba(30,20,50,.06);
  color-scheme:light;
}
@media (prefers-color-scheme: light){
  :root:not([data-theme="dark"]){
    --bg:#f7f5fb; --bg2:#f0edf6; --surface:#ffffff; --surface2:#f3f0f8; --line:#e2dcec;
    --text:#1c1726; --muted:#5f566f; --faint:#8a819b;
    --accent:#6b4fd8; --accent-ink:#ffffff;
    --vl:#c8452f; --vl-bg:rgba(200,69,47,.10);
    --l:#9a6a00;  --l-bg:rgba(154,106,0,.10);
    --p:#1f7f6e;  --p-bg:rgba(31,127,110,.10);
  --fin:#6a4fc4; --fin-bg:rgba(106,79,196,.10);
    --good:#1d8a4c; --good-bg:rgba(29,138,76,.10);
    --warn:#a85d00; --warn-bg:rgba(168,93,0,.10);
    --shadow:0 1px 2px rgba(30,20,50,.06), 0 6px 18px rgba(30,20,50,.06);
    color-scheme:light;
  }
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-padding-top:136px}
body{margin:0;background:var(--bg);color:var(--text);font:16px/1.6 "Inter",system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;overflow-x:hidden}
a{color:var(--accent)}
h1,h2,h3{line-height:1.25;letter-spacing:-.01em}
button{font:inherit;color:inherit}
.wrap{max-width:1180px;margin:0 auto;padding:0 16px}

/* top bar */
.topbar{position:sticky;top:0;z-index:30;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(--line)}
.topbar .wrap{display:flex;align-items:center;gap:12px;min-height:56px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--text);font-weight:700;white-space:nowrap}
.brand .dot{width:26px;height:26px;border-radius:8px;background:linear-gradient(135deg,var(--accent),#ff8fd1);display:grid;place-items:center;color:#14101b;font-size:14px;font-weight:800}
.brand small{display:block;font-weight:500;color:var(--muted);font-size:12px;line-height:1.1}
.coursenav{display:flex;gap:6px;overflow-x:auto;scrollbar-width:none;flex:1;min-width:0;padding:8px 0}
.coursenav::-webkit-scrollbar{display:none}
.coursenav a{flex:none;text-decoration:none;color:var(--muted);font-size:13px;font-weight:600;padding:6px 10px;border-radius:999px;border:1px solid var(--line)}
.coursenav a:hover{color:var(--text)}
.coursenav a[aria-current="page"]{color:var(--accent-ink);background:var(--course);border-color:transparent}
.iconbtn{flex:none;width:38px;height:38px;border-radius:10px;border:1px solid var(--line);background:var(--surface);display:grid;place-items:center;cursor:pointer}
.iconbtn svg{width:18px;height:18px}

/* hero */
.hero{padding:28px 0 8px}
.eyebrow{font-size:12px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;color:var(--course)}
.hero h1{font-size:clamp(26px,4.4vw,40px);margin:6px 0 8px}
.hero p.lede{color:var(--muted);margin:0 0 14px;max-width:760px}
.facts{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 6px;padding:0;list-style:none}
.facts li{background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:6px 12px;font-size:13px;color:var(--muted)}
.facts li b{color:var(--text);font-weight:600}
.callout{border:1px solid var(--line);border-left:3px solid var(--warn);background:var(--surface);border-radius:10px;padding:10px 14px;color:var(--muted);font-size:14px;margin:12px 0}
.callout b{color:var(--text)}

/* index cards */
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:14px;margin:18px 0 28px}
.ccard{position:relative;display:flex;flex-direction:column;gap:10px;text-decoration:none;color:var(--text);background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:18px;box-shadow:var(--shadow);overflow:hidden;transition:transform .15s ease,border-color .15s ease}
.ccard:hover{transform:translateY(-2px);border-color:var(--c)}
.ccard::before{content:"";position:absolute;inset:0 0 auto 0;height:4px;background:var(--c)}
.ccard .code{font-size:12px;font-weight:700;letter-spacing:.06em;color:var(--c)}
.ccard h2{font-size:21px;margin:0}
.ccard .when{font-size:14px;color:var(--muted)}
.ccard .count{display:flex;align-items:baseline;gap:8px}
.ccard .count b{font-size:34px;line-height:1;font-variant-numeric:tabular-nums}
.ccard .count span{color:var(--muted);font-size:13px}
.ccard .days{position:absolute;top:16px;right:16px;font-size:12px;font-weight:700;color:var(--c);background:color-mix(in srgb,var(--c) 14%,transparent);padding:4px 9px;border-radius:999px}
.tagbar{display:flex;height:8px;border-radius:999px;overflow:hidden;background:var(--surface2)}
.tagbar i{display:block;height:100%}
.legend{display:flex;flex-wrap:wrap;gap:10px;font-size:12px;color:var(--muted)}
.legend span::before{content:"";display:inline-block;width:8px;height:8px;border-radius:2px;margin-right:5px;background:var(--k)}
.progress{height:6px;border-radius:999px;background:var(--surface2);overflow:hidden}
.progress i{display:block;height:100%;width:0;background:var(--good);transition:width .3s}
.ptext{font-size:12px;color:var(--muted)}
.section-title{font-size:13px;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:26px 0 8px}
.how-list{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:12px;margin:0 0 30px}
.how-list div{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:14px;font-size:14px;color:var(--muted)}
.how-list b{display:block;color:var(--text);margin-bottom:4px}
.btn{display:inline-flex;align-items:center;gap:8px;border:1px solid var(--line);background:var(--surface);color:var(--text);border-radius:10px;padding:8px 14px;font-size:14px;font-weight:600;text-decoration:none;cursor:pointer}
.btn:hover{border-color:var(--accent)}
.btn.primary{background:var(--accent);color:var(--accent-ink);border-color:transparent}

/* course layout */
.layout{display:grid;grid-template-columns:1fr;gap:24px;padding-bottom:80px}
@media (min-width:1000px){.layout{grid-template-columns:260px minmax(0,1fr)}}
.toc{align-self:start}
@media (min-width:1000px){.toc{position:sticky;top:132px;max-height:calc(100vh - 150px);overflow:auto;padding-right:4px}}
.toc details{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:10px 12px}
.toc summary{cursor:pointer;font-weight:700;font-size:14px;list-style:none;display:flex;justify-content:space-between;align-items:center}
.toc summary::-webkit-details-marker{display:none}
.toc summary::after{content:"▾";color:var(--muted)}
.toc details[open] summary::after{content:"▴"}
.toc ol{list-style:none;margin:8px 0 0;padding:0}
.toc li a{display:flex;justify-content:space-between;gap:8px;padding:6px 8px;border-radius:8px;text-decoration:none;color:var(--muted);font-size:13.5px;line-height:1.35}
.toc li a:hover,.toc li a.active{background:var(--surface2);color:var(--text)}
.toc li a .n{flex:none;font-variant-numeric:tabular-nums;font-size:12px;color:var(--faint)}
.toc li a .n.done{color:var(--good)}

/* toolbar */
.toolbar{position:sticky;top:56px;z-index:20;background:color-mix(in srgb,var(--bg) 92%,transparent);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);border-bottom:1px solid var(--line);padding:10px 0;margin-bottom:8px}
.toolbar .wrap{display:flex;flex-wrap:wrap;gap:8px;align-items:center}
.search{flex:1 1 220px;min-width:0;position:relative}
.search input{width:100%;background:var(--surface);border:1px solid var(--line);color:var(--text);border-radius:10px;padding:9px 12px 9px 34px;font-size:15px}
.search input:focus{outline:2px solid var(--accent);outline-offset:0;border-color:transparent}
.search svg{position:absolute;left:10px;top:50%;transform:translateY(-50%);width:16px;height:16px;color:var(--faint)}
.chips{display:flex;gap:6px;overflow-x:auto;scrollbar-width:none;max-width:100%}
.chips::-webkit-scrollbar{display:none}
.chip{flex:none;border:1px solid var(--line);background:var(--surface);color:var(--muted);border-radius:999px;padding:6px 11px;font-size:13px;font-weight:600;cursor:pointer}
.chip[aria-pressed="true"]{background:var(--text);color:var(--bg);border-color:transparent}
.switch{display:inline-flex;align-items:center;gap:8px;font-size:13px;color:var(--muted);cursor:pointer;user-select:none;flex:none}
.switch input{appearance:none;width:34px;height:20px;border-radius:999px;background:var(--surface2);border:1px solid var(--line);position:relative;cursor:pointer;margin:0}
.switch input::after{content:"";position:absolute;top:2px;left:2px;width:14px;height:14px;border-radius:50%;background:var(--muted);transition:transform .15s}
.switch input:checked{background:var(--accent)}
.switch input:checked::after{transform:translateX(14px);background:var(--accent-ink)}
.status{width:100%;display:flex;align-items:center;gap:10px;font-size:12.5px;color:var(--muted)}
.status .progress{flex:1;max-width:280px}

/* content */
.content{min-width:0}
.content section{margin-bottom:34px}
.content h2{font-size:clamp(21px,2.6vw,26px);margin:28px 0 12px;padding-top:6px}
.content h3{font-size:18px;margin:22px 0 8px}
.content p{margin:0 0 12px}
.content ul,.content ol{padding-left:22px}
.table-wrap{overflow-x:auto;margin:0 0 16px;border:1px solid var(--line);border-radius:12px;background:var(--surface)}
table{border-collapse:collapse;width:100%;font-size:14.5px}
th,td{text-align:left;vertical-align:top;padding:9px 12px;border-bottom:1px solid var(--line)}
th{background:var(--surface2);font-size:13px;color:var(--muted);font-weight:700}
tr:last-child td{border-bottom:0}
code{font-family:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,monospace;font-size:.92em}

/* question card */
.q{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px 16px 12px;margin:0 0 14px;box-shadow:var(--shadow);position:relative}
.q.got{border-color:color-mix(in srgb,var(--good) 55%,var(--line))}
.q.rev{border-color:color-mix(in srgb,var(--warn) 60%,var(--line))}
.qhead{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin-bottom:8px}
.qid{font-weight:800;font-size:14px;font-variant-numeric:tabular-nums}
.tag{font-size:12px;font-weight:700;border-radius:999px;padding:3px 9px}
.tag.vl{color:var(--vl);background:var(--vl-bg)}
.tag.l{color:var(--l);background:var(--l-bg)}
.tag.p{color:var(--p);background:var(--p-bg)}
.tag.fin{color:var(--fin);background:var(--fin-bg)}
.q[data-tag="fin"]{border-style:dashed}
.marks{font-size:12px;color:var(--muted)}
.qmark{margin-left:auto;display:flex;gap:6px}
.qmark button{border:1px solid var(--line);background:transparent;color:var(--muted);border-radius:8px;padding:4px 9px;font-size:12px;font-weight:600;cursor:pointer}
.qmark button.on-got{background:var(--good-bg);color:var(--good);border-color:transparent}
.qmark button.on-rev{background:var(--warn-bg);color:var(--warn);border-color:transparent}
.stem p:last-child{margin-bottom:8px}
.qactions{display:flex;flex-wrap:wrap;gap:8px;margin:6px 0 4px}
.qactions button{border:1px solid var(--line);background:var(--surface2);color:var(--text);border-radius:9px;padding:7px 12px;font-size:13.5px;font-weight:600;cursor:pointer}
.qactions button[aria-expanded="true"]{background:transparent;color:var(--muted)}
.reveal{border-top:1px dashed var(--line);margin-top:10px;padding-top:10px}
.reveal .lbl{display:block;font-size:11px;font-weight:800;letter-spacing:.08em;text-transform:uppercase;margin-bottom:4px}
.reveal.how .lbl{color:var(--accent)}
.reveal.ans .lbl{color:var(--good)}
.reveal p:last-child{margin-bottom:4px}
body.show-all .reveal{display:block!important}
body.show-all .qactions{display:none}

/* answer keys */
details.key{border:1px solid var(--line);border-radius:var(--radius);background:var(--bg2);margin:0 0 16px}
details.key>summary{cursor:pointer;padding:14px 16px;font-weight:700;display:flex;gap:10px;align-items:center;list-style:none}
details.key>summary::-webkit-details-marker{display:none}
details.key>summary::before{content:"🔒";font-size:15px}
details.key[open]>summary::before{content:"🔓"}
details.key>summary small{font-weight:500;color:var(--muted)}
details.key>.inner{padding:0 16px 8px}

/* rapid-fire blur */
table.rapid td:last-child{cursor:pointer;transition:filter .15s}
table.rapid td:last-child.hid{filter:blur(6px);user-select:none}
.rapidbar{display:flex;gap:8px;margin:0 0 10px}

/* filtering */
body.filtering .content section>*:not(h2):not(.q):not(.bucket){display:none}
body.filtering .content .bucket>*:not(.q){display:none}
.q.hide,section.hide{display:none!important}
.empty{display:none;color:var(--muted);text-align:center;padding:40px 0}
body.filtering .empty.show{display:block}
mark{background:color-mix(in srgb,var(--accent) 35%,transparent);color:inherit;border-radius:3px;padding:0 1px}

.foot{border-top:1px solid var(--line);color:var(--faint);font-size:13px;padding:22px 0 40px}
.totop{position:fixed;right:16px;bottom:16px;z-index:25;width:44px;height:44px;border-radius:12px;border:1px solid var(--line);background:var(--surface);box-shadow:var(--shadow);display:grid;place-items:center;cursor:pointer;opacity:0;pointer-events:none;transition:opacity .2s}
.totop.show{opacity:1;pointer-events:auto}

@media (max-width:640px){
  .brand small{display:none}
  .topbar .wrap{flex-wrap:wrap;gap:6px 10px;padding-top:8px}
  .brand{flex:1}
  .coursenav{order:3;flex-basis:100%;padding:0 0 8px}
  .toolbar{position:static}
  .qmark{margin-left:0;width:100%}
  .hero{padding-top:20px}
  html{scroll-padding-top:112px}
}
@media print{
  .topbar,.toolbar,.toc,.qactions,.qmark,.totop,.rapidbar{display:none!important}
  .reveal{display:block!important}
  details.key{display:block}
  details.key>.inner{display:block}
  body{background:#fff;color:#000}
  .q{box-shadow:none;break-inside:avoid}
  table.rapid td:last-child.hid{filter:none}
}