:root{
  --bg:#0d0b14;
  --surface:#161320;
  --surface-2:#1e1a2b;
  --line:#2f2942;
  --fg:#f2eff9;
  --muted:#aaa3bf;
  --pink:#e371cb;
  --lav:#9b92dc;
  --teal:#6ccdb6;
  --coral:#f27b60;
  --tri:#190f17;
  --grad:linear-gradient(90deg,var(--pink),var(--lav) 50%,var(--teal));
  --f-display:"Lobster Two",Georgia,"Times New Roman",serif;
  --f-body:"Figtree",system-ui,-apple-system,"Segoe UI",sans-serif;
  --f-math:"STIX Two Text","Times New Roman",serif;
  --f-ar:"Cairo","Segoe UI",Tahoma,system-ui,sans-serif;
  color-scheme:dark;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--bg);color:var(--fg);
  font:16px/1.6 var(--f-body);
  padding-left:max(16px,env(safe-area-inset-left,0px));
  padding-right:max(16px,env(safe-area-inset-right,0px));
  padding-block:0;
}
.wrap{max-width:760px;margin:0 auto;padding-block:20px 56px}
b,strong{font-weight:700}
.kicker,.eyebrow{font-size:12px;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin:0}
h1,h2,h3,h4{margin:0;text-wrap:balance}
h1.display{
  font-family:var(--f-display);font-style:italic;font-weight:700;
  font-size:clamp(42px,12vw,68px);line-height:1.1;margin:6px 0 10px;padding-right:.12em;
  background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent;-webkit-text-fill-color:transparent;
}
.lead{color:var(--muted);max-width:56ch;margin:0 0 24px}
.seg{display:inline-flex;flex-wrap:wrap;gap:4px;background:var(--surface);border:1px solid var(--line);border-radius:22px;padding:4px}
.seg button{font:inherit;font-weight:600;font-size:15px;color:var(--muted);background:none;border:0;padding:8px 16px;border-radius:999px;cursor:pointer;min-height:40px}
.seg button[aria-selected="true"]{color:#150f1c;background:var(--grad)}
button:focus-visible,a:focus-visible,input:focus-visible{outline:2px solid var(--teal);outline-offset:2px}
.chap-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(210px,1fr));gap:10px;margin-top:14px}
.chap{display:flex;flex-direction:column;gap:2px;padding:14px 16px;border-radius:12px;background:var(--surface);border:1px solid var(--line);color:var(--fg);text-decoration:none;min-width:0}
.chap strong{font-size:16px}
.chap small{color:var(--muted);font-size:13px}
a.chap{border-color:var(--pink)}
a.chap small{color:var(--teal)}
.chap.soon{opacity:.55}

.chapter{margin-top:56px;padding-top:8px}
.chapter h2{font-family:var(--f-display);font-style:italic;font-weight:700;font-size:clamp(38px,10vw,54px);line-height:1.1;margin-top:6px}
.toc{display:flex;flex-wrap:wrap;gap:8px;margin:18px 0 0;padding:0;list-style:none}
.toc a{display:block;padding:7px 14px;border-radius:999px;border:1px solid var(--line);background:var(--surface);color:var(--fg);text-decoration:none;font-size:14px}
.toc a:hover{border-color:var(--teal)}

.lesson{margin-top:44px;padding-top:36px;border-top:1px solid var(--line)}
.lesson h3{font-family:var(--f-display);font-style:italic;font-weight:700;font-size:clamp(30px,8vw,40px);line-height:1.15;margin:4px 0 10px}
.lesson p{margin:0 0 14px;max-width:62ch}
.stage{background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:8px;margin:18px 0 12px}
.stage svg{display:block;width:100%;height:auto}
.controls{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin:12px 0}
.btn{font:inherit;font-weight:600;color:var(--fg);cursor:pointer;min-height:44px;padding:9px 18px;border-radius:999px;border:1.5px solid transparent;
  background:linear-gradient(var(--surface-2),var(--surface-2)) padding-box,var(--grad) border-box}
.btn:active{transform:translateY(1px)}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin:10px 0}
.chip{font-family:var(--f-math);font-style:italic;font-size:17px;padding:5px 13px;border-radius:999px;border:1px solid var(--line);background:var(--surface-2);font-variant-numeric:tabular-nums}
.chip.plain{font-style:normal;font-family:var(--f-body);font-size:15px}
.srow{display:grid;grid-template-columns:1fr auto;gap:0 12px;align-items:baseline;margin:10px 0 14px}
.srow .sname{grid-area:1/1;min-width:0}
.srow output{grid-area:1/2}
.srow input[type=range]{grid-area:2/1/3/3;width:100%;margin:2px 0 0}
.srow .sname{font-family:var(--f-math);font-style:italic;font-size:18px}
.srow output{font-variant-numeric:tabular-nums;text-align:right;font-weight:600}
input[type=range]{width:100%;min-width:0;accent-color:var(--pink);height:32px}
.ineq{list-style:none;margin:10px 0;padding:0;display:grid;gap:6px}
.ineq li{display:flex;justify-content:space-between;gap:12px;padding:8px 14px;border-radius:10px;background:var(--surface);border:1px solid var(--line);font-variant-numeric:tabular-nums}
.ineq .y{color:var(--teal);font-weight:700}
.ineq .n{color:var(--coral);font-weight:700}
.verdict{font-weight:600;font-size:17px;margin:12px 0}
.verdict.ok{color:var(--teal)}.verdict.bad{color:var(--coral)}.verdict.flat{color:var(--lav)}
.info{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:14px 16px;margin:12px 0}
.info h4{font-family:var(--f-display);font-style:italic;font-size:26px;margin-bottom:6px}
.info p{margin:0 0 8px}
.info p:last-child{margin:0}
.retenir{margin-top:22px;padding:14px 18px;border-radius:14px;border:1.5px solid transparent;
  background:linear-gradient(var(--surface),var(--surface)) padding-box,var(--grad) border-box}
.retenir h4{font-family:var(--f-display);font-style:italic;font-size:24px;margin-bottom:4px}
.retenir p{margin:0 0 8px}
.retenir p:last-child{margin:0}
.ar-lead{font-family:var(--f-ar);text-align:right;margin-top:-12px}
.ar-title{font-family:var(--f-ar);font-size:20px;color:var(--teal);margin:4px 0 14px;text-align:right}
.ar{margin-top:20px;padding:14px 18px 16px;border-radius:14px;background:var(--surface);border:1px solid var(--teal);font-family:var(--f-ar);line-height:1.9;font-size:17px}
.ar summary{cursor:pointer;font-weight:700;color:var(--teal);font-size:18px;min-height:32px}
.ar p{margin:8px 0}
.ar bdi{white-space:nowrap}
.ar .math{font-size:1em}
.ar-use{padding:8px 12px;border-radius:10px;background:var(--surface-2)}
.ar-words{list-style:none;margin:6px 0 0;padding:0;display:flex;flex-wrap:wrap;gap:8px}
.ar-words li{display:flex;gap:8px;align-items:baseline;padding:4px 12px;border-radius:999px;border:1px solid var(--line);background:var(--surface-2);font-size:15px}
.fr-w{font-family:var(--f-body);color:var(--lav);font-size:14px}
.chap .ar-t{font-family:var(--f-ar);font-size:14px;color:var(--lav);text-align:right;display:block;margin-top:2px}
.math{font-family:var(--f-math);font-style:italic;font-size:1.08em;white-space:nowrap}

.quiz{display:grid;gap:18px;margin-top:18px}
.q{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:14px 16px}
.q p{margin:0 0 10px;font-weight:600}
.opts{display:grid;gap:8px}
.opt{font:inherit;text-align:left;color:var(--fg);background:var(--surface-2);border:1.5px solid var(--line);border-radius:10px;padding:10px 14px;min-height:44px;cursor:pointer}
.opt.ok{border-color:var(--teal)}
.opt.ko{border-color:var(--coral)}
.opt[disabled]{cursor:default}
.fb{margin:10px 0 0;font-size:15px;color:var(--muted)}
.score{font-weight:700;font-size:18px;margin-top:14px}
footer{margin-top:56px;color:var(--muted);font-size:14px}

svg .tri{fill:var(--tri);stroke:#fff;stroke-width:2.6;stroke-linejoin:round}
svg .tri-o{fill:none;stroke:#fff;stroke-width:2.6;stroke-linejoin:round}
svg .vl{font-family:var(--f-math);font-style:italic;font-size:22px;fill:#fff;text-anchor:middle;dominant-baseline:central;pointer-events:none;user-select:none}
svg .pl{font-family:var(--f-math);font-style:italic;font-size:19px;text-anchor:middle;dominant-baseline:central;pointer-events:none;user-select:none}
svg .wl{font-family:var(--f-body);font-weight:700;font-size:13px;fill:#fff;text-anchor:middle;dominant-baseline:central;pointer-events:none;user-select:none}
svg .sumtxt{font-family:var(--f-math);font-weight:500;font-size:19px;fill:var(--fg);text-anchor:middle}
svg .note{font-family:var(--f-body);font-weight:600;font-size:14px;text-anchor:middle;pointer-events:none}
svg .floor{stroke:#fff;stroke-width:2.6;stroke-linecap:round;opacity:.4}
svg .ln{fill:none;stroke-width:2.6;stroke-linecap:round}
svg .dash{fill:none;stroke-width:1.6;stroke-dasharray:5 5;opacity:.85}
svg .arc{fill:none;stroke-width:2;stroke-dasharray:6 5}
svg .ra{fill:none;stroke-width:1.7}
svg .draw{stroke-dasharray:1;stroke-dashoffset:1;animation:draw .9s ease forwards}
@keyframes draw{to{stroke-dashoffset:0}}
svg .handle{fill:#fff;stroke-width:3.5}
svg .hd{outline:none}
svg .hd:focus-visible .handle{stroke-width:7}
.back{display:inline-block;margin:0 0 14px;color:var(--muted);text-decoration:none;font-size:14px}
.back:hover{color:var(--fg)}
.view.chapter{margin-top:8px}
.fr{display:inline-flex;flex-direction:column;align-items:center;vertical-align:middle;line-height:1.15;font-family:var(--f-math);font-style:normal;margin:0 .15em}
.fr>span:first-child{border-bottom:1.5px solid currentColor;padding:0 .25em}
mark{background:rgba(227,113,203,.28);color:var(--fg);border-radius:6px;padding:0 5px}
.calc .line{font-family:var(--f-math);font-size:22px;margin:8px 0 0}
.calc .why{color:var(--muted);font-size:14px;margin:0 0 6px}
.digits{display:flex;flex-wrap:wrap;gap:5px;margin:12px 0;min-height:48px}
.dg{min-width:38px;height:46px;display:grid;place-items:center;border-radius:9px;background:var(--surface-2);border:1px solid var(--line);font:700 24px var(--f-math)}
.dg.cm{min-width:22px;background:var(--pink);color:#150f1c;border-color:var(--pink)}
.tbl{border-collapse:collapse;margin:10px 0}
.tbl td,.tbl th{border:1px solid var(--line);padding:8px 14px;text-align:center;font-variant-numeric:tabular-nums}
.tbl td.on{background:rgba(108,205,182,.2);outline:2px solid var(--teal)}
.big{font-family:var(--f-math);font-size:24px;margin:10px 0}
.scroll-x{overflow-x:auto}

.kinds{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin:6px 0 14px}
.kind{font:inherit;text-align:left;color:var(--fg);background:var(--surface);border:1.5px solid var(--line);border-radius:16px;padding:14px 16px;cursor:pointer;min-height:84px;display:flex;flex-direction:column;gap:2px;min-width:0}
.kind strong{font-size:18px}
.kind small{color:var(--muted);font-size:14px;line-height:1.4}
.kind .ar-t{font-family:var(--f-ar);color:var(--lav);font-size:15px;display:block;text-align:right}
.kind[aria-pressed="true"]{border-color:transparent;background:linear-gradient(var(--surface-2),var(--surface-2)) padding-box,var(--grad) border-box}
.kind-hint{color:var(--muted);margin:0 0 14px}
.kind-hint .ar-t{display:block;font-family:var(--f-ar);color:var(--lav);text-align:right}
#ord,#pion{margin-top:6px}
#ord>.kicker,#pion>.kicker{margin:10px 0 8px}
@media (max-width:520px){.kinds{grid-template-columns:1fr}}
.btn.ghost{background:none;border:1.5px solid var(--line)}
a.btn{display:inline-flex;align-items:center;text-decoration:none}
.px-hero{padding:16px 18px;border-radius:16px;background:var(--surface);border:1px solid var(--line);margin:16px 0}
.px-hero h3{font-family:var(--f-display);font-style:italic;font-size:34px;line-height:1.1;margin:2px 0 8px}
.px-hero p{margin:0 0 8px}
.ar-note{font-family:var(--f-ar);color:var(--teal);line-height:1.9;font-size:16px;text-align:right}
.px-step{display:grid;grid-template-columns:34px minmax(0,1fr);gap:12px;margin:20px 0}
.px-n{margin:0;width:32px;height:32px;border-radius:50%;display:grid;place-items:center;font-weight:700;color:#150f1c;background:var(--grad)}
.px-step h4{font-size:19px;margin-bottom:2px}
.px-step p{margin:0 0 6px}
.px-sub{color:var(--muted)}
.chap.extra{border-style:dashed;border-color:var(--lav)}
.chap.extra small{color:var(--lav)}
.px-stars i{font-style:normal;color:#4a4560;font-size:17px;letter-spacing:2px}
.px-stars i.on{color:#ffcf5c}
.px-star-line{font-weight:600;margin:12px 0}
.px-set{display:grid;gap:12px;margin:12px 0}
.px-item{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:14px 16px}
.px-item.is-ok{border-color:var(--teal)}
.px-item.is-ko{border-color:var(--coral)}
.px-q{margin:0 0 10px;font-weight:600}
.px-row{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.px-row input{font:inherit;color:var(--fg);background:var(--surface-2);border:1.5px solid var(--line);border-radius:10px;padding:9px 12px;min-height:44px;width:100%;flex:1 1 120px;max-width:200px}
.px-u{color:var(--muted)}
.px-tools{margin-top:8px}
.px-hint{margin:8px 0 0;padding:8px 12px;border-radius:10px;background:var(--surface-2);color:var(--lav);font-size:15px}
.px-score{font-weight:600;margin:10px 0}
.px-ex{font-size:18px;margin:14px 0 6px}
.px-board{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:10px 14px;min-height:56px;font-family:var(--f-math);font-size:20px;overflow-x:auto}
.px-line{padding:4px 0}
.px-line.new{animation:pxin .45s ease}
@keyframes pxin{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}
.px-cap{color:var(--muted);margin:8px 0 4px;min-height:24px}
.px-line sup{font-size:.7em}
@media (prefers-reduced-motion:reduce){.px-line.new{animation:none}}
:root{--lamp:#ffcf5c}
svg .wire{fill:none;stroke:#fff;stroke-width:2.6;stroke-linecap:round;stroke-linejoin:round}
svg .thin{fill:none;stroke-width:1.6;stroke-linecap:round}
svg .tag{font-family:var(--f-body);font-weight:600;font-size:13px;text-anchor:middle;dominant-baseline:central;pointer-events:none;user-select:none}
svg .small{font-family:var(--f-body);font-size:12px;text-anchor:middle;dominant-baseline:central;fill:var(--muted);pointer-events:none}
.opts-grid{display:flex;flex-wrap:wrap;gap:8px;margin:8px 0 14px}
.btn.sm{min-height:40px;padding:6px 14px;font-size:14px}
.tbl.wide{width:100%;font-size:15px}
.tbl th{background:var(--surface-2)}
.sub{font-size:.7em;line-height:0}
.big,.px-ex{overflow-x:auto;max-width:100%}
.big .math,.px-ex .math{white-space:normal}