/* Public pages: front page, pricing, not found. Builds on base.css. */
body{background:var(--bg)}
/* in-page jumps (#faq, #how-to …) stop below the sticky site header instead of under it; .dir-sec sets its own, larger offset */
:where([id]){scroll-margin-top:calc(var(--dir-top,64px) + 16px)}
.hero{padding-block:clamp(40px,8vw,92px) 28px}
.hero-title{font-family:var(--f-display);font-weight:700;font-size:clamp(40px,7.4vw,96px);line-height:.98;letter-spacing:-.04em;margin:0;max-width:13ch;text-wrap:balance}
.hero-row{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:24px 48px;align-items:end;margin-top:28px}
.hero-sub{font-size:clamp(16px,1.6vw,19px);line-height:1.55;color:var(--muted);max-width:52ch;margin:0}
.hero-cta{display:flex;flex-wrap:wrap;gap:10px;align-items:center;justify-content:flex-end}
.hero-note{flex-basis:100%;margin:2px 0 0;font-size:13.5px;color:var(--muted);text-align:end}
@media (max-width:820px){.hero-row{grid-template-columns:1fr}.hero-cta{justify-content:flex-start}.hero-note{text-align:start}}

.demo{background:var(--surface);border:1px solid var(--line);border-radius:18px;overflow:hidden;box-shadow:0 40px 80px -48px rgba(0,0,0,.35)}
.demo-bar{display:flex;flex-wrap:wrap;justify-content:space-between;align-items:center;gap:10px 16px;padding:12px 14px;border-bottom:1px solid var(--line);background:var(--sunk)}
.demo-topics{display:flex;flex-wrap:wrap;gap:6px}
.demo-topics button{border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:6px 13px;font-size:13.5px;font-weight:600;color:var(--muted)}
.demo-topics button:hover{color:var(--ink);border-color:var(--muted)}
.demo-topics button[aria-pressed="true"]{background:var(--acc-soft);border-color:var(--acc);color:var(--ink)}
.demo-tools{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.demo-tools select{height:36px;max-width:220px;border:1px solid var(--line);border-radius:9px;background:var(--surface);padding:0 8px;font:inherit;font-size:13.5px;color:inherit}
.demo .diagram{border-bottom:1px solid var(--line);min-height:120px}
.demo-body{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(0,1fr)}
.demo-body .diagram{border-bottom:0;border-inline-end:1px solid var(--line);display:flex;align-items:center;padding:28px 16px}
.demo-body .diagram svg{min-width:0}
@media (max-width:900px){.demo-body{grid-template-columns:1fr}.demo-body .diagram{border-inline-end:0;border-bottom:1px solid var(--line)}.demo-body .diagram svg{min-width:460px}}
.demo-solution{border:0;border-top:1px solid var(--line);border-radius:0}
.demo-foot{font-size:14px;color:var(--muted);margin:14px 2px 0}
.demo-foot a{color:var(--acc-text)}
@media (prefers-reduced-motion:no-preference){
  .draw .w,.draw .el,.draw .aw,.draw .mem,.draw .zz,.draw .dash{stroke-dasharray:var(--len);stroke-dashoffset:var(--len);animation:draw 1.1s cubic-bezier(.6,0,.2,1) forwards}
  .draw .el{fill-opacity:0;animation:draw 1.1s cubic-bezier(.6,0,.2,1) forwards,fillin .4s .8s forwards}
  .draw text,.draw .ah,.draw .dot,.draw .sgn{opacity:0;animation:fillin .4s .75s forwards}
  @keyframes draw{to{stroke-dashoffset:0}}
  @keyframes fillin{to{opacity:1;fill-opacity:1}}
}

.sec{padding-block:clamp(48px,8vw,96px) 0}
.sec h2,.final h2{font-family:var(--f-display);font-weight:700;font-size:clamp(28px,3.6vw,44px);letter-spacing:-.03em;line-height:1.05;margin:0;text-wrap:balance}
.sec-head{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px 48px;align-items:end;margin-bottom:34px}
.sec-head p{margin:0;color:var(--muted);font-size:16px;max-width:46ch}
@media (max-width:760px){.sec-head{grid-template-columns:1fr}}

.feats{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:24px}
.feat{border-top:1px solid var(--line);padding-top:16px}
.feat h3{font-size:17px;margin:0 0 6px}
.feat p{margin:0;color:var(--muted);font-size:15px}
@media (max-width:900px){.feats{grid-template-columns:1fr 1fr}}
@media (max-width:480px){.feats{grid-template-columns:1fr}}

.price-strip{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:28px 48px;align-items:center;background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:clamp(22px,4vw,40px)}
.price-strip p{color:var(--muted);margin:10px 0 0;max-width:52ch}
.price-cols{display:flex;gap:28px;align-items:center;flex-wrap:wrap}
.pcol{display:flex;flex-direction:column;gap:2px;min-width:120px}
.pcol b{font-size:14px}
.pbig{font-family:var(--f-display);font-size:38px;font-weight:700;letter-spacing:-.03em;line-height:1.1}
@media (max-width:900px){.price-strip{grid-template-columns:1fr}}

.faq-wrap{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,2fr);gap:20px 48px}
@media (max-width:760px){.faq-wrap{grid-template-columns:1fr}}
.faq details{border-top:1px solid var(--line);padding:4px 0}
.faq details:last-child{border-bottom:1px solid var(--line)}
.faq summary{cursor:pointer;list-style:none;font-weight:600;font-size:16.5px;padding:14px 32px 14px 0;position:relative}
[dir="rtl"] .faq summary{padding:14px 0 14px 32px}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"";position:absolute;inset-inline-end:4px;top:50%;width:10px;height:10px;border-right:1.8px solid var(--muted);border-bottom:1.8px solid var(--muted);transform:translateY(-70%) rotate(45deg);transition:transform .15s}
.faq details[open] summary::after{transform:translateY(-30%) rotate(-135deg)}
.faq p{margin:0 0 16px;color:var(--muted);max-width:64ch}

.final{display:flex;flex-wrap:wrap;justify-content:space-between;align-items:center;gap:20px;padding-block:24px 8px;border-top:2px solid var(--acc);padding-top:36px}

/* pricing page */
.plans4{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin-top:8px}
@media (max-width:980px){.plans4{grid-template-columns:1fr 1fr}}
@media (max-width:520px){.plans4{grid-template-columns:1fr}}
.plans4 .plan{padding:22px 18px 18px}
.plans4 .plan.featured{padding:21px 17px 17px}
.plist{list-style:none;padding:0;margin:14px 0 18px;display:flex;flex-direction:column;gap:7px;font-size:14px}
.plist li{display:flex;gap:8px}
.plist li::before{content:"";flex:none;width:14px;height:14px;margin-top:3px;background:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cpath d='M3.5 8.5l3 3 6-7' fill='none' stroke='%236B6B6B' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E") center/14px no-repeat}
.vatnote{color:var(--muted);font-size:13.5px;margin-top:16px}
.ptitle{padding-block:clamp(36px,6vw,72px) 28px}
.ptitle h1{font-family:var(--f-display);font-size:clamp(34px,5vw,60px);letter-spacing:-.035em;line-height:1;margin:0;max-width:16ch}
.ptitle p{color:var(--muted);font-size:17px;max-width:56ch;margin:16px 0 0}

/* not found */
.nf{min-height:70vh;display:flex;flex-direction:column;justify-content:center;gap:16px;padding-block:60px}
.nf h1{font-family:var(--f-display);font-size:clamp(36px,6vw,72px);letter-spacing:-.04em;line-height:1;margin:0}
.nf p{color:var(--muted);font-size:17px;margin:0;max-width:50ch}
.nf .row{display:flex;gap:10px;flex-wrap:wrap;margin-top:8px}
.foot a.brand{display:inline-flex;padding:0;margin-bottom:10px}
.foot p{margin:0 0 14px;max-width:34ch}
.foot .brand{color:var(--ink)}

/* ===================== v3: front page ===================== */
.eyebrow{display:inline-flex;align-items:center;gap:8px;border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:6px 13px;font-size:13.5px;color:var(--muted);margin:0 0 22px}
.dotlive{width:8px;height:8px;border-radius:50%;background:var(--acc);box-shadow:0 0 0 4px var(--acc-soft)}
.hero-title{background:linear-gradient(100deg,var(--ink) 55%,var(--acc-text));-webkit-background-clip:text;background-clip:text;color:transparent}
.demo-body.nodia{grid-template-columns:1fr}

.tour-sec{padding-block:20px 0}
.tour{position:relative;display:grid;grid-template-columns:minmax(0,1fr) 290px;border:1px solid var(--line);border-radius:20px;background:var(--surface);overflow:hidden;box-shadow:0 40px 90px -50px color-mix(in srgb,var(--acc) 55%,transparent)}
.tour-frame{position:relative;overflow:hidden;background:var(--bg);border-inline-end:1px solid var(--line)}
/* reserve the stage height before landing.js sizes the frame (same ratios as fit() there), so the hero does not jump */
.tour-frame{container-type:inline-size}.tour-frame::before{content:"";display:block;padding-top:58.3334%}
@container (max-width:639.9px){.tour-frame::before{padding-top:80%}}
.tour-steps{list-style:none;margin:0;padding:10px 0;display:flex;flex-direction:column;justify-content:center}
.tour-steps button{width:100%;border:0;background:transparent;text-align:start;padding:13px 22px;display:flex;flex-direction:column;gap:3px;border-inline-start:2px solid var(--line);color:var(--muted)}
.tour-steps button b{font-size:15px;color:var(--muted);transition:color .2s}
.tour-steps button span{font-size:13.5px;line-height:1.45}
.tour-steps button[aria-current="true"]{border-inline-start-color:var(--acc);background:linear-gradient(90deg,var(--acc-soft),transparent)}
[dir="rtl"] .tour-steps button[aria-current="true"]{background:linear-gradient(270deg,var(--acc-soft),transparent)}
.tour-steps button[aria-current="true"] b{color:var(--ink)}
.tour-pause{position:absolute;right:10px;bottom:10px;width:30px;height:30px;opacity:.85;border-radius:50%;border:1px solid var(--line);background:var(--surface);z-index:3;display:grid;place-items:center}
.tour-pause::before{content:"";width:10px;height:12px;border-inline:3.5px solid var(--ink);box-sizing:border-box}
.tour-pause.paused::before{width:0;height:0;border:0;border-left:11px solid var(--ink);border-top:7px solid transparent;border-bottom:7px solid transparent;margin-left:3px}
@media (max-width:900px){.tour{grid-template-columns:1fr}.tour-frame{border-inline-end:0;border-bottom:1px solid var(--line)}
  .tour-steps{flex-direction:row;overflow-x:auto;scroll-snap-type:x mandatory;padding:0;scrollbar-width:none}
  .tour-steps li{flex:0 0 78%;scroll-snap-align:start}
  .tour-steps button{border-inline-start:0;border-top:2px solid var(--line);height:100%;padding:14px 18px}
  .tour-steps button[aria-current="true"]{border-top-color:var(--acc);background:var(--acc-soft)}}

.stage{position:absolute;left:0;top:0;width:960px;height:560px;transform-origin:0 0;transition:transform .45s cubic-bezier(.45,0,.2,1);background:var(--bg);font-size:14px;color:var(--ink);user-select:none;pointer-events:none}
[dir="rtl"] .stage{direction:ltr}
.st-bar{height:40px;display:flex;align-items:center;gap:7px;padding:0 16px;border-bottom:1px solid var(--line);background:var(--surface)}
.st-bar i{width:10px;height:10px;border-radius:50%;background:var(--soft);box-shadow:inset 0 0 0 1px var(--line)}
.st-bar span{margin-left:18px;font-family:var(--f-mono);font-size:12px;color:var(--muted);background:var(--sunk);border:1px solid var(--line);border-radius:7px;padding:3px 12px}
.st-rail{position:absolute;left:0;top:40px;bottom:0;width:232px;border-right:1px solid var(--line);padding:18px}
.st-lbl{font-size:12px;color:var(--muted);margin-bottom:8px;font-weight:600}
.st-tl{margin-top:20px}
.st-fields{display:grid;grid-template-columns:1fr 1fr;gap:7px}
.st-fields span{border:1px solid var(--line);border-radius:8px;padding:8px 9px;font-size:12.5px;font-weight:600;background:var(--surface);transition:all .2s}
.st-fields span.on{border-color:var(--acc);background:var(--acc-soft)}
.st-topics{display:none;flex-direction:column;gap:2px}
.st-topics.on{display:flex;animation:stIn .35s ease-out}
.st-topics span{padding:7px 10px;border-radius:7px;font-size:13.5px;transition:all .2s}
.st-topics span.on{background:var(--surface);box-shadow:inset 3px 0 0 var(--acc),0 0 0 1px var(--line);font-weight:600}
.st-main{position:absolute;left:232px;right:0;top:40px;bottom:0;padding:22px 26px}
.st-empty{display:none;height:100%;place-content:center;text-align:center;gap:4px;color:var(--muted)}
.st-empty b{font-family:var(--f-display);font-size:22px;color:var(--ink)}
.st-empty.on{display:grid}
.st-prob{display:none;border:1px solid var(--line);border-radius:14px;background:var(--surface);overflow:hidden}
.st-prob.on{display:block;animation:stIn .45s ease-out}
.st-head{display:flex;justify-content:space-between;align-items:center;padding:11px 16px;border-bottom:1px solid var(--line)}
.st-head b{font-family:var(--f-display);font-size:19px;letter-spacing:-.01em}
.st-seg{display:flex;gap:2px;background:var(--sunk);border:1px solid var(--line);border-radius:8px;padding:2px}
.st-seg i{font-style:normal;font-size:12px;font-weight:600;padding:4px 10px;border-radius:6px;color:var(--muted)}
.st-seg i.on{background:var(--surface);color:var(--ink);box-shadow:0 0 0 1px var(--line)}
.st-dia{background:var(--sunk);border-bottom:1px solid var(--line);padding:12px}
.st-dia svg{display:block;height:142px;width:auto;margin:0 auto;overflow:visible}
.st-dia tspan{transition:fill .3s}
.stage.swap .st-dia tspan[class^="v"]{fill:var(--acc-text)}
.st-q{margin:14px 16px 10px;font-size:15.5px}
.st-ans{display:flex;align-items:stretch;margin:0 16px}
.st-sym,.st-in,.st-unit{border:1.5px solid var(--line);display:flex;align-items:center;padding:0 12px;height:40px;font-family:var(--f-math);font-size-adjust:.5}
.st-sym{border-radius:9px 0 0 9px;background:var(--sunk);font-weight:600}
.st-in{border-inline:0;width:170px;font-size:15px}
.st-unit{border-radius:0 9px 9px 0;color:var(--muted);margin-right:10px}
.st-caret{display:inline-block;width:1.5px;height:18px;background:var(--acc);margin-left:1px;animation:blink 1s steps(1) infinite}
@keyframes blink{50%{opacity:0}}
.st-btn{display:inline-flex;align-items:center;border:1px solid var(--line);border-radius:9px;padding:0 13px;height:38px;font-weight:600;font-size:13px;background:var(--surface)}
.st-btn.pri{background:var(--acc);border-color:var(--acc);color:#fff}
.st-ans .st-btn{height:40px}
.st-hint{display:none;gap:10px;margin:12px 16px 0;padding:10px 12px;background:var(--sunk);border:1px solid var(--line);border-radius:9px;font-size:13.5px}
.st-hint span{font-family:var(--f-mono);font-size:11.5px;color:var(--muted);padding-top:2px}
.st-hint.on{display:flex;animation:stIn .35s ease-out}
.st-fb{display:none;margin:12px 16px 0;padding:10px 12px;border-radius:9px;background:var(--good-soft);color:var(--good);font-weight:500;font-size:14px}
.st-fb.on{display:block;animation:stIn .35s ease-out}
.st-prob[data-p="mcq"] .st-fb{margin-bottom:16px;display:block;visibility:hidden;opacity:0;transform:translateY(4px);transition:opacity .3s,transform .3s,visibility 0s .3s}
.st-prob[data-p="mcq"] .st-fb.on{visibility:visible;opacity:1;transform:none;animation:none;transition:opacity .3s,transform .3s}
.st-tools{display:flex;gap:8px;padding:14px 16px;margin-top:14px;border-top:1px solid var(--line)}
.st-next{margin-left:auto}
.st-opts{display:grid;gap:8px;margin:6px 16px 0}
.st-opts span{display:flex;gap:12px;align-items:center;border:1.5px solid var(--line);border-radius:10px;padding:9px 12px;font-size:14.5px;transition:border-color .2s,background-color .2s}
.st-opts i{font-style:normal;width:26px;height:26px;border-radius:7px;display:grid;place-items:center;font-family:var(--f-mono);font-size:12.5px;background:var(--sunk);border:1px solid var(--line);color:var(--muted)}
.st-opts span.sel{border-color:var(--acc);background:var(--acc-soft)}
.st-opts span.sel i{background:var(--acc);color:#fff;border-color:var(--acc)}
.st-opts span.good{border-color:var(--good);background:var(--good-soft)}
.st-opts span.good i{background:var(--good);color:var(--surface);border-color:var(--good)}
.st-cursor{position:absolute;left:0;top:0;width:26px;height:26px;margin:-5px 0 0 -6px;z-index:5;transition:transform .7s cubic-bezier(.45,0,.2,1)}
.st-cursor svg{width:26px;height:26px;position:relative;z-index:1;filter:drop-shadow(0 2px 3px rgba(0,0,0,.35))}
.st-cursor path{fill:#fff;stroke:#111;stroke-width:1.4;stroke-linejoin:round}
.st-ripple{position:absolute;left:-6px;top:-8px;width:30px;height:30px;border-radius:50%;background:var(--acc);opacity:0}
.st-cursor.down .st-ripple{animation:rip .45s ease-out}
@keyframes rip{from{opacity:.55;transform:scale(.3)}to{opacity:0;transform:scale(1.6)}}
@keyframes stIn{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}

.fields{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:12px}
.fcard{display:flex;flex-direction:column;gap:4px;padding:18px;border:1px solid var(--line);border-radius:14px;background:var(--surface);text-decoration:none;color:inherit;transition:border-color .15s,transform .15s}
.fcard:hover{border-color:var(--acc-line);transform:translateY(-2px)}
.fcard b{font-size:16px;margin-top:8px}
.fcard small{color:var(--muted);font-size:13.5px;line-height:1.45}
.ficon{width:36px;height:36px;border-radius:10px;background:var(--acc-soft);color:var(--acc-text);display:grid;place-items:center}
.ficon svg{width:19px;height:19px}
.fcount{margin-top:auto;padding-top:10px;font-family:var(--f-mono);font-size:11.5px;color:var(--muted)}

/* contact page */
.contact{padding-bottom:64px}
.contact-grid{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:24px;align-items:start;margin-top:8px}
@media (max-width:820px){.contact-grid{grid-template-columns:minmax(0,1fr)}}
.cform{margin-top:0;padding:22px}
.cform .setlbl{margin-bottom:8px}
.crow{display:grid;grid-template-columns:1fr 1fr;gap:12px}
@media (max-width:560px){.crow{grid-template-columns:1fr}}
/* the calculator pages reuse the names .cform and .crow further down (a two-column input grid and result rows); keep the contact form's own layout */
.contact .cform{display:block;border-radius:14px;padding:22px}
.contact .crow{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px;align-items:start;padding:0;border-bottom:0;font-size:inherit}
@media (max-width:560px){.contact .crow{grid-template-columns:minmax(0,1fr)}}
.cform textarea{min-height:150px}
.hp{position:absolute;left:-9999px;width:1px;height:1px;opacity:0}
.cside{display:flex;flex-direction:column;gap:10px}
.cbox{border:1px solid var(--line);border-radius:12px;padding:14px 16px;background:var(--surface);display:flex;flex-direction:column;gap:4px;font-size:14px}
.cbox span{color:var(--muted);font-size:13.5px}
.cbox a{color:var(--acc-text);font-weight:600;text-decoration:none;word-break:break-all}
.cdone{margin-top:0;padding:34px 24px;text-align:center;display:flex;flex-direction:column;align-items:center;gap:6px}
.cdone h2{font-family:var(--f-display);margin:8px 0 0;font-size:22px}
.cdone p{color:var(--muted);margin:0 0 12px}
.okmark{width:54px;height:54px;border-radius:50%;background:var(--good-soft);color:var(--good);display:grid;place-items:center}
.okmark svg{width:28px;height:28px;stroke-dasharray:24;stroke-dashoffset:0}
@media (prefers-reduced-motion:no-preference){.cdone:not([hidden]) .okmark{animation:pop .45s cubic-bezier(.2,1.4,.4,1)}.cdone:not([hidden]) .okmark svg{animation:draw .5s .15s ease-out both}}
@keyframes pop{from{transform:scale(.4);opacity:0}to{transform:none;opacity:1}}
@keyframes draw{from{stroke-dashoffset:24}to{stroke-dashoffset:0}}

/* public practice pages */
.seo{padding-bottom:64px;max-width:900px}
.seo-crumbs{margin-top:28px;font-size:13.5px;color:var(--muted)}
.seo-crumbs a{color:var(--acc-text);text-decoration:none}
.seo-title{padding-top:18px}
.seo-title h1{max-width:22ch;font-size:clamp(30px,4.4vw,50px)}
.ctitle{padding-bottom:0}.ctitle h1{max-width:none;font-size:clamp(26px,3.4vw,40px)}.ctitle p{margin-top:8px;font-size:15.5px}.ctitle+.calcbox{margin-top:16px}
.seo-cabout{margin-top:18px}.seo-cabout .seo-lead{margin:0;max-width:72ch}
.seo-cta{display:flex;flex-wrap:wrap;align-items:center;gap:12px 16px;margin-top:22px}
.seo-cta .muted{font-size:13.5px;color:var(--muted)}
.seo h2{font-family:var(--f-display);font-size:24px;letter-spacing:-.015em;margin:44px 0 14px}
.seo-levels ol{list-style:none;padding:0;margin:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:10px}
.seo-levels li{border:1px solid var(--line);border-radius:12px;padding:12px 14px;background:var(--surface);display:flex;flex-direction:column;gap:2px}
.seo-levels li span{color:var(--muted);font-size:14px}
.ex{background:var(--surface);border:1px solid var(--line);border-radius:14px;overflow:hidden;margin-bottom:16px}
.ex-head{display:flex;justify-content:space-between;align-items:center;padding:10px 18px;border-bottom:1px solid var(--line);font-size:13px}
.ex-n{font-weight:700}.ex-lvl{color:var(--muted);font-family:var(--f-mono);font-size:12px}
.ex-body{padding:18px;display:flex;flex-direction:column;gap:14px}
.ex-ask{margin:0;font-size:15px}
.ex-opts{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.ex-opts li{display:flex;gap:12px;align-items:center;border:1.5px solid var(--line);border-radius:10px;padding:9px 12px}
.ex-opts .k{width:26px;height:26px;border-radius:7px;display:grid;place-items:center;font-family:var(--f-mono);font-size:12.5px;background:var(--sunk);border:1px solid var(--line);color:var(--muted);flex:none}
.ex-more{border-top:1px solid var(--line);padding-top:12px}
.ex-more summary{cursor:pointer;font-weight:600;color:var(--acc-text);font-size:14.5px}
.ex-hints{margin:10px 0 0;padding-inline-start:22px;display:grid;gap:6px;font-size:14.5px}
.ex-sol{margin-top:12px;border:0;padding:0}
.seo-how ul{margin:0;padding-inline-start:20px;display:grid;gap:6px;color:var(--muted)}
.seo-links{display:flex;flex-wrap:wrap;gap:8px}
.seo-links a,.seo-groups a{border:1px solid var(--line);border-radius:999px;padding:7px 13px;text-decoration:none;font-size:14px;background:var(--surface);transition:border-color .15s,background .15s}
.seo-links a:hover,.seo-groups a:hover{border-color:var(--acc);background:var(--acc-soft)}
.seo-end{margin-top:40px;padding:26px;border:1px solid var(--line);border-radius:16px;background:var(--surface)}
.seo-end .seo-cta{margin:0}
.seo-groups{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:18px}
.seo-groups h3{font-size:12px;letter-spacing:.07em;text-transform:uppercase;color:var(--muted);margin:0 0 8px}
.seo-groups div{display:flex;flex-wrap:wrap;gap:8px;align-content:flex-start}
.seo-groups h3{flex-basis:100%}
.seo-branch h2{margin-top:36px}
.fields-more{margin:22px 0 0;display:flex;justify-content:center}

/* hero with the walkthrough beside the text, so the demo is visible without scrolling */
.hero{padding-block:clamp(18px,3vw,40px) 18px}
.hero-grid{display:grid;grid-template-columns:minmax(0,1fr);gap:26px}
.hero-text .eyebrow{margin-bottom:16px}
.hero-text .hero-title{font-size:clamp(34px,5.4vw,60px);max-width:14ch}
.hero-text .hero-sub{margin-top:16px;font-size:clamp(15.5px,1.4vw,18px)}
.hero-text .hero-cta{justify-content:flex-start;margin-top:22px}
.hero-text .hero-note{text-align:start}
.hero-demo .tour{grid-template-columns:1fr}
.hero-demo .tour-frame{border-inline-end:0;border-bottom:1px solid var(--line)}
.hero-demo .tour-steps{flex-direction:row;overflow-x:auto;scroll-snap-type:x mandatory;padding:0;scrollbar-width:none}
.hero-demo .tour-steps li{flex:1 0 0;min-width:150px;scroll-snap-align:start}
.hero-demo .tour-steps button{border-inline-start:0;border-top:2px solid var(--line);height:100%;padding:11px 14px}
.hero-demo .tour-steps button b{font-size:13.5px}
.hero-demo .tour-steps button span{display:none}
.hero-demo .tour-steps button[aria-current="true"]{border-top-color:var(--acc);background:var(--acc-soft)}
@media (min-width:900px){
  .hero .wrap.hero-grid{max-width:1240px}
  .hero-grid{grid-template-columns:minmax(0,4fr) minmax(0,7fr);align-items:center;gap:clamp(28px,3.5vw,48px)}
  .hero-text .hero-title{font-size:clamp(36px,4.3vw,60px)}
}
@media (min-width:900px) and (max-width:1100px){.hero-text .hero-sub{font-size:15px}.hero-text .hero-cta .btn.lg:not(.primary){display:none}}
@media (max-width:900px){.hero-demo .tour-steps li{flex:0 0 46%}}
@media (max-width:600px){.hero-text .hero-sub{display:none}.hero-text .hero-cta{margin-top:16px}.hero-text .hero-cta .btn.lg:not(.primary){display:none}.hero-demo .tour-steps li{flex:0 0 62%}}

/* course pages, course index, formula sheets on topic pages */
.fsheet{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:10px}
.fsheet div{background:var(--surface)}
.ctopics{list-style:none;margin:0;padding:0;display:grid;gap:10px;counter-reset:ct}
.ctopics a{display:grid;grid-template-columns:34px 1fr auto;grid-template-rows:auto auto;column-gap:12px;align-items:center;border:1px solid var(--line);border-radius:14px;padding:14px 16px;background:var(--surface);text-decoration:none;color:inherit;transition:border-color .15s,background .15s}
.ctopics a::before{counter-increment:ct;content:counter(ct);grid-row:1/3;width:30px;height:30px;border-radius:9px;display:grid;place-items:center;background:var(--acc-soft);color:var(--acc-text);font-family:var(--f-mono);font-size:13px;font-weight:700}
.ctopics a:hover{border-color:var(--acc);background:var(--acc-soft)}
.ctopics b{font-size:16px}
.ctopics span{grid-column:2;color:var(--muted);font-size:13.5px}
.ctopics small{grid-row:1/3;grid-column:3;font-size:12px;color:var(--muted);font-family:var(--f-mono)}
.seo-tips ul{margin:0;padding:0;list-style:none;display:grid;gap:10px}
.seo-tips li{border-inline-start:3px solid var(--acc);padding-block:6px;padding-inline-start:14px;line-height:1.55}
.ccards{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:12px}
.ccard{display:flex;flex-direction:column;gap:6px;border:1px solid var(--line);border-radius:14px;padding:16px;background:var(--surface);text-decoration:none;color:inherit;transition:border-color .15s,background .15s,transform .15s}
.ccard:hover{border-color:var(--acc);background:var(--acc-soft);transform:translateY(-1px)}
.ccard b{font-size:16.5px}
.ccard span{color:var(--muted);font-size:13.5px;line-height:1.5}
.course-links{justify-content:center}
@media (max-width:600px){.ctopics a{grid-template-columns:30px 1fr}.ctopics small{display:none}}

/* calculators */
.calcbox{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:18px;margin-top:22px;align-items:start}
.cform{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px;background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:18px}
.cfield{display:flex;flex-direction:column;gap:6px;font-size:13.5px;font-weight:600}
.cfield.wide{grid-column:1/-1}
.cfield small{font-weight:500;color:var(--muted)}
.cfield input,.cfield select{width:100%;box-sizing:border-box;font:inherit;font-weight:500;font-family:var(--f-mono);font-size:15px;padding:10px 12px;border:1.5px solid var(--line);border-radius:10px;background:var(--bg);color:var(--ink);min-width:0}
.cfield input:focus,.cfield select:focus{outline:none;border-color:var(--acc)}
.cout{background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:18px}
.seo .cout h2{margin:0 0 12px;font-size:18px}
.cres{display:grid;gap:8px}
.crow{display:flex;justify-content:space-between;gap:12px;align-items:baseline;padding:8px 0;border-bottom:1px solid var(--line);font-size:14.5px}
.crow:last-child{border-bottom:0}
.crow span{color:var(--muted)}
.crow b{font-family:var(--f-math);font-size-adjust:.5;font-weight:600;text-align:end;direction:ltr;unicode-bidi:isolate}
.crow b small{color:var(--muted);font-weight:500}
.crow.main b{font-size:20px;color:var(--acc-text)}
.ctab{width:100%;border-collapse:collapse;margin-top:12px;font-family:var(--f-math);font-size-adjust:.5;font-size:13.5px}
.ctab th,.ctab td{padding:6px 8px;border-bottom:1px solid var(--line);text-align:end}
.ctab th:first-child,.ctab td:first-child{text-align:start}
.cnote{font-size:13px;color:var(--muted);margin:12px 0 0}
.cerr{color:var(--bad);margin:0}
.seo-calc-steps .solution{border:1px solid var(--line);border-radius:14px;padding:18px;background:var(--surface)}
@media (max-width:820px){.calcbox{grid-template-columns:1fr}}
@media (max-width:480px){.cform{grid-template-columns:minmax(0,1fr)}}
.seo-calc-steps .math div{white-space:normal;overflow-wrap:anywhere}
.cgrp{grid-column:1/-1;font-size:11.5px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);padding-top:12px;margin-top:2px;border-top:1px solid var(--line)}
.cform>.cgrp:first-child{padding-top:0;margin-top:0;border-top:0}
.cfield[hidden]{display:none}
.seo-lead{max-width:72ch;color:var(--muted);line-height:1.6;margin:12px 0 0}
.seo-cfig .diagram{border:1px solid var(--line);border-radius:16px;padding:14px 8px}
.sfbm svg{max-width:900px;min-width:520px}
.dpos{fill:color-mix(in srgb,var(--acc) 20%,transparent)}
.dneg{fill:color-mix(in srgb,var(--bad) 20%,transparent)}
.dline{stroke-width:2.2}
.gd{stroke:var(--line);stroke-width:1;stroke-dasharray:3 4}
.seo-faq{display:grid;gap:8px}
.seo-faq h2{margin-bottom:6px}
.faq{border:1px solid var(--line);border-radius:12px;background:var(--surface);padding:12px 16px}
.faq summary{cursor:pointer;font-weight:600}
.faq p{margin:10px 0 2px;line-height:1.6;color:var(--muted)}
.sfbm svg.nw{min-width:0}
.sfbm .nw .lbl{font-size:15px}.sfbm .nw .lbl.s{font-size:14px}.sfbm .nw .lbl.k{font-size:13px}
@media (max-width:640px){.seo-cfig .diagram{padding:10px 4px}}

/* printable worksheets */
.ws{display:grid;grid-template-columns:minmax(0,1fr);gap:16px;margin-top:20px}
.wsq{border:1px solid var(--line);border-radius:14px;background:var(--surface);padding:16px 18px;break-inside:avoid;page-break-inside:avoid}
.wsq-h{display:flex;justify-content:space-between;align-items:center;margin-bottom:8px}
.wsq .diagram{border:1px solid var(--line);border-radius:10px;margin:8px 0}
.wsq-ans{margin-top:12px;font-family:var(--f-math);font-size-adjust:.5;font-size:15px}
.wsq-ans .blank{display:inline-block;width:160px;border-bottom:1.5px solid var(--ink);margin:0 4px}
.ws-meta{display:none}
.ws-key{margin-top:36px;padding:20px;border:1px dashed var(--line);border-radius:14px}
.wskey{list-style:none;padding:0;margin:0;display:grid;gap:6px;font-family:var(--f-math);font-size-adjust:.5;font-size:14px}
@media print{
  @page{margin:14mm}
  html,body{background:#fff!important;color:#000}
  :root{--ink:#000;--muted:#444;--surface:#fff;--sunk:#fff;--line:#bbb;--bg:#fff}
  .nav,.foot,.noprint,.seo-rel,.seo-end{display:none!important}
  .ws-meta{display:block;font-size:13px;margin-top:6px}
  .seo-title h1{font-size:22px}
  .wsq{border:1px solid #bbb;padding:10px 12px}
  .wsq .diagram svg{min-width:0;max-width:520px}
  .ws-key{break-before:page;page-break-before:always;border:0;padding:0}
}

/* how-to guides on topic pages */
.gsteps{counter-reset:gs;list-style:none;padding:0;margin:0;display:grid;gap:10px}
.gsteps li{counter-increment:gs;position:relative;padding:12px 14px 12px 52px;border:1px solid var(--line);border-radius:12px;background:var(--surface);line-height:1.55}
.gsteps li::before{content:counter(gs);position:absolute;inset-inline-start:14px;top:12px;width:26px;height:26px;border-radius:8px;display:grid;place-items:center;background:var(--acc-soft);color:var(--acc-text);font-family:var(--f-mono);font-weight:700;font-size:13px}
[dir="rtl"] .gsteps li{padding:12px 52px 12px 14px}
.seo-guide h3{margin:22px 0 10px;font-size:16px}
.gmist{margin:0;padding-inline-start:20px;display:grid;gap:6px;color:var(--muted)}
.disclaimer{font-size:12.5px;color:var(--muted);margin-top:14px;max-width:70ch}

/* "Learn from scratch" lesson on topic pages (shares .lex/.lfig/.eq with the app's Learn view in base.css) */
.seo-learn .seo-pre{color:var(--muted);margin:0 0 10px}
.seo-learn .seo-pre a{color:var(--acc-text)}
.seo-learn .lsec{border:1px solid var(--line);border-radius:14px;background:var(--surface);padding:20px 22px;margin:0 0 14px;line-height:1.65;max-width:820px}
.seo-learn .lsec h3{display:flex;align-items:center;gap:10px;margin:0 0 10px;font-size:18px}
.seo-learn .lsec-n{width:26px;height:26px;flex:none;border-radius:50%;display:grid;place-items:center;background:var(--acc-soft);color:var(--acc-text);font-size:13px;font-weight:700}
.seo-learn p{margin:0 0 10px}
.seo-learn ul,.seo-learn ol{margin:0 0 12px;padding-inline-start:22px;display:grid;gap:5px}
.seo-learn .lex h4{margin:2px 0 6px;font-size:15px}
.seo-learn .lex-q{margin:4px 0 0;font-weight:600}
.seo-learn details.lcheck{display:block;margin-top:14px}
.seo-learn details.lcheck summary{cursor:pointer;font-weight:600}
.seo-learn details.lcheck[open] summary{margin-bottom:10px}
.seo-learn-cta{margin-top:6px}
@media (max-width:560px){.seo-learn .lsec{padding:16px}}
/* topic pages: local names, FAQ, learning path */
.seo-aka{margin:8px 0 0;color:var(--muted);font-size:14.5px;max-width:72ch}
.seo-topic-faq .faq-a{margin:10px 0 2px;line-height:1.6;color:var(--muted)}
.seo-topic-faq .faq-a p{margin:0 0 8px;color:inherit}
.seo-topic-faq .faq-a ol,.seo-topic-faq .faq-a ul{margin:0 0 8px;padding-inline-start:22px;display:grid;gap:4px}
.seo-path h3{font-size:12px;letter-spacing:.07em;text-transform:uppercase;color:var(--muted);margin:14px 0 8px}
/* long topic pages: the browser skips layout and paint of sections far below the fold until they scroll near */
.seo-learn .lsec,.seo-ex .ex,.seo-topic-faq,.seo-how,.seo-rel,.seo-end{content-visibility:auto;contain-intrinsic-size:auto 480px}
@media print{.seo-learn .lsec,.seo-ex .ex,.seo-topic-faq,.seo-how{content-visibility:visible}}
/* topic pages: the free sample problem right under the title (server/seo.js tryCard, public/practice.js) */
.seo-ttop{padding-bottom:20px}
.tcard{box-shadow:0 30px 60px -44px rgba(0,0,0,.35)}
.tcard-head{display:flex;justify-content:space-between;align-items:center;gap:10px;padding:9px 16px;border-bottom:1px solid var(--line);background:var(--sunk);font-size:13px}
.tcard-tag{display:inline-flex;align-items:center;gap:9px;font-weight:700}
.tcard .q{padding:18px}
.tcard [data-d="feedback"]:empty,.tcard .hints:empty{display:none}
.tools .tnext-now{margin-inline-start:auto}.tools .tnext-now[hidden]{display:none}
.tnext{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:12px 16px;padding:16px 18px;border-top:1px solid var(--acc-line);background:var(--acc-soft)}
.tnext p{margin:0;flex:1 1 240px;font-size:15.5px}
.tnext p span{display:block;margin-top:2px;color:var(--muted);font-size:13.5px}
.tnext-b{display:flex;flex-wrap:wrap;gap:8px}
.seo-topcta .seo-cta{margin-top:20px}
@media (max-width:600px){
  .seo-crumbs{margin-top:14px}
  .seo-ttop{padding-top:8px;padding-bottom:12px}
  .seo-ttop h1{font-size:25px;line-height:1.08}
  .seo-ttop .seo-aka{margin-top:6px;font-size:13px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
  .seo-ttop p:not(.seo-aka){font-size:14.5px;margin-top:8px;display:-webkit-box;-webkit-line-clamp:2;line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
  .tcard{margin-inline:-6px;border-radius:14px}
  .demo-body .diagram{padding:14px 8px} /* topic pages and the home page demo: the whole circuit fits the phone */
  .demo-body .diagram svg{min-width:0}
  .tcard .q{padding:14px;gap:12px}
  .tnext{padding:14px}
  .tnext-b,.tnext-b .btn{flex:1 1 auto;justify-content:center}
}
.tcard .solution h2{margin-top:0}

/* calculator search (server/seo.js calcSearchBox) */
.csearch{display:flex;gap:8px;margin-top:14px;max-width:560px}
.csearch input{flex:1;min-width:0;font:inherit;font-size:16px;padding:11px 14px;border:1px solid var(--line);border-radius:12px;background:var(--surface);color:inherit}
.csearch input:focus{outline:2px solid var(--acc);outline-offset:1px;border-color:var(--acc)}
.csearch-none{margin-top:10px;color:var(--muted)}
.cnavrow{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 16px}
.cnavrow .csearch{margin-top:0;flex:0 1 340px}
.cnavrow .csearch input{padding:8px 12px;font-size:15px}
.ccard[hidden],.seo-branch[hidden]{display:none}

/* home: popular topics, courses and calculators as three short lists */
.pop2{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:28px}
.pop2 h3{font-size:15px;margin:0 0 10px;color:var(--muted);font-weight:600;letter-spacing:.02em}
.poplist{display:flex;flex-direction:column;border-top:1px solid var(--line)}
.poplist a{padding:9px 2px;border-bottom:1px solid var(--line);text-decoration:none;color:inherit;font-size:15px;transition:color .15s,padding .15s}
.poplist a:hover{color:var(--acc-text);padding-left:6px}
.popmore{display:inline-block;margin-top:12px;font-weight:600;text-decoration:none;color:var(--acc-text)}
@media (max-width:820px){.pop2{grid-template-columns:minmax(0,1fr);gap:22px}}
.ws-teach{margin:12px 0 0;font-size:14px;color:var(--muted);max-width:70ch}
.ws-teach b{color:var(--ink)}

/* ===== library directories: /practice, /courses, /calculators, /worksheets (server/seo.js dirBody, public/practice.js) ===== */
.seo.seo-dir{max-width:1180px}
.dir-head{padding-bottom:6px}
.dir-head h1{max-width:20ch}
.dir-vh{position:absolute;width:1px;height:1px;margin:-1px;padding:0;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}
.dir [hidden],.dir-nav [hidden]{display:none!important}
/* the four directories, one row of quiet links */
.dir-lib{display:flex;flex-wrap:wrap;gap:4px;margin-top:18px;margin-inline-start:-11px}
.dir-lib a{display:inline-flex;align-items:center;gap:7px;padding:6px 11px;border:1px solid transparent;border-radius:999px;font-size:14px;font-weight:500;color:var(--muted);text-decoration:none;transition:color .15s,background-color .15s,border-color .15s}
.dir-lib a svg{width:15px;height:15px;flex:none}
.dir-lib a:hover{color:var(--ink);background:var(--soft)}
.dir-lib a[aria-current="page"]{color:var(--ink);font-weight:600;background:var(--surface);border-color:var(--line)}
.dir-lib a[aria-current="page"] svg{color:var(--acc-text)}
/* worksheets: how a worksheet works */
.dir-note{margin-top:18px;max-width:760px;border:1px solid var(--line);border-radius:14px;background:var(--surface);padding:14px 16px}
.dir-note ul{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;align-items:center;gap:8px 22px}
.dir-note li{display:inline-flex;align-items:center;gap:7px;font-size:14px;font-weight:600}
.dir-note li svg{width:16px;height:16px;color:var(--acc-text);flex:none}
.dir-lv{display:inline-flex;align-items:center;gap:8px}
.dir-lv i{font-style:normal}
.dir-lv i+i::before{content:"→";margin-inline-end:8px;color:var(--muted);font-weight:400}
[dir="rtl"] .dir-lv i+i::before{content:"←"}
.dir-note li:first-child::before{content:"";width:16px;height:16px;flex:none;border-radius:4px;background:linear-gradient(90deg,var(--acc-soft),var(--acc))}
.ptitle .dir-note p{margin:10px 0 0;font-size:13.5px;line-height:1.55;max-width:none}
.dir-note p b{color:var(--ink)}
/* filter box */
.dir-q{position:relative;margin-top:22px;max-width:560px}
.dir-q svg{position:absolute;inset-inline-start:14px;top:50%;width:18px;height:18px;margin-top:-9px;color:var(--muted);pointer-events:none}
.dir-q input{width:100%;box-sizing:border-box;font:inherit;font-size:16px;padding:12px 14px;padding-inline-start:42px;border:1px solid var(--line);border-radius:12px;background:var(--surface);color:var(--ink)}
.dir-q input::placeholder{color:var(--muted)}
.dir-q input:focus{outline:2px solid var(--acc);outline-offset:1px;border-color:var(--acc)}
/* layout: field navigator + grouped content */
.dir{display:grid;grid-template-columns:220px minmax(0,1fr);gap:48px;align-items:start;margin-top:30px}
.dir-nav{position:sticky;top:calc(var(--dir-top,64px) + 20px);max-height:calc(100vh - var(--dir-top,64px) - 40px);overflow:auto;overscroll-behavior:contain;padding:2px 2px 8px;font-size:14px}
.dir-ng{margin-top:14px}
.dir-nav>a:first-child{margin-bottom:-4px}
.dir-ngh{margin:0 0 4px;padding-inline:10px;font-size:11.5px;font-weight:700;letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.dir-nav a{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:6px 10px;border-radius:8px;color:var(--muted);text-decoration:none;line-height:1.3;transition:color .15s,background-color .15s}
.dir-nav a small{font-size:12px;color:var(--muted);font-variant-numeric:tabular-nums}
.dir-nav a:hover{color:var(--ink);background:var(--soft)}
.dir-nav a[aria-current="true"]{color:var(--ink);font-weight:600;background:var(--surface);box-shadow:inset 2px 0 0 var(--acc),0 0 0 1px var(--line)}
[dir="rtl"] .dir-nav a[aria-current="true"]{box-shadow:inset -2px 0 0 var(--acc),0 0 0 1px var(--line)}
.dir-sec{scroll-margin-top:calc(var(--dir-top,64px) + 16px)}
.dir-sec+.dir-sec{margin-top:40px}
.dir-sh{display:flex;align-items:center;gap:10px;padding-bottom:10px;margin-bottom:16px;border-bottom:1px solid var(--line)}
.seo .dir-sh h2{margin:0;font-size:22px;line-height:1.2}
.dir-n{font-size:12.5px;font-weight:600;color:var(--muted);background:var(--soft);border-radius:999px;padding:2px 8px;font-variant-numeric:tabular-nums}
/* topics and worksheets: sub-groups as small headed lists, flowing into columns */
.dir-cols{columns:230px 3;column-gap:36px}
.dir-grp{break-inside:avoid;padding-bottom:20px}
.dir-grp h3{margin:0 0 2px;font-size:11.5px;font-weight:700;letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.dir-list{list-style:none;margin:0;padding:0}
.dir-list li{display:flex;align-items:baseline;justify-content:space-between;gap:12px;padding:7px 0;border-bottom:1px solid var(--line);font-size:14.5px;line-height:1.4}
.dir-list li>a:first-child{color:var(--ink);text-decoration:none;min-width:0}
.dir-list li>a:first-child:hover{color:var(--acc-text);text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:1px}
.dir-go{flex:none;font-size:12.5px;font-weight:600;color:var(--muted);text-decoration:none;opacity:0;transition:opacity .15s}
.dir-go:hover{color:var(--acc-text);text-decoration:underline;text-underline-offset:3px}
.dir-list li:hover .dir-go,.dir-list li:focus-within .dir-go{opacity:1}
@media (hover:none){.dir-go{opacity:1}}
.dir-meta{flex:none;font-size:12px;color:var(--muted);white-space:nowrap;font-variant-numeric:tabular-nums}
/* courses and calculators: compact cards, title + one line */
.dir-cards{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:8px}
.dir-card{display:flex;flex-direction:column;gap:3px;height:100%;box-sizing:border-box;padding:10px 14px;border:1px solid var(--line);border-radius:10px;background:var(--surface);color:inherit;text-decoration:none;transition:border-color .15s,background-color .15s}
.dir-card b{font-size:14.5px;font-weight:600;line-height:1.35;display:-webkit-box;-webkit-line-clamp:2;line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.dir-card span{font-size:12.5px;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.dir-card em{font-style:normal}
.dir-card:hover{border-color:var(--acc-line);background:var(--acc-soft)}
.dir-none{margin:0;padding:28px 16px;text-align:center;color:var(--muted);border:1px dashed var(--line);border-radius:12px}
.dir-none a{color:var(--acc-text);font-weight:600}
/* phones and narrow windows: the navigator becomes a sticky row of chips */
@media (max-width:959.98px){
  .dir{display:block;margin-top:20px}
  .dir-nav{top:var(--dir-top,64px);z-index:20;display:flex;gap:6px;max-height:none;overflow-x:auto;overflow-y:hidden;scrollbar-width:none;margin-inline:-16px;padding:10px 16px;background:color-mix(in srgb,var(--bg) 92%,transparent);backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px);border-bottom:1px solid var(--line);margin-bottom:18px}
  .dir-nav::-webkit-scrollbar{display:none}
  .dir-ng{display:contents}
  .dir-ngh{display:none}
  .dir-nav>a:first-child{margin-bottom:0}
  .dir-nav a{flex:none;white-space:nowrap;gap:6px;padding:6px 12px;border:1px solid var(--line);border-radius:999px;background:var(--surface);font-size:13.5px;color:var(--ink)}
  .dir-nav a[aria-current="true"],[dir="rtl"] .dir-nav a[aria-current="true"]{background:var(--acc-soft);border-color:var(--acc);box-shadow:none}
  .dir-sec{scroll-margin-top:calc(var(--dir-top,64px) + 70px)}
  .dir-sec+.dir-sec{margin-top:32px}
  .seo .dir-sh h2{font-size:20px}
}
@media (max-width:600px){
  .dir-head h1{font-size:30px}
  .dir-head>p{font-size:15.5px;margin-top:10px}
  .dir-lib{margin-top:14px;flex-wrap:nowrap;overflow-x:auto;scrollbar-width:none;gap:2px;margin-inline:-16px;padding-inline:7px}
  .dir-lib::-webkit-scrollbar{display:none}
  .dir-lib a{flex:none;padding:6px 9px;font-size:13.5px;gap:6px}
  .dir-lib a svg{display:none}
  .dir-note{padding:12px 14px}
  .dir-note ul{gap:6px 16px}
  .dir-note li{font-size:13.5px}
  .ptitle .dir-note p{font-size:13px}
  .dir-q{margin-top:16px}
  .dir-cards{grid-template-columns:minmax(0,1fr)}
}
/* footer: links to the review and video profiles */
.fsoc{display:inline-flex;flex-wrap:wrap;gap:6px 14px;align-items:center}
.fsoc a{display:inline-flex;align-items:center;gap:6px;color:var(--muted);text-decoration:none}
.fsoc a:hover{color:var(--ink)}
.fsoc svg{width:15px;height:15px}
/* subject pages (/subjects/<branch>): a short head with counters, section tabs, topic groups as cards, courses and calculators */
.seo.seo-subj{max-width:1180px}
.sj-head{padding:22px 0 8px}
.sj-eyebrow{margin:0 0 8px;font-size:12px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;color:var(--acc-text)}
.sj-head h1{font-family:var(--f-display);font-size:clamp(30px,4.2vw,50px);letter-spacing:-.03em;line-height:1.04;margin:0;max-width:20ch}
.sj-desc{color:var(--muted);font-size:17px;max-width:60ch;margin:14px 0 0}
.sj-stats{display:flex;flex-wrap:wrap;gap:10px;margin:22px 0 4px}
.sj-stat{display:grid;grid-template-columns:auto auto;grid-template-rows:auto auto;column-gap:12px;align-items:center;padding:12px 18px 12px 14px;border:1px solid var(--line);border-radius:14px;background:var(--surface);color:inherit;text-decoration:none;min-width:150px;transition:border-color .15s,transform .15s}
.sj-stat:hover{border-color:var(--acc-line);transform:translateY(-1px)}
.sj-stat i{grid-row:1/3;width:38px;height:38px;border-radius:10px;background:var(--acc-soft);color:var(--acc-text);display:grid;place-items:center}
.sj-stat i svg{width:19px;height:19px}
.sj-stat b{font-size:22px;line-height:1.1;font-weight:750;font-variant-numeric:tabular-nums}
.sj-stat span{font-size:13px;color:var(--muted)}
.sj-head .seo-cta{margin-top:18px}
.sj-tabs{position:sticky;top:64px;z-index:5;display:flex;gap:4px;margin:26px 0 6px;padding:6px 0;background:var(--bg);border-bottom:1px solid var(--line)}
.sj-tabs a{padding:7px 12px;border-radius:8px;font-size:14px;font-weight:600;color:var(--muted);text-decoration:none}
.sj-tabs a:hover{background:var(--soft);color:var(--ink)}
.sj-sec{padding-top:22px;margin-bottom:18px;scroll-margin-top:120px}
.sj-sh{display:flex;align-items:baseline;justify-content:space-between;gap:12px;margin-bottom:14px}
.sj-sh h2{display:flex;align-items:center;gap:10px;margin:0;font-size:24px;letter-spacing:-.02em}
.sj-sh h2 svg{width:20px;height:20px;color:var(--acc-text)}
.sj-sh>a{font-size:14px;font-weight:600;color:var(--acc-text);text-decoration:none;white-space:nowrap}
.sj-n{display:inline-block;font-size:12px;font-weight:700;color:var(--muted);background:var(--soft);border-radius:999px;padding:2px 8px;line-height:1.4}
.sj-groups{columns:3 300px;column-gap:12px}
.sj-card{break-inside:avoid;margin:0 0 12px;border:1px solid var(--line);border-radius:14px;background:var(--surface);padding:14px 16px 8px}
.sj-card header{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:4px}
.sj-card h3{margin:0;font-size:12px;font-weight:700;letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.sj-card ul{list-style:none;margin:0;padding:0}
.sj-card li{display:flex;align-items:center;gap:10px;border-top:1px solid var(--line)}
.sj-card li:first-child{border-top:0}
.sj-t{flex:1;min-width:0;display:flex;flex-direction:column;padding:9px 0;color:var(--ink);text-decoration:none;font-size:14.5px;line-height:1.35}
.sj-t small{font-size:12px;color:var(--muted)}
.sj-t:hover span{color:var(--acc-text);text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:1px}
.sj-go{flex:none;font-size:12.5px;font-weight:600;color:var(--acc-text);text-decoration:none;padding:5px 10px;border-radius:999px;background:var(--acc-soft);opacity:.85}
.sj-go:hover{opacity:1}
.sj-sub{margin:4px 0 10px;font-size:12px;font-weight:700;letter-spacing:.07em;text-transform:uppercase;color:var(--muted)}
.sj-sub~.sj-sub{margin-top:20px}
.sj-items{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:10px}
.sj-item{display:flex;flex-direction:column;gap:3px;padding:12px 14px;border:1px solid var(--line);border-radius:12px;background:var(--surface);color:inherit;text-decoration:none;transition:border-color .15s}
.sj-item:hover{border-color:var(--acc-line)}
.sj-item b{font-size:14.5px;font-weight:600;line-height:1.35}
.sj-item>span,.sj-ct>span{font-size:12.5px;color:var(--muted)}
.sj-calc{flex-direction:row;align-items:center;gap:12px}
.sj-calc i{flex:none;width:32px;height:32px;border-radius:9px;background:var(--soft);color:var(--acc-text);display:grid;place-items:center}
.sj-calc i svg{width:16px;height:16px}
.sj-ct{display:flex;flex-direction:column;gap:2px;min-width:0}
.sj-ct span{white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
@media (max-width:820px){.sj-tabs{top:0}.sj-stat{min-width:0;flex:1 1 140px}}
.sj-stat i svg,.sj-sh h2 svg,.sj-calc i svg{display:block;flex:none}
@media (max-width:560px){.sj-stats{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px}.sj-stat{grid-template-columns:1fr;grid-template-rows:auto;justify-items:start;padding:10px 12px;min-width:0}.sj-stat i{grid-row:auto;width:32px;height:32px;margin-bottom:6px}.sj-stat b{font-size:20px}}

/* "Embed this calculator" box on calculator pages, and the embedded page itself (/embed/<calculator>) */
.seo-embed{margin-top:14px}.seo-embed summary{display:inline-block;cursor:pointer;list-style:none;font-size:12.5px;color:var(--muted);border:1px solid var(--line);border-radius:8px;padding:3px 9px}.seo-embed summary::-webkit-details-marker{display:none}.seo-embed summary:hover{color:var(--ink)}.seo-embed[open] summary,.seo-embed details[open] summary{margin-bottom:4px}
.seo-embed textarea{display:block;width:100%;margin:10px 0;padding:10px;font:13px/1.45 ui-monospace,Menlo,Consolas,monospace;border:1px solid var(--line);border-radius:10px;background:var(--surface);color:var(--ink);resize:vertical}
.embedpage .gut{padding-top:6px}.embedpage .ctitle h1{font-size:22px}.embedpage .calcbox{margin-top:12px}
.embedcredit{margin:18px 0 8px;font-size:13px;color:var(--muted)}