[hidden]{display:none!important}
:root{
  --navy:#17304f; --navy-2:#1f3d63; --orange:#e08a2e; --paper:#fcfaf6; --card:#ffffff;
  --sand:#f8ead9; --ink:#1b2533; --muted:#5b6575; --line:#e3ddd3; --on-navy:#f3f5f8; --on-navy-muted:#b9c4d3;
  --ok:#2f7d4f; --ok-bg:#e4f2e9; --warn:#9a5b00; --warn-bg:#fff1d6;
  --display:"Source Serif 4", Georgia, "Times New Roman", serif;
  --body:"Lato", "Segoe UI", system-ui, sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --navy:#0f2037; --navy-2:#162b47; --orange:#f0a04b; --paper:#0d1521; --card:#142033;
  --sand:#1b2a3f; --ink:#e8ecf2; --muted:#9aa7b8; --line:#24344b; --on-navy:#f3f5f8; --on-navy-muted:#a9b6c7;
  --ok:#6fcf97; --ok-bg:#16301f; --warn:#f5c26b; --warn-bg:#33270f; color-scheme:dark}}
:root[data-theme="dark"]{
  --navy:#0f2037; --navy-2:#162b47; --orange:#f0a04b; --paper:#0d1521; --card:#142033;
  --sand:#1b2a3f; --ink:#e8ecf2; --muted:#9aa7b8; --line:#24344b; --on-navy:#f3f5f8; --on-navy-muted:#a9b6c7;
  --ok:#6fcf97; --ok-bg:#16301f; --warn:#f5c26b; --warn-bg:#33270f; color-scheme:dark}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--body);font-size:17px;line-height:1.6}
.wrap{max-width:1080px;margin:0 auto;padding-inline:20px}
h1,h2,h3{font-family:var(--display);line-height:1.15;text-wrap:balance;margin:0}
h2{font-size:clamp(1.5rem,3vw,2rem)}
p{margin:0}
a{color:inherit}
img,svg{max-width:100%}
:focus-visible{outline:3px solid var(--orange);outline-offset:3px;border-radius:4px}
.eyebrow{font-size:.78rem;letter-spacing:.16em;text-transform:uppercase;font-weight:700;color:var(--orange)}
.muted{color:var(--muted)}
header.top{background:var(--navy);color:var(--on-navy)}
nav.main{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap;padding-block:16px}
nav.main .brand{font-family:var(--display);font-weight:700;font-size:1.1rem;text-decoration:none}
nav.main ul{display:flex;gap:6px;list-style:none;margin:0;padding:0;flex-wrap:wrap;font-size:.95rem}
nav.main ul a{text-decoration:none;color:var(--on-navy-muted);padding:7px 12px;border-radius:6px;display:block}
nav.main ul a:hover{color:var(--on-navy)}
nav.main ul a[aria-current="page"]{background:var(--navy-2);color:var(--on-navy)}
nav.main ul a.book{background:var(--orange);color:#1b1206;font-weight:700}
.btn{display:inline-block;padding:12px 20px;border-radius:8px;font-weight:700;text-decoration:none;font-size:1rem;border:2px solid transparent;cursor:pointer;font-family:inherit;line-height:1.3}
.btn.primary{background:var(--orange);color:#1b1206}
.btn.ghost{border-color:var(--on-navy-muted);color:var(--on-navy);background:transparent}
.btn.line{border-color:var(--line);background:var(--card);color:var(--ink)}
.btn.small{padding:7px 12px;font-size:.88rem}
.btn:hover{filter:brightness(1.06)}
.btn[disabled]{opacity:.45;cursor:default}
.hero{padding-block:40px 56px;display:grid;grid-template-columns:1.4fr 1fr;gap:40px;align-items:end}
.hero h1{font-size:clamp(2.1rem,5vw,3.4rem);color:var(--on-navy);margin-top:12px}
.hero h1 em{font-style:normal;color:var(--orange)}
.hero p.lede{color:var(--on-navy-muted);font-size:1.1rem;margin-top:16px;max-width:34em}
.cta-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:26px}
.marked{background:var(--navy-2);border-radius:10px;padding:20px 22px;font-size:.95rem}
.marked .q0{color:var(--on-navy-muted);font-size:.85rem;margin-bottom:12px}
.marked ol{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.marked li{display:flex;justify-content:space-between;gap:12px;border-bottom:1px dashed rgba(255,255,255,.14);padding-bottom:8px}
.marked li span:last-child{font-family:var(--display);font-weight:700;color:var(--orange);white-space:nowrap}
.marked .total{margin-top:12px;font-size:.85rem;color:var(--on-navy-muted)}
.page-head{padding-block:32px 40px}
.page-head h1{font-size:clamp(1.8rem,4.2vw,2.7rem);color:var(--on-navy);margin-top:10px}
.page-head p{color:var(--on-navy-muted);margin-top:12px;max-width:42em}
.crumbs{font-size:.88rem;color:var(--on-navy-muted)}
.crumbs a{color:var(--on-navy-muted)}
section{padding-block:52px}
section + section{border-top:1px solid var(--line)}
.sec-head{display:grid;gap:10px;margin-bottom:26px;max-width:42em}
.sec-head p{color:var(--muted)}
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:20px}
.card{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:22px;min-width:0}
.card h3{font-size:1.2rem;margin-bottom:6px}
.lvl{font-size:.8rem;color:var(--orange);font-weight:700;letter-spacing:.06em;text-transform:uppercase;margin-bottom:8px}
.card ul{margin:0;padding-left:18px;color:var(--muted)}
.band{margin-top:20px;background:var(--sand);border-radius:10px;padding:22px;display:grid;grid-template-columns:1fr auto;gap:20px;align-items:center}
.band h3{font-size:1.2rem;margin-bottom:4px}
.band p{color:var(--muted)}
.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:28px}
.step .n{font-family:var(--display);font-weight:700;font-size:2.4rem;color:var(--orange);line-height:1}
.step h3{font-size:1.2rem;margin:8px 0 6px}
.step p{color:var(--muted)}
.prices{display:grid;grid-template-columns:1.2fr 1fr;gap:28px;align-items:start}
table{width:100%;border-collapse:collapse;font-variant-numeric:tabular-nums;background:var(--card);border:1px solid var(--line);border-radius:10px;overflow:hidden}
th,td{text-align:left;padding:12px 16px;border-bottom:1px solid var(--line);vertical-align:top}
th{font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);font-weight:700}
td.p,th.p{text-align:right}
td.p{font-family:var(--display);font-weight:700;font-size:1.2rem}
tr:last-child td{border-bottom:0}
.terms{display:grid;gap:14px}
.term{padding-left:16px;border-left:3px solid var(--orange)}
.term b{display:block}
.term span{color:var(--muted);font-size:.95rem}
.about{display:grid;grid-template-columns:1fr 1fr;gap:40px}
.about p + p{margin-top:14px}
.creds{border-top:1px solid var(--line);margin:0}
.creds div{display:flex;justify-content:space-between;gap:16px;padding-block:11px;border-bottom:1px solid var(--line)}
.creds dt{color:var(--muted)}
.creds dd{margin:0;font-weight:700;text-align:right}
/* directory */
.dir{display:grid;gap:36px}
.dir h2{font-size:1.5rem;margin-bottom:14px}
.subjects{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px}
.subj-card{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:18px 20px;display:grid;gap:8px;align-content:start;min-width:0}
.subj-card h3{font-size:1.15rem}
.subj-card ul{list-style:none;margin:0;padding:0;display:grid;gap:2px;font-size:.93rem}
.subj-card li a{text-decoration:none;display:flex;justify-content:space-between;gap:8px;padding:3px 0;border-bottom:1px dotted var(--line)}
.subj-card li a:hover{color:var(--orange)}
.subj-card li a span{color:var(--muted);font-variant-numeric:tabular-nums}
.count{font-size:.85rem;color:var(--muted)}
/* questions */
.qlist{display:grid;gap:18px;min-width:0}
.q{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:20px 22px;min-width:0}
.q .meta{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin-bottom:10px;font-size:.82rem}
.q .num{font-family:var(--display);font-weight:700;font-size:1.1rem;margin-right:4px}
.chip{border:1px solid var(--line);border-radius:999px;padding:2px 10px;color:var(--muted)}
.chip.d1{border-color:transparent;background:var(--ok-bg);color:var(--ok)}
.chip.d2{border-color:transparent;background:var(--sand);color:var(--orange)}
.chip.d3{border-color:transparent;background:var(--navy-2);color:var(--on-navy)}
.chip.d4{border-color:transparent;background:var(--navy);color:var(--on-navy)}
.chip.mk{margin-left:auto;font-weight:700;color:var(--ink)}
.stem{font-size:1.03rem;overflow-x:auto}
.stem p{margin:0 0 .6em}
.stem pre,.ms pre,.model pre{background:var(--sand);padding:12px 14px;border-radius:6px;overflow-x:auto;font-size:.9rem;line-height:1.45}
.stem table{width:auto;margin:.4em 0 .8em}
.diagram{margin:12px 0;max-width:520px;color:var(--ink)}
.diagram svg{width:100%;height:auto}
.ctrl{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}
.ms{list-style:none;margin:14px 0 0;padding:0;display:grid;gap:6px}
.ms li{display:grid;grid-template-columns:1fr auto auto;gap:12px;align-items:center;padding:8px 12px;border-radius:6px;background:var(--sand);min-width:0}
.ms li > span:first-child{min-width:0;overflow-x:auto}
.ms li .code{font-family:var(--display);font-weight:700;color:var(--orange);white-space:nowrap}
.ms li label{font-size:.82rem;color:var(--muted);display:flex;align-items:center;gap:4px;cursor:pointer;white-space:nowrap}
.ms li.tip{grid-template-columns:1fr;background:transparent;border:1px dashed var(--orange);font-size:.93rem}
.ms li.ans{grid-template-columns:1fr;background:transparent;border:1px solid var(--line);font-size:.93rem}
.levels{margin-top:10px}
.check{margin-top:12px;background:var(--warn-bg);color:var(--warn);border-radius:6px;padding:8px 12px;font-size:.9rem}
.qid{font-family:ui-monospace,Consolas,monospace;font-size:.78rem;color:var(--muted)}
/* guides */
.guide{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:22px;display:grid;gap:16px;min-width:0}
.guide h3{font-size:1.3rem}
.guide .qbox{background:var(--sand);border-radius:8px;padding:16px 18px}
.guide ul{margin:0;padding-left:20px}
.model{border-left:3px solid var(--orange);padding-left:16px}
.model mark{background:var(--sand);color:inherit;border-bottom:2px solid var(--orange);padding:0 2px;cursor:help}
.notes{display:grid;gap:8px;font-size:.93rem}
.notes div{padding:8px 12px;background:var(--sand);border-radius:6px}
.notes b{color:var(--orange)}
details.fold summary{cursor:pointer;font-weight:700}
details.fold[open] summary{margin-bottom:10px}
/* builder */
.builder{display:grid;grid-template-columns:320px 1fr;gap:32px;align-items:start}
.panel{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:20px;display:grid;gap:18px}
.panel fieldset{border:0;margin:0;padding:0;display:grid;gap:6px;min-width:0}
.panel legend{font-size:.78rem;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);font-weight:700;margin-bottom:6px}
.panel label{display:flex;gap:8px;align-items:flex-start;font-size:.93rem;cursor:pointer}
.panel select{font:inherit;padding:8px 10px;border-radius:8px;border:1px solid var(--line);background:var(--paper);color:var(--ink);width:100%}
.panel .row{display:flex;gap:8px;flex-wrap:wrap}
.topicbox{max-height:320px;overflow:auto;display:grid;gap:4px;padding-right:4px}
.seg{display:flex;border:1px solid var(--line);border-radius:8px;overflow:hidden}
.seg button{flex:1;border:0;background:transparent;color:var(--ink);padding:8px 6px;font:inherit;font-size:.88rem;cursor:pointer}
.seg button[aria-pressed="true"]{background:var(--navy);color:var(--on-navy)}
.paperbar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;background:var(--navy);color:var(--on-navy);border-radius:10px;padding:16px 20px;margin-bottom:18px}
.paperbar .big{font-family:var(--display);font-weight:700;font-size:1.3rem}
.paperbar .sub{color:var(--on-navy-muted);font-size:.9rem}
.timer{font-family:var(--display);font-weight:700;font-size:1.4rem;font-variant-numeric:tabular-nums}
.score{margin-top:18px;background:var(--sand);border-radius:10px;padding:20px 22px;display:grid;gap:8px}
.score .big{font-family:var(--display);font-weight:700;font-size:1.6rem}
.empty{border:1px dashed var(--line);border-radius:10px;padding:40px 24px;text-align:center;color:var(--muted)}
.contact{background:var(--navy);color:var(--on-navy)}
.contact h2{color:var(--on-navy)}
.contact .sec-head p{color:var(--on-navy-muted)}
.cbox{background:var(--navy-2);border-radius:10px;padding:22px;min-width:0}
.cbox .lbl{font-size:.8rem;letter-spacing:.12em;text-transform:uppercase;color:var(--on-navy-muted);font-weight:700}
.cbox .val{font-family:var(--display);font-size:1.35rem;font-weight:700;margin:6px 0 14px;user-select:all;overflow-wrap:anywhere}
.copy{background:transparent;border:1px solid var(--on-navy-muted);color:var(--on-navy);border-radius:6px;padding:7px 12px;font:inherit;font-size:.9rem;cursor:pointer;margin-left:8px}
footer{background:var(--navy);color:var(--on-navy-muted);font-size:.85rem;padding-block:20px;border-top:1px solid var(--navy-2)}
footer .wrap{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}
mjx-container{overflow-x:auto;overflow-y:hidden;max-width:100%}
@media (max-width:860px){
  .hero,.prices,.about,.grid2,.band,.builder{grid-template-columns:1fr}
  .grid3,.steps{grid-template-columns:1fr}
  section{padding-block:40px}
}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}