@import url("https://fonts.googleapis.com/css2?family=Atkinson+Hyperlegible+Next:ital,wght@0,400;0,500;0,700;0,800;1,400&family=Atkinson+Hyperlegible+Mono:wght@400;500;700&family=Atkinson+Hyperlegible:wght@400;700&family=Instrument+Serif&display=swap");
/* Trial Balance v4: an editorial revision site set on ledger paper.
   Layout: sticky header with mega menus; lessons in a two-column reading layout (section sidebar + article);
   the home page opens on a deep-green ledger band where a journal entry writes itself. */
:root{
  --bg:#F6F7FA; --panel:#FFFFFF; --ink:#141B2D; --ink-2:#2A3450; --muted:#5C6680; --rule:#DDE2EC; --rule-strong:#A9B2C6;
  --ledger:#EEF1F7; --accent:#24457A; --accent-deep:#18325C; --accent-ink:#FFFFFF; --accent-soft:#E3EAF6;
  --band:#13223F; --band-2:#1B2E52; --band-ink:#EEF2FA; --band-muted:#A9B6D2; --gold-hi:#D9AC4B;
  --ok:#2F7A55; --ok-soft:#E3F1E9; --bad:#B8392B; --bad-soft:#FBEAE7; --margin:#C9972B;
  --gold:#C9972B; --gold-soft:#FAF1DC; --gold-ink:#6B4E0E;
  --shadow:0 1px 2px rgba(15,25,50,.05),0 12px 32px -12px rgba(15,25,50,.18);
  --shadow-sm:0 1px 2px rgba(15,25,50,.06),0 4px 12px -6px rgba(15,25,50,.12);
  --display:"Newsreader",Georgia,"Times New Roman",serif;
  --serif:var(--display);
  --sans:"Public Sans",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
  --mono:"JetBrains Mono",ui-monospace,"SF Mono",Menlo,Consolas,monospace;
  --ease:cubic-bezier(.2,.7,.2,1);
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --bg:#0C1120; --panel:#131A2B; --ink:#E6EAF3; --ink-2:#CBD2E2; --muted:#98A2B8; --rule:#243049; --rule-strong:#3E4B66;
  --ledger:#19223A; --accent:#8FB0E8; --accent-deep:#5F84C4; --accent-ink:#0A1020; --accent-soft:#1C2A48;
  --band:#0A1328; --band-2:#101D3A; --band-ink:#E9EEF8; --band-muted:#9FB0D0; --gold-hi:#E0B85A;
  --ok:#5BC08E; --ok-soft:#173327; --bad:#FF8A73; --bad-soft:#381C17; --margin:#D9AC4B;
  --gold:#E0B85A; --gold-soft:#2E2614; --gold-ink:#F0D68E;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 12px 32px -12px rgba(0,0,0,.6);
  --shadow-sm:0 1px 2px rgba(0,0,0,.35),0 4px 12px -6px rgba(0,0,0,.5);
  color-scheme:dark;
}}
:root[data-theme="dark"]{
  --bg:#0C1120; --panel:#131A2B; --ink:#E6EAF3; --ink-2:#CBD2E2; --muted:#98A2B8; --rule:#243049; --rule-strong:#3E4B66;
  --ledger:#19223A; --accent:#8FB0E8; --accent-deep:#5F84C4; --accent-ink:#0A1020; --accent-soft:#1C2A48;
  --band:#0A1328; --band-2:#101D3A; --band-ink:#E9EEF8; --band-muted:#9FB0D0; --gold-hi:#E0B85A;
  --ok:#5BC08E; --ok-soft:#173327; --bad:#FF8A73; --bad-soft:#381C17; --margin:#D9AC4B;
  --gold:#E0B85A; --gold-soft:#2E2614; --gold-ink:#F0D68E;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 12px 32px -12px rgba(0,0,0,.6);
  --shadow-sm:0 1px 2px rgba(0,0,0,.35),0 4px 12px -6px rgba(0,0,0,.5);
  color-scheme:dark;
}
*{box-sizing:border-box}
body{background:var(--bg);color:var(--ink);font-family:var(--sans);font-size:16px;line-height:1.6;}
a{color:var(--accent)}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
h1,h2,h3{font-family:var(--serif);font-weight:600;line-height:1.2;text-wrap:balance;margin:0}
h1{font-size:clamp(2rem,4vw,2.75rem)}
h2{font-size:1.6rem}
h3{font-size:1.2rem;margin-top:1.4rem}
p{margin:0 0 .8rem}
.mono,.amt,input.num{font-family:var(--mono);font-variant-numeric:tabular-nums}

/* top bar */
.top{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:var(--bg);border-bottom:1px solid var(--rule)}
.top-in{max-width:1220px;margin:0 auto;padding-inline:16px;padding-block:12px;display:flex;align-items:center;gap:16px}
.brand{display:flex;align-items:baseline;gap:10px;text-decoration:none;color:var(--ink)}
.brand b{font-family:var(--serif);font-size:1.45rem;font-weight:600}
.brand span{font-size:.8rem;color:var(--muted);letter-spacing:.06em;text-transform:uppercase}
.menu-btn{margin-left:auto;display:none}

.shell{max-width:1220px;margin:0 auto;padding-inline:16px;display:grid;grid-template-columns:230px minmax(0,1fr);gap:48px;padding-block:28px 80px}
.side{position:sticky;top:calc(env(safe-area-inset-top,0px) + 76px);align-self:start;max-height:calc(100vh - 100px);overflow:auto;font-size:.95rem}
.side h4{font-family:var(--sans);font-size:.72rem;letter-spacing:.09em;text-transform:uppercase;color:var(--muted);margin:1.2rem 0 .4rem;font-weight:600}
.side h4:first-child{margin-top:0}
.side a{display:flex;justify-content:space-between;gap:8px;padding:5px 10px;border-radius:6px;color:var(--ink);text-decoration:none}
.side a:hover{background:var(--ledger)}
.side a.on{background:var(--accent-soft);color:var(--accent);font-weight:600}
.side a small{color:var(--muted);font-family:var(--mono);font-size:.75rem;font-weight:400}
main{min-width:0}
.eyebrow{font-size:.75rem;letter-spacing:.09em;text-transform:uppercase;color:var(--muted);font-weight:600;margin-bottom:.5rem}
.lede{font-size:1.1rem;color:var(--muted);max-width:62ch;margin-top:.8rem}
.jump{display:flex;flex-wrap:wrap;gap:8px;margin:1.2rem 0 0}
.jump a{font-size:.85rem;padding:4px 12px;border:1px solid var(--rule-strong);border-radius:999px;text-decoration:none;color:var(--ink)}
.jump a:hover{border-color:var(--accent);color:var(--accent)}
section.block{margin-top:2.6rem}
section.block > h2{padding-bottom:.5rem;border-bottom:2px solid var(--ink);margin-bottom:1.1rem;display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap}
section.block > h2 small{font-family:var(--sans);font-size:.8rem;font-weight:500;color:var(--muted)}
.prose{max-width:72ch}
.prose ul,.prose ol{padding-left:1.3rem;margin:0 0 .9rem}
.prose li{margin-bottom:.3rem}
.formula{font-family:var(--mono);font-size:1.05rem;background:var(--ledger);border-left:3px solid var(--margin);padding:10px 14px;margin:.4rem 0 1rem;border-radius:0 6px 6px 0}
.note{border-left:3px solid var(--accent);background:var(--accent-soft);padding:10px 14px;border-radius:0 6px 6px 0;margin:.8rem 0 1rem;font-size:.95rem}
.note.warn{border-left-color:var(--bad);background:var(--bad-soft)}
.note b:first-child{margin-right:.3rem}

/* ledger tables */
.scroll{overflow-x:auto;-webkit-overflow-scrolling:touch;margin:.4rem 0 1rem}
table.ledger{border-collapse:collapse;width:100%;min-width:420px;background:var(--panel);font-size:.95rem}
table.ledger th{text-align:left;font-size:.75rem;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);font-weight:600;padding:8px 10px;border-bottom:2px solid var(--ink)}
table.ledger td{padding:6px 10px;border-bottom:1px solid var(--rule);vertical-align:middle}
table.ledger .amt{text-align:right;white-space:nowrap;width:8.5rem}
table.ledger th.amt{text-align:right}
table.ledger td.amt-in{width:9rem;padding:4px 6px}
table.ledger .cr-line{padding-left:2.2rem}
table.ledger tr.narr td{font-style:italic;color:var(--muted);font-size:.88rem;border-bottom:1px solid var(--rule-strong)}
table.ledger tr.sec td{background:var(--ledger);font-weight:600;font-size:.82rem;letter-spacing:.05em;text-transform:uppercase}
table.ledger tr.title td{font-family:var(--serif);font-weight:600;font-size:1.05rem;text-align:center;border-bottom:2px solid var(--ink);background:var(--panel)}
table.ledger td.ind{padding-left:1.8rem}
table.ledger tr.bold td{font-weight:600}
table.ledger td.tl{border-top:1px solid var(--ink)}
table.ledger td.dbl{border-top:1px solid var(--ink);border-bottom:3px double var(--ink)}
table.ledger td.label{width:auto}
table.ledger.simple td,table.ledger.simple th{vertical-align:top}
table.ledger.fields td:first-child{width:auto}

input.num,select,textarea{font:inherit;color:var(--ink);background:var(--panel);border:1px solid var(--rule-strong);border-radius:6px;padding:6px 8px}
input.num{width:100%;min-width:6.5rem;text-align:right;font-size:.95rem}
select{width:100%;min-width:10rem;padding-right:4px}
textarea{width:100%;min-height:8rem;resize:vertical;line-height:1.5}
input.num.ok,select.ok{border-color:var(--ok);background:var(--ok-soft)}
input.num.bad,select.bad{border-color:var(--bad);background:var(--bad-soft)}

/* buttons */
button{font:inherit;cursor:pointer}
.btn{background:var(--accent);color:var(--accent-ink);border:1px solid var(--accent);border-radius:8px;padding:8px 16px;font-weight:600;font-size:.92rem}
.btn:hover{filter:brightness(1.08)}
.ghost{background:transparent;color:var(--ink);border:1px solid var(--rule-strong);border-radius:8px;padding:7px 14px;font-size:.9rem}
.ghost:hover{border-color:var(--accent);color:var(--accent)}
.icon-btn{background:none;border:none;color:var(--muted);font-size:1.2rem;line-height:1;padding:4px 8px;border-radius:6px}
.icon-btn:hover{color:var(--bad);background:var(--bad-soft)}
.seg{display:inline-flex;flex-wrap:wrap;gap:4px}
.seg button{background:var(--panel);color:var(--ink);border:1px solid var(--rule-strong);border-radius:6px;padding:4px 11px;font-size:.85rem}
.seg button[aria-pressed="true"]{background:var(--accent);border-color:var(--accent);color:var(--accent-ink);font-weight:600}
.seg.ok button[aria-pressed="true"]{background:var(--ok);border-color:var(--ok)}
.seg.bad button[aria-pressed="true"]{background:var(--bad);border-color:var(--bad);color:#fff}
.seg.bad{outline:1px dashed var(--bad);outline-offset:3px;border-radius:6px}

/* question cards */
.q{background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:20px;margin-bottom:22px}
.q-head{display:flex;align-items:center;gap:10px;flex-wrap:wrap;margin-bottom:.7rem}
.q-head h3{margin:0;font-size:1.1rem}
.tag{font-size:.72rem;letter-spacing:.07em;text-transform:uppercase;font-weight:600;color:var(--muted);border:1px solid var(--rule);border-radius:999px;padding:2px 9px}
.q-head .ghost{margin-left:auto;padding:4px 12px;font-size:.82rem}
.q-prompt{margin-bottom:.8rem}
.q-prompt ol,.q-prompt ul{padding-left:1.3rem;margin:.3rem 0}
.q-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:.6rem}
.fb{margin-top:14px;padding:12px 14px;border-radius:8px;font-size:.95rem}
.fb.good{background:var(--ok-soft);border-left:3px solid var(--ok)}
.fb.part{background:var(--bad-soft);border-left:3px solid var(--bad)}
.fb.shown{background:var(--ledger);border-left:3px solid var(--rule-strong)}
.fb p:last-child{margin-bottom:0}
.hint{font-size:.85rem;color:var(--muted)}

/* T-account */
.t-wrap{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.15fr);gap:22px;align-items:start}
.tx-list{list-style:none;margin:0;padding:0;display:grid;gap:6px}
.tx-list li{display:grid;grid-template-columns:1fr auto auto;gap:10px;align-items:center;padding:6px 0;border-bottom:1px solid var(--rule);font-size:.93rem}
.tx-list li .amt{font-family:var(--mono)}
.tacc{background:var(--panel);font-size:.9rem;min-width:340px}
.tacc-name{text-align:center;font-family:var(--serif);font-weight:600;font-size:1.05rem;padding-bottom:4px;border-bottom:2px solid var(--ink)}
.tacc-cols{display:grid;grid-template-columns:1fr 1fr}
.tacc-side + .tacc-side{border-left:2px solid var(--ink)}
.tacc-h{font-size:.72rem;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);font-weight:600;padding:4px 8px}
.trow{display:flex;justify-content:space-between;gap:8px;padding:4px 8px;border-bottom:1px solid var(--rule);min-height:30px}
.trow .amt{font-family:var(--mono);font-variant-numeric:tabular-nums}
.trow.tot{font-weight:600}
.trow.tot .amt{border-top:1px solid var(--ink);border-bottom:3px double var(--ink)}
.trow.bd{color:var(--accent);font-weight:600}
.trow.run{color:var(--muted);font-size:.82rem;border-bottom:none}
.t-fields{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:12px;margin-top:16px}
.t-fields label{display:block;font-size:.85rem;color:var(--muted);margin-bottom:4px}

/* classify rows */
.cls{display:grid;gap:0}
.cls-row{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;padding:8px 0;border-bottom:1px solid var(--rule)}
.mcq{display:grid;gap:8px}
.mcq label{display:flex;gap:10px;align-items:flex-start;padding:9px 12px;border:1px solid var(--rule);border-radius:8px;cursor:pointer}
.mcq label:hover{border-color:var(--rule-strong)}
.mcq label.ok{border-color:var(--ok);background:var(--ok-soft)}
.mcq label.bad{border-color:var(--bad);background:var(--bad-soft)}
.mcq input{margin-top:.35rem;accent-color:var(--accent)}
.points label{display:flex;gap:8px;align-items:flex-start;padding:4px 0}
.points input{margin-top:.35rem;accent-color:var(--accent)}
.model{background:var(--ledger);padding:12px 14px;border-radius:8px;margin:.6rem 0}

/* home */
.hero{padding-block:8px 8px}
.hero h1{font-size:clamp(2.3rem,5vw,3.4rem)}
.hero .cta{display:flex;gap:12px;flex-wrap:wrap;margin-top:1.4rem}
.hero .cta a{text-decoration:none}
.steps{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:16px;margin-top:1rem}
.steps div{border-top:2px solid var(--ink);padding-top:10px}
.steps b{display:block;font-family:var(--serif);font-size:1.1rem;margin-bottom:4px}
.steps p{color:var(--muted);font-size:.93rem}
.topic-list{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px}
.topic{display:block;text-decoration:none;color:var(--ink);background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:16px}
.topic:hover{border-color:var(--accent)}
.topic b{font-family:var(--serif);font-size:1.12rem;display:block;margin-bottom:4px}
.topic p{color:var(--muted);font-size:.9rem;margin-bottom:10px}
.meter{height:6px;background:var(--ledger);border-radius:99px;overflow:hidden}
.meter i{display:block;height:100%;background:var(--accent);border-radius:99px}
.topic small{display:block;margin-top:6px;font-size:.8rem;color:var(--muted)}
.pager{display:flex;justify-content:space-between;gap:12px;margin-top:3rem;padding-top:1.2rem;border-top:1px solid var(--rule);flex-wrap:wrap}
.pager a{text-decoration:none;color:var(--ink);max-width:48%}
.pager a small{display:block;color:var(--muted);font-size:.78rem;text-transform:uppercase;letter-spacing:.07em}
.pager a b{font-family:var(--serif);font-size:1.1rem}
.pager a.next{text-align:right;margin-left:auto}
.score{position:sticky;top:calc(env(safe-area-inset-top,0px) + 62px);z-index:5;background:var(--bg);padding:10px 0;border-bottom:1px solid var(--rule);margin-bottom:18px;display:flex;gap:16px;align-items:center;flex-wrap:wrap;font-size:.95rem}
.score b{font-family:var(--mono)}
.std{border-top:1px solid var(--rule);padding-top:.9rem;margin-top:1rem}
.std h3{margin-top:0}
.std .code{font-family:var(--mono);font-size:.8rem;color:var(--accent);font-weight:500;letter-spacing:.03em}

@media (max-width: 880px){
  .shell{grid-template-columns:1fr;gap:20px;padding-block:16px 60px}
  .menu-btn{display:inline-block}
  .side{display:none;position:static;max-height:none;background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:14px}
  .side.open{display:block}
  .t-wrap{grid-template-columns:1fr}
  .score{top:calc(env(safe-area-inset-top,0px) + 58px)}
}
@media (max-width: 480px){
  .brand span{display:none}
  .q{padding:14px}
  table.ledger{font-size:.88rem}
  .tx-list li{grid-template-columns:1fr auto;}
  .tx-list li .seg{grid-column:1 / -1}
}
@media (prefers-reduced-motion: reduce){*{transition:none!important;scroll-behavior:auto!important}}

/* ---------- website layout ---------- */
.wrap{max-width:1080px;margin:0 auto;padding-inline:16px}
.site-head{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:var(--bg);border-bottom:1px solid var(--rule)}
.head-in{display:flex;align-items:center;gap:20px;padding-block:12px;flex-wrap:wrap}
.site-nav{display:flex;gap:2px;margin-left:auto;flex-wrap:wrap}
.site-nav a{padding:6px 12px;border-radius:6px;color:var(--ink);text-decoration:none;font-size:.95rem}
.site-nav a:hover{background:var(--ledger)}
.site-nav a[aria-current="page"]{color:var(--accent);font-weight:600}
main.wrap{padding-block:28px 72px}
.article{max-width:860px}
.crumbs{font-size:.85rem;color:var(--muted);margin-bottom:1.2rem}
.crumbs a{color:var(--muted)}
.toc{display:flex;flex-wrap:wrap;gap:6px 16px;align-items:center;margin-top:1.4rem;font-size:.92rem;padding:10px 14px;background:var(--panel);border:1px solid var(--rule);border-radius:8px}
.toc b{font-size:.72rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted)}
.topic-rows{border-top:1px solid var(--rule)}
.topic-row{display:grid;grid-template-columns:minmax(0,17rem) 1fr auto;gap:18px;padding:14px 0;border-bottom:1px solid var(--rule);align-items:baseline;text-decoration:none;color:var(--ink)}
.topic-row b{font-family:var(--serif);font-size:1.15rem;font-weight:600}
.topic-row span{color:var(--muted);font-size:.95rem}
.topic-row em{font-style:normal;color:var(--accent);font-size:.88rem;white-space:nowrap}
.topic-row:hover b{color:var(--accent)}
.feature{display:grid;grid-template-columns:1fr auto;gap:16px;align-items:center;background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:18px 20px}
.feature p{margin:0;color:var(--muted)}
.site-foot{border-top:2px solid var(--ink);background:var(--panel);padding-block:32px 40px;font-size:.92rem}
.foot-in{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:24px}
.site-foot h4{font-family:var(--sans);font-size:.72rem;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:0 0 .5rem}
.site-foot ul{list-style:none;padding:0;margin:0 0 1rem}
.site-foot li{margin:.3rem 0}
.site-foot a{color:var(--ink);text-decoration:none}
.site-foot a:hover{color:var(--accent)}
.site-foot .brandline b{font-family:var(--serif);font-size:1.3rem}
.site-foot .brandline p{color:var(--muted)}
.q-head a.hint{text-decoration:none}
@media (max-width:760px){
  .menu-btn{display:inline-block;margin-left:auto}
  .site-nav{display:none;width:100%;flex-direction:column;margin-left:0}
  .site-nav.open{display:flex}
  .topic-row{grid-template-columns:1fr;gap:2px}
  .feature{grid-template-columns:1fr}
}
/* ---------- white, Times New Roman, simpler ---------- */
body{font-size:18px;line-height:1.65}
h1,h2,h3{font-weight:700}
.eyebrow{letter-spacing:.04em}

.head-in{padding-block:14px}
.site-nav{margin-left:0}
.site-nav a{font-size:1.08rem}
.brand{margin-left:auto;display:flex;align-items:center;gap:10px;color:var(--ink);text-decoration:none}
.brand b{font-size:1.55rem;font-weight:700}
.brand svg{flex:none}
.plain{border:1px solid var(--rule-strong);border-left:4px solid var(--accent);padding:16px 20px;border-radius:0 8px 8px 0;background:var(--panel);margin-bottom:1rem}
.plain p{font-size:1.08rem;margin-bottom:.6rem}
.plain p:last-child{margin-bottom:0}
.plain .eg{background:var(--ledger);padding:10px 14px;border-radius:6px}
dl.words{display:grid;grid-template-columns:minmax(0,13rem) 1fr;margin:.4rem 0 0;border-top:1px solid var(--rule);max-width:72ch}
dl.words dt,dl.words dd{margin:0;padding:9px 0;border-bottom:1px solid var(--rule)}
dl.words dt{font-weight:700;padding-right:16px}
table.ledger th{letter-spacing:.03em;font-size:.8rem}
input.num,select,textarea{font-size:1rem}


@media (min-width:761px){.menu-btn{display:none}}
@media (max-width:760px){.menu-btn{margin-left:0;order:1}.brand{order:2}.site-nav{order:3}dl.words{grid-template-columns:1fr}dl.words dt{border-bottom:none;padding-bottom:0}}

section.block,[id]{scroll-margin-top:90px}
details.qa{border-bottom:1px solid var(--rule);padding:10px 0}
details.qa summary{cursor:pointer;font-weight:700;list-style-position:outside}
details.qa p{margin:.6rem 0 0}
.email{border:1px solid var(--rule-strong);border-radius:8px;margin:1rem 0 1.4rem;background:var(--panel);max-width:72ch}
.email-h{background:var(--ledger);padding:10px 16px;border-bottom:1px solid var(--rule);font-size:.95rem;display:grid;gap:2px}
.email-b{padding:14px 16px}
.email-b ol{padding-left:1.3rem}
h3.doc-h{margin-top:1.6rem}
.prose{max-width:none}
.prose > p,.prose > ul,.prose > ol,.prose > h3,.prose > .formula,.prose > .note{max-width:72ch}
table.xl{border-collapse:collapse;font-family:Arial,Helvetica,sans-serif;font-size:.85rem;background:var(--panel);min-width:420px}
table.xl th,table.xl td{border:1px solid var(--rule);padding:3px 8px;white-space:nowrap}
table.xl th,table.xl td.rn{background:var(--ledger);color:var(--muted);text-align:center;font-weight:400}
table.xl td.n{text-align:right}
code{font-family:"Courier New",Courier,monospace;font-size:.92em;background:var(--ledger);padding:1px 4px;border-radius:3px}
.checklist{display:grid;gap:0;border-top:1px solid var(--rule);max-width:80ch}
.checklist label{display:flex;gap:10px;align-items:flex-start;padding:9px 0;border-bottom:1px solid var(--rule);cursor:pointer}
.checklist input,.done-row input{width:18px;height:18px;margin-top:.3rem;accent-color:var(--accent);flex:none}
.done-row{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:1.2rem;padding:12px 16px;border:1px solid var(--rule-strong);border-radius:8px}
.done-row label{font-weight:700;cursor:pointer}
.done-row a{margin-left:auto}
.summary{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:14px;margin-top:1.4rem}
.summary div{border-top:2px solid var(--ink);padding-top:8px}
.summary b{display:block;font-size:1.8rem;font-variant-numeric:tabular-nums}
.summary span{color:var(--muted)}
.pill{display:inline-block;font-size:.8rem;padding:1px 10px;border-radius:999px;border:1px solid var(--rule-strong)}
.pill.p-done{background:var(--ok-soft);border-color:var(--ok);color:var(--ok);font-weight:700}
.pill.p-prog{background:var(--gold-soft);border-color:var(--gold);color:var(--gold-ink)}
.pill.p-none{color:var(--muted)}
.gl-tools{display:flex;gap:12px;align-items:center;flex-wrap:wrap;margin:1.2rem 0 .8rem}
.gl-tools input{font:inherit;padding:8px 12px;border:1px solid var(--rule-strong);border-radius:8px;width:min(420px,100%)}
.gl-letters{display:flex;flex-wrap:wrap;gap:4px;margin-bottom:1rem}
.gl-letters a{display:inline-block;min-width:2rem;text-align:center;padding:3px 6px;border:1px solid var(--rule);border-radius:6px;text-decoration:none;color:var(--ink)}
.gl-letters a:hover{border-color:var(--accent);color:var(--accent)}
.gl-group h2{font-size:1.4rem;border-bottom:2px solid var(--ink);padding-bottom:4px;margin:1.6rem 0 .4rem}
dl.words.gl{max-width:none}
dl.words.gl .gl-item{display:contents}
.gl-item[hidden]{display:none!important}
.gl-see{display:block;font-size:.88rem;color:var(--muted);margin-top:2px}
.site-nav a{padding:6px 8px;font-size:1rem}
.head-in{gap:12px}
p.acca{font-size:.95rem;margin-top:.8rem;display:flex;flex-wrap:wrap;gap:6px 8px;align-items:center}
.acca-tag{display:inline-block;border:1px solid var(--accent);color:var(--accent);border-radius:999px;padding:1px 10px;font-size:.85rem}
p.acca a{font-size:.88rem}
.exam-setup{background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:20px}
.exam-setup h2{font-size:1.3rem;margin-bottom:.4rem}
.exam-setup select{min-width:0}
.exam-setup .btn{margin-top:.4rem}
.exam .q-actions .ghost,.exam .q-head .ghost{display:none}
.clock{font-variant-numeric:tabular-nums;font-size:1.15rem}
.clock.low{color:var(--bad)}
.exam-result{border:2px solid var(--accent);border-radius:10px;padding:18px 20px;margin-bottom:22px;background:var(--panel)}
.exam-result h2{font-size:1.4rem;margin-bottom:.4rem}
.exam-foot{margin-top:10px}
.score .btn{padding:5px 14px}

.exam-result,#test-root{scroll-margin-top:150px}
.gl-item dd p{margin:0 0 .35rem}
.gl-m b,.gl-e b,.gl-n b{font-weight:700}
.gl-e{background:var(--ledger);padding:6px 10px;border-radius:6px}
.gl-n{border-left:3px solid var(--bad);padding-left:10px}
.kw-eg{display:block;margin-top:4px;font-size:.93rem;color:var(--muted);background:var(--ledger);padding:4px 8px;border-radius:6px}
/* real-statement look */
.fs-sheet{background:var(--panel);border:1px solid var(--rule);box-shadow:var(--shadow);padding:26px 30px 22px;margin:.6rem 0 1.2rem;max-width:760px}
.fs-head{text-align:center;margin-bottom:14px}
.fs-co{font-weight:700;font-size:1.15rem}
.fs-title{font-weight:700;font-size:1.05rem;margin-top:2px}
.fs-period{font-style:italic;color:var(--muted)}
table.fs{border-collapse:collapse;width:100%;min-width:380px;font-size:1rem}
table.fs td{padding:4px 8px;border:none;vertical-align:bottom}
table.fs .amt{text-align:right;white-space:nowrap;width:8rem;font-variant-numeric:tabular-nums}
table.fs tr.fs-hd td{font-weight:700;padding-bottom:8px}
table.fs tr.fs-sec td{font-weight:700;padding-top:14px}
table.fs tr.fs-b td{font-weight:700}
table.fs td.fs-ind{padding-left:1.8rem}
table.fs td.tl{border-top:1px solid var(--ink)}
table.fs td.dbl{border-top:1px solid var(--ink);border-bottom:3px double var(--ink)}
table.fs td.fs-blank{padding:2px 6px}
table.fs input.fs-in{border:none;border-bottom:1.5px dotted var(--rule-strong);border-radius:0;background:transparent;padding:2px 2px;min-width:0;width:100%;text-align:right;font:inherit;font-weight:inherit}
table.fs input.fs-in:focus{outline:none;background:var(--gold-soft);border-bottom:1.5px solid var(--accent)}
table.fs input.fs-in.ok{background:transparent;color:var(--ok);border-bottom:1.5px solid var(--ok)}
table.fs input.fs-in.bad{background:var(--bad-soft);color:var(--bad);border-bottom:1.5px solid var(--bad)}
@media (max-width:480px){.fs-sheet{padding:16px 12px}}
.fs-annot .fs-sheet{max-width:820px}
table.fs2 .amt{width:7rem}
table.fs2 tr.fs-hd td{font-size:.9rem;line-height:1.3}
.mk{display:inline-flex;align-items:center;justify-content:center;min-width:1.35rem;height:1.35rem;padding:0 4px;border-radius:999px;background:var(--accent);color:var(--accent-ink);font-size:.75rem;font-weight:700;margin-left:6px;vertical-align:middle;font-style:normal}
h3.fs-nh{margin-top:1.4rem}
ol.fs-notes{padding-left:0;list-style:none;display:grid;gap:0;max-width:80ch;counter-reset:none}
ol.fs-notes li{display:grid;grid-template-columns:2rem 1fr;gap:8px;padding:8px 0;border-bottom:1px solid var(--rule)}
ol.fs-notes li::before{content:attr(value);display:inline-flex;align-items:center;justify-content:center;width:1.5rem;height:1.5rem;border-radius:999px;background:var(--accent);color:var(--accent-ink);font-size:.8rem;font-weight:700}
ol.steps-list{padding-left:1.4rem;max-width:80ch}
ol.steps-list li{margin-bottom:.5rem}

.fs-wide{max-width:900px}
table.fs-multi .amt{width:6.5rem}


/* =================== v4: editorial website =================== */
@view-transition{navigation:auto}
::view-transition-old(root){animation:vtOut .18s ease both}
::view-transition-new(root){animation:vtIn .32s var(--ease) both}
@keyframes vtOut{to{opacity:0}}
@keyframes vtIn{from{opacity:0;transform:translateY(8px)}}
html{background:var(--bg);scroll-behavior:smooth}
body{background:var(--bg);color:var(--ink);font-family:var(--sans);font-size:17px;line-height:1.7;overflow-x:clip;-webkit-font-smoothing:antialiased}
h1,h2,h3{font-family:var(--display);font-weight:500;letter-spacing:-.015em;color:var(--ink)}
h1{font-size:clamp(2.3rem,5vw,3.5rem);line-height:1.04;letter-spacing:-.025em}
h2{font-size:clamp(1.6rem,3vw,2rem);line-height:1.15}
h3{font-size:1.3rem;font-weight:600;line-height:1.3;margin-top:1.8rem;margin-bottom:.4rem}
p{margin:0 0 1rem}
a{color:var(--accent);text-underline-offset:3px;text-decoration-thickness:1px}
a:hover{text-decoration-thickness:2px}
::selection{background:var(--accent-soft)}
code{overflow-wrap:anywhere;word-break:break-word;font-family:var(--mono);background:var(--ledger);color:var(--ink)}
.mono,.amt,input.num{font-family:var(--mono);font-variant-numeric:tabular-nums}
.eyebrow{display:flex;align-items:center;gap:10px;font-family:var(--sans);font-size:.74rem;font-weight:600;letter-spacing:.14em;text-transform:uppercase;color:var(--accent);margin-bottom:.9rem}
.eyebrow::before{content:"";width:28px;height:1px;background:currentColor}
.lede{font-family:var(--display);font-size:1.3rem;line-height:1.5;color:var(--muted);max-width:60ch;font-style:italic}
.crumbs{font-size:.84rem;color:var(--muted);margin-bottom:1.6rem}
.crumbs a{color:var(--muted);text-decoration:none}
.crumbs a:hover{color:var(--accent)}

/* ---------- header ---------- */
.readbar{position:fixed;left:0;right:0;top:env(safe-area-inset-top,0px);height:2px;z-index:40;background:var(--accent);transform-origin:0 50%;transform:scaleX(0)}
.site-head{position:sticky;top:env(safe-area-inset-top,0px);z-index:30;background:color-mix(in srgb,var(--bg) 92%,transparent);backdrop-filter:saturate(1.3) blur(14px);-webkit-backdrop-filter:saturate(1.3) blur(14px);border-bottom:1px solid var(--rule);transition:box-shadow .3s}
.site-head.scrolled{box-shadow:var(--shadow-sm)}
.hdr{display:flex;align-items:center;gap:22px;min-height:64px}
.hdr .brand{display:flex;align-items:center;gap:10px;color:var(--ink);text-decoration:none;flex:none;margin:0}
.hdr .brand b{font-family:var(--display);font-weight:600;font-size:1.4rem;letter-spacing:-.02em}
.brand svg rect{fill:var(--panel);stroke:var(--ink)}
.brand svg line{stroke:var(--accent)}
.brand:hover svg{transform:rotate(-6deg)}
.brand svg{transition:transform .4s var(--ease)}
.mnav{display:flex;align-items:center;gap:2px;margin-right:auto}
.mt,.ml{position:relative;display:inline-flex;align-items:center;gap:6px;background:none;border:0;padding:8px 11px;font:500 .93rem/1 var(--sans);color:var(--ink-2);text-decoration:none;border-radius:8px;cursor:pointer}
.mt::after,.ml::after{content:"";position:absolute;left:11px;right:11px;bottom:3px;height:1.5px;background:var(--accent);transform:scaleX(0);transform-origin:left;transition:transform .3s var(--ease)}
.mt:hover::after,.ml:hover::after,.mt[aria-expanded="true"]::after,.mt.here::after,.ml.here::after{transform:scaleX(1)}
.mt:hover,.ml:hover,.mt[aria-expanded="true"]{color:var(--ink)}
.mt svg{width:10px;height:10px;transition:transform .3s var(--ease);stroke:currentColor;fill:none;stroke-width:2}
.mt[aria-expanded="true"] svg{transform:rotate(180deg)}
.mp{position:absolute;left:0;right:0;top:100%;background:var(--panel);border-bottom:1px solid var(--rule);box-shadow:var(--shadow);opacity:0;visibility:hidden;transform:translateY(-8px);transition:opacity .22s var(--ease),transform .28s var(--ease),visibility 0s .28s}
.mp.open{opacity:1;visibility:visible;transform:none;transition:opacity .22s var(--ease),transform .28s var(--ease)}
.mp-in{display:grid;grid-template-columns:260px minmax(0,1fr);gap:40px;padding-block:28px 32px}
.mp-intro .num{font-family:var(--display);font-style:italic;font-size:2.6rem;line-height:1;color:var(--accent)}
.mp-intro b{display:block;font-family:var(--display);font-size:1.5rem;font-weight:500;margin:.4rem 0 .4rem}
.mp-intro p{color:var(--muted);font-size:.93rem}
.mp-list{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:2px 24px}
.mp-list a{display:block;padding:9px 12px;border-radius:10px;text-decoration:none;color:var(--ink);transition:background .2s}
.mp-list a:hover{background:var(--ledger)}
.mp-list a b{display:block;font-weight:600;font-size:.95rem}
.mp-list a span{display:block;font-size:.83rem;color:var(--muted);line-height:1.45;display:-webkit-box;-webkit-line-clamp:1;-webkit-box-orient:vertical;overflow:hidden}
.mp.open .mp-list li{animation:rise .4s var(--ease) both;animation-delay:calc(var(--i) * 18ms)}
@keyframes rise{from{opacity:0;transform:translateY(6px)}}
.tools{display:flex;align-items:center;gap:6px;flex:none}
.srch{display:inline-flex;align-items:center;gap:10px;background:var(--panel);border:1px solid var(--rule);border-radius:10px;padding:7px 10px 7px 12px;color:var(--muted);font:inherit;font-size:.88rem;cursor:pointer;transition:border-color .2s,box-shadow .2s;min-width:180px}
.srch:hover{border-color:var(--rule-strong);box-shadow:var(--shadow-sm)}
.srch svg,.icon-b svg{width:16px;height:16px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round}
.srch kbd{margin-left:auto;font:500 .72rem var(--mono);border:1px solid var(--rule);border-radius:5px;padding:1px 6px;color:var(--muted)}
.icon-b{display:inline-grid;place-content:center;width:38px;height:38px;border-radius:10px;border:1px solid transparent;background:none;color:var(--ink-2);cursor:pointer;text-decoration:none;transition:background .2s,border-color .2s}
.icon-b:hover{background:var(--panel);border-color:var(--rule)}
.icon-b .sun{display:none}
:root[data-theme="dark"] .icon-b .sun{display:block}
:root[data-theme="dark"] .icon-b .moon{display:none}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]) .icon-b .sun{display:block}:root:not([data-theme="light"]) .icon-b .moon{display:none}}
.burger{display:none}
.drawer{position:fixed;inset:0;top:calc(env(safe-area-inset-top,0px) + 64px);background:var(--bg);z-index:29;overflow:auto;padding:12px 16px 40px;opacity:0;visibility:hidden;transform:translateY(-10px);transition:opacity .25s var(--ease),transform .3s var(--ease),visibility 0s .3s}
.drawer.open{opacity:1;visibility:visible;transform:none;transition:opacity .25s var(--ease),transform .3s var(--ease)}
.drawer details{border-bottom:1px solid var(--rule)}
.drawer summary{list-style:none;cursor:pointer;display:flex;justify-content:space-between;align-items:center;padding:14px 4px;font-family:var(--display);font-size:1.35rem}
.drawer summary::-webkit-details-marker{display:none}
.drawer summary small{font:500 .75rem var(--sans);color:var(--muted);letter-spacing:.08em}
.drawer details ul{list-style:none;margin:0 0 12px;padding:0}
.drawer details a{display:block;padding:8px 4px;color:var(--ink);text-decoration:none;border-radius:8px}
.drawer details a.here{color:var(--accent);font-weight:600}
.drawer .dl{display:block;padding:14px 4px;font-family:var(--display);font-size:1.35rem;color:var(--ink);text-decoration:none;border-bottom:1px solid var(--rule)}
@media (max-width:1060px){.srch{min-width:0}.srch span,.srch kbd{display:none}}
@media (max-width:920px){.mnav{display:none}.burger{display:inline-grid}.hdr{justify-content:space-between}.tools{margin-left:auto}}
body.lock{overflow:hidden}

/* search palette */
.pal{position:fixed;inset:0;z-index:50;display:grid;align-items:start;justify-items:center;padding:12vh 16px 16px;background:color-mix(in srgb,var(--ink) 30%,transparent);backdrop-filter:blur(3px);-webkit-backdrop-filter:blur(3px);opacity:0;transition:opacity .2s}
.pal.open{opacity:1}
.pal-box{width:min(640px,100%);background:var(--panel);border:1px solid var(--rule);border-radius:16px;box-shadow:var(--shadow);overflow:hidden;transform:translateY(-8px) scale(.98);transition:transform .25s var(--ease)}
.pal.open .pal-box{transform:none}
.pal-in{display:flex;align-items:center;gap:10px;padding:14px 16px;border-bottom:1px solid var(--rule)}
.pal-in svg{width:18px;height:18px;fill:none;stroke:var(--muted);stroke-width:2}
.pal-in input{flex:1;border:0;background:none;font:inherit;font-size:1.05rem;color:var(--ink);outline:none;min-width:0}
.pal-res{max-height:52vh;overflow:auto;padding:6px}
.pal-res a{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:2px 12px;padding:10px 12px;border-radius:10px;text-decoration:none;color:var(--ink)}
.pal-res a small{grid-column:1;color:var(--muted);font-size:.83rem;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.pal-res a em{grid-row:1 / span 2;grid-column:2;align-self:center;font-style:normal;font-size:.72rem;letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
.pal-res a.sel{background:var(--accent-soft)}
.pal-res p{padding:14px;color:var(--muted);margin:0}

/* ---------- buttons ---------- */
.btn,.ghost{display:inline-flex;align-items:center;justify-content:center;gap:8px;border-radius:999px;font-weight:600;font-size:.95rem;text-decoration:none;transition:background .2s,color .2s,border-color .2s,transform .2s var(--ease),box-shadow .2s;letter-spacing:0}
.btn{background:var(--accent);color:var(--accent-ink);border:1px solid var(--accent);padding:10px 20px}
.btn:hover{background:var(--accent-deep);border-color:var(--accent-deep);box-shadow:var(--shadow-sm);filter:none}
.ghost{background:transparent;color:var(--ink);border:1px solid var(--rule-strong);padding:9px 18px}
.ghost:hover{border-color:var(--ink);color:var(--ink)}
.btn:active,.ghost:active{transform:translateY(1px)}
.btn .arr,.ghost .arr{transition:transform .3s var(--ease)}
.btn:hover .arr,.ghost:hover .arr{transform:translateX(4px)}
.q-head .ghost{padding:5px 13px;font-size:.82rem}
.menu-btn{display:none!important}

/* ---------- home hero ---------- */
.hero-band{background:var(--band);color:var(--band-ink);margin-inline:calc(50% - 50vw);padding-inline:calc(50vw - 50%);margin-top:-28px;position:relative;overflow:hidden;isolation:isolate}
.hero-band::before{content:"";position:absolute;inset:0;z-index:-1;background:repeating-linear-gradient(to bottom,transparent 0 35px,color-mix(in srgb,var(--band-ink) 7%,transparent) 35px 36px);mask-image:linear-gradient(100deg,transparent 30%,#000 70%);-webkit-mask-image:linear-gradient(100deg,transparent 30%,#000 70%)}
.hero-band::after{content:"";position:absolute;top:0;bottom:0;left:max(16px,calc(50% - 540px + 56%));width:1px;background:color-mix(in srgb,var(--margin) 70%,transparent);z-index:-1;transform-origin:top;animation:drawY 1.2s .2s var(--ease) both}
@keyframes drawY{from{transform:scaleY(0)}}
.hero2{display:grid;grid-template-columns:minmax(0,1.1fr) minmax(0,1fr);gap:48px;align-items:center;padding-block:72px 84px}
.hero2 .eyebrow{color:var(--band-muted)}
.hero2 h1{color:var(--band-ink);font-size:clamp(2.6rem,6vw,4.4rem)}
.hero2 h1 em{font-style:italic;color:color-mix(in srgb,var(--accent) 60%,var(--band-ink))}
.hero2 .lede{color:var(--band-muted);margin-top:1.2rem}
.hero2 .cta{display:flex;gap:12px;flex-wrap:wrap;margin-top:2rem}
.hero2 .btn{background:var(--band-ink);color:var(--band);border-color:var(--band-ink)}
.hero2 .btn:hover{background:#fff;border-color:#fff}
.hero2 .ghost{color:var(--band-ink);border-color:color-mix(in srgb,var(--band-ink) 35%,transparent)}
.hero2 .ghost:hover{border-color:var(--band-ink)}
.hero2 > div > *{animation:rise .8s var(--ease) both}
.hero2 > div > *:nth-child(2){animation-delay:.08s}.hero2 > div > *:nth-child(3){animation-delay:.16s}.hero2 > div > *:nth-child(4){animation-delay:.24s}
.hero-stats{display:flex;gap:28px;flex-wrap:wrap;margin-top:2.4rem;padding-top:1.4rem;border-top:1px solid color-mix(in srgb,var(--band-ink) 15%,transparent)}
.hero-stats div{display:grid}
.hero-stats b{font-family:var(--display);font-size:2rem;font-weight:500;line-height:1;color:var(--band-ink);font-variant-numeric:tabular-nums}
.hero-stats span{font-size:.8rem;color:var(--band-muted);letter-spacing:.04em}
/* the journal card */
.jcard{background:var(--panel);color:var(--ink);border-radius:14px;box-shadow:0 30px 60px -20px rgba(0,0,0,.5);padding:22px 24px 20px;transform:rotate(1.2deg);animation:cardIn 1s .15s var(--ease) both;position:relative}
@keyframes cardIn{from{opacity:0;transform:translateY(30px) rotate(4deg)}}
.jcard:hover{transform:rotate(0)}
.jcard{transition:transform .6s var(--ease)}
.jhead{display:flex;justify-content:space-between;align-items:baseline;border-bottom:2px solid var(--ink);padding-bottom:8px;margin-bottom:4px}
.jhead b{font-family:var(--display);font-size:1.15rem;font-weight:600}
.jhead span{font:500 .72rem var(--mono);color:var(--muted);letter-spacing:.06em}
.jrow{display:grid;grid-template-columns:minmax(0,1fr) 5.5rem 5.5rem;gap:8px;padding:8px 0;border-bottom:1px solid var(--rule);font-size:.95rem;align-items:baseline}
.jrow.h{font:600 .7rem var(--sans);letter-spacing:.1em;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--rule-strong)}
.jrow .amt{text-align:right;font-size:.9rem}
.jrow.cr span:first-child{padding-left:1.6rem}
.jrow.nar{font-family:var(--display);font-style:italic;color:var(--muted);font-size:.92rem}
.jrow.tot{border-bottom:0;font-weight:600}
.jrow.tot .amt{border-top:1px solid var(--ink);box-shadow:0 3px 0 -1px var(--panel),0 4px 0 -1px var(--ink)}
.jcard .w{display:inline-block;clip-path:inset(0 100% 0 0);animation:write .7s steps(18,end) both}
@keyframes write{to{clip-path:inset(0 0 0 0)}}
.jcard .d1{animation-delay:.9s}.jcard .d2{animation-delay:1.3s}.jcard .d3{animation-delay:1.8s}.jcard .d4{animation-delay:2.2s}.jcard .d5{animation-delay:2.7s}.jcard .d6{animation-delay:3.1s}.jcard .d7{animation-delay:3.5s}
.jstamp{position:absolute;right:18px;bottom:-16px;display:inline-flex;align-items:center;gap:6px;background:var(--accent);color:var(--accent-ink);font:600 .8rem var(--sans);padding:6px 12px;border-radius:999px;box-shadow:var(--shadow-sm);animation:stamp .5s 4s cubic-bezier(.3,1.6,.5,1) both}
.jstamp svg{width:14px;height:14px;fill:none;stroke:currentColor;stroke-width:3}
@keyframes stamp{from{opacity:0;transform:scale(1.6) rotate(-8deg)}}
.jcard.cycle .w{animation:none;clip-path:inset(0 100% 0 0)}
.jcard.cycle .jstamp{animation:none;opacity:0}

/* ---------- home chapters ---------- */
.chapter{margin-top:88px}
.chap-h{display:grid;grid-template-columns:auto minmax(0,1fr);gap:4px 28px;align-items:end;margin-bottom:28px;padding-bottom:20px;border-bottom:1px solid var(--rule)}
.chap-h .num{font-family:var(--display);font-style:italic;font-size:clamp(3rem,7vw,5rem);line-height:.8;color:var(--accent);grid-row:span 2}
.chap-h h2{font-size:clamp(1.8rem,3.4vw,2.5rem);margin:0;padding:0;border:0;display:block}
.chap-h p{margin:0;color:var(--muted);max-width:62ch}
.topic-rows{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:14px;border:0}
.topic-row{position:relative;display:flex;flex-direction:column;gap:6px;padding:22px 22px 18px;background:var(--panel);border:1px solid var(--rule);border-radius:14px;text-decoration:none;color:var(--ink);transition:transform .35s var(--ease),box-shadow .35s var(--ease),border-color .35s;overflow:hidden}
.topic-row::before{content:"";position:absolute;left:0;right:0;top:0;height:2px;background:var(--accent);transform:scaleX(0);transform-origin:left;transition:transform .45s var(--ease)}
.topic-row:hover{transform:translateY(-4px);box-shadow:var(--shadow);border-color:var(--rule-strong)}
.topic-row:hover::before{transform:scaleX(1)}
.topic-row b{font-family:var(--display);font-size:1.28rem;font-weight:500;line-height:1.25}
.topic-row span{color:var(--muted);font-size:.92rem;line-height:1.55;flex:1}
.topic-row em{font-style:normal;font-size:.82rem;font-weight:600;color:var(--accent);margin-top:8px;display:flex;justify-content:space-between;align-items:center}
.topic-row em::after{content:"→";transition:transform .35s var(--ease)}
.topic-row:hover em::after{transform:translateX(5px)}
.topic-row .done-mark{position:absolute;top:16px;right:16px;display:inline-flex;align-items:center;gap:4px;font-size:.72rem;font-weight:600;color:var(--ok);background:var(--ok-soft);padding:2px 9px;border-radius:999px}
.steps{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:0;margin-top:1rem;border-top:1px solid var(--rule)}
.steps div{padding:20px 24px 8px 0;border:0;background:none}
.steps div + div{padding-left:24px;border-left:1px solid var(--rule)}
.steps b{font-family:var(--display);font-weight:500;font-size:1.3rem}
.feature{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:20px;align-items:center;background:var(--panel);border:1px solid var(--rule);border-radius:14px;padding:24px 26px}
.duo{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:14px}
.duo h2{font-size:1.5rem;margin-bottom:.6rem}
@media (max-width:860px){.hero2{grid-template-columns:1fr;padding-block:48px 64px}.jcard{max-width:520px}.hero-band::after{display:none}.steps div + div{padding-left:0;border-left:0;border-top:1px solid var(--rule)}}

/* ---------- lesson layout ---------- */
main.wrap{padding-block:28px 96px}
main.with-side{max-width:1240px;display:grid;grid-template-columns:250px minmax(0,1fr);gap:56px;align-items:start}
.lside{position:sticky;top:calc(env(safe-area-inset-top,0px) + 92px);max-height:calc(100vh - 110px);overflow:auto;font-size:.9rem;padding-right:6px;scrollbar-width:thin}
.lside h4{font:600 .7rem var(--sans);letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin:0 0 .6rem}
.lside ol{list-style:none;margin:0 0 1.8rem;padding:0;counter-reset:t;border-left:1px solid var(--rule)}
.lside ol a{position:relative;display:grid;grid-template-columns:1.6rem minmax(0,1fr);padding:6px 8px 6px 14px;color:var(--ink-2);text-decoration:none;line-height:1.4;transition:color .2s,background .2s}
.lside ol a::before{counter-increment:t;content:counter(t,decimal-leading-zero);font:500 .72rem var(--mono);color:var(--muted);padding-top:2px}
.lside ol a::after{content:"";position:absolute;left:-1px;top:6px;bottom:6px;width:2px;background:var(--accent);transform:scaleY(0);transition:transform .3s var(--ease)}
.lside ol a:hover{color:var(--ink)}
.lside ol a.here{color:var(--ink);font-weight:600}
.lside ol a.here::after{transform:scaleY(1)}
.lside ol a.done::before{content:"✓";color:var(--ok)}
.lside ul{list-style:none;margin:0;padding:0}
.lside ul a{display:block;padding:5px 0 5px 14px;color:var(--muted);text-decoration:none;border-left:1px solid var(--rule);transition:color .2s,border-color .2s}
.lside ul a.on{color:var(--accent);border-left-color:var(--accent);font-weight:600}
.with-side .article{max-width:780px}
.with-side .toc{display:none}
@media (max-width:1000px){main.with-side{display:block}.lside{display:none}.with-side .toc{display:flex}}
.article h1{margin-bottom:.2rem}
.toc{border:1px solid var(--rule);border-radius:12px;background:var(--panel)}
.toc a{font-weight:600;text-decoration:none}
section.block{margin-top:3.4rem}
section.block > h2{display:flex;align-items:baseline;gap:14px;border-bottom:0;padding-bottom:0;margin-bottom:1.2rem}
section.block > h2::after{content:"";flex:1;height:1px;background:var(--rule);transform-origin:left;transition:transform 1s var(--ease)}
section.block.rv > h2::after{transform:scaleX(0)}
section.block.rv.in > h2::after{transform:scaleX(1)}
.plain{position:relative;border:1px solid var(--rule);border-radius:14px;background:var(--panel);padding:22px 24px 22px 44px;overflow:hidden}
.plain::before{content:"";position:absolute;left:26px;top:0;bottom:0;width:1px;background:color-mix(in srgb,var(--margin) 55%,transparent)}
.plain::after{content:"";position:absolute;inset:0;pointer-events:none;background:repeating-linear-gradient(to bottom,transparent 0 29px,color-mix(in srgb,var(--accent) 7%,transparent) 29px 30px)}
.plain p{font-size:1.04rem}
.plain .eg{background:var(--ledger);border-radius:10px;position:relative;z-index:1}
dl.words dt{font-family:var(--display);font-weight:600;font-size:1.05rem}
.kw-eg{color:var(--ink-2)}
.formula{border-left:0;border-radius:10px;background:var(--ledger);box-shadow:inset 3px 0 0 var(--margin);font-weight:500;color:var(--ink)}
.note{border-left:0;border-radius:12px;box-shadow:inset 3px 0 0 var(--accent)}
.note.warn{box-shadow:inset 3px 0 0 var(--bad)}
.acca-tag{border:1px solid var(--rule);color:var(--ink-2);background:var(--panel);font-weight:500}
table.ledger{background:var(--panel)}
table.ledger tbody tr{transition:background .2s}
table.ledger tbody tr:hover td{background:var(--ledger)}
.pager{border-top:0;gap:14px;margin-top:4rem}
.pager a{flex:1;min-width:240px;max-width:none;border:1px solid var(--rule);border-radius:14px;padding:16px 20px;background:var(--panel);transition:transform .35s var(--ease),box-shadow .35s,border-color .35s}
.pager a:hover{transform:translateY(-3px);box-shadow:var(--shadow);border-color:var(--rule-strong)}
.pager a b{font-family:var(--display);font-weight:500;font-size:1.2rem}
.done-row{border:1px solid var(--rule);border-radius:12px;background:var(--panel)}

/* ---------- questions ---------- */
.q{background:var(--panel);border:1px solid var(--rule);border-radius:16px;padding:24px;transition:border-color .5s,box-shadow .5s}
.q:focus-within{box-shadow:var(--shadow-sm);border-color:var(--rule-strong)}
.q.solved{border-color:color-mix(in srgb,var(--ok) 50%,var(--rule))}
.q-head h3{font-size:1.2rem;margin:0}
.tag{border:1px solid var(--rule);background:none;color:var(--muted);border-radius:999px}
.fb{border-radius:12px;border-left:0!important;animation:fbIn .45s var(--ease) both}
@keyframes fbIn{from{opacity:0;transform:translateY(-6px)}}
.fb.good{background:var(--ok-soft)}
.fb.part{background:var(--bad-soft)}
.fb.shown{background:var(--ledger)}
.fb-title{display:flex;align-items:center;gap:8px}
.tick{width:22px;height:22px;flex:none;fill:none;stroke:var(--ok);stroke-width:2;stroke-linecap:round;stroke-linejoin:round}
.tick circle{stroke-dasharray:66;stroke-dashoffset:66;animation:dash .6s var(--ease) forwards}
.tick path{stroke-dasharray:16;stroke-dashoffset:16;animation:dash .35s .45s var(--ease) forwards}
@keyframes dash{to{stroke-dashoffset:0}}
.fb.good .fb-title b{color:var(--ok)}
.mcq label{border-radius:10px;transition:border-color .2s,background .2s}
.mcq label:has(input:checked){border-color:var(--accent);background:var(--accent-soft)}
.seg button{border-radius:8px;transition:background .2s,border-color .2s,color .2s}
input.num,select,textarea{border-radius:8px;transition:border-color .2s,box-shadow .2s}
input.num:focus,select:focus,textarea:focus{border-color:var(--accent);outline:none;box-shadow:0 0 0 3px var(--accent-soft)}

/* ---------- footer ---------- */
.site-foot{border-top:1px solid var(--rule);background:var(--panel);padding-block:56px 48px}
.site-foot .brandline b{font-family:var(--display);font-weight:500;font-size:1.6rem}
.site-foot h4{margin-top:.2rem}
.site-foot a{transition:color .2s}
.totop{position:fixed;right:18px;bottom:calc(env(safe-area-inset-bottom,0px) + 18px);z-index:20;width:44px;height:44px;border-radius:50%;border:1px solid var(--rule);background:var(--panel);color:var(--ink);box-shadow:var(--shadow-sm);display:grid;place-content:center;cursor:pointer;opacity:0;transform:translateY(12px);pointer-events:none;transition:opacity .3s,transform .3s var(--ease)}
.totop.show{opacity:1;transform:none;pointer-events:auto}
.totop svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2}

/* ---------- scroll reveal ---------- */
.rv{opacity:0;transform:translateY(22px);transition:opacity .8s var(--ease),transform .8s var(--ease);transition-delay:var(--d,0s)}
.rv.in{opacity:1;transform:none}
@media (prefers-reduced-motion: reduce){
  *,*::before,*::after{animation:none!important;transition:none!important}
  .rv{opacity:1;transform:none}
  .jcard .w{clip-path:none}
  html{scroll-behavior:auto}
}
body{margin:0}
.hdr .brand{order:0;margin:0}
.hdr .mnav{order:1}
.hdr .tools{order:2}
.mt,.ml{white-space:nowrap}
.plain::after{display:none}
.topic-row em{width:100%}
.topic-row em::after{margin-left:auto}
.hero-stats{gap:14px 28px}
@media (max-width:1300px){.srch{min-width:0}.srch span,.srch kbd{display:none}}
@media (max-width:1120px){.mnav{display:none}.burger{display:inline-grid}.tools{margin-left:auto}}
@media (max-width:1120px) and (min-width:921px){.drawer{max-width:none}}
.site-head .wrap.hdr{max-width:1240px;gap:18px}
@media (max-width:1400px){.srch{min-width:0;padding:9px}.srch span,.srch kbd{display:none}}
@media (max-width:1200px){.mnav{display:none}.burger{display:inline-grid}.tools{margin-left:auto}}

.hero2 h1 em{color:var(--gold-hi)}
@media (max-width:420px){.icon-b{width:34px;height:34px}.srch{padding:7px}.tools{gap:2px}.hdr .brand b{font-size:1.25rem}.hdr{gap:10px}}
/* Trial Balance logo: a navy disc with a gold GS and a bite out of the edge */
.gs-logo{overflow:visible;transition:transform .8s var(--ease);transform-style:preserve-3d}
.gs-ring{fill:none;stroke:#D9AC4B;stroke-width:.9;opacity:.6}
.gs-mark{fill:#D9AC4B;font:600 13px "Newsreader",Georgia,"Times New Roman",serif;letter-spacing:-.4px}
.gs-disc{fill:#13223F;stroke:#D9AC4B;stroke-width:.6;stroke-opacity:.5}
.brand:hover .gs-logo{transform:rotateY(360deg)}
.hdr .brand svg{transform:none}
.brand:hover svg.gs-logo{transform:rotateY(360deg)}
.gs-logo mask rect{fill:#fff!important;stroke:none!important}.gs-logo mask circle{fill:#000!important}

/* =================== animated explainers + videos =================== */
.xp{background:var(--band);color:var(--band-ink);border-radius:18px;overflow:hidden;box-shadow:var(--shadow);position:relative;isolation:isolate}
.xp::before{content:"";position:absolute;inset:0;z-index:-1;background:repeating-linear-gradient(to bottom,transparent 0 31px,rgba(255,255,255,.035) 31px 32px)}
.xp-top{display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:14px 20px;border-bottom:1px solid rgba(255,255,255,.08)}
.xp-top b{font-family:var(--display);font-weight:500;font-size:1.15rem;color:var(--band-ink)}
.xp-badge{font:600 .66rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:#13223F;background:var(--gold-hi);padding:3px 9px;border-radius:999px}
.xp-count{margin-left:auto;font:500 .78rem var(--mono);color:var(--band-muted)}
.xp-stage{padding:22px 22px 10px;min-height:300px;font-size:.93rem;color:var(--band-ink)}
.xp-stage .xa{font-family:var(--mono);font-variant-numeric:tabular-nums;text-align:right;white-space:nowrap}
.xp-cap{margin:0;padding:12px 22px 14px;min-height:5.2em;font-family:var(--display);font-size:1.12rem;line-height:1.45;color:var(--band-ink);border-top:1px solid rgba(255,255,255,.08);background:rgba(0,0,0,.14)}
.xp-ctl{display:flex;align-items:center;gap:8px;padding:10px 16px 14px;background:rgba(0,0,0,.14)}
.xp-b{display:grid;place-content:center;width:38px;height:38px;border-radius:50%;border:1px solid rgba(255,255,255,.18);background:rgba(255,255,255,.06);color:var(--band-ink);cursor:pointer;transition:background .2s,transform .2s}
.xp-b:hover:not(:disabled){background:rgba(255,255,255,.14)}
.xp-b:disabled{opacity:.35;cursor:default}
.xp-b svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2.2;stroke-linecap:round;stroke-linejoin:round}
.xp-play{width:46px;height:46px;background:var(--gold-hi);border-color:var(--gold-hi);color:#13223F}
.xp-play:hover:not(:disabled){background:#F0C766}
.xp-play svg{fill:currentColor;stroke:none;width:20px;height:20px}
.xp-seg{flex:1;display:flex;gap:4px;margin-left:8px}
.xp-seg button{flex:1;height:18px;padding:0;border:0;background:none;cursor:pointer;display:flex;align-items:center}
.xp-seg button i{display:block;height:4px;border-radius:2px;background:var(--gold-hi);width:0;box-shadow:0 0 0 100vmax rgba(255,255,255,.14) inset}
.xp-seg button{position:relative}
.xp-seg button::before{content:"";position:absolute;left:0;right:0;top:7px;height:4px;border-radius:2px;background:rgba(255,255,255,.16)}
.xp-seg button i{position:relative;box-shadow:none}
.xp-seg button.cur::before{background:rgba(255,255,255,.28)}
/* stage element states */
.xp-stage [data-s],.xp-stage [data-e]{transition:opacity .5s var(--ease),transform .5s var(--ease),background .4s,box-shadow .4s}
.xp-stage .off{opacity:0;transform:translateY(8px);pointer-events:none}
.xp-stage .on{opacity:1;transform:none}
.xp-stage .hl{background:rgba(217,172,75,.16);box-shadow:0 0 0 1.5px rgba(217,172,75,.75);border-radius:8px}
.xp-stage .flip{animation:flip .5s var(--ease)}
@keyframes flip{0%{opacity:.2;transform:translateY(-6px)}100%{opacity:1;transform:none}}
.xp-stage h5{margin:0 0 8px;font:600 .7rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--gold-hi)}
.xr{display:flex;justify-content:space-between;gap:10px;padding:6px 8px;border-bottom:1px solid rgba(255,255,255,.08)}
.xr.cr span:first-child{padding-left:1.2rem}
.xr.ghost{visibility:hidden}
.xr.sub{color:var(--band-muted);font-style:italic;border-bottom:0}
.xr.tot{border-bottom:0;font-weight:600}
.xr.bd{color:var(--gold-hi);font-weight:600}
.xa.dbl{border-top:1px solid currentColor;border-bottom:3px double currentColor}
.xa.tl{border-top:1px solid currentColor}
.x-check{margin-top:14px;display:inline-flex;align-items:center;gap:8px;padding:6px 14px;border-radius:999px;background:#2F7A55;color:#fff;font-weight:600;font-size:.88rem}
.x-note{margin-top:12px;padding:8px 12px;border-radius:10px;background:rgba(255,255,255,.07);color:var(--band-ink);font-size:.88rem}
.x-note.warn{background:rgba(255,138,115,.14)}
.x-q{display:inline-block;padding:8px 14px;border-radius:10px;background:var(--band-ink);color:#13223F;font-family:var(--display);font-style:italic;font-size:1.05rem;margin-bottom:12px}
/* equation */
.x-eq{display:grid;grid-template-columns:minmax(0,1fr) auto minmax(0,1fr) auto minmax(0,1fr);gap:10px;align-items:start}
.x-col{background:rgba(255,255,255,.05);border-radius:12px;padding:10px 8px;min-width:0}
.x-op{font-family:var(--display);font-size:2rem;color:var(--gold-hi);align-self:center}
.x-tot{display:flex;justify-content:space-between;padding:8px 8px 2px;margin-top:4px;border-top:2px solid rgba(255,255,255,.35);font-weight:600}
.x-tot b{font-family:var(--mono)}
/* dead clic */
.x-dc{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.x-dcc{background:rgba(255,255,255,.05);border-radius:12px;padding:10px}
.x-l{padding:5px 8px;font-size:1rem}
.x-l b{font-family:var(--display);font-size:1.35rem;color:var(--gold-hi);font-weight:600}
.x-l em{font-style:normal;color:var(--gold-hi);font-weight:600}
.x-ex{margin-top:14px}
.x-an{display:grid;gap:4px;margin-bottom:10px}
/* tables */
.x-tbl{background:rgba(255,255,255,.04);border-radius:12px;padding:6px 10px}
.xs3,.xs4{display:grid;grid-template-columns:minmax(0,1fr) 6.5rem 6.5rem;gap:8px;padding:6px 8px;border-bottom:1px solid rgba(255,255,255,.07);align-items:baseline}
.xs4{grid-template-columns:minmax(0,1fr) 5.5rem 5.5rem 6rem}
.xh{font:600 .68rem var(--sans);letter-spacing:.1em;text-transform:uppercase;color:var(--band-muted);border-bottom:1px solid rgba(255,255,255,.3)}
.xs3.narr{font-family:var(--display);font-style:italic;color:var(--band-muted)}
.xs3.tot,.xs4.tot{border-bottom:0}
.xs4.tl{border-top:1px solid rgba(255,255,255,.35)}
.ind{font-style:normal;padding-left:1.4rem;display:inline-block}
.x-stt{font-family:var(--display);font-weight:600;text-align:center;padding:4px 0 8px;border-bottom:2px solid rgba(255,255,255,.5);margin-bottom:4px}
.stmt .xs3{padding-block:4px}
/* T account */
.x-t{max-width:560px;margin:0 auto}
.x-tn{text-align:center;font-family:var(--display);font-size:1.2rem;font-weight:600;padding-bottom:6px;border-bottom:2px solid var(--band-ink)}
.x-tc{display:grid;grid-template-columns:1fr 1fr}
.x-ts + .x-ts{border-left:2px solid var(--band-ink)}
.x-th{font:600 .68rem var(--sans);letter-spacing:.1em;color:var(--band-muted);padding:4px 8px}
/* timeline */
.x-year,.x-tl{display:grid;grid-template-columns:6.5rem minmax(0,1fr);gap:8px;align-items:center}
.x-mo{display:grid;grid-template-columns:repeat(12,minmax(0,1fr));gap:3px}
.x-year i{font:500 .7rem var(--mono);text-align:center;color:var(--band-muted);font-style:normal}
.x-tl{margin-top:8px}
.x-tll{font-weight:600;font-size:.9rem}
.x-mo b{display:block;height:22px;border-radius:5px;transition-delay:var(--d,0ms)}
.x-mo b.paid{background:#4F8BE8}
.x-mo b.owed{background:repeating-linear-gradient(45deg,var(--gold-hi) 0 5px,rgba(217,172,75,.45) 5px 10px)}
.x-mo b.empty{background:rgba(255,255,255,.06)}
.x-fig{display:flex;flex-wrap:wrap;gap:6px 14px;margin:8px 0 6px 7rem;font-size:.86rem}
.x-fig span{padding:2px 8px}
.x-fig .o{color:var(--gold-hi)}.x-fig .k{font-weight:600}.x-fig .p{color:#8FC0FF}
.x-jn{display:grid;gap:6px;margin-top:10px;font:500 .84rem var(--mono)}
.x-jn span{padding:6px 10px;background:rgba(255,255,255,.06);border-radius:8px}
/* depreciation */
.x-dep{display:grid;grid-template-columns:minmax(0,1.4fr) minmax(0,1fr);gap:18px;align-items:end}
.x-leg{grid-column:1 / -1;font:600 .7rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--gold-hi)}
.x-bars{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:8px;align-items:end;height:220px}
.x-bar{display:flex;flex-direction:column;align-items:center;justify-content:flex-end;height:100%;gap:4px}
.x-bar i{display:block;width:100%;max-width:48px;border-radius:6px 6px 2px 2px;background:linear-gradient(180deg,#6FA3F0,#3B6FC4);transition:height .7s var(--ease)}
.x-bar b{font-size:.74rem;font-weight:500}
.x-bar span{font-size:.72rem;color:var(--band-muted)}
.x-side{display:grid;gap:8px;align-self:center}
.x-f{padding:10px 12px;border-radius:10px;background:rgba(255,255,255,.07);font:500 .84rem/1.5 var(--mono)}
.x-f b{color:var(--gold-hi)}
/* margin */
.x-mm{margin-bottom:14px}
.x-mmh{display:flex;justify-content:space-between;font-weight:600;padding:0 4px 6px}
.x-split{display:grid;grid-template-columns:4fr 1fr;height:54px;border-radius:10px;overflow:hidden}
.x-split > div{display:flex;flex-direction:column;justify-content:center;padding:0 12px;font-size:.8rem}
.x-split .c{background:#3B6FC4}.x-split .p{background:var(--gold-hi);color:#13223F}
.x-split b{font-size:.95rem}
.x-lab{display:grid;gap:4px;margin-top:10px;font-size:.9rem}
.x-lab b{color:var(--gold-hi)}

b.qm{color:var(--gold-hi)}
@media (max-width:560px){
  .xp-stage{padding:16px 12px 8px;font-size:.84rem}
  .x-eq{grid-template-columns:1fr;gap:6px}.x-op{text-align:center;font-size:1.4rem;line-height:1}
  .x-dc{grid-template-columns:1fr 1fr;gap:8px}.x-l{font-size:.88rem;padding:4px}
  .xs3{grid-template-columns:minmax(0,1fr) 4.8rem 4.8rem;gap:4px;padding:5px 4px}
  .xs4{grid-template-columns:minmax(0,1fr) 4rem 4rem 4.6rem;gap:4px;padding:5px 2px;font-size:.78rem}
  .x-year,.x-tl{grid-template-columns:4.6rem minmax(0,1fr)}.x-fig{margin-left:0}
  .x-dep{grid-template-columns:1fr}.x-bars{height:170px}
  .xp-cap{font-size:1rem}.xp-seg{margin-left:2px}
}
/* videos */
.vids{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px;margin-top:.6rem}
.vid{display:flex;flex-direction:column;background:var(--panel);border:1px solid var(--rule);border-radius:14px;overflow:hidden;text-decoration:none;color:var(--ink);transition:transform .35s var(--ease),box-shadow .35s,border-color .35s}
a.vid:hover{transform:translateY(-3px);box-shadow:var(--shadow);border-color:var(--rule-strong)}
.vid-th{position:relative;display:block;aspect-ratio:16/9;max-width:100%;background:linear-gradient(135deg,var(--band),var(--band-2));overflow:hidden}
.vid-th img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;transition:transform .5s var(--ease)}
a.vid:hover .vid-th img{transform:scale(1.04)}
.vid-th iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.vid-pl{position:absolute;left:50%;top:50%;width:56px;height:56px;margin:-28px 0 0 -28px;border-radius:50%;background:rgba(19,34,63,.85);display:grid;place-content:center;color:#fff;transition:transform .3s var(--ease),background .3s}
.vid-pl svg{width:22px;height:22px;fill:currentColor;margin-left:3px}
a.vid:hover .vid-pl{transform:scale(1.1);background:#D9AC4B;color:#13223F}
.vid-tx{display:grid;gap:2px;padding:12px 14px 14px}
.vid-tx b{font-weight:600;font-size:.95rem;line-height:1.35}
.vid-tx small{color:var(--muted);font-size:.8rem}
#watch h3{margin-top:2rem}
.x-trk{position:relative;flex:1;width:100%;max-width:52px}
.x-trk i{position:absolute;left:0;right:0;bottom:0;max-width:none}
.x-trk i b{position:absolute;left:50%;bottom:100%;transform:translate(-50%,-4px);white-space:nowrap}
.x-bars{padding-top:22px}
.xr{min-height:2.3em;align-items:center}
.x-lab .off,.x-side .off{display:none}
/* explainer scenes: statements, year 3, industry, jobs */
.x-card{background:rgba(255,255,255,.06);border-radius:12px;padding:10px 12px;display:grid;gap:3px;min-width:0}
.x-card b{font:600 .72rem var(--sans);letter-spacing:.08em;text-transform:uppercase;color:var(--band-muted)}
.x-card span{font-size:.92rem;line-height:1.45}
.x-card em{font-style:normal;font-family:var(--mono);color:var(--gold-hi);font-weight:600}
.x-card em.big{display:block;font-family:var(--display);font-size:1.9rem;font-weight:500;line-height:1.1;color:var(--gold-hi)}
.x-card.gold{background:rgba(217,172,75,.2)}
.x-card.dim{opacity:.7}
.x-card.mono span{font-family:var(--mono);font-size:.85rem}
.x-cards{display:grid;gap:10px}
.x-cards.c2{grid-template-columns:repeat(2,minmax(0,1fr))}
.x-cards.c3{grid-template-columns:repeat(3,minmax(0,1fr))}
.x-cards.c5{grid-template-columns:repeat(5,minmax(0,1fr));margin-top:12px}
.x-cards.c5 .x-card{text-align:center}
.x-two{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:10px}
.x-split2{display:grid;grid-template-columns:minmax(0,1.6fr) minmax(0,1fr);gap:14px;align-items:start}
.x-gauges{display:grid;gap:10px}
.x-sort{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}
.x-bin{background:rgba(255,255,255,.04);border-radius:12px;padding:10px;display:flex;flex-wrap:wrap;gap:6px;align-content:flex-start}
.x-bin h5{width:100%}
.x-bin .x-card,.x-bin .x-tbl{width:100%;margin-top:6px}
.x-chip{display:inline-block;padding:5px 11px;border-radius:999px;background:#3B6FC4;color:#fff;font-size:.85rem}
.x-chip.gold{background:var(--gold-hi);color:#13223F}
.x-wf{display:grid;grid-template-columns:repeat(6,minmax(0,1fr));gap:8px;height:230px;padding-top:20px}
.x-wfc{display:flex;flex-direction:column;height:100%;gap:4px;min-width:0}
.x-wft{position:relative;flex:1}
.x-wft i{position:absolute;left:12%;right:12%;border-radius:4px}
.x-wft i.up{background:#4F8BE8}.x-wft i.down{background:#E0674B}.x-wft i.tot{background:var(--gold-hi)}
.x-wft i b{position:absolute;left:50%;bottom:100%;transform:translate(-50%,-3px);font-size:.72rem;white-space:nowrap}
.x-wfc > span{font-size:.72rem;color:var(--band-muted);text-align:center;line-height:1.2}
.x-steps{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:12px}
.x-stp{display:inline-flex;align-items:center;gap:6px;padding:5px 10px 5px 5px;border-radius:999px;background:rgba(255,255,255,.07);font-size:.86rem}
.x-stp i{display:grid;place-content:center;width:22px;height:22px;border-radius:50%;background:var(--gold-hi);color:#13223F;font:700 .75rem var(--sans);font-style:normal}
.x-flow{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:8px;margin-bottom:6px}
.x-tlbar{display:grid;grid-template-columns:1fr auto 3fr;gap:6px;align-items:stretch}
.x-ph{border-radius:10px;padding:10px 12px;display:grid;gap:2px}
.x-ph.r{background:rgba(224,103,75,.3)}.x-ph.d{background:rgba(79,139,232,.35)}.x-ph.m{background:rgba(217,172,75,.25);font-size:.8rem;text-align:center;align-content:center}
.x-ph b{font-weight:600}.x-ph span{font-family:var(--mono);font-size:.82rem}
.x-star{display:grid;gap:8px}
.x-sr{display:grid;grid-template-columns:40px 7rem minmax(0,1fr);gap:12px;align-items:center;padding:8px 10px;border-radius:12px;background:rgba(255,255,255,.05)}
.x-sr i{display:grid;place-content:center;width:36px;height:36px;border-radius:50%;background:var(--gold-hi);color:#13223F;font:700 1.1rem var(--display);font-style:normal}
.x-sr b{font-family:var(--display);font-size:1.1rem;font-weight:500}
.x-sr span{color:var(--band-muted);font-size:.9rem}
.x-bar2{display:flex;margin-top:12px;border-radius:8px;overflow:hidden;font:600 .8rem var(--sans)}
.x-bar2 span{padding:6px 0;text-align:center;background:rgba(255,255,255,.12)}
.x-bar2 span.big{background:var(--gold-hi);color:#13223F}
.x-xl{border-radius:8px;overflow:hidden;font-size:.85rem;background:rgba(255,255,255,.04)}
.x-xr{display:grid;grid-template-columns:1fr 1fr 1fr 1fr;gap:6px;padding:5px 10px;border-bottom:1px solid rgba(255,255,255,.07)}
.x-xr.h{font:600 .68rem var(--sans);letter-spacing:.06em;text-transform:uppercase;color:var(--band-muted)}
.x-arrows{display:grid;gap:6px;margin:10px 0}
.x-arr{padding:7px 12px;border-radius:999px;background:rgba(255,255,255,.07);font-size:.86rem}
.x-arr.r::after{content:" →"}.x-arr.l::before{content:"← "}
.x-check2{display:grid;gap:6px}
.x-ck{display:flex;align-items:center;gap:10px;padding:7px 10px;border-radius:10px;background:rgba(255,255,255,.05)}
.x-ck i{display:grid;place-content:center;width:22px;height:22px;border-radius:50%;background:#2F7A55;color:#fff;font-style:normal;font-size:.8rem}
.x-fc{position:relative;display:grid;grid-template-columns:repeat(7,minmax(0,1fr));gap:8px;height:230px;padding-bottom:20px}
.x-fcz{position:absolute;left:0;right:0;height:1px;background:rgba(255,255,255,.4)}
.x-fcl{position:absolute;left:0;right:0;border-top:2px dashed #E0674B}
.x-fcl span{position:absolute;right:0;top:2px;font-size:.7rem;color:#FF9C85}
.x-fcc{position:relative;height:100%}
.x-fcc i{position:absolute;left:15%;right:15%;background:#4F8BE8;border-radius:3px}
.x-fcc i.neg{background:#8FA3C4}.x-fcc i.bad{background:#E0674B}
.x-fcc b{position:absolute;left:50%;transform:translateX(-50%);font-size:.72rem;white-space:nowrap}
.x-fcc > span{position:absolute;left:0;right:0;bottom:-20px;text-align:center;font-size:.72rem;color:var(--band-muted)}
.xs4.dimrow{opacity:.55}
.x-xr.hl,.xs4.hl{border-radius:6px}
@media (max-width:560px){
  .x-cards.c2,.x-cards.c3,.x-two,.x-split2,.x-sort,.x-flow{grid-template-columns:1fr}
  .x-cards.c5{grid-template-columns:repeat(5,minmax(0,1fr));gap:4px}.x-cards.c5 .x-card{padding:6px 2px}.x-cards.c5 .x-card span{font-size:.7rem}
  .x-wf{height:190px;gap:4px}.x-fc{height:190px;gap:4px}
  .x-sr{grid-template-columns:34px minmax(0,1fr);row-gap:0}.x-sr span{grid-column:2}
  .x-tlbar{grid-template-columns:1fr}
  .x-xr{font-size:.74rem;gap:2px;padding:5px 6px}
}
.xs4{grid-template-columns:minmax(0,1fr) 6.5rem 7.5rem 7.5rem}
.xs4 .xa{white-space:normal}
.x-two .xs3{grid-template-columns:minmax(0,1fr) 3.4rem 4.8rem;gap:6px}
.x-fcl span{left:0;right:auto;top:-18px}
@media (max-width:560px){.xs4{grid-template-columns:minmax(0,1fr) 4rem 4.4rem 4.6rem}}
.x-xr span:nth-child(3){padding-right:10px}

/* =================== v6: gradient artwork look =================== */
:root{
  --bg:#F5F4F8; --panel:#FFFFFF; --ink:#232326; --ink-2:#3A3A40; --muted:#6E6E78; --rule:#E6E4EC; --rule-strong:#C4C1CE;
  --ledger:#F1EFF5; --accent:#5B3DF5; --accent-deep:#4527D6; --accent-ink:#FFFFFF; --accent-soft:#ECE8FF;
  --band:#2B2B2F; --band-2:#35353A; --band-ink:#F5F5F7; --band-muted:#A9A9B3; --gold-hi:#FF8A5C;
  --ok:#1F8A5B; --ok-soft:#E2F4EA; --bad:#D6453D; --bad-soft:#FCEBE9; --margin:#FF4F8B;
  --gold:#E0672F; --gold-soft:#FFEFE6; --gold-ink:#8A3A12;
  --shadow:0 1px 2px rgba(40,30,70,.05),0 18px 40px -18px rgba(40,30,70,.22);
  --shadow-sm:0 1px 2px rgba(40,30,70,.06),0 6px 16px -8px rgba(40,30,70,.16);
  --display:"Instrument Serif","Times New Roman",Georgia,serif;
  --serif:var(--display);
  --sans:"Geist",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
  --mono:"Geist Mono",ui-monospace,"SF Mono",Menlo,Consolas,monospace;
  --grad:linear-gradient(100deg,#FF4F8B,#FF8A3D 55%,#8A4DFF);
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --bg:#111113; --panel:#1B1B1F; --ink:#F0F0F3; --ink-2:#D2D2D8; --muted:#9C9CA8; --rule:#2A2A31; --rule-strong:#44444D;
  --ledger:#202026; --accent:#A796FF; --accent-deep:#8C77FF; --accent-ink:#111113; --accent-soft:#2A2446;
  --band:#232327; --band-2:#2C2C31; --band-ink:#F5F5F7; --band-muted:#A9A9B3; --gold-hi:#FF9A73;
  --ok:#4FC98D; --ok-soft:#17301F; --bad:#FF7F73; --bad-soft:#3A1C19; --margin:#FF6FA0;
  --gold:#FF9A6B; --gold-soft:#3A2418; --gold-ink:#FFC9AE;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 18px 40px -18px rgba(0,0,0,.7);--shadow-sm:0 1px 2px rgba(0,0,0,.35),0 6px 16px -8px rgba(0,0,0,.5);
  color-scheme:dark;}}
:root[data-theme="dark"]{
  --bg:#111113; --panel:#1B1B1F; --ink:#F0F0F3; --ink-2:#D2D2D8; --muted:#9C9CA8; --rule:#2A2A31; --rule-strong:#44444D;
  --ledger:#202026; --accent:#A796FF; --accent-deep:#8C77FF; --accent-ink:#111113; --accent-soft:#2A2446;
  --band:#232327; --band-2:#2C2C31; --band-ink:#F5F5F7; --band-muted:#A9A9B3; --gold-hi:#FF9A73;
  --ok:#4FC98D; --ok-soft:#17301F; --bad:#FF7F73; --bad-soft:#3A1C19; --margin:#FF6FA0;
  --gold:#FF9A6B; --gold-soft:#3A2418; --gold-ink:#FFC9AE;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 18px 40px -18px rgba(0,0,0,.7);--shadow-sm:0 1px 2px rgba(0,0,0,.35),0 6px 16px -8px rgba(0,0,0,.5);
  color-scheme:dark;}
body{font-family:var(--sans);font-size:16.5px;letter-spacing:-.003em}
body::before{content:"";position:fixed;inset:-10%;z-index:-2;pointer-events:none;background:
  radial-gradient(40% 35% at 10% 12%,color-mix(in srgb,#E9F2C4 70%,transparent),transparent 70%),
  radial-gradient(38% 40% at 92% 8%,color-mix(in srgb,#E4E1FB 80%,transparent),transparent 70%),
  radial-gradient(45% 40% at 85% 85%,color-mix(in srgb,#F1F4CF 60%,transparent),transparent 70%),
  radial-gradient(40% 40% at 8% 90%,color-mix(in srgb,#E8E4FA 70%,transparent),transparent 70%)}
:root[data-theme="dark"] body::before{opacity:.06}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]) body::before{opacity:.06}}
h1,h2{font-family:var(--display);font-weight:400;letter-spacing:-.02em}
h1{font-size:clamp(2.6rem,5.6vw,4rem);line-height:1}
h2{font-size:clamp(1.8rem,3.4vw,2.4rem);line-height:1.08}
h3{font-family:var(--sans);font-weight:600;font-size:1.08rem;letter-spacing:-.01em}
.lede{font-family:var(--sans);font-style:normal;font-size:1.12rem;color:var(--muted)}
.eyebrow{color:var(--accent)}
a{color:var(--accent)}
.site-head{background:color-mix(in srgb,var(--panel) 72%,transparent);border-bottom-color:color-mix(in srgb,var(--rule) 70%,transparent)}
.hdr .brand b{font-family:var(--display);font-weight:400;font-size:1.55rem;letter-spacing:-.01em}
.mt,.ml{font-weight:500}
.mt::after,.ml::after{background:var(--ink)}
.gs-disc{fill:url(#gs-g);stroke:none}
.gs-ring{stroke:#fff;opacity:.55}
.gs-mark{fill:#fff;font-family:"Instrument Serif",Georgia,serif;font-weight:400;font-size:15px}
/* buttons */
.btn{background:var(--band);border-color:var(--band);color:#fff;border-radius:10px;padding:11px 20px;font-weight:500}
.btn:hover{background:#000;border-color:#000}
:root[data-theme="dark"] .btn{background:#F5F5F7;border-color:#F5F5F7;color:#111}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]) .btn{background:#F5F5F7;border-color:#F5F5F7;color:#111}}
.ghost{border-radius:10px;background:var(--panel);border-color:var(--rule);font-weight:500}
.ghost:hover{border-color:var(--ink)}
/* cards */
.topic-row,.q,.feature,.pager a,.toc,.done-row,.summary div,.vid,.exam-setup,.exam-result{border-radius:20px;border:1px solid color-mix(in srgb,var(--rule) 80%,transparent);background:var(--panel);box-shadow:var(--shadow-sm)}
.topic-row{padding:24px 24px 20px}
.topic-row::before{height:3px;background:var(--grad)}
.topic-row b{font-family:var(--display);font-size:1.45rem;font-weight:400;letter-spacing:-.01em}
.topic-row em{color:var(--ink)}
.topic-row:hover{border-color:var(--rule-strong);box-shadow:var(--shadow)}
.plain{border-radius:20px;border:1px solid var(--rule);background:var(--panel)}
.plain::before{background:var(--grad);width:2px}
.formula{background:var(--ledger);box-shadow:inset 3px 0 0 var(--margin);border-radius:12px}
.note{border-radius:14px}
section.block > h2::after{background:var(--rule)}
dl.words dt{font-family:var(--display);font-weight:400;font-size:1.25rem}
table.ledger{border-radius:10px;overflow:hidden}
/* home hero */
.hero3{padding-block:36px 8px}
.h3-card{max-width:1000px;margin:0 auto;background:var(--panel);border-radius:30px;overflow:hidden;box-shadow:0 40px 90px -40px rgba(70,40,110,.45),0 1px 2px rgba(0,0,0,.04);animation:rise .9s var(--ease) both}
.h3-text{text-align:center;padding:60px 24px 26px;position:relative;z-index:1}
.h3-text .eyebrow{justify-content:center}
.h3-text .eyebrow::before{display:none}
.h3-text h1{font-size:clamp(3rem,8vw,5.6rem);line-height:.95;color:var(--ink)}
.h3-text h1 em{font-style:italic;background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent;padding-right:.05em}
.h3-text .lede{margin:1.1rem auto 0;max-width:34rem}
.h3-text .cta{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;margin-top:1.6rem}
.h3-art{position:relative;height:clamp(380px,46vw,520px);display:grid;place-items:center;margin-top:-30px}
.h3-art canvas{position:absolute;inset:0;width:100%;height:100%;-webkit-mask-image:linear-gradient(to bottom,transparent 0,#000 26%);mask-image:linear-gradient(to bottom,transparent 0,#000 26%)}
.h3-art .jcard{width:min(520px,86%);z-index:1;margin-top:40px}
.hero-stats{display:flex;justify-content:center;gap:12px 40px;flex-wrap:wrap;max-width:1000px;margin:28px auto 0;padding-top:0;border:0}
.hero-stats div{text-align:center}
.hero-stats b{font-family:var(--display);font-weight:400;font-size:2.4rem;color:var(--ink);background:none;-webkit-text-fill-color:currentColor}
.hero-stats span{color:var(--muted);font-size:.85rem;letter-spacing:0}
.jstamp{background:var(--band);color:#fff}
/* chapter bands */
.chapter{margin-top:96px}
.ch-band{position:relative;isolation:isolate;border-radius:30px;overflow:hidden;min-height:320px;display:grid;place-items:center;padding:56px 16px;margin-bottom:28px}
.ch-band canvas{position:absolute;inset:0;width:100%;height:100%;z-index:-2}
.ch-letters{position:absolute;inset:0;z-index:-1;pointer-events:none;font:400 .95rem var(--mono);color:rgba(255,255,255,.8);letter-spacing:.3em}
.ch-letters span{position:absolute}
.chapter .ch-band .chap-h{display:block;background:rgba(43,43,47,.94);color:#fff;border-radius:24px;padding:34px 40px;max-width:620px;text-align:center;margin:0;border:0;box-shadow:0 30px 60px -25px rgba(0,0,0,.5)}
.chapter .ch-band .chap-h::after{display:none}
.chapter .ch-band .chap-h .num{display:block;font-size:1rem;font-family:var(--mono);font-style:normal;letter-spacing:.2em;color:rgba(255,255,255,.6);background:none;-webkit-text-fill-color:currentColor;margin-bottom:10px}
.chapter .ch-band .chap-h h2{color:#fff;font-size:clamp(2.2rem,5vw,3.4rem);line-height:1}
.chapter .ch-band .chap-h p{color:#CFCFD6;margin:.8rem auto 0;max-width:30rem}
/* lesson title card */
.lhero{position:relative;isolation:isolate;border-radius:30px;overflow:hidden;min-height:360px;display:grid;place-items:center;padding:48px 20px;margin:0 0 1.4rem}
.lhero canvas{position:absolute;inset:0;width:100%;height:100%;z-index:-1}
.lh-card{max-width:620px;text-align:center;padding:34px 38px;border-radius:26px;background:linear-gradient(165deg,rgba(255,255,255,.34),rgba(255,255,255,.08) 60%),rgba(70,30,90,.16);-webkit-backdrop-filter:blur(26px) saturate(1.3);backdrop-filter:blur(26px) saturate(1.3);border:1px solid rgba(255,255,255,.5);box-shadow:0 30px 60px -30px rgba(60,20,80,.45),inset 0 1px 0 rgba(255,255,255,.5);color:#fff;animation:rise .8s var(--ease) both}
.lh-card h1{color:#fff;margin:0;text-shadow:0 2px 18px rgba(40,10,60,.25)}
.lh-card .lede{color:rgba(255,255,255,.92);margin:.9rem auto 0;text-shadow:0 1px 10px rgba(40,10,60,.3)}
.lh-card .eyebrow{color:#fff;justify-content:center;margin-bottom:1rem}
.lh-card .eyebrow::before{background:#fff}
/* explainer player in charcoal with a warm gradient */
.xp{--band:#2A2A2E;--band-2:#333338;--band-ink:#F5F5F7;--band-muted:#A9A9B3;--gold-hi:#FF8A5C}
.xp-badge{background:var(--grad);color:#fff}
.xp-play{background:var(--grad);border:0;color:#fff}
.xp-play:hover:not(:disabled){background:var(--grad);filter:brightness(1.08)}
.xp-seg button i{background:var(--grad)}
.xp-stage .hl{background:rgba(255,138,92,.14);box-shadow:0 0 0 1.5px rgba(255,138,92,.8)}
.x-chip.gold,.x-split .p,.x-sr i,.x-stp i,.x-bar2 span.big{background:var(--gold-hi);color:#221}
.readbar{background:var(--grad)}
.totop{background:var(--band);color:#fff;border-color:var(--band)}
.vid-pl{background:rgba(43,43,47,.85)}
a.vid:hover .vid-pl{background:#FF8A5C;color:#fff}
.lside ol a::after{background:var(--grad)}
.lside ul a.on{color:var(--ink);border-left-color:var(--ink)}
.site-foot{background:color-mix(in srgb,var(--panel) 80%,transparent)}
.site-foot .brandline b{font-family:var(--display);font-weight:400;font-size:1.8rem}
@media (max-width:760px){
  .h3-text{padding:44px 16px 20px}.h3-art{height:420px}
  .ch-band{min-height:260px;padding:40px 12px;border-radius:22px}.chapter .ch-band .chap-h{padding:26px 22px}
  .lhero{min-height:300px;padding:32px 12px;border-radius:22px}.lh-card{padding:26px 20px}
}
.jrow.nar span:first-child{grid-column:1 / -1}
.xp-stage .off{opacity:0!important}
/* journal card: stop the handwriting reveal from clipping the last digit */
.jcard .w{padding-right:.18em;margin-right:-.18em}
@keyframes write{to{clip-path:inset(-4px -.5em -4px -4px)}}
@media (prefers-reduced-motion: reduce){.jcard .w{clip-path:none}}
/* no clipping safety nets */
.x-two .xs4{grid-template-columns:minmax(0,1fr) 3.4rem 3.6rem 3.6rem;gap:4px}
.x-tbl{overflow-x:auto;max-width:100%}
.xp-stage > *{max-width:100%}
.jcard .w.done{clip-path:none!important;animation:none}
/* show every description in full: no "…" truncation anywhere */
.pal-res a small{white-space:normal;overflow:visible;text-overflow:clip;line-height:1.4}
.mp-list a span{display:block;-webkit-line-clamp:unset;overflow:visible}

/* ===== v7: practice tools (exam questions, review, flashcards, written, summaries) ===== */
.ex-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px;margin:18px 0 8px}
.ex-card{display:flex;flex-direction:column;gap:6px;padding:20px;border-radius:16px;background:var(--panel);border:1px solid var(--rule);color:var(--ink);text-decoration:none;transition:transform .25s var(--ease,ease),box-shadow .25s,border-color .25s}
.ex-card:hover{transform:translateY(-3px);box-shadow:var(--shadow);border-color:var(--accent)}
.ex-card small{font:600 .7rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.ex-card b{font:400 1.35rem/1.2 var(--display,var(--serif))}
.ex-meta{font-size:.88rem;color:var(--muted)}
.ex-best{font-size:.85rem;color:var(--muted);margin-top:auto;padding-top:8px;border-top:1px solid var(--rule)}
.ex-best b{color:var(--ink)}
.ex-back{display:inline-block;margin:6px 0 14px;font-size:.92rem}
.ex-head{display:grid;grid-template-columns:minmax(0,1fr) 260px;gap:20px;align-items:start;margin-bottom:12px}
.ex-head h2{margin:.2rem 0 .4rem}
.ex-timer{position:sticky;top:76px;z-index:5;background:var(--panel);border:1px solid var(--rule);border-radius:16px;padding:14px 16px;box-shadow:var(--shadow-sm)}
.ex-tl{display:flex;justify-content:space-between;align-items:baseline;gap:8px}
.ex-tl span{font-size:.8rem;color:var(--muted);text-transform:uppercase;letter-spacing:.1em}
.ex-time{font:600 1.7rem/1.15 var(--mono);font-variant-numeric:tabular-nums}
.ex-bar{height:6px;border-radius:6px;background:var(--rule);overflow:hidden;margin:8px 0 10px}
.ex-bar i{display:block;height:100%;width:0;background:var(--grad,var(--accent));transition:width 1s linear}
.ex-tb{display:flex;gap:8px;flex-wrap:wrap}
.ex-timer.low .ex-time{color:var(--gold-ink,#b25b00)}
.ex-timer.over .ex-time{color:var(--bad)}
.ex-scen{background:var(--ledger);border-radius:16px;padding:18px 20px;margin:6px 0 20px}
.ex-scen > :first-child{margin-top:0}.ex-scen > :last-child{margin-bottom:0}
.ex-part{background:var(--panel);border:1px solid var(--rule);border-radius:16px;padding:18px 20px;margin-bottom:14px}
.ex-ph{display:grid;grid-template-columns:auto minmax(0,1fr) auto;gap:12px;align-items:baseline}
.ex-ph p{margin:0}
.ex-m{font:600 .78rem var(--mono);color:var(--muted);white-space:nowrap}
.ex-part .scroll{margin-top:10px}
.ex-part textarea{width:100%;min-height:150px;margin-top:10px}
.ex-got{display:inline-block;margin-top:10px;padding:3px 10px;border-radius:999px;background:var(--accent-soft);color:var(--accent-ink,var(--accent));font:600 .85rem var(--mono)}
.ex-ms{margin-top:10px;padding:12px 14px;border-radius:12px;background:var(--ok-soft);font-size:.94rem}
.ex-ms p{margin:.3rem 0 0}
.ex-part select{max-width:100%}
.ex-actions{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin:18px 0}
.btnlink{text-decoration:none}
.ex-result{padding:18px 20px;border-radius:16px;background:var(--panel);border:1px solid var(--accent)}
.ex-score{font-size:1.1rem;margin:0 0 .3rem}.ex-score b{font:400 2rem var(--display,var(--serif));margin-right:6px}
@media (max-width:760px){.ex-head{grid-template-columns:1fr}.ex-timer{top:64px}.ex-ph{grid-template-columns:auto minmax(0,1fr)}.ex-m{grid-column:2}}

.empty-note{padding:26px;border-radius:16px;background:var(--panel);border:1px dashed var(--rule-strong);text-align:center}
.empty-note b{font:400 1.5rem var(--display,var(--serif))}
.rv-top{display:flex;justify-content:space-between;align-items:center;gap:14px;flex-wrap:wrap;margin:12px 0}
.rv-top p{margin:0}
.rv-h{display:flex;align-items:baseline;flex-wrap:wrap;gap:6px 12px;margin:30px 0 12px}
.rv-h small{font:600 .72rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--muted)}
.rv-h a{font:500 .88rem var(--sans);margin-left:auto}
.rv-ok{font:600 .75rem var(--sans);padding:3px 10px;border-radius:999px;background:var(--ok-soft);color:var(--ok)}
.q.rv-done{opacity:.75}

.fc-stats{display:grid;grid-template-columns:minmax(0,1.3fr) minmax(0,1fr);gap:16px;align-items:end;margin:14px 0 6px}
.fc-stats .hint{grid-column:1 / -1;margin:0}
.fc-nums{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:8px}
.fc-nums div{background:var(--panel);border:1px solid var(--rule);border-radius:14px;padding:12px 10px;text-align:center}
.fc-nums b{display:block;font:400 1.8rem/1.1 var(--display,var(--serif))}
.fc-nums span{font-size:.78rem;color:var(--muted)}
.fc-boxes{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:6px;height:110px;align-items:end}
.fc-box{display:flex;flex-direction:column;align-items:center;justify-content:flex-end;height:100%;gap:2px}
.fc-box i{display:block;width:100%;border-radius:8px 8px 3px 3px;background:var(--grad,var(--accent));max-height:70%}
.fc-box b{font:600 .8rem var(--mono)}.fc-box span{font-size:.72rem;color:var(--muted)}
.fc-setup{background:var(--panel);border:1px solid var(--rule);border-radius:16px;padding:18px 20px;margin:16px 0}
.fc-setup .t-fields{margin-top:0}
.fc-setup label span{display:block;margin-bottom:4px}
.fc-setup select{width:100%}
.fc-btns{display:flex;gap:10px;flex-wrap:wrap;margin-top:14px}
.fc-stage{margin:18px 0}
.fc-prog{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-bottom:10px;color:var(--muted);font-size:.9rem}
.fc-card{perspective:1400px;cursor:pointer;outline:none;max-width:680px;margin:0 auto}
.fc-inner{position:relative;display:grid;transition:transform .55s cubic-bezier(.2,.7,.2,1);transform-style:preserve-3d}
.fc-card.flip .fc-inner{transform:rotateY(180deg)}
.fc-face{grid-area:1 / 1;min-height:280px;padding:28px;border-radius:22px;background:var(--panel);border:1px solid var(--rule);box-shadow:var(--shadow);backface-visibility:hidden;-webkit-backface-visibility:hidden;display:flex;flex-direction:column;justify-content:center;gap:10px;overflow-wrap:anywhere}
.fc-front{text-align:center;align-items:center;background:linear-gradient(var(--panel),var(--panel)) padding-box,var(--grad,var(--accent)) border-box;border:2px solid transparent}
.fc-front small{font:600 .72rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.fc-front b{font:400 clamp(1.7rem,4vw,2.5rem)/1.15 var(--display,var(--serif))}
.fc-back{transform:rotateY(180deg)}
.fc-back b{font:400 1.5rem var(--display,var(--serif))}
.fc-back p{margin:0}
.fc-eg{background:var(--ledger);padding:10px 12px;border-radius:10px;font-size:.94rem}
.fc-card:focus-visible .fc-face{outline:3px solid var(--accent);outline-offset:3px}
.fc-keys{text-align:center}
.fc-ans{display:flex;justify-content:center;gap:12px;margin-top:6px}
kbd{font:500 .72rem var(--mono);padding:1px 5px;border-radius:4px;border:1px solid var(--rule-strong);margin-left:4px}
@media (max-width:760px){.fc-stats{grid-template-columns:1fr}.fc-nums{grid-template-columns:repeat(3,minmax(0,1fr))}.fc-face{min-height:240px;padding:22px}}
@media (prefers-reduced-motion:reduce){.fc-inner{transition:none}}

.wr-tip{background:var(--ledger);border-radius:16px;padding:16px 20px;margin:14px 0}
.wr-tip ol{margin:.4rem 0 0;padding-left:1.2rem;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:4px 20px}
.wr-bar{display:flex;justify-content:space-between;align-items:center;gap:10px;flex-wrap:wrap;margin:14px 0}
.wr-chips{display:flex;gap:6px;flex-wrap:wrap}
.chip{font:500 .88rem var(--sans);padding:6px 14px;border-radius:999px;border:1px solid var(--rule-strong);background:transparent;color:var(--ink);cursor:pointer}
.chip.on{background:var(--ink);color:var(--bg);border-color:var(--ink)}
.q.wr-flash{box-shadow:0 0 0 3px var(--accent)}

.sum-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px;margin:18px 0}
.sum-card{padding:20px;border-radius:16px;background:var(--panel);border:1px solid var(--rule);display:flex;flex-direction:column;gap:8px}
.sum-card small{font:600 .7rem var(--sans);letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.sum-card b{font:400 1.3rem/1.2 var(--display,var(--serif))}
.sum-card p{margin:0;font-size:.9rem;color:var(--muted)}
.sum-card .sum-links{display:flex;gap:10px;flex-wrap:wrap;margin-top:auto;padding-top:8px}
.sheet{background:var(--panel);border:1px solid var(--rule);border-radius:18px;padding:24px;margin:26px 0}
.sheet h2{margin-top:0}
.sheet-grid{columns:2 300px;column-gap:26px}
.sheet-t{break-inside:avoid;margin:0 0 14px;padding-top:10px;border-top:1px solid var(--rule)}
.sheet-t h3{font-size:1rem;margin:0 0 4px}
.sheet-t h3 a{color:inherit;text-decoration:none}
.sheet-t ul{margin:0;padding-left:1.05rem;font-size:.9rem}
.sheet-t li{margin:2px 0}
.foot-in{grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:28px 24px}
.site-foot .brandline{grid-column:1 / -1;max-width:46ch}
[hidden]{display:none!important}

/* ===== v8: use the width of large screens ===== */
:root{--maxw:1600px;--gut:clamp(16px,3vw,48px)}
.wrap{max-width:var(--maxw);padding-inline:var(--gut)}
.site-head .wrap.hdr{max-width:var(--maxw)}
main.with-side{max-width:var(--maxw);grid-template-columns:clamp(230px,17vw,290px) minmax(0,1fr);gap:clamp(40px,4vw,72px)}
.with-side .article,.article{max-width:1180px}
.prose > p,.prose > ul,.prose > ol,.prose > h3,.prose > .formula,.prose > .note,.lede,dl.words,.checklist,ol.fs-notes,ol.steps-list,.email{max-width:88ch}
.h3-card{max-width:min(1480px,100%)}
@media (min-width:1500px){
  html{font-size:106.25%}
  .topic-rows{grid-template-columns:repeat(auto-fill,minmax(320px,1fr))}
}
@media (min-width:2000px){html{font-size:112.5%}:root{--maxw:1800px}}
@media (min-width:1500px){.chapter .ch-band .chap-h{max-width:780px}.chapter .ch-band .chap-h p{max-width:36rem}.ch-band{min-height:360px}}
.summary div{padding:18px 22px}
.summary b{font-family:var(--display,var(--serif));font-weight:400;font-size:2.2rem;line-height:1.1}


/* ===== v9: Atkinson Hyperlegible everywhere, for easier reading (dyslexia, ADHD, low vision) ===== */
:root{
  --display:"Atkinson Hyperlegible Next","Atkinson Hyperlegible",Verdana,Tahoma,sans-serif;
  --serif:var(--display);
  --sans:"Atkinson Hyperlegible Next","Atkinson Hyperlegible",Verdana,Tahoma,sans-serif;
  --mono:"Atkinson Hyperlegible Mono","Atkinson Hyperlegible Next",Verdana,ui-monospace,monospace;
}
html{font-size:106.25%}
@media (min-width:1500px){html{font-size:112.5%}}
@media (min-width:2000px){html{font-size:118.75%}}
body{font-family:var(--sans);line-height:1.65;letter-spacing:.01em;word-spacing:.04em}
.prose p,.prose li,.plain p,dl.words dd,.q-prompt,.lede{line-height:1.7}
/* headings: bold sans, normal tracking */
h1,h2,h3,h4,.h3-text h1,.chap-h h2,.lh-card h1,.topic-row b,.ex-card b,.sum-card b,.fc-front b,.fc-back b,.empty-note b,.ex-score b,.summary b,.fc-nums b,.site-foot .brandline b,.mp-intro b,.pager b,.xp-title,.x-card b{font-family:var(--display);letter-spacing:-.005em}
h1,.h3-text h1,.lh-card h1,.chap-h h2{font-weight:800;line-height:1.08}
h2{font-weight:700;line-height:1.15}
h3,.topic-row b,.ex-card b,.sum-card b,.mp-intro b,.pager b{font-weight:700}
.fc-front b,.fc-back b,.empty-note b,.ex-score b,.summary b,.fc-nums b{font-weight:700}
.h3-text h1{font-size:clamp(2.4rem,6.4vw,5rem)}
.lh-card h1{font-size:clamp(2rem,4.6vw,3.6rem)}
.chapter .ch-band .chap-h h2{font-size:clamp(1.9rem,4.4vw,3rem);line-height:1.08}
/* no italics: slanted text is harder to read */
em,i,cite,.lede,table.ledger tr.narr td,.fs-period,.jrow.nar,.xr.sub,.x-q,.xs3.narr,.chap-h .num,.mp-intro .num,.hero2 h1 em,.h3-text h1 em{font-style:normal}
.prose em,.plain em,.q-prompt em,dd em{font-weight:700}
.lede{font-family:var(--sans)}
/* numbers: the mono face keeps figures lined up and unmistakable */
td.amt,th.amt,.amt,input.num,.xa,.ex-time,.fc-box b,.formula,.jcard .amt,code{font-family:var(--mono);font-variant-numeric:tabular-nums}
code{font-size:.9em}
table.xl{font-family:var(--sans)}
.hdr .brand b{font-weight:700;font-size:1.3rem;letter-spacing:-.01em;white-space:nowrap}
@media (max-width:480px){.hdr .brand b{font-size:1.08rem}.hdr .brand svg{width:30px;height:30px}.hdr{gap:8px}}
@media (max-width:380px){.hdr .brand b{font-size:.98rem}.hdr .brand svg{width:26px;height:26px}.hdr{gap:6px}}
table.ledger.simple:not(:has(.amt)){min-width:0}table.ledger.simple:not(:has(.amt)) td{overflow-wrap:anywhere;hyphens:auto}

/* ===== v10: explainer motion (smooth easing, overlapping entrances, one idea per step) ===== */
:root{--xe:cubic-bezier(.22,1,.36,1);--xin:cubic-bezier(.4,0,1,1)}
.xp-stage [data-s],.xp-stage [data-e],.xp-stage [data-hl]{
  transition:opacity .75s var(--xe) var(--xd,0ms),transform .8s var(--xe) var(--xd,0ms),
             background-color .5s var(--xe) calc(var(--xd,0ms) + 120ms),box-shadow .5s var(--xe) calc(var(--xd,0ms) + 120ms),filter .5s var(--xe)}
.xp-stage .off{opacity:0!important;transform:translateY(14px) scale(.985);transition:opacity .28s var(--xin),transform .28s var(--xin)}
.xp-stage .on{opacity:1;transform:none}
/* quiet surroundings: earlier items step back so this step's idea leads */
.xp-stage .on.xq{opacity:.46;filter:saturate(.6)}
/* highlight by contrast, not glow */
.xp-stage .hl,.xp-stage .on.hl{background:rgba(255,138,92,.17);box-shadow:inset 3px 0 0 #FF8A5C;border-radius:8px;opacity:1;filter:none}
.x-stp.hl{box-shadow:inset 0 0 0 1.5px #FF8A5C}
.xp-stage .flip{animation:xflip .55s var(--xe)}
@keyframes xflip{0%{opacity:0;transform:translateY(-8px)}100%{opacity:1;transform:none}}
.xp-stage .rolling{color:#FFB38F}
.x-bar i,.x-trk i{transition:height 1s var(--xe) var(--xd,0ms)}
.xp-cap.capin{animation:xcap .6s var(--xe)}
@keyframes xcap{0%{opacity:0;transform:translateY(6px)}100%{opacity:1;transform:none}}
.xp-seg i{transition:width .25s linear}
@media (prefers-reduced-motion:reduce){
  .xp-stage [data-s],.xp-stage [data-e],.xp-stage [data-hl],.xp-stage .off{transition:none!important}
  .xp-cap.capin,.xp-stage .flip{animation:none}
}
.xp-stage .x-card.dim.on:not(.hl){opacity:.7}

/* ===== v11: read aloud ===== */
.tts-go{display:inline-flex;align-items:center;gap:6px;font:600 .85rem var(--sans);letter-spacing:0;color:var(--accent);background:var(--accent-soft);border:1px solid transparent;border-radius:999px;padding:5px 12px 5px 9px;cursor:pointer;line-height:1.2;white-space:nowrap;transition:background .2s,color .2s,border-color .2s}
.tts-go svg{width:17px;height:17px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;flex:none}
.tts-go svg path:first-child{fill:currentColor;stroke:none}
.tts-go:hover{border-color:var(--accent)}
.tts-go:focus-visible,.tts-b:focus-visible,.xp-voice:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.tts-go.active{background:var(--accent);color:#fff}
.tts-go.big{font-size:1rem;padding:10px 18px 10px 14px}
.tts-go.big svg{width:20px;height:20px}
section.block > h2 .tts-go{align-self:center;font-size:.8rem;font-family:var(--sans);font-weight:600}
.q-head .tts-go{font-size:.78rem;padding:4px 10px 4px 8px}
.q-head .tts-go.tts-q{margin-left:auto}
.q-head .tts-go.tts-q + button{margin-left:8px}
.tts-start{display:flex;flex-wrap:wrap;align-items:center;gap:10px 14px;margin:1.4rem 0 .4rem}
.tts-set{display:inline-flex;align-items:center;gap:6px}
.tts-set svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round}
.tts-hint{color:var(--muted);font-size:.9rem;flex-basis:100%}
@media (min-width:760px){.tts-hint{flex-basis:auto}}
/* what is being read */
.tts-on{background:color-mix(in srgb,var(--accent) 7%,transparent);box-shadow:-10px 0 0 color-mix(in srgb,var(--accent) 7%,transparent),inset 3px 0 0 var(--accent);border-radius:6px;transition:background .3s}
::highlight(gs-tts){background-color:color-mix(in srgb,#FFB23D 42%,transparent);color:inherit}
/* player bar */
.tts-bar{position:fixed;left:50%;transform:translateX(-50%);bottom:calc(env(safe-area-inset-bottom,0px) + 16px);z-index:40;display:flex;align-items:center;gap:6px;
  padding:8px 10px;border-radius:999px;background:var(--band,#2B2B2F);color:#fff;box-shadow:0 18px 40px -12px rgba(0,0,0,.45);max-width:calc(100% - 32px);animation:ttsin .45s var(--xe,ease)}
@keyframes ttsin{from{opacity:0;transform:translate(-50%,14px)}to{opacity:1;transform:translate(-50%,0)}}
.tts-b{display:grid;place-items:center;width:38px;height:38px;border-radius:50%;border:0;background:transparent;color:inherit;cursor:pointer;flex:none}
.tts-b:hover{background:rgba(255,255,255,.12)}
.tts-b svg{width:20px;height:20px;fill:currentColor;stroke:currentColor;stroke-width:0}
.tts-b[data-a="stop"] svg,.tts-b[data-a="settings"] svg,.tts-panel .tts-b svg{fill:none;stroke-width:2;stroke-linecap:round}
.tts-main{background:var(--grad,#FF8A3D);width:44px;height:44px}
.tts-main:hover{background:var(--grad,#FF8A3D);filter:brightness(1.08)}
.tts-lab{display:grid;min-width:0;padding:0 8px;line-height:1.2}
.tts-lab b{font-size:.86rem}
.tts-lab small{font-size:.76rem;color:#C9C6D3;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;max-width:220px}
.tts-rate{font:600 .82rem var(--mono);background:rgba(255,255,255,.1);color:#fff;border:1px solid rgba(255,255,255,.18);border-radius:999px;padding:6px 8px}
.tts-rate option{color:#111}
@media (max-width:560px){.tts-lab{display:none}.tts-bar{gap:2px;padding:6px 8px}}
body.tts-playing .totop{bottom:calc(env(safe-area-inset-bottom,0px) + 84px)}
/* settings */
.tts-panel{position:fixed;left:50%;transform:translateX(-50%);bottom:calc(env(safe-area-inset-bottom,0px) + 84px);z-index:41;width:min(460px,calc(100% - 32px));
  background:var(--panel);color:var(--ink);border:1px solid var(--rule);border-radius:18px;padding:16px 18px 18px;box-shadow:0 24px 60px -20px rgba(0,0,0,.4);display:grid;gap:10px}
body:not(.tts-playing) .tts-panel{bottom:auto;top:50%;transform:translate(-50%,-50%)}
.tts-ph{display:flex;justify-content:space-between;align-items:center}
.tts-ph b{font-size:1.05rem}
.tts-panel .tts-b{color:var(--ink);width:34px;height:34px}.tts-panel .tts-b:hover{background:var(--ledger)}
.tts-panel label{font-size:.85rem;color:var(--muted)}
.tts-panel select{width:100%;font:inherit;padding:8px 10px;border-radius:10px;border:1px solid var(--rule-strong);background:var(--panel);color:var(--ink)}
.tts-row{display:flex;gap:8px;flex-wrap:wrap}
.tts-tip{margin:0;background:var(--ledger);border-radius:12px;padding:10px 12px;font-size:.9rem}
.tts-tip ol{margin:.4rem 0 0;padding-left:1.2rem;display:grid;gap:3px}
/* explainer narration button */
.xp-voice svg{fill:none!important;stroke:currentColor;stroke-width:2;stroke-linecap:round}
.xp-voice svg path:first-child{fill:currentColor!important;stroke:none}
.xp-voice .w1,.xp-voice .w2{opacity:.35;transition:opacity .3s}
.xp-voice.on{background:var(--grad,#FF8A3D)!important;color:#fff}
.xp-voice.on .w1,.xp-voice.on .w2{opacity:1}
.fc-say{display:inline-flex;align-items:center;gap:6px}
.fc-say svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round}
.fc-say svg path:first-child{fill:currentColor;stroke:none}
.fc-prog{flex-wrap:wrap}
@media (prefers-reduced-motion:reduce){.tts-bar{animation:none}}
.tts-bar .tts-rate{width:auto;flex:none;min-width:0}
.tts-lab{min-width:120px;max-width:240px}
.tts-lab b{white-space:nowrap}
.tts-b[data-a="prev"] svg,.tts-b[data-a="next"] svg{stroke-width:2.2;stroke-linejoin:round}
h1.tts-on,h2.tts-on,h3.tts-on,h4.tts-on{background:none;box-shadow:none}

/* ===== v12: keep the sidebar + article centred as one block at every width ===== */
main.with-side{grid-template-columns:clamp(230px,17vw,290px) minmax(0,1180px);justify-content:center}
.with-side .article{max-width:none;width:100%}
main.wrap:not(.with-side) > .article{margin-inline:auto}
@media (max-width:1000px){.with-side .article{max-width:1180px;margin-inline:auto}}

/* ===== v13: term tips for words a later topic teaches ===== */
.tt-term{text-decoration:underline dotted color-mix(in srgb,var(--accent) 70%,transparent);text-decoration-thickness:2px;text-underline-offset:3px;cursor:help;border-radius:3px}
.tt-term:hover,.tt-term:focus-visible{background:var(--accent-soft);outline:none}
.tt-term:focus-visible{box-shadow:0 0 0 2px var(--accent)}
.tt-pop{position:absolute;z-index:60;background:var(--panel);color:var(--ink);border:1px solid var(--rule);border-radius:14px;box-shadow:0 18px 40px -14px rgba(0,0,0,.35);padding:12px 14px;font-size:.92rem;line-height:1.5}
.tt-pop b{display:block;font-size:1rem;margin-bottom:2px}
.tt-pop p{margin:0 0 6px}
.tt-pop a{font-size:.85rem;font-weight:600}

/* ===== v14: Ask a tutor ===== */
.ch-fab{position:fixed;left:18px;bottom:calc(env(safe-area-inset-bottom,0px) + 18px);z-index:30;display:inline-flex;align-items:center;gap:8px;padding:11px 18px 11px 14px;border:0;border-radius:999px;
  background:var(--grad,var(--accent));color:#fff;font:700 .95rem var(--sans);cursor:pointer;box-shadow:0 14px 30px -10px rgba(91,61,245,.55);transition:transform .25s var(--xe,ease),opacity .2s}
.ch-fab:hover{transform:translateY(-2px)}
.ch-fab:focus-visible,.ch-ib:focus-visible,.ch-send:focus-visible,.ch-chip:focus-visible,.ch-ask:focus-visible,.ch-mini:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.ch-fab svg,.ch-ask svg{width:20px;height:20px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}
.ch-fab.hide{opacity:0;pointer-events:none;transform:translateY(10px)}
body.tts-playing .ch-fab{bottom:calc(env(safe-area-inset-bottom,0px) + 84px)}
.ch-box{position:fixed;left:18px;bottom:calc(env(safe-area-inset-bottom,0px) + 18px);z-index:45;width:min(440px,calc(100vw - 36px));height:min(640px,calc(100vh - 110px));
  display:flex;flex-direction:column;background:var(--panel);color:var(--ink);border:1px solid var(--rule);border-radius:22px;box-shadow:0 30px 70px -20px rgba(20,10,60,.45);overflow:hidden;animation:chin .4s var(--xe,ease)}
@keyframes chin{from{opacity:0;transform:translateY(16px) scale(.98)}to{opacity:1;transform:none}}
.ch-head{display:flex;align-items:center;gap:6px;padding:14px 12px 12px 18px;border-bottom:1px solid var(--rule);background:linear-gradient(90deg,color-mix(in srgb,#FF4F8B 10%,var(--panel)),color-mix(in srgb,#8A4DFF 10%,var(--panel)))}
.ch-head > div{flex:1;min-width:0;display:grid}
.ch-head b{font-size:1.05rem}
.ch-ctx{font-size:.8rem;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.ch-ib{display:grid;place-items:center;width:36px;height:36px;border-radius:50%;border:0;background:transparent;color:var(--ink);cursor:pointer;flex:none}
.ch-ib:hover{background:var(--ledger)}
.ch-ib svg{width:20px;height:20px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round}
.ch-log{flex:1;overflow-y:auto;padding:16px 16px 8px;display:flex;flex-direction:column;gap:12px;overscroll-behavior:contain}
.ch-msg{max-width:92%;display:grid;gap:4px}
.ch-msg.me{align-self:flex-end}
.ch-msg.me .ch-body{background:var(--ink);color:var(--bg);border-radius:18px 18px 4px 18px;padding:10px 14px;white-space:pre-wrap;overflow-wrap:anywhere}
.ch-msg.ai .ch-body{background:var(--ledger);border-radius:18px 18px 18px 4px;padding:10px 14px;overflow-wrap:anywhere;line-height:1.6}
.ch-body p{margin:0 0 .55em}.ch-body p:last-child{margin-bottom:0}
.ch-body ul,.ch-body ol{margin:.2em 0 .6em;padding-left:1.2em}.ch-body li{margin:.15em 0}
.ch-body h4{margin:.6em 0 .25em;font-size:1rem}
.ch-body code{font-family:var(--mono);font-size:.9em;background:var(--panel);padding:1px 4px;border-radius:4px}
.ch-tbl{overflow-x:auto;margin:.3em 0 .7em}
.ch-tbl table{border-collapse:collapse;font-size:.9rem;min-width:100%}
.ch-tbl th,.ch-tbl td{padding:5px 8px;border-bottom:1px solid var(--rule);text-align:left}
.ch-tbl th{font-size:.78rem;text-transform:uppercase;letter-spacing:.05em;color:var(--muted)}
.ch-tbl .n{text-align:right;font-family:var(--mono);font-variant-numeric:tabular-nums;white-space:nowrap}
.ch-tools{display:flex;gap:6px}
.ch-mini{display:inline-flex;align-items:center;gap:5px;border:0;background:none;color:var(--muted);font:600 .78rem var(--sans);cursor:pointer;padding:3px 6px;border-radius:8px}
.ch-mini:hover{background:var(--ledger);color:var(--ink)}
.ch-mini svg{width:15px;height:15px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round}.ch-mini svg path:first-child{fill:currentColor;stroke:none}
.ch-wait{display:flex;align-items:center;gap:4px;color:var(--muted)}
.ch-wait span{width:6px;height:6px;border-radius:50%;background:var(--accent);animation:chdot 1.1s infinite ease-in-out}
.ch-wait span:nth-child(2){animation-delay:.15s}.ch-wait span:nth-child(3){animation-delay:.3s;margin-right:6px}
@keyframes chdot{0%,80%,100%{opacity:.25;transform:translateY(0)}40%{opacity:1;transform:translateY(-3px)}}
.ch-err{color:var(--bad);font-weight:600}.ch-note{color:var(--muted);font-size:.85rem}
.ch-sug{display:flex;flex-wrap:wrap;gap:6px;padding:0 16px 10px}
.ch-sug:empty{display:none}
.ch-chip{border:1px solid var(--rule-strong);background:var(--panel);color:var(--ink);border-radius:999px;padding:6px 12px;font:500 .85rem var(--sans);cursor:pointer;text-align:left}
.ch-chip:hover{border-color:var(--accent);color:var(--accent)}
.ch-form{display:flex;align-items:flex-end;gap:8px;padding:10px 12px;border-top:1px solid var(--rule)}
.ch-form textarea{flex:1;resize:none;font:inherit;font-size:1rem;line-height:1.45;padding:10px 12px;border-radius:14px;border:1px solid var(--rule-strong);background:var(--bg);color:var(--ink);max-height:140px}
.ch-form textarea:focus{outline:2px solid var(--accent);outline-offset:0;border-color:transparent}
.ch-send{display:grid;place-items:center;width:44px;height:44px;border-radius:50%;border:0;background:var(--grad,var(--accent));color:#fff;cursor:pointer;flex:none}
.ch-send svg{width:20px;height:20px;fill:currentColor}
.ch-send.stop{background:var(--ink);color:var(--bg)}
.ch-foot{margin:0;padding:0 16px 10px;font-size:.74rem;color:var(--muted)}
.ch-sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}
.ch-ask{display:inline-flex;align-items:center;gap:5px;font:600 .78rem var(--sans);color:var(--accent);background:transparent;border:1px solid color-mix(in srgb,var(--accent) 40%,transparent);border-radius:999px;padding:4px 10px 4px 8px;cursor:pointer;margin-left:6px}
.ch-ask svg{width:15px;height:15px}
.ch-ask:hover{background:var(--accent-soft)}
body.ch-none .ch-ask{display:none}
@media (max-width:560px){
  .ch-fab{left:12px;bottom:calc(env(safe-area-inset-bottom,0px) + 12px);padding:10px 14px 10px 12px;font-size:.88rem}
  .ch-box{left:0;right:0;bottom:0;width:100%;height:min(88vh,calc(100vh - 40px));border-radius:22px 22px 0 0;padding-bottom:env(safe-area-inset-bottom,0px)}
}
@media (prefers-reduced-motion:reduce){.ch-box{animation:none}.ch-wait span{animation:none;opacity:.6}}
.ch-form textarea{min-height:0;width:auto;height:46px}
.ch-voice svg .sp{fill:currentColor;stroke:none}
.ch-voice svg .off{display:none}
.ch-voice.muted svg .w1,.ch-voice.muted svg .w2{display:none}
.ch-voice.muted svg .off{display:inline}
.ch-voice:not(.muted){color:var(--accent)}
.ch-voice.talking .w1{animation:chw 1s infinite ease-in-out}.ch-voice.talking .w2{animation:chw 1s .2s infinite ease-in-out}
@keyframes chw{0%,100%{opacity:.25}50%{opacity:1}}
@media (prefers-reduced-motion:reduce){.ch-voice.talking .w1,.ch-voice.talking .w2{animation:none}}
.ch-code{display:flex;gap:8px;margin-top:10px;flex-wrap:wrap}
.ch-code input{flex:1;min-width:140px;font:inherit;padding:9px 12px;border-radius:12px;border:1px solid var(--rule-strong);background:var(--panel);color:var(--ink)}
.ch-code input:focus{outline:2px solid var(--accent);border-color:transparent}

/* ---------- v15: voice mode (talk to the tutor) ---------- */
.vm-fab{position:fixed;left:174px;bottom:calc(env(safe-area-inset-bottom,0px) + 18px);z-index:30;width:46px;height:46px;border-radius:50%;border:0;display:grid;place-items:center;
  background:var(--accent);color:var(--accent-ink);box-shadow:0 6px 18px rgba(10,20,40,.25);cursor:pointer;transition:transform .2s}
.vm-fab:hover{transform:translateY(-2px)}
.vm-fab svg,.ch-talk svg,.vm-b svg{width:22px;height:22px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}
.vm-fab:focus-visible,.vm-b:focus-visible,.vm-orb:focus-visible{outline:3px solid var(--accent);outline-offset:3px}
.ch-none .vm-fab,.ch-open .vm-fab,.vm-open .vm-fab,.vm-open .ch-fab{display:none}
.vm{position:fixed;left:18px;bottom:calc(env(safe-area-inset-bottom,0px) + 18px);z-index:60;width:300px;max-height:calc(100vh - 36px);display:flex;flex-direction:column;align-items:center;gap:10px;padding:14px 16px 14px;
  border-radius:22px;background:radial-gradient(120% 90% at 50% 30%,#1B2A4D 0%,#0B1122 80%);color:#EEF2FA;text-align:center;box-shadow:0 18px 50px rgba(5,10,25,.45);overflow:hidden}
.vm[hidden]{display:none}
.vm-top{display:flex;flex-direction:column;gap:0;line-height:1.3}
.vm-top b{font-size:15px}.vm-top small{color:#A9B6D1;font-size:13px}
.vm-orb{position:relative;width:96px;aspect-ratio:1;margin:8px 0 4px;flex:none;border:0;border-radius:50%;background:none;cursor:pointer;padding:0}
.vm-orb span{position:absolute;inset:0;border-radius:50%}
.vm-orb .o1{background:radial-gradient(circle at 35% 30%,#CFE0FF,#6F96E0 45%,#2E4F8E 80%);box-shadow:0 0 30px rgba(120,160,240,.45)}
.vm-orb .o2,.vm-orb .o3{border:2px solid rgba(160,190,250,.35);opacity:0}
.vm[data-st=listening] .o1{animation:vmBreathe 2.6s ease-in-out infinite}
.vm[data-st=listening] .o2{animation:vmRing 2.6s ease-out infinite}
.vm[data-st=thinking] .o1{animation:vmThink 1.1s ease-in-out infinite}
.vm[data-st=speaking] .o1{animation:vmTalk .5s ease-in-out infinite alternate}
.vm[data-st=speaking] .o2{animation:vmRing 1.2s ease-out infinite}
.vm[data-st=speaking] .o3{animation:vmRing 1.2s ease-out .6s infinite}
.vm[data-st=muted] .o1{filter:grayscale(.8) brightness(.7)}
@keyframes vmBreathe{50%{transform:scale(1.05)}}
@keyframes vmThink{50%{transform:scale(.9);filter:brightness(1.2)}}
@keyframes vmTalk{from{transform:scale(.97)}to{transform:scale(1.09)}}
@keyframes vmRing{from{transform:scale(1);opacity:.8}to{transform:scale(1.45);opacity:0}}
@media (prefers-reduced-motion:reduce){.vm-orb span{animation:none!important}.vm[data-st=speaking] .o1{box-shadow:0 0 90px rgba(150,190,255,.8)}}
.vm-status{margin:0;font-size:16px;font-weight:600;min-height:1.4em}
.vm-said{margin:0;font-size:15px;color:#C9D4EA;max-height:4.5em;overflow:hidden}.vm-said:empty{display:none}
.vm-log{width:100%;max-height:34vh;overflow:auto;text-align:left;background:rgba(255,255,255,.06);border-radius:12px;padding:10px 12px;font-size:15px}
.vm-log p{margin:0 0 10px;line-height:1.5;white-space:pre-wrap}.vm-log p.me{color:#AFC6F2}.vm-log p.me::before{content:"You: ";font-weight:700}.vm-log p.ai::before{content:"Tutor: ";font-weight:700}
.vm-bar{display:flex;gap:14px;margin-top:2px}
.vm-b{width:46px;height:46px;flex:none;border-radius:50%;border:0;display:grid;place-items:center;background:rgba(255,255,255,.12);color:#fff;cursor:pointer}
.vm-b:hover{background:rgba(255,255,255,.2)}.vm-b[aria-pressed=true]:not(.vm-mic){background:rgba(255,255,255,.28)}
.vm-mic .off{display:none}.vm-mic.muted{background:#fff;color:#0B1122}.vm-mic.muted .off{display:inline}
.vm-end{background:#C8413A}.vm-end:hover{background:#DA4D45}
.vm-tip{margin:0;font-size:12px;line-height:1.4;color:#8F9DBB}
@media (max-width:560px){.vm{left:8px;right:8px;width:auto;bottom:calc(env(safe-area-inset-bottom,0px) + 8px)}}

/* ---------- v16: cost vs revaluation diagram ---------- */
.vc{margin:22px 0;padding:16px;border:1px solid var(--rule);border-radius:14px;background:var(--panel)}
.vc-cap{display:flex;flex-direction:column;gap:2px;margin-bottom:12px}.vc-cap b{font-size:17px}.vc-cap span{color:var(--muted);font-size:15px}
.vc-ctl{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:12px}
.vc-seg{display:inline-flex;border:1px solid var(--rule-strong);border-radius:999px;overflow:hidden}
.vc-seg button{border:0;background:none;color:var(--ink);padding:7px 14px;font:inherit;font-size:15px;cursor:pointer}
.vc-seg button+button{border-left:1px solid var(--rule)}
.vc-seg button[aria-pressed=true]{background:var(--accent);color:var(--accent-ink);font-weight:600}
.vc-seg button:focus-visible,.vc-nav button:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.vc-body{display:grid;grid-template-columns:1fr 190px;gap:12px;align-items:center}
@media (max-width:640px){.vc-body{grid-template-columns:1fr}}
.vc-chart svg{width:100%;height:auto;display:block}
.vc-axis{stroke:var(--rule-strong);stroke-width:1.5}.vc-lab,.vc-zone{fill:var(--muted);font-size:12px}
.vc-up{fill:#2E8B57;opacity:.07}.vc-down{fill:#C8413A;opacity:.07}
.vc-cost{stroke:var(--ink-2);stroke-width:2;stroke-dasharray:6 5}.vc-cl{fill:var(--ink-2);font-size:13px;font-weight:600}
.vc-mv{fill:none;stroke:var(--muted);stroke-width:2;stroke-dasharray:3 5;opacity:.8}
.vc-ca{fill:none;stroke:var(--accent);stroke-width:4;stroke-linecap:round}
.vc-dot{fill:var(--accent)}.vc-mvd{fill:var(--muted)}
.vc-v{fill:var(--ink);font-size:14px;font-weight:700}.vc-mvv{fill:var(--muted);font-size:12px}
.vc-bs{border:1px solid var(--rule);border-radius:10px;padding:10px 12px;font-size:15px;background:var(--ledger)}
.vc-bs div{display:flex;justify-content:space-between;gap:8px;padding:3px 0}.vc-bs .vc-bh{font-weight:700;border-bottom:1px solid var(--rule-strong);margin-bottom:4px}
.vc-key{display:flex;flex-wrap:wrap;gap:16px;font-size:14px;color:var(--muted);margin:6px 0 4px}
.vc-key i{display:inline-block;width:22px;height:0;margin-right:6px;vertical-align:middle}.k-ca{border-top:4px solid var(--accent)}.k-mv{border-top:2px dashed var(--muted)}
.vc-say{min-height:7.5em}.vc-t{font-weight:700;margin:8px 0 2px;font-size:17px}.vc-d{margin:0 0 8px}
.vc-fx{display:flex;flex-wrap:wrap;gap:8px}
.vc-chip{border-radius:999px;padding:3px 12px;font-size:14px;border:1px solid}
.vc-chip.oci{color:#1E6B45;border-color:#7BC09A;background:#EAF6EF}.vc-chip.pl{color:#9A2E28;border-color:#E39A95;background:#FBECEB}.vc-chip.nil{color:var(--muted);border-color:var(--rule-strong)}
:root[data-theme=dark] .vc-chip.oci{color:#9FE0BC;background:#13301F;border-color:#2E6B48}:root[data-theme=dark] .vc-chip.pl{color:#F2B0AB;background:#3A1715;border-color:#7A3530}
@media (prefers-color-scheme:dark){:root:not([data-theme=light]) .vc-chip.oci{color:#9FE0BC;background:#13301F;border-color:#2E6B48}:root:not([data-theme=light]) .vc-chip.pl{color:#F2B0AB;background:#3A1715;border-color:#7A3530}}
.vc-nav{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:10px}.vc-n{color:var(--muted);font-size:14px}
.vc-nav button:disabled{opacity:.4;cursor:default}