:root{--paper:#fbf8f1;--card:#fff;--ink:#1b2230;--muted:#5b6474;--line:#ddd5c4;--accent:#0d6b4d;--accent-ink:#fff;--accent-soft:#e3f1ea;--hl:#ffe98a;--bad:#b3261e;--bad-soft:#fbe7e5;--good:#0d6b4d;--good-soft:#e3f1ea;--focus:#1f5fbf;--shadow:0 1px 2px rgba(27,34,48,.06),0 4px 14px rgba(27,34,48,.05);color-scheme:light}
@media (prefers-color-scheme:dark){:root{--paper:#14171d;--card:#1c2028;--ink:#e9e6df;--muted:#a3abb8;--line:#343a46;--accent:#46b88c;--accent-ink:#0b1a13;--accent-soft:#1d3a2f;--hl:#6b5a12;--bad:#ff8a80;--bad-soft:#3d2120;--good:#46b88c;--good-soft:#1d3a2f;--focus:#8ab4ff;--shadow:none;color-scheme:dark}}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.55 system-ui,-apple-system,"Segoe UI",Roboto,"Noto Sans",sans-serif}
a{color:var(--accent)}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,label:focus-within{outline:3px solid var(--focus);outline-offset:2px}
h1,h2,h3{font-family:Georgia,"Times New Roman",serif;line-height:1.2;font-weight:700;letter-spacing:-.01em}
h1{font-size:clamp(1.7rem,4.6vw,2.6rem);margin:.2em 0 .4em}
h2{font-size:clamp(1.3rem,3vw,1.7rem);margin:1.8em 0 .5em}
h3{font-size:1.1rem;margin:1.2em 0 .3em}
p{margin:.5em 0 .9em}
small,.muted{color:var(--muted)}
.wrap{max-width:1060px;margin:0 auto;padding:0 16px}
.narrow{max-width:720px}
.skip{position:absolute;left:-999px}.skip:focus{left:16px;top:8px;background:var(--card);padding:6px 10px;z-index:9}
header.top{border-bottom:1px solid var(--line);background:var(--paper)}
header.top .wrap{display:flex;align-items:center;gap:14px;min-height:56px;flex-wrap:wrap}
.logo{font-weight:800;font-size:1.15rem;color:var(--ink);text-decoration:none;display:flex;align-items:center;gap:8px}
.logo svg{width:26px;height:26px}
nav.main{display:flex;gap:4px 14px;flex-wrap:wrap;margin-left:auto;font-size:.95rem}
nav.main a{color:var(--ink);text-decoration:none;padding:6px 2px;border-bottom:2px solid transparent}
nav.main a[aria-current=page]{border-color:var(--accent)}
main{padding:18px 0 40px}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;min-height:46px;padding:10px 18px;border-radius:10px;border:2px solid var(--accent);background:var(--accent);color:var(--accent-ink);font:inherit;font-weight:700;text-decoration:none;cursor:pointer}
.btn.ghost{background:transparent;color:var(--accent)}
.btn.small{min-height:38px;padding:6px 12px;font-size:.92rem}
.btn[disabled]{opacity:.5;cursor:not-allowed}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.hero{display:grid;grid-template-columns:1.05fr 1fr;gap:28px;align-items:start;padding-top:8px}
.kicker{display:inline-block;background:var(--hl);color:var(--ink);padding:2px 8px;border-radius:4px;font-size:.88rem;font-weight:700}
.lead{font-size:1.08rem}
.card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px;box-shadow:var(--shadow)}
.facts{width:100%;border-collapse:collapse;font-size:.95rem;background:var(--card);border:1px solid var(--line);border-radius:12px;overflow:hidden}
.facts th,.facts td{text-align:left;padding:9px 12px;border-bottom:1px solid var(--line);vertical-align:top}
.facts th{width:42%;font-weight:600}
.facts tr:last-child th,.facts tr:last-child td{border-bottom:0}
.cite{font-size:.82rem;color:var(--muted)}
.cite a{color:var(--muted)}
.levels{display:grid;grid-template-columns:1fr 1fr;gap:16px}
.levels .card h3{margin-top:0}
.levels ul{padding-left:1.1em;margin:.4em 0 1em}
.two{display:grid;grid-template-columns:1.4fr 1fr;gap:24px;align-items:start}
.note{border-left:4px solid var(--hl);background:var(--card);padding:10px 14px;border-radius:0 10px 10px 0}
/* question card: answer-sheet bubbles */
.qmeta{display:flex;gap:8px;flex-wrap:wrap;font-size:.82rem;color:var(--muted);margin-bottom:8px}
.qmeta span{border:1px solid var(--line);border-radius:999px;padding:1px 9px}
.stim{white-space:pre-wrap;background:var(--paper);border:1px dashed var(--line);border-radius:10px;padding:12px;margin:0 0 12px;font-size:.95rem;max-height:46vh;overflow:auto}
.stim.table{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.85rem;white-space:pre;overflow-x:auto}
.qtext{font-size:1.06rem;font-weight:600;margin:0 0 12px;white-space:pre-wrap}
.choices{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.choice{display:flex;gap:12px;align-items:flex-start;width:100%;text-align:left;background:var(--card);color:var(--ink);border:1.5px solid var(--line);border-radius:10px;padding:10px 12px;font:inherit;cursor:pointer;min-height:48px}
.choice:hover{border-color:var(--accent)}
.bubble{flex:0 0 28px;height:28px;border-radius:50%;border:2px solid var(--ink);display:grid;place-items:center;font-size:.8rem;font-weight:700;line-height:1}
.choice[aria-pressed=true] .bubble,.choice.picked .bubble{background:var(--ink);color:var(--paper)}
.choice.right{border-color:var(--good);background:var(--good-soft)}
.choice.right .bubble{background:var(--good);border-color:var(--good);color:var(--accent-ink)}
.choice.wrong{border-color:var(--bad);background:var(--bad-soft)}
.choice.wrong .bubble{background:var(--bad);border-color:var(--bad);color:#fff}
.choice[disabled]{cursor:default}
.why{margin-top:12px;padding:12px 14px;border-radius:10px;background:var(--paper);border:1px solid var(--line)}
.why b.ok{color:var(--good)}.why b.no{color:var(--bad)}
.why .src{font-size:.85rem;margin:.4em 0 0}
.qfoot{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-top:14px;flex-wrap:wrap}
.linkbtn{background:none;border:0;color:var(--muted);font:inherit;font-size:.85rem;text-decoration:underline;cursor:pointer;padding:6px 0}
/* setup forms */
fieldset{border:1px solid var(--line);border-radius:12px;padding:12px 14px;margin:0 0 14px;background:var(--card)}
legend{font-weight:700;padding:0 6px}
.opts{display:flex;flex-wrap:wrap;gap:8px}
.opt{display:flex;align-items:center;gap:8px;border:1.5px solid var(--line);border-radius:10px;padding:8px 12px;cursor:pointer;min-height:44px;background:var(--paper)}
.opt:has(input:checked){border-color:var(--accent);background:var(--accent-soft)}
.opt input{accent-color:var(--accent);width:18px;height:18px;margin:0}
label.field{display:block;font-weight:600;margin:0 0 4px}
input[type=email],input[type=text],textarea,select{width:100%;font:inherit;padding:10px 12px;border:1.5px solid var(--line);border-radius:10px;background:var(--card);color:var(--ink);min-height:46px}
.check{display:flex;gap:10px;align-items:flex-start;font-size:.93rem}
.check input{width:20px;height:20px;margin-top:2px;flex:0 0 20px;accent-color:var(--accent)}
.hp{position:absolute;left:-5000px;width:1px;height:1px;overflow:hidden}
.msg{padding:10px 14px;border-radius:10px;margin:10px 0}
.msg.ok{background:var(--good-soft);border:1px solid var(--good)}
.msg.err{background:var(--bad-soft);border:1px solid var(--bad)}
/* progress */
.bars{display:grid;gap:8px}
.bar{display:grid;grid-template-columns:110px 1fr 64px;gap:10px;align-items:center;font-size:.92rem}
.bar .track{height:10px;background:var(--line);border-radius:999px;overflow:hidden}
.bar .fill{height:100%;background:var(--accent);border-radius:999px}
.stat{font-size:2rem;font-weight:800;font-family:Georgia,serif}
/* mock exam */
.examhead{position:sticky;top:0;z-index:5;background:var(--paper);border-bottom:1px solid var(--line);padding:8px 0;margin-bottom:12px}
.examhead .row{justify-content:space-between}
.timer{font-variant-numeric:tabular-nums;font-weight:800;font-size:1.2rem}
.timer.low{color:var(--bad)}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(38px,1fr));gap:5px;margin-top:10px}
.grid button{min-height:36px;border:1.5px solid var(--line);background:var(--card);color:var(--ink);border-radius:7px;font:inherit;font-size:.8rem;cursor:pointer;padding:0}
.grid button.done{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.grid button.flag{box-shadow:inset 0 -4px 0 var(--hl)}
.grid button.cur{outline:2px solid var(--accent);outline-offset:1px}
.grid button.right{background:var(--good);border-color:var(--good);color:var(--accent-ink)}
.grid button.wrong{background:var(--bad);border-color:var(--bad);color:#fff}
details.nav summary{cursor:pointer;font-weight:600;padding:6px 0}
.price{font-family:Georgia,serif;font-size:2.2rem;font-weight:800}
.price s{font-size:1rem;color:var(--muted);font-weight:400}
ul.plain{padding-left:1.1em}
ul.plain li{margin:.3em 0}
footer.site{border-top:1px solid var(--line);padding:22px 0 34px;font-size:.88rem;color:var(--muted)}
footer.site a{color:var(--muted)}
footer.site p{margin:.3em 0}
.disclaim{font-weight:600;color:var(--ink)}
.hidden{display:none!important}
@media (max-width:600px){.facts,.facts tbody,.facts tr,.facts th,.facts td{display:block;width:100%}.facts th{border-bottom:0;padding-bottom:0}.facts td{padding-top:2px}}
@media (max-width:820px){.hero,.two,.levels{grid-template-columns:1fr}.hero{gap:18px}nav.main{margin-left:0;width:100%;gap:2px 12px;font-size:.9rem}header.top .wrap{padding-top:6px;padding-bottom:4px;gap:4px}}
@media (prefers-reduced-motion:no-preference){.choice,.btn{transition:border-color .12s,background-color .12s}}
@media print{header.top,footer.site,.examhead,.qfoot{display:none}}