:root{--navy:#13263e;--blue:#164b73;--gold:#ffd84d;--ink:#17344b;--muted:#51697c;--line:#cddce6;--green:#237548;--red:#ad382f}*{box-sizing:border-box}body{margin:0;font:17px/1.4 system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--ink);background:#f1f5f8}a{color:var(--blue)}button,input,select{font:inherit}button,select{cursor:pointer}button{min-height:44px;border:1px solid var(--blue);border-radius:8px;padding:9px 15px;background:var(--blue);color:white;font-weight:700}button:hover{background:var(--navy)}button.secondary{background:white;color:var(--blue)}button.secondary:hover{background:#eaf2f7}button:disabled{opacity:.4;cursor:default}button:focus-visible,select:focus-visible,input:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid #a26900;outline-offset:3px}[hidden]{display:none!important}.skip{position:absolute;top:-70px;left:12px;z-index:5;background:white;padding:10px}.skip:focus{top:10px}.site-header{background:var(--navy);border-bottom:3px solid var(--gold)}.header-inner{max-width:960px;margin:auto;padding:5px 20px;display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:50px}.brand{display:inline-flex;align-items:center;min-height:44px;font-size:20px;letter-spacing:-.04em;font-weight:800;color:white;text-decoration:none;white-space:nowrap}.brand span{color:var(--gold)}.skills-back{font-size:14px;color:#d5e5ef;min-height:44px;display:inline-flex;align-items:center;white-space:nowrap}main{width:100%;max-width:640px;margin:auto;padding:20px 20px 18px}h1{font-size:29px;line-height:1.15;margin:0 0 15px;letter-spacing:-.03em}h2{font-size:23px;line-height:1.2;margin:0}h3{font-size:17px;margin:0 0 9px}.selector{margin-bottom:13px}.selector label{display:block;font-size:13px;font-weight:650;margin-bottom:5px}select{width:100%;min-height:45px;border:1px solid #9bb1c1;border-radius:8px;padding:8px 32px 8px 12px;background:white;color:var(--ink);font-size:16px}.quiz-card{padding:20px 22px 17px;border:1px solid var(--line);border-radius:13px;background:white;box-shadow:0 5px 20px #13263e07}.status-row{display:flex;justify-content:space-between;align-items:center;gap:12px;font-size:13px;color:var(--muted)}.question{font-size:36px;line-height:1.2;font-weight:750;font-variant-numeric:tabular-nums;margin:22px 0 20px;letter-spacing:-.015em;overflow-wrap:anywhere}.question .from-unit{white-space:nowrap}.question .arrow{font-size:.75em;font-weight:400;color:#738d9e;margin:0 .13em}.question .to-unit{white-space:nowrap}.answer-label{font-size:13px;display:block;margin-bottom:5px}.answer-row{display:flex;align-items:center;gap:9px}.answer-row input{width:100%;min-width:0;flex:1;min-height:49px;padding:8px 11px;border:2px solid #8ba5b7;border-radius:8px;color:var(--ink);font-size:22px;font-variant-numeric:tabular-nums;background:white}.answer-row input.correct{background:#effaf3;border-color:var(--green)}.answer-row input.incorrect{background:#fff5f2;border-color:var(--red)}.answer-unit{font-size:20px;font-weight:650;white-space:nowrap}.answer-row button{flex:none;padding:10px 13px;min-height:49px}.feedback{font-size:15px;min-height:2.6em;line-height:1.3;margin:12px 0 8px}.feedback.correct{color:var(--green);font-weight:650}.feedback.incorrect,.feedback.invalid{color:var(--red)}.action-row{display:grid;grid-template-columns:1fr 1fr 1.2fr;gap:9px}.action-row button{font-size:15px;padding:9px 10px}.help-box{border-left:3px solid var(--gold);border-radius:2px;background:#fffbee;padding:11px 13px;margin-top:12px;font-size:15px;line-height:1.4;overflow-wrap:anywhere}.help-box strong{color:var(--green)}.progress-track{height:4px;background:#e3ebf0;border-radius:4px;overflow:hidden;margin-top:16px}.progress-track span{height:100%;display:block;background:var(--blue)}.tools{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:7px}.text-button{min-height:44px;border:0;background:transparent;color:var(--blue);padding:6px 0;font-size:13px;font-weight:600;text-decoration:underline}.text-button:hover{background:none;color:var(--blue)}#best{font-size:12px;color:var(--muted)}.small-note{font-size:12px;color:var(--muted);text-align:center;margin:0 0 4px}.result-score{font-size:43px;font-weight:800;color:var(--green);line-height:1.1;margin:18px 0 13px}#result-note{font-size:15px;margin:0 0 20px}.result-actions{display:grid;grid-template-columns:1fr 1fr;gap:10px}.answer-review{margin-top:20px;border-top:1px solid var(--line);padding-top:12px}.answer-review summary{cursor:pointer;color:var(--blue);font-size:15px;font-weight:650}.answer-review ol{padding-left:24px;font-size:15px}.answer-review li{padding:6px 0}.answer-review .answer{font-weight:750;color:var(--green)}dialog{width:min(590px,calc(100% - 24px));max-height:85svh;padding:0;border:1px solid var(--line);border-radius:13px;color:var(--ink);background:white}dialog::backdrop{background:#13263e80}.guide-head{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:15px 18px;border-bottom:1px solid var(--line);position:sticky;top:0;background:white;z-index:1}.guide-head button{font-size:14px}.guide-body{padding:17px 18px;font-size:15px}.guide-body>p{margin:0 0 15px}.guide-example{border:1px solid var(--line);padding:11px;border-radius:7px;margin:12px 0}.guide-example summary{cursor:pointer;color:var(--blue);font-weight:700}.guide-example p{margin:10px 0 0}.reference-list{margin:12px 0 0}.reference-list>div{padding:8px 0;border-top:1px solid #e1e8ed;display:grid;grid-template-columns:1fr 1fr;gap:12px}.reference-list dt{font-weight:650}.reference-list dd{margin:0}.unit-pairs>div{display:flex;justify-content:space-between;gap:10px;margin-top:9px;padding:9px;background:#eef4f8}.unit-equation{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:9px;padding:12px;background:#eef4f8;margin-top:10px}.fraction{display:inline-flex;flex-direction:column;text-align:center;line-height:1.3}.fraction>span:first-child{border-bottom:1px solid currentColor;padding-bottom:3px}.fraction>span:last-child{padding-top:3px}noscript{display:block;background:#fff1c9;padding:14px}
@media(max-width:600px){.header-inner{padding:3px 14px;min-height:46px}.brand{font-size:18px}.skills-back{font-size:13px}main{padding:13px 12px 10px}h1{font-size:25px;margin-bottom:10px}.selector{margin-bottom:10px}.selector label{font-size:12px;margin-bottom:4px}.quiz-card{padding:15px 15px 13px}.question{font-size:31px;margin:18px 0 17px}.answer-unit{font-size:17px}.answer-row{gap:7px}.answer-row input{font-size:21px;padding:7px 9px}.answer-row button{font-size:15px;padding:9px 11px}.feedback{font-size:14px;margin:10px 0 7px;min-height:2.6em}.action-row{gap:7px}.action-row button{font-size:14px;padding:9px 6px}.progress-track{margin-top:13px}.tools{margin-top:5px}.small-note{font-size:11px}.result-score{font-size:38px}.result-actions button{padding:9px 6px;font-size:15px}.guide-body{padding:13px}.guide-head{padding:12px 13px}.reference-list>div{grid-template-columns:1fr 1fr;gap:8px}}
@media(max-width:360px){.question{font-size:27px}.quiz-card{padding:13px 12px}.answer-unit{font-size:15px}.answer-row input{font-size:20px}.answer-row button{padding:9px}.action-row button{font-size:13px}#best{font-size:11px}}
@media(max-height:660px) and (max-width:600px){main{padding-top:9px}h1{font-size:23px;margin-bottom:8px}.question{margin:12px 0 13px}.feedback{min-height:2.4em}.quiz-card{padding-top:12px;padding-bottom:11px}.progress-track{margin-top:10px}.small-note{margin-bottom:0}}
@media(max-height:540px) and (max-width:600px){.answer-focused .site-header,.answer-focused h1,.answer-focused .selector,.answer-focused .tools,.answer-focused .small-note{display:none}.answer-focused main{padding-top:8px}.answer-focused .question{margin:10px 0}.answer-focused .feedback{margin:7px 0}.answer-focused .quiz-card{padding-top:10px}.answer-focused .answer-label{display:none}.answer-focused .status-row{font-size:12px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}