:root{--ink:#1B3045;--sub:#53697D;--line:#D5E3ED;--bg:#F3F7FA;--paper:#fff;--blue:#236F99;--teal:#187E72;--amber:#AD731F}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:"Noto Sans CJK SC","PingFang SC","Microsoft YaHei",Arial,sans-serif;font-size:15px;line-height:1.82}
main{max-width:1030px;margin:24px auto 80px;padding:0 18px}.top{background:linear-gradient(125deg,#14354E,#255C76);color:white;padding:26px 32px;border-radius:20px;margin-bottom:20px}
h1{margin:2px 0;font-size:25px;line-height:1.55}.desc{font-size:13px;opacity:.9;margin-top:7px;line-height:1.75}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:12px}.chip{border:1px solid #B9CFDC;border-radius:99px;padding:3px 12px;font-size:12px;background:#EBF4FA;color:#275B78}
.top .chip{color:#fff;background:#FFFFFF18;border-color:#FFFFFF60}
.card{border:1px solid var(--line);border-radius:14px;padding:22px 24px;background:white;margin:15px 0;break-inside:avoid-page}
h2{font-size:18px;line-height:1.5;margin:0 0 8px}.meta{font-size:12px;color:var(--sub);margin:4px 0 13px}.stem{font-size:16px;font-weight:500;line-height:2.0;margin:12px 0 17px}
.option{display:flex;gap:12px;align-items:flex-start;padding:11px 14px;border:1px solid #DCE8EF;border-radius:11px;margin:8px 0;background:#FAFCFE;line-height:1.75;break-inside:avoid-page}
.optletter{display:inline-flex;align-items:center;justify-content:center;min-width:24px;height:24px;border:1px solid #B7CDD9;border-radius:50%;font-weight:700;font-size:12px;color:#1C5879}
.option>span:nth-child(2){flex:1;min-width:0}.figure{width:100%;max-width:720px;height:auto;display:block;margin:10px auto 3px;border:0}
.figurecaption{font-size:12px;color:var(--sub);text-align:center;margin:0 0 8px}.hint{background:#F2F8FB;padding:8px 12px;border-left:3px solid #6EA7BE;font-size:13px;color:#476279;margin:12px 0}
.answer-rule{height:40px;border-bottom:1px dashed #BCCDD9;margin:12px 0}
.steps{counter-reset:item;margin:12px 0 8px;padding-left:28px}.steps li{margin:10px 0;line-height:2.05;break-inside:avoid}.answer{border-radius:9px;background:#E9F5F0;color:#165F51;padding:9px 12px;font-weight:700;margin:10px 0}
.formulabox{background:#EDF5FA;border:1px solid #D7E5EE;border-radius:9px;padding:12px 14px;margin:10px 0;font-size:14px;line-height:2}.warning{border-left:3px solid #D4A55B;padding:8px 12px;background:#FFF9EB;color:#715725;font-size:14px}
.below{font-size:12px;color:var(--sub);margin:10px 0}.toolbar{display:flex;gap:8px;flex-wrap:wrap;margin:16px 0}.btn{border:1px solid #AAC8D8;border-radius:10px;padding:10px 13px;background:#fff;color:#195374;font-size:14px;font-weight:600;cursor:pointer}
.btn.primary{background:#246989;color:white;border-color:#246989}.btn:focus-visible,input:focus-visible{outline:3px solid #8CCAE2;outline-offset:2px}.btn:hover{filter:brightness(.96)}.btn:disabled{opacity:.5;cursor:not-allowed}
.tab{background:#fff;border:1px solid #CCDCE5;border-radius:10px;padding:8px 14px;cursor:pointer}.tab.active{background:#E3F1F8;border-color:#237DA1;font-weight:700}
.summary{background:#EDF7F2;border:1px solid #C6E2D6;padding:16px 20px;border-radius:12px;margin:12px 0;color:#15523E}
.progress{height:8px;background:#D5E4EC;border-radius:99px;overflow:hidden;margin:8px 0}.progress>div{background:#2C8A91;height:100%;transition:width .2s}
.guess-row{display:flex;align-items:center;flex-wrap:wrap;gap:14px;margin-top:13px;font-size:13px;color:#40576A}
.guess-row input{width:16px;height:16px;accent-color:#23759A;vertical-align:middle}.auto-tag{background:#F9F1DE;color:#79551C;border-radius:99px;padding:3px 9px;font-size:12px}.ok{color:#137251}.bad{color:#B64339}
pre{white-space:pre-wrap;overflow-wrap:anywhere}.foot{color:var(--sub);font-size:12px;margin:22px 0 40px}
math,mjx-container{max-width:100%;}mjx-container[display="true"]{overflow-x:auto;overflow-y:hidden;max-width:100%;padding:8px 0;margin:10px 0!important}
.card .stem mjx-container{vertical-align:middle!important}.option mjx-container{vertical-align:middle!important}.steps mjx-container{vertical-align:middle!important}
@media(max-width:600px){body{font-size:14px}main{margin:0 auto;padding:0 11px 24px}.top{border-radius:0 0 16px 16px;padding:20px 18px}.card{padding:16px 14px}.stem{font-size:15px}.option{padding:10px}.figure{max-width:100%}h1{font-size:21px}}
@page{size:A4;margin:16mm 13mm}
@media print{body{background:white;font-size:11.4px;line-height:1.65}main{max-width:none;margin:0;padding:0}.top{background:none!important;color:#17354C;padding:4mm 0 5mm;border-radius:0;border-bottom:2px solid #2D657F;margin:0 0 5mm}.top h1{font-size:17px}.top .chip{background:white;color:#45677B;border-color:#C4D1DB}.card{border:0;border-radius:0;border-bottom:1px solid #C4D2DD;padding:10px 0;margin:9px 0;break-inside:auto}h2{font-size:13px}.meta{font-size:9px;margin:2px 0 6px}.stem{font-size:11.6px;margin:6px 0;line-height:1.7}.option{background:white;border:0;margin:0;padding:2px 5px;font-size:10.3px;line-height:1.55}.optletter{min-width:18px;height:18px;font-size:9px}.figure{max-width:135mm;max-height:40mm;object-fit:contain;margin:5px auto 0}.figurecaption{font-size:8px}.hint{font-size:9px}.answer-rule{height:16px}.steps{margin:2px 0;font-size:10.2px}.steps li{line-height:1.65;margin:4px 0;break-inside:auto}.formulabox{padding:6px;font-size:9px}.warning{font-size:9px}.answer{padding:5px;font-size:10px}.below,.foot{font-size:9px}.toolbar,#nav-tabs,#summary,#quiz-progress,.no-print{display:none!important}mjx-container[display="true"]{overflow:visible;max-width:100%;padding:4px 0!important}body.student-print .card{break-inside:avoid-page;page-break-inside:avoid}a{color:inherit;text-decoration:none}}