:root{font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif;color:#19343d;background:#f4f6f7;font-synthesis:none;font-size:16px;--ink:#19343d;--teal:#177a70;--line:#dfe6e8;--lime:#c4f478}*{box-sizing:border-box}body{margin:0}button,input{font:inherit}button{cursor:pointer}button:disabled{cursor:default;opacity:.5}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #278bce;outline-offset:4px}button{color:inherit}header{height:84px;background:white;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 5vw;gap:20px}.brand{display:flex;align-items:center;gap:12px}.mark{display:grid;place-items:center;background:var(--ink);color:var(--lime);width:42px;height:42px;border-radius:12px;font:36px Georgia}.brand strong{font-size:22px;letter-spacing:2px}.brand small{font-size:12px;color:#63767c;display:block;letter-spacing:1.6px;margin-top:4px}.header-right{font-size:14px;display:flex;align-items:center;gap:18px}.pill{display:inline-flex;align-items:center;border:1px solid #c8dcd7;background:#f0f8f5;color:#17685e;border-radius:20px;padding:7px 12px;font-size:13px}.shell{max-width:1250px;margin:40px auto;padding:0 28px;display:grid;grid-template-columns:210px minmax(0,1fr);gap:40px}.sidebar{padding-top:10px}.eyebrow{font-size:12px;letter-spacing:1.8px;color:#6b7e84;font-weight:600}.nav{margin:24px 0 44px;display:grid;gap:8px}.nav button{border:0;text-align:left;border-radius:9px;background:transparent;padding:14px 16px;display:flex;gap:12px;font-size:15px}.nav button.active{color:#176f63;background:#e2efe9;font-weight:600}.nav span{opacity:.65}.side-note{border-top:1px solid var(--line);padding-top:22px;color:#6c7e83;font-size:14px;line-height:1.9}.side-note strong{font-weight:500;color:#354f58}.heading{display:flex;align-items:flex-start;justify-content:space-between;gap:20px;margin-bottom:26px}h1{font-size:30px;letter-spacing:-1px;font-weight:650;margin:8px 0 12px}p{line-height:1.7;color:#6b7a80;margin:8px 0}.step-label{font-size:13px;letter-spacing:2px;color:#24796e}.session-count{font:italic 50px Georgia;color:#d4dfe0;white-space:nowrap}.panel{background:white;border:1px solid var(--line);border-radius:16px;padding:28px;margin-bottom:20px}.section-title{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px;gap:10px}h2{font-size:18px;margin:0}.muted{font-size:14px;color:#657b81}.topic-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.topic{position:relative;display:block;border:1px solid #dce4e6;border-radius:10px;padding:18px;cursor:pointer;background:#fff;transition:.15s}.topic:has(input:checked){border-color:#28877a;background:#f3faf7;box-shadow:0 0 0 1px #28877a}.topic input{position:absolute;right:16px;top:18px;width:18px;height:18px;accent-color:#18776b}.topic strong{font-size:16px;display:block;padding-right:24px}.topic .en{font-size:12px;color:#789087;margin-top:5px}.formula{font:20px Georgia,"Times New Roman",serif;color:#34544e;margin-top:18px;line-height:1.45;overflow-wrap:anywhere}.rules{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.rules .topic{padding:16px}.rules .formula{font-size:17px}.config-bottom{display:flex;align-items:center;justify-content:space-between;gap:16px;margin:26px 0}.primary{background:var(--ink);color:white;border:0;border-radius:9px;padding:15px 24px;font-weight:600;min-height:50px;display:inline-flex;align-items:center;justify-content:center;gap:20px}.primary:hover{background:#24515b}.primary.lime{background:var(--lime);color:#183329}.ghost{border:1px solid #d6e0e3;background:white;padding:10px 16px;border-radius:8px;min-height:44px}.link-btn{background:transparent;border:0;color:#3b6d70;padding:8px;font-size:14px}.session-options{display:flex;gap:8px;margin-top:12px}.session-options label{border:1px solid var(--line);border-radius:7px;padding:8px 12px;font-size:14px;cursor:pointer}.session-options input{accent-color:var(--teal)}.mini-banner{background:var(--ink);color:white;border-radius:12px;padding:19px 22px;display:flex;align-items:center;justify-content:space-between;margin-top:22px;gap:15px}.mini-banner p{font-size:14px;color:#bcd0d1;margin:4px 0 0}.mini-banner b{font:italic 34px Georgia;color:var(--lime)}.quiz-top{display:flex;justify-content:space-between;align-items:center;font-size:14px;margin-bottom:14px}.progress-track{background:#e1e8e9;height:5px;border-radius:6px;overflow:hidden;margin-bottom:26px}.progress-fill{height:100%;background:#258675;transition:width .3s}.question-meta{display:flex;align-items:center;gap:12px;color:#6c8186;font-size:14px}.level-bars{display:flex;gap:4px}.level-bars i{display:block;width:6px;height:14px;border-radius:2px;background:#dbe6e6}.level-bars i.on{background:#258675}.question{background-color:#fff;background-image:linear-gradient(#f1f5f6 1px,transparent 1px),linear-gradient(90deg,#f1f5f6 1px,transparent 1px);background-size:24px 24px;border:1px solid var(--line);border-radius:13px;padding:26px;margin:16px 0 22px}.question h2{font-weight:500;font-size:16px;color:#57717a}.question .equation{font-size:32px;text-align:center;padding:32px 0;overflow-x:auto}.domain{font-size:13px;color:#687f86;text-align:center}.options{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.option{display:flex;align-items:center;gap:14px;text-align:left;background:white;border:1px solid #d8e2e4;border-radius:10px;padding:18px 16px;min-height:94px;transition:.15s;max-width:100%}.option:hover:not(:disabled){border-color:#2c8a7e;background:#f7fbfa}.letter{display:grid;place-items:center;flex-shrink:0;width:30px;height:30px;background:#f0f4f5;border-radius:7px;color:#678088;font-size:14px}.option.selected{border:2px solid #258675;background:#f0f9f5;padding:17px 15px}.option.selected .letter{background:#248070;color:white}.option:disabled{opacity:1}.option.correct{border-color:#278567;background:#eff9f2}.option.wrong{border-color:#d38573;background:#fff3ee}.option.correct .letter{background:#267c60;color:white}.option.wrong .letter{background:#ae5946;color:white}.option .expression{font-size:21px;overflow-x:auto;min-width:0;padding:6px 0}.quiz-actions{display:flex;align-items:center;justify-content:space-between;margin-top:22px;gap:12px}.feedback{margin-top:22px;background:#f0f8f3;border:1px solid #c5dfcf;border-radius:12px;padding:22px;scroll-margin-top:20px}.feedback.error{background:#fff8f2;border-color:#ecd5bf}.feedback h3{margin:0 0 12px;font-size:18px}.feedback p{color:#3f5f62;font-size:15px}.feedback .solution{padding:14px 0;font-size:22px;overflow-x:auto}.steps{line-height:2;color:#49646c;font-size:15px}.steps p{margin:10px 0}.adapt{border-top:1px solid #d5e2dd;margin-top:14px;padding-top:14px;font-size:14px;color:#466b61}.stats-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-bottom:24px}.stat{padding:24px;background:#fff;border:1px solid var(--line);border-radius:12px}.stat b{display:block;font-size:32px;font-weight:550;margin-bottom:8px}.stat span{font-size:14px;color:#6c8186}.skill-row{display:grid;grid-template-columns:120px 1fr 100px;gap:18px;align-items:center;padding:20px 0;border-bottom:1px solid #ebeff0}.skill-row:last-child{border:0}.skill-row .progress-track{margin:8px 0;height:6px}.status{font-size:13px;color:#42726b;text-align:right}.empty{padding:38px;text-align:center;color:#6d8289}.record{display:flex;align-items:center;gap:14px;padding:16px 0;border-bottom:1px solid var(--line)}.record-icon{color:#218263;font-size:21px}.record-icon.bad{color:#b6664e}.record .record-main{flex:1;min-width:0}.record p{font-size:14px;margin:4px 0}.record math{font-size:19px}.notice{font-size:13px;color:#6b8086;line-height:1.7}.error-text{color:#ad4e3b;font-size:14px}.footer{font-size:12px;color:#7a8e94;display:flex;justify-content:space-between;margin:26px 0;gap:15px}math{font-family:"STIX Two Math","Cambria Math",math;max-width:none}dialog{border:1px solid var(--line);border-radius:14px;padding:28px;max-width:420px;width:calc(100% - 32px);color:var(--ink)}dialog::backdrop{background:#16313e66}dialog .quiz-actions{justify-content:flex-end}@media(min-width:1450px){.shell{margin-top:56px}}@media(max-width:1000px){.shell{grid-template-columns:160px minmax(0,1fr);gap:24px}.rules{grid-template-columns:1fr}.rules .topic{display:flex;align-items:center;gap:18px;padding-right:46px}.rules .formula{margin:0;font-size:17px}.rules .en{display:none}.rules .topic strong{padding:0;white-space:nowrap}}@media(max-width:720px){header{height:72px;padding:0 20px}.header-right .header-text{display:none}.brand strong{font-size:20px}.brand small{font-size:10px}.shell{display:block;padding:0 18px;margin:0 auto}.sidebar{padding:0}.sidebar>.eyebrow,.side-note{display:none}.nav{display:flex;margin:18px 0 26px;gap:5px;border-bottom:1px solid var(--line);padding-bottom:12px}.nav button{padding:11px 13px;font-size:14px;justify-content:center;flex:1;white-space:nowrap}.nav span{display:none}.heading{margin-bottom:20px}h1{font-size:25px;margin-top:8px}.heading p{font-size:14px}.session-count{font-size:40px}.panel{padding:20px 16px;border-radius:12px}.topic{padding:15px 12px}.topic input{right:12px;top:15px}.topic .en{font-size:11px}.formula{font-size:18px}.rules .topic{display:block}.rules .formula{margin-top:12px;font-size:18px}.section-title .muted{font-size:12px}.config-bottom{align-items:stretch;flex-direction:column}.config-bottom .primary{width:100%}.question{padding:20px 14px}.question .equation{font-size:28px;padding:28px 0}.options{grid-template-columns:1fr;gap:9px}.option{min-height:70px;padding:13px 14px}.option.selected{padding:12px 13px}.option .expression{font-size:22px}.quiz-actions .primary{flex:1}.stats-grid{gap:8px}.stat{padding:18px 12px}.stat b{font-size:27px}.stat span{font-size:12px}.skill-row{grid-template-columns:90px 1fr;gap:10px}.skill-row .status{grid-column:2;text-align:left}.footer{line-height:1.7;font-size:11px}.mini-banner{padding:17px}.quiz-top{font-size:13px}.feedback{padding:18px}.session-options{flex-wrap:wrap}}@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}

/* Selection is blue; grading is green/red and also labelled in text. */
.option.selected{border-color:#3774c3;background:#f0f5ff}
.option.selected .letter{background:#3774c3;color:#fff}
.option.correct{border:2px solid #228449;background:#eaf8ef;padding:17px 15px}
.option.correct .letter{background:#228449;color:#fff}
.option.wrong{border:2px solid #c73743;background:#fff0f1;padding:17px 15px}
.option.wrong .letter{background:#c73743;color:#fff}
.result-mark{margin-left:auto;flex-shrink:0;font-size:13px;font-weight:650;white-space:nowrap;color:#176738}
.option.wrong .result-mark{color:#af2530}
@media(max-width:720px){.option.correct,.option.wrong{padding:12px 13px}.result-mark{font-size:12px}.option:has(.result-mark){gap:10px}}

/* Focused practice: the work and the next action share the first viewport. */
body[data-view="quiz"] .shell{margin-top:20px}
body[data-view="quiz"] .footer{display:none}
.practice-surface .quiz-top{margin-bottom:6px;min-height:34px}
.practice-surface>.progress-track{margin-bottom:10px;height:4px}
.quiz-panel{padding:18px;margin-bottom:0}
.quiz-panel .question-meta{gap:9px}
.quiz-panel .question{padding:12px 16px;margin:10px 0 12px}
.quiz-panel .question .equation{padding:14px 0;font-size:28px}
.quiz-panel .section-title{margin-bottom:9px}
.quiz-panel .options{gap:8px}
.quiz-panel .option{min-height:76px;padding:10px 12px}
.quiz-panel .option.selected,.quiz-panel .option.correct,.quiz-panel .option.wrong{padding:9px 11px}
.practice-actions{margin-top:12px}
.action-status{display:flex;align-items:center;gap:8px;flex-wrap:wrap;font-size:14px}
.action-status .link-btn{min-height:44px}
.answer-right{color:#176738}.answer-wrong{color:#af2530}
.explanation{scroll-margin-top:12px;padding-bottom:16px}
.explanation[hidden]{display:none}
.explanation .feedback{margin-top:14px}
@media(max-width:720px){
 body[data-view="quiz"] header{height:42px;padding:0 12px}
 body[data-view="quiz"] .mark{width:28px;height:28px;font-size:25px;border-radius:8px}
 body[data-view="quiz"] .brand{gap:8px}
 body[data-view="quiz"] .brand strong{font-size:17px}
 body[data-view="quiz"] .brand small{display:none}
 body[data-view="quiz"] .header-right .pill{border:0;background:none;padding:0;font-size:12px}
 body[data-view="quiz"] .sidebar{display:none}
 body[data-view="quiz"] .shell{margin:0;padding:0 10px}
 body[data-view="quiz"] main{padding-bottom:calc(74px + env(safe-area-inset-bottom,0px))}
 .practice-surface{padding-top:3px}
 .practice-surface .quiz-top{margin:0;min-height:34px;font-size:13px}
 .practice-surface .quiz-top .link-btn{min-height:34px;padding:6px 0 6px 12px}
 .practice-surface>.progress-track{margin:0 0 6px;height:3px}
 .quiz-panel{padding:10px;border-radius:10px}
 .quiz-panel .question-meta{gap:7px;font-size:12px}
 .quiz-panel .question-meta .pill{padding:4px 8px;font-size:12px}
 .quiz-panel .level-bars i{height:11px;width:5px}
 .quiz-panel .question{padding:8px 10px;margin:7px 0 8px;border-radius:8px}
 .quiz-panel .question h2{font-size:14px}
 .quiz-panel .question .equation{padding:9px 0;font-size:25px}
 .quiz-panel .domain{font-size:12px;line-height:1.3}
 .quiz-panel .section-title{margin-bottom:6px}
 .quiz-panel .section-title .muted{font-size:12px}
 .quiz-panel .options{grid-template-columns:repeat(2,minmax(0,1fr));gap:6px}
 .quiz-panel .option,.quiz-panel .option.selected,.quiz-panel .option.correct,.quiz-panel .option.wrong{position:relative;display:flex;align-items:center;justify-content:center;min-height:76px;padding:24px 7px 7px;border-width:2px;gap:0;border-radius:8px}
 .quiz-panel .option .letter{position:absolute;top:5px;left:6px;width:21px;height:21px;font-size:12px;border-radius:5px}
 .quiz-panel .option .expression{font-size:19px;padding:1px 0;width:100%;text-align:center}
 .quiz-panel .option .result-mark{position:absolute;right:6px;top:7px;font-size:12px;line-height:17px}
 .quiz-panel .options.wide-options{grid-template-columns:1fr;gap:5px}
 .quiz-panel .wide-options .option,.quiz-panel .wide-options .option.selected,.quiz-panel .wide-options .option.correct,.quiz-panel .wide-options .option.wrong{min-height:52px;padding:6px 49px 6px 34px}
 .quiz-panel .wide-options .option .letter{top:50%;transform:translateY(-50%)}
 .quiz-panel .wide-options .option .result-mark{top:50%;transform:translateY(-50%)}
 .quiz-panel .wide-options .option .expression{font-size:19px;padding:0}
 .practice-actions{position:fixed;z-index:30;left:0;right:0;bottom:0;margin:0;padding:9px 12px calc(9px + env(safe-area-inset-bottom,0px));background:#fff;border-top:1px solid #dbe5e7;box-shadow:0 -3px 12px #19343d0a;gap:10px;min-height:66px}
 .practice-actions .action-status{flex:1;min-width:0;gap:0;display:flex;flex-direction:column;align-items:flex-start;justify-content:center;font-size:14px}
 .practice-actions .action-status .link-btn{padding:0;min-height:24px;font-size:13px;text-align:left}
 .practice-actions .primary{flex:0 0 46%;min-height:46px;padding:10px 14px;gap:12px}
 .explanation{padding-bottom:12px}
 .explanation .feedback{padding:16px}
}
@media(max-width:720px) and (max-height:650px){
 .quiz-panel .question .equation{padding:5px 0;font-size:23px}
 .quiz-panel .question{margin:5px 0 6px;padding:6px 9px}
 .quiz-panel .option,.quiz-panel .option.selected,.quiz-panel .option.correct,.quiz-panel .option.wrong{min-height:68px;padding-top:22px;padding-bottom:5px}
 .quiz-panel .options.wide-options .option{min-height:48px;padding-top:4px;padding-bottom:4px}
}
@media(max-width:720px){body[data-view="quiz"] header{display:none}}
.mode-tabs{display:flex;gap:6px;padding:5px;border:1px solid #d7e4e4;background:#eaf0f1;border-radius:11px;margin-bottom:18px}.mode-tabs button{flex:1;min-height:48px;border:0;border-radius:7px;background:transparent;font-size:18px;font-weight:600;color:#688087}.mode-tabs button.active{background:#19343d;color:#fff;box-shadow:0 2px 5px #19343d1a}.scope-controls{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:20px}.board-control{display:flex;align-items:center;gap:10px;font-size:14px;margin:8px 0 18px;color:#56737b}.scope-controls .board-control{margin:0}.board-control select{font:inherit;color:#19343d;background:#fff;border:1px solid #ccdce0;min-height:44px;border-radius:7px;padding:8px 10px;max-width:100%}.scope-note{border-top:1px solid #dbe4e5;margin:22px 0;padding:16px 0;font-size:14px;line-height:1.8;color:#607b80}.scope-note summary{cursor:pointer;color:#315a64}.scope-note a{display:block;color:#24776b;margin-top:6px}.topic-note{font-size:12px;line-height:1.6;color:#65807d;margin-top:10px;padding-right:2px}.formula-row{padding:18px 0;border-bottom:1px solid #e5ebec}.formula-row:last-child{border:0}.formula-row .formula{margin-top:8px;font-size:20px}.identity-reference{margin-top:18px}.identity-reference p{font-size:15px;color:#43666c}.question-hint{font-size:13px;color:#466e72;margin:5px 0;text-align:center}.question-hint math{font-size:17px}.question .equation>div+div{margin-top:6px}.question .equation small{font:14px sans-serif}.topic .formula{font-size:18px;line-height:1.6}.topic .en{font-size:12px}.quiz-panel .question h2{line-height:1.5}.quiz-panel .option .expression math{white-space:nowrap}
@media(max-width:720px){.nav button{padding:10px 8px}.scope-controls{align-items:flex-start;gap:5px}.scope-controls .link-btn{font-size:13px;padding:8px 5px}.board-control{font-size:13px;gap:6px}.board-control select{max-width:195px;font-size:13px}.topic .formula{font-size:17px}.mode-tabs button{min-height:44px;font-size:17px}.topic-note{font-size:12px}.question .equation>div+div{margin-top:4px}.formula-row .formula{font-size:18px}}

/* Compact category selection: names first, optional individual choices. */
.selection-list{border:1px solid var(--line);border-radius:12px;background:#fff;overflow:hidden}
.selection-group+.selection-group{border-top:1px solid var(--line)}
.selection-group-row{display:flex;align-items:center;min-height:54px;padding:0 14px;gap:10px}
.selection-parent{display:flex;align-items:center;gap:10px;flex:1;min-width:0;min-height:48px;cursor:pointer;font-size:15px}
.selection-parent input,.selection-children input{width:18px;height:18px;margin:0;accent-color:#258372;flex-shrink:0;cursor:pointer}
.selection-count{color:#71868a;font-size:12px;font-variant-numeric:tabular-nums}
.selection-expand{border:0;background:transparent;color:#34756b;min-height:44px;padding:0 7px;font:inherit;font-size:13px;cursor:pointer}
.selection-expand span{margin-left:5px}
.selection-children{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:4px 12px;padding:4px 14px 12px 42px;background:#f7faf9}
.selection-children[hidden]{display:none}
.selection-children label{display:flex;align-items:center;gap:9px;min-height:44px;font-size:14px;cursor:pointer;line-height:1.4}
.selection-children label span{overflow-wrap:anywhere}
.selection-notice{margin:10px 0 14px}
.selection-expand:focus-visible,.selection-parent input:focus-visible,.selection-children input:focus-visible{outline:2px solid #3774c3;outline-offset:3px}
body[data-view="setup"] .scope-controls{align-items:center;margin-bottom:8px}
body[data-view="setup"] .config-bottom{margin-top:14px}
@media(max-width:720px){
 body[data-view="setup"] header{height:54px}
 body[data-view="setup"] .nav{margin:8px 0 12px;padding-bottom:7px}
 body[data-view="setup"] .heading{margin-bottom:12px}
 body[data-view="setup"] .heading .step-label{display:none}
 body[data-view="setup"] h1{font-size:23px;margin:0 0 6px}
 body[data-view="setup"] .heading p{margin:0;font-size:13px}
 body[data-view="setup"] .mode-tabs{margin-bottom:8px}
 body[data-view="setup"] .scope-controls .link-btn{min-height:40px;padding:7px}
 .selection-group-row{min-height:49px;padding:0 11px;gap:6px}
 .selection-parent{min-height:48px;font-size:14px}
 .selection-children{grid-template-columns:repeat(2,minmax(0,1fr));padding:4px 11px 10px 15px;gap:3px 10px}
 .selection-children label{font-size:13px}
 body[data-view="setup"] .config-bottom{gap:12px}
 body[data-view="setup"] .config-bottom>div{display:flex;align-items:center;justify-content:space-between;gap:10px;font-size:14px}
 body[data-view="setup"] .session-options{margin-top:0;gap:12px}
}

/* Four compact length choices, including open-ended adaptive practice. */
.session-length{flex:1;min-width:0}
.session-length .session-options{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:6px;margin-top:8px}
.session-length .session-options label{display:flex;align-items:center;justify-content:center;gap:5px;min-height:44px;padding:5px 8px;border:1px solid var(--line);border-radius:7px;white-space:nowrap;cursor:pointer;font-size:14px}
.session-length .session-options label:has(input:checked){background:#edf8f5;border-color:#258372;color:#196657}
.session-length input{accent-color:#258372;margin:0}
@media(max-width:720px){body[data-view="setup"] .config-bottom>.session-length{display:block}.session-length .session-options label{padding:5px 3px;font-size:14px}body[data-view="setup"] .session-length .session-options{gap:5px;margin-top:8px}}

.question .equation .problem-context{font-family:inherit;font-size:15px;font-style:normal;line-height:1.6;text-align:left;margin:7px 0;color:#31535b}.question .equation .problem-context:first-child{margin-top:0}
@media(max-width:720px){.question .equation .problem-context{font-size:14px;line-height:1.45;margin:5px 0}.quiz-panel .question:has(.problem-context) .equation{padding:5px 0}}

.selection-layer{padding:8px 12px;background:#edf3f3;color:#446870;font-size:13px;font-weight:600;border-top:1px solid var(--line)}.selection-layer:first-child{border-top:0}

.selection-basic-note{font-size:13px;color:#668086;white-space:nowrap}.selection-group-row:has(input[value^="basic_"]){background:#f5faf8}