:root{--bg:#f6f4ef;--ink:#242532;--muted:#74737e;--line:#dfded9;--purple:#665399;--purple-light:#eae5f3;--green:#d8e9b7;--dark-green:#344b2b;--white:#fffefa;--yellow:#f2d789;--red:#a9423f;--radius:18px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:100px}body{margin:0;background:var(--bg);color:var(--ink);font-family:"Noto Sans TC","PingFang TC","Microsoft JhengHei",sans-serif;line-height:1.75}button,input,select{font:inherit}button,a,input,summary,select{-webkit-tap-highlight-color:transparent}button{cursor:pointer}button:disabled{cursor:default}a{color:inherit;text-decoration:none}button{border:0}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible,select:focus-visible{outline:3px solid #8d75c6;outline-offset:4px}header{height:86px;max-width:1280px;padding:0 52px;display:flex;align-items:center;justify-content:space-between;margin:auto;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;font-size:18px;font-weight:800;gap:12px;letter-spacing:.5px}.brand-symbol{font-size:42px;font-weight:400;line-height:1;transform:rotate(-8deg)}.brand-light{font-weight:400;margin-left:6px}.header-right{display:flex;align-items:center;gap:25px;font-size:12px}.local-badge{color:var(--muted)}.local-badge i{display:inline-block;width:6px;height:6px;background:#74875a;border-radius:50%;margin-right:6px}.mini-button{background:transparent;border:1px solid var(--line);padding:8px 13px;border-radius:7px;font-size:12px;color:var(--ink)}.mini-button span{margin-left:12px;color:var(--purple)}main{max-width:1176px;margin:auto;padding:0 12px}.hero{display:grid;grid-template-columns:1.15fr 1fr;gap:75px;align-items:center;padding:65px 0 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button.active{width:24px;background:var(--purple)}.step-nav .primary{padding:9px 16px;font-size:12px}.step-nav .text-button{font-size:12px;padding:7px}.tip{font-size:12px;background:#f9f3e3;border:1px solid #ece0bf;padding:12px 16px;border-radius:8px;margin-top:21px;color:#786439}.tip b{margin-right:8px}.trig-controls{display:flex;justify-content:center;gap:7px;margin-top:8px}.trig-controls button{background:#ede8f5;color:var(--purple);padding:5px 12px;border-radius:5px;font-size:12px}.trig-controls button.active{background:var(--purple);color:white}.flashcards{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}.flashcard{min-height:215px;text-align:left;background:var(--white);border:1px solid var(--line);border-radius:12px;padding:21px;display:flex;flex-direction:column;color:var(--ink);transition:transform .2s,background .2s}.flashcard:hover{transform:translateY(-3px);border-color:#a494bf}.card-number{font-family:Georgia,serif;font-size:16px;color:#aaa2b8}.flashcard h3{font-size:16px;line-height:1.6;margin:21px 0 12px}.flashcard p{font-size:12px;line-height:1.9;margin:12px 0;color:#62566f}.flashcard .card-cue{font-size:11px;margin-top:auto;color:var(--purple)}.flashcard.flipped{background:var(--purple-light);border-color:#cfc3e2}.flashcard.flipped h3{margin:12px 0 0;font-size:12px;color:var(--purple)}.flashcard strong{font-size:17px;display:block;color:#47375d}.soft-banner{margin-top:24px;background:#eeede7;padding:18px 22px;border-radius:10px;display:flex;align-items:center;justify-content:space-between;font-size:12px;color:var(--muted)}.quiz-shell{max-width:800px;margin:auto;background:var(--white);border:1px solid var(--line);border-radius:var(--radius);padding:33px 42px}.quiz-intro{text-align:center;padding:18px 0}.quiz-icon{display:flex;align-items:center;justify-content:center;width:67px;height:67px;background:var(--purple-light);color:var(--purple);border-radius:50%;font-family:Georgia,serif;font-size:36px;margin:0 auto 19px}.quiz-intro h3{font-size:23px;margin:0 0 8px}.quiz-intro p{font-size:13px;color:var(--muted);margin:0 0 20px}.quiz-stats{display:flex;justify-content:center;gap:32px;font-size:12px;margin:20px 0 28px}.quiz-stats b{font-size:20px;display:block;color:var(--purple)}.quiz-top{display:flex;justify-content:space-between;font-size:11px;color:var(--muted)}.quiz-bar{height:4px;background:#e9e6ed;border-radius:9px;margin:12px 0 25px}.quiz-bar>div{height:100%;background:var(--purple);border-radius:9px;transition:width .2s}.quiz-source{display:flex;align-items:center;gap:10px}.quiz-shell h3.question{font-size:20px;font-weight:600;line-height:1.8;margin:15px 0 23px}.choices{display:grid;grid-template-columns:1fr 1fr;gap:12px}.choice{padding:14px;text-align:left;background:white;border:1px solid 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.mini-button{border:0;color:var(--muted)}.quiz-score{font-family:Georgia,serif;font-size:62px;color:var(--purple);line-height:1.2}.quiz-score small{font-size:22px;color:var(--muted)}.results-list{text-align:left;margin-top:30px}.result-row{display:flex;gap:12px;align-items:center;padding:12px 0;border-top:1px solid var(--line);font-size:12px}.result-row b{color:var(--purple);margin-right:auto}.result-row span{color:var(--muted)}.result-row button{font-size:11px;background:none;color:var(--purple);padding:7px}.result-actions{display:flex;justify-content:center;gap:15px;flex-wrap:wrap}.filter-label{font-size:11px;color:var(--muted)}select{margin-left:10px;padding:9px 14px;border:1px solid var(--line);background:var(--white);border-radius:7px;color:var(--ink);font-size:12px;max-width:180px}.source-note{padding:16px 18px;border-radius:8px;background:#eae8e1;font-size:12px;color:#76716c;margin-bottom:24px}.solution{border:1px solid var(--line);border-radius:10px;margin-bottom:12px;background:var(--white);overflow:hidden}.solution summary{list-style:none;padding:17px 21px;cursor:pointer;display:flex;align-items:center;gap:20px}.solution summary::-webkit-details-marker{display:none}.solution-number{color:var(--purple);font:16px Georgia,serif;min-width:32px}.solution-title{font-size:14px;font-weight:600;flex:1}.solution-tag{font-size:10px;color:var(--muted)}.solution-plus{font-size:20px;color:#91899e}.solution[open] .solution-plus{transform:rotate(45deg)}.solution-body{border-top:1px solid var(--line);padding:22px 25px;display:grid;grid-template-columns:230px 1fr;gap:30px}.solution-body .diagram-stage{height:220px;min-height:0}.solution-text .statement{font-size:13px;color:#67626d;margin-top:0;line-height:1.9}.solution-text ol{font-size:13px;padding-left:20px;line-height:1.9}.solution-text li{padding:4px 0 4px 5px}.answer{background:#edf2e6;border:1px solid #dde6cf;border-radius:7px;padding:10px 14px;color:#3b5431;font-size:14px}.answer b{margin-right:12px;font-size:10px}.source-warning{font-size:11px;color:#8b6a3e;border-left:2px solid #d5be90;padding-left:9px}.closing{border-top:1px solid var(--line);padding:39px 0 45px;display:flex;align-items:center;justify-content:space-between}.closing h2{font-size:24px;margin-top:11px}.closing p{font-size:12px;color:var(--muted)}.closing-symbol{font-family:Georgia,serif;font-size:100px;color:#bfb3d3;line-height:1;margin-right:30px}footer{max-width:1176px;margin:0 auto;padding:25px 12px 30px;border-top:1px solid var(--line);display:flex;flex-wrap:wrap;justify-content:space-between;gap:16px;font-size:10px;color:#87828d}footer>span{font-weight:700;color:#66606c}footer p{margin:0}.progress-details{width:100%;font-size:11px}.progress-details summary{cursor:pointer;display:inline-block;color:var(--purple)}.progress-details p{margin:10px 0}.skip{position:absolute;left:10px;top:-60px;z-index:999;background:white;padding:10px}.skip:focus{top:5px}#toast{position:fixed;bottom:25px;left:50%;transform:translateX(-50%);background:var(--ink);color:white;font-size:12px;padding:11px 24px;border-radius:9px;z-index:50;opacity:0;pointer-events:none;transition:opacity .2s;max-width:90vw;text-align:center}#toast.show{opacity:1}@keyframes appear{from{opacity:.3;transform:translateY(5px)}to{opacity:1;transform:none}}@media(min-width:1400px){.hero{padding-top:80px;padding-bottom:70px}}@media(max-width:1000px){header{padding:0 30px}main,footer{padding-left:30px;padding-right:30px}.hero{gap:35px}.hero-lab{padding:18px}.hero-actions{gap:15px}.lesson-layout{grid-template-columns:200px 1fr;gap:18px}.lesson-content{padding:24px}.lesson-body{gap:18px}.flashcards{grid-template-columns:repeat(2,1fr)}.solution-body{grid-template-columns:190px 1fr}.header-right{gap:15px}.local-badge{display:none}}@media(max-width:720px){header{height:72px;padding:0 21px}.brand{font-size:16px;gap:8px}.brand-symbol{font-size:34px}.brand-light{margin-left:4px}.mini-button{padding:7px 10px;font-size:10px}.header-right{gap:0}.header-right .mini-button{font-size:0}.header-right .mini-button span{font-size:11px;margin:0}.hero{grid-template-columns:1fr;gap:32px;padding:35px 0 40px}.hero-copy{padding:0 2px}main,footer{padding-left:22px;padding-right:22px}h1{font-size:42px;margin:18px 0 16px;line-height:1.35}.hero-copy>p{font-size:13px}.hero-actions{margin:23px 0 24px;gap:23px}.primary{padding:12px 18px;font-size:13px}.text-button{font-size:12px}.hero-meta{gap:21px;font-size:10px}.hero-meta b{font-size:18px}.hero-lab{transform:none;box-shadow:5px 6px 0 #e9e6e1;padding:18px 22px 14px}.hero-lab>*{transform:none}.hero-lab #heroDiagram{height:200px}.main-nav{margin-inline:-22px;padding-inline:8px}.main-nav button{font-size:12px;padding:16px 2px;white-space:nowrap}.main-nav button span{display:none}.main-nav button.active:after{left:12%;right:12%}.view{padding:30px 0 35px;min-height:500px}.section-heading{align-items:start;gap:10px;flex-direction:column;margin-bottom:22px}.section-heading h2{font-size:22px}.section-heading>p{font-size:11px}.eyebrow{font-size:9px;letter-spacing:1.5px}.lesson-layout{display:block}#lessonNav{display:grid;grid-template-columns:1fr 1fr;gap:7px;margin-bottom:16px}.lesson-nav-button{padding:12px 10px;margin:0;border:1px solid var(--line);gap:10px;border-radius:8px}.lesson-nav-button .topic-num{font-size:16px}.lesson-nav-button b{font-size:12px}.lesson-nav-button small{font-size:9px}.done-dot{font-size:10px}.lesson-content{padding:20px 18px}.lesson-content h3{font-size:20px;margin-top:15px}.lesson-source{font-size:9px}.lesson-body{grid-template-columns:1fr;gap:20px}.diagram-stage{min-height:195px}.lesson-body .math-diagram{max-height:210px}.lesson-intro{font-size:12px;margin-bottom:17px}.step-area h4{font-size:16px}.step-area p{font-size:12px}.math-line{font-size:16px}.step-nav{gap:15px}.tip{font-size:11px;padding:12px}.flashcards{gap:11px}.flashcard{padding:16px;min-height:210px}.flashcard h3{font-size:14px;margin-top:18px}.flashcard p{font-size:11px}.flashcard strong{font-size:15px}.soft-banner{padding:15px;align-items:start;gap:7px;flex-direction:column;font-size:11px}.quiz-shell{padding:23px 18px}.quiz-shell h3.question{font-size:17px}.choices{grid-template-columns:1fr}.choice{font-size:13px;padding:12px}.quiz-intro h3{font-size:21px}.quiz-intro p{font-size:12px}.quiz-stats{gap:28px}.quiz-bottom .primary{font-size:12px;padding:10px 17px}.result-row{font-size:11px;gap:8px}.solution summary{padding:16px 14px;gap:10px}.solution-number{min-width:28px;font-size:14px}.solution-title{font-size:12px}.solution-tag{display:none}.solution-body{display:block;padding:18px 16px}.solution-body .diagram-stage{height:195px;margin-bottom:20px}.solution-text .statement,.solution-text ol{font-size:12px}.source-note{font-size:11px;padding:13px}.answer{font-size:13px}.closing{padding:30px 0}.closing h2{font-size:21px}.closing p{font-size:11px;max-width:260px}.closing-symbol{font-size:65px;margin:0 0 0 10px}footer{padding-top:20px;gap:7px}footer>p{width:100%}.result-actions{gap:10px}.quiz-score{font-size:54px}.filter-label{margin-top:4px}}@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{animation:none!important;transition:none!important}}@media print{header,.hero,.main-nav,.closing,footer,.step-nav{display:none}.view{display:none!important}#solutions{display:block!important}.solution-body{display:grid!important}.solution{break-inside:avoid}}
/* Practice unit: isolated submission-gated question state. */
.main-nav{grid-template-columns:repeat(5,1fr)}.practice-statbar{display:flex;align-items:center;gap:42px;padding:22px 25px;background:#ebe7f2;border:1px solid #ded6e9;border-radius:12px}.practice-statbar>div{display:flex;flex-direction:column;gap:2px}.practice-statbar b{font:28px Georgia,serif;color:#5c477e}.practice-statbar b small{font:13px sans-serif;color:var(--muted)}.practice-statbar span{font-size:11px;color:#7a7086}.practice-statbar>.mini-button{margin-left:auto;background:#fffefa}.practice-statbar>.mini-button:disabled{opacity:.4}.practice-overall{height:4px;background:#e2dded;border-radius:8px;margin:10px 0 28px;overflow:hidden}.practice-overall>span{height:100%;background:var(--purple);display:block}.practice-pick-heading{display:flex;align-items:center;justify-content:space-between;gap:16px;margin:22px 0 17px}.practice-pick-heading h3{font-size:17px;margin:0}.practice-pick-heading>span{font-size:10px;color:var(--muted)}.practice-groups{display:grid;grid-template-columns:repeat(4,1fr);gap:13px}.practice-group{display:flex;flex-direction:column;gap:15px;text-align:left;background:var(--white);border:1px solid var(--line);padding:18px;border-radius:10px;min-height:156px;transition:transform .2s}.practice-group:hover{border-color:var(--purple);transform:translateY(-2px)}.practice-group-top{display:flex;justify-content:space-between;align-items:center;font-size:10px;color:var(--purple);letter-spacing:.5px}.practice-group strong{font-size:14px;line-height:1.65;color:var(--ink)}.practice-group-meta{font-size:10px;color:var(--muted);margin-top:auto}.practice-mini-progress{height:3px;background:#ece9f0;border-radius:8px;display:block;margin-top:-6px}.practice-mini-progress i{display:block;background:#a395bf;height:100%;border-radius:8px}.practice-privacy{font-size:11px;color:var(--muted);margin:20px 0}.practice-toolbar{display:flex;align-items:center;justify-content:space-between;gap:18px;margin:8px 0 20px}.practice-toolbar label{font-size:11px;color:var(--muted);display:flex;align-items:center;gap:5px}.practice-toolbar select{max-width:310px}.practice-retry-label{font-size:11px;color:var(--purple)}.practice-question{border:1px solid var(--line);border-radius:16px;background:var(--white);padding:27px}.practice-question-top{display:flex;align-items:center;justify-content:space-between;gap:15px;font-size:11px;color:var(--muted)}.practice-question-dots{display:flex;gap:7px;flex-wrap:wrap;margin:21px 0 26px;padding-bottom:20px;border-bottom:1px solid var(--line);max-height:145px;overflow:auto}.practice-question-dots button{min-width:38px;padding:5px 9px;border:1px solid #ddd6e6;color:#716879;border-radius:6px;background:white;font-size:12px}.practice-question-dots button.current{outline:2px solid var(--purple);outline-offset:2px}.practice-question-dots button.done-right{background:#edf3e4;color:#4e6740}.practice-question-dots button.done-wrong{background:#f9eae5;color:#9a584a}.practice-question-layout{display:grid;grid-template-columns:1fr 1fr;gap:36px}.practice-prompt h3{font-size:18px;line-height:1.95;font-weight:600;margin:10px 0 20px;white-space:pre-line}.practice-figure{background:#f5f3ef;border-radius:10px;padding:14px;display:flex;align-items:center;justify-content:center;min-height:200px}.practice-figure svg{max-width:100%;width:100%;height:auto;max-height:270px;overflow:visible}.practice-figure-note{font-size:10px;color:var(--muted);text-align:center;margin:7px 0}.practice-answer-area fieldset{padding:0;margin:0;border:0;min-width:0}.practice-answer-area legend{font-size:12px;font-weight:600;margin:0 0 12px}.practice-options{display:grid;grid-template-columns:1fr;gap:11px}.practice-option{display:flex;align-items:center;gap:10px;padding:13px;border:1px solid #ddd8e3;border-radius:8px;font-size:13px;line-height:1.8;cursor:pointer;position:relative}.practice-option input{accent-color:var(--purple);flex-shrink:0;width:16px;height:16px;margin:0}.practice-option-letter{font-size:11px;color:var(--muted)}.practice-option.picked{border-color:var(--purple);background:#f0ebf6}.practice-option:focus-within{outline:2px solid var(--purple);outline-offset:2px}.practice-option.right{background:#edf3e4;border-color:#93a780}.practice-option.wrong{background:#f9ebe7;border-color:#c59082}.practice-option input:disabled{opacity:1}.practice-answer-area fieldset:disabled .practice-option{cursor:default}.practice-error{font-size:12px;color:#a0493d;min-height:20px;margin:13px 0 9px}.practice-submit,.practice-next{width:100%;font-size:13px}.practice-lock-note{font-size:10px;color:var(--muted);margin:10px 0;text-align:center}.practice-explanation{margin:5px 0 20px;background:#edf3e6;border-left:3px solid #91a775;padding:16px 18px;border-radius:8px;font-size:12px;line-height:1.9}.practice-explanation.is-wrong{background:#faf0e8;border-color:#c09974}.practice-explanation>strong{font-size:13px}.practice-correct-answer{font-weight:700;font-size:14px;margin:8px 0;color:#405c35}.practice-explanation ol{padding-left:19px;margin:10px 0 0}.practice-explanation li{padding:4px 0 4px 4px;white-space:pre-line}.practice-summary{max-width:720px;margin:auto;padding:35px;background:var(--white);border:1px solid var(--line);border-radius:16px;text-align:center}.practice-summary .eyebrow{justify-content:center}.practice-summary h3{font-size:22px;line-height:1.7;margin:15px 0 23px}.practice-summary p{font-size:12px;color:var(--muted);margin:16px 0 22px}.practice-summary-list{margin-top:27px}.practice-summary-list button{display:flex;justify-content:space-between;align-items:center;gap:12px;width:100%;text-align:left;background:none;padding:14px 0;border-top:1px solid var(--line);font-size:12px;color:var(--ink)}.practice-summary-list button span:last-child{font-size:10px;color:var(--purple)}@media(max-width:1000px){.practice-groups{grid-template-columns:repeat(3,1fr)}.practice-question{padding:24px}.practice-question-layout{gap:24px}}@media(max-width:720px){.main-nav button{font-size:11px;letter-spacing:0}.practice-statbar{padding:18px 16px;gap:22px;flex-wrap:wrap}.practice-statbar b{font-size:25px}.practice-statbar b small{font-size:11px}.practice-statbar span{font-size:10px}.practice-statbar>.mini-button{width:100%;margin-left:0}.practice-overall{margin-bottom:22px}.practice-pick-heading{align-items:start;flex-direction:column;gap:6px}.practice-pick-heading h3{font-size:15px}.practice-groups{grid-template-columns:repeat(2,1fr);gap:10px}.practice-group{padding:14px 12px;gap:13px;min-height:155px}.practice-group strong{font-size:12px}.practice-group-meta{font-size:9px}.practice-toolbar{align-items:flex-start;flex-direction:column;gap:7px}.practice-toolbar label{width:100%;font-size:10px;gap:0}.practice-toolbar select{flex:1;min-width:0;max-width:calc(100% - 52px);font-size:11px}.practice-question{padding:18px 15px}.practice-question-top{font-size:10px;gap:8px}.practice-question-dots{gap:8px;margin:20px 0 22px}.practice-question-dots button{min-width:36px;font-size:11px}.practice-question-layout{grid-template-columns:1fr;gap:24px}.practice-prompt h3{font-size:16px;line-height:1.9;margin:10px 0 15px}.practice-figure{padding:10px;min-height:170px}.practice-figure svg{max-height:250px}.practice-option{font-size:13px;min-height:52px;padding:12px;gap:8px}.practice-option input{width:18px;height:18px}.practice-error{font-size:11px}.practice-explanation{font-size:12px;padding:15px}.practice-correct-answer{font-size:13px}.practice-summary{padding:26px 18px}.practice-summary h3{font-size:20px}.practice-summary-list button{font-size:11px;gap:7px}.practice-summary-list button span:last-child{font-size:9px}.practice-privacy{font-size:10px}}@media(max-width:370px){.practice-statbar{gap:16px}.main-nav button{font-size:10px}.practice-question-dots{gap:6px}.practice-question-dots button{min-width:32px}.practice-group strong{font-size:11px}}@media print{#practice{display:none!important}}

.practice-hero-link{display:inline-block;font-size:11px;color:var(--purple);margin:-9px 0 21px;padding:7px 11px;border:1px solid #d7cee5;border-radius:6px;background:#eee9f5}.practice-hero-link strong{font-weight:700;margin:0 4px}.practice-hero-link:hover{background:#e4dcef}@media(max-width:720px){.practice-hero-link{font-size:10px;margin:0 0 20px}}