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#8eb795;outline-offset:4px}[hidden]{display:none!important}h1,h2,h3,h4,p{margin:0}h1{font-size:var(--font-page,1.625rem);line-height:1.45;font-weight:600;letter-spacing:normal}h2{font-size:var(--font-section,1.375rem);font-weight:600;line-height:1.6}h3{font-size:var(--font-lead,1.125rem);font-weight:600;line-height:1.7}h4{font-size:var(--font-lead,1.125rem);font-weight:600}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.tutorial-header{height:84px;display:flex;align-items:center;justify-content:space-between;gap:20px;max-width:1280px;padding:0 40px;margin:auto;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:11px;color:#3c6949;font-size:18px;font-weight:600;line-height:1.4}.brand small{display:block;font-size:var(--font-small,.9375rem);font-weight:400;color:#526456;letter-spacing:normal;margin-top:2px}.tutorial-header nav{display:flex;align-items:center;gap:25px;font-size:var(--font-small,.9375rem);color:#526456}.tutorial-header nav a:hover{text-decoration:underline}.eyebrow{font-size:var(--font-small,.9375rem);letter-spacing:normal;color:#526456;margin-bottom:10px}.lead{color:#526456;font-size:var(--font-small,.9375rem);line-height:1.95;margin-top:15px;max-width:760px}.level-tag{font-size:var(--font-small,.9375rem);display:inline-block;background:#eaf2e3;color:#526456;border:1px solid #deead4;border-radius:4px;padding:2px 8px;line-height:1.65}.tutorial-index{max-width:1160px;padding:46px 36px 65px;margin:auto}.index-heading{margin-bottom:32px}.study-path{margin-top:25px;display:flex;gap:10px;align-items:center;flex-wrap:wrap;font-size:var(--font-small,.9375rem);color:#526456}.study-path>span{margin-right:4px}.study-path a{background:#fff;border:1px solid var(--line);padding:7px 11px;border-radius:6px}.study-path b{display:inline-grid;place-items:center;width:18px;height:18px;border-radius:50%;background:#e9f1e0;margin-right:7px;font-size:var(--font-small,.9375rem);color:#526456}.tutorial-filters{display:grid;grid-template-columns:auto minmax(150px,1fr) 160px;gap:13px;align-items:center;background:#fff;border:1px solid var(--line);border-radius:9px;padding:16px 20px;margin-bottom:35px;font-size:var(--font-small,.9375rem);color:#526456}.tutorial-filters input,.tutorial-filters select{border:1px solid #dce5d4;border-radius:5px;padding:9px 12px;color:#4f6d45;background:#fbfcf8;width:100%;min-width:0}.tutorial-filters p{grid-column:2 / -1;font-size:var(--font-body,1rem);color:#526456;line-height:1}.tutorial-group{margin:30px 0}.tutorial-group>h2{font-size:var(--font-section,1.375rem);margin-bottom:16px;color:#5d7d4e;font-weight:600}.lesson-cards{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.lesson-card{display:flex;flex-direction:column;background:#fff;border:1px solid var(--line);border-radius:9px;padding:20px;transition:transform .15s,border-color .15s}.lesson-card:hover{transform:translateY(-2px);border-color:#a4c393;box-shadow:0 4px 14px #36552d08}.lesson-card>div{display:flex;gap:7px;align-items:center;justify-content:space-between}.learned-badge{font-size:var(--font-small,.9375rem);color:#526456}.lesson-card h3{font-size:var(--font-lead,1.125rem);color:#527448;margin:12px 0 8px;font-weight:600}.lesson-card p{font-size:var(--font-body,1rem);color:#526456;line-height:1.85;flex:1}.card-link{font-size:var(--font-body,1rem);color:#526456;margin-top:16px}.lesson-card.is-learned{border-color:#b6cda9}.no-results{padding:60px 20px;text-align:center;color:#526456}.reader-layout{max-width:1240px;margin:36px auto 70px;display:grid;grid-template-columns:185px minmax(0,1fr);gap:44px;padding:0 40px}.lesson-outline{align-self:start;position:sticky;top:25px;padding-top:10px}.back-link{font-size:var(--font-body,1rem);color:#526456;display:block;margin-bottom:28px}.lesson-outline nav{display:flex;flex-direction:column;gap:9px;font-size:var(--font-small,.9375rem)}.lesson-outline nav a{color:#526456}.lesson-outline nav a:hover{color:#3d7652}.outline-note{margin-top:25px;padding-top:15px;border-top:1px solid var(--line);font-size:var(--font-small,.9375rem);line-height:1.8;color:#526456}.lesson{min-width:0;background:#fff;border:1px solid #e0e7d8;border-radius:12px;padding:38px 44px}.lesson-heading{padding-bottom:25px;border-bottom:1px solid #e7eddf}.lesson-heading h1{margin-top:12px;font-size:var(--font-page,1.625rem);font-weight:600}.reader-actions{display:flex;gap:25px;align-items:center;justify-content:space-between;margin-top:20px;font-size:var(--font-small,.9375rem);color:#526456}.reader-actions label{display:flex;align-items:center;gap:6px;cursor:pointer}.reader-actions button{border:1px solid #dce6d2;background:#fbfcf8;color:#526456;padding:5px 11px;border-radius:5px;font-size:var(--font-body,1rem)}input[type=checkbox]{accent-color:#548c54}.lesson>section{margin-top:31px;scroll-margin-top:25px}.lesson>section>h2{margin-bottom:14px}.lesson p,.lesson li{font-size:var(--font-reading,1.125rem);color:#526456;line-height:var(--line-reading,1.666667)}.lesson p+p{margin-top:12px}.memory-tip{background:#edf5e6;border-left:3px solid #90b57b;padding:17px 20px;font-size:17px;line-height:1.8;color:#527744;border-radius:0 7px 7px 0}.related-links{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin-top:15px;font-size:var(--font-small,.9375rem);color:#526456}.related-links a{border:1px solid #e1e9d9;background:#fafcf7;border-radius:4px;padding:4px 9px;color:#526456}.condition-note{font-size:var(--font-small,.9375rem)!important;background:#fbf4e2;color:#9b854b!important;border-radius:6px;padding:11px 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1fr;gap:20px;border-top:1px solid #e4ecda;margin-top:38px;padding-top:22px;font-size:var(--font-small,.9375rem)}.lesson-pagination>a:last-child{text-align:right}.lesson-pagination small{display:block;color:#526456;font-size:var(--font-small,.9375rem);margin-bottom:5px}.tutorial-footer{max-width:1160px;margin:0 auto;padding:23px 35px;border-top:1px solid var(--line);display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap;font-size:var(--font-small,.9375rem);color:#526456}.tutorial-footer a{color:#526456}@media(max-width:1020px){.reader-layout{gap:25px;grid-template-columns:150px minmax(0,1fr);padding:0 25px}.lesson{padding:30px}.tutorial-header{padding:0 28px}.lesson-cards{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:760px){.tutorial-header{height:auto;min-height:75px;padding:15px 18px;gap:12px;flex-wrap:wrap}.brand{font-size:16px}.brand small{font-size:var(--font-small,.9375rem)}.tutorial-header nav{gap:15px;font-size:var(--font-small,.9375rem)}.tutorial-index{padding:28px 18px 45px}h1{font-size:var(--font-page,1.625rem);font-weight:600}.lead{font-size:var(--font-small,.9375rem)}.study-path{gap:7px}.study-path>span{width:100%}.study-path a{font-size:var(--font-body,1rem);padding:5px 8px}.tutorial-filters{grid-template-columns:minmax(0,1fr) 115px;padding:13px;gap:8px}.tutorial-filters>label:first-child{grid-column:1 / -1;font-size:var(--font-body,1rem)}.tutorial-filters p{grid-column:1 / -1}.reader-layout{display:block;padding:0 14px;margin:20px auto 40px}.lesson-outline{position:static;padding:0 7px 16px}.lesson-outline .back-link{margin-bottom:12px}.lesson-outline .eyebrow,.outline-note{display:none}.lesson-outline nav{flex-direction:row;flex-wrap:wrap;gap:6px 15px;font-size:var(--font-small,.9375rem)}.lesson{padding:24px 20px;border-radius:9px}.lesson-heading h1{font-size:var(--font-page,1.625rem);font-weight:600}.lesson p,.lesson li{font-size:var(--font-reading,1.125rem);line-height:var(--line-reading,1.666667)}.lesson h2{font-size:var(--font-section,1.375rem);font-weight:600}.memory-tip{font-size:var(--font-small,.9375rem);padding:14px 16px}.lesson-demo{padding:13px}.demo-heading{flex-wrap:wrap;gap:9px}.demo-heading h3{font-size:var(--font-lead,1.125rem);font-weight:600}.demo-controls{gap:5px}.demo-controls button{font-size:var(--font-body,1rem);padding:6px 8px}.demo-controls [data-demo-zoom]{margin-left:0}.parent-card,.quiz{padding:16px}.tutorial-footer{padding:20px;gap:8px}.lesson-cards{gap:10px}.lesson-card{padding:15px}.lesson-card h3{font-size:var(--font-lead,1.125rem);font-weight:600}.lesson-card p{font-size:var(--font-body,1rem)}}@media(max-width:440px){.lesson-cards{grid-template-columns:1fr}.tutorial-header nav{width:100%;justify-content:space-between}.lesson{padding:22px 15px}.lesson-heading h1{font-size:var(--font-page,1.625rem);font-weight:600}.reader-actions{font-size:var(--font-small,.9375rem);gap:10px}.lesson-pagination{gap:12px;font-size:var(--font-small,.9375rem)}.related-links a{font-size:var(--font-body,1rem)}}@media print{body{background:#fff}.tutorial-header,.lesson-outline,.reader-actions,.demo-controls,.lesson-pagination,.tutorial-footer,.demo-heading .button,.quiz-options button span{display:none!important}.reader-layout{display:block;margin:0;padding:0}.lesson{border:0;padding:0;max-width:none}.lesson h1{font-size:22pt}.lesson h2{font-size:15pt}.lesson p,.lesson li{font-size:10pt}.lesson>section{break-inside:avoid;margin-top:6mm}.lesson-demo{break-inside:avoid;background:#fff;padding:3mm;border-color:#cbd6c1}.diagram-scroll{max-width:125mm;overflow:visible;background:#fff}.lesson-diagram{min-width:0!important}.memory-tip,.parent-card,.level-tag{-webkit-print-color-adjust:exact;print-color-adjust:exact}.lesson-demo svg{-webkit-print-color-adjust:exact;print-color-adjust:exact}.proof ol,.result-list ul{max-height:none;overflow:visible}.quiz{break-inside:avoid}.usage-flow{overflow:visible}.usage-flow svg{min-width:0}}

/* Paired examples and five independent, initially unspoiled practice variants. */
.course-exercise-count{font-size:var(--font-small,.9375rem);color:#526456;margin-top:13px}.practice-set{border-top:2px solid #dce9d1;padding-top:25px}.practice-toolbar{display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:16px 0}.practice-tabs{display:flex;gap:6px;flex-wrap:wrap}.practice-tabs button,.practice-next{border:1px solid #dce6d1;border-radius:5px;background:#fff;color:#526456;padding:7px 11px;font-size:var(--font-body,1rem)}.practice-tabs button[aria-pressed=true]{background:#eaf3e1;border-color:#acc69a;color:#487436}.practice-tabs span{color:#508948}#exercise-progress-count{font-size:var(--font-small,.9375rem);color:#526456;margin-left:auto}.practice-next{color:#588047}.exercise-card{border:1px solid #d9e6cc;background:#fcfef9;border-radius:9px;padding:20px}.exercise-task{margin-top:12px!important;color:#62834f!important;font-size:var(--font-small,.9375rem)!important}.variation-note{font-size:var(--font-small,.9375rem)!important;color:#526456!important;margin-top:6px!important;margin-bottom:16px}.practice-diagram{margin-top:12px}.exercise-hint,.exercise-answer{border-top:1px solid #e2ead9;padding-top:13px;margin-top:16px;font-size:var(--font-small,.9375rem);color:#526456}.exercise-hint summary,.exercise-answer summary{cursor:pointer;color:#698951}.exercise-hint p,.exercise-answer p,.exercise-answer li{font-size:var(--font-body,1rem);margin-top:8px}.exercise-answer .diagram-scroll{margin-top:15px}.exercise-completion{display:flex;align-items:center;gap:7px;font-size:var(--font-small,.9375rem);color:#526456;margin-top:20px;padding-top:15px;border-top:1px solid #e2ead9}.exercise-card .proof{max-width:100%}.operation-demo ol{padding-left:20px;margin-top:15px}.operation-demo li{font-size:var(--font-body,1rem)}.operation-demo .diagram-scroll{margin-top:15px}@media(max-width:760px){.exercise-card{padding:13px}.practice-tabs button,.practice-next{padding:6px 9px;font-size:var(--font-body,1rem)}#exercise-progress-count{margin-left:0}.practice-toolbar{gap:9px}.exercise-task{font-size:var(--font-small,.9375rem)!important}}@media print{.practice-toolbar,.exercise-completion{display:none!important}.exercise-card{break-inside:avoid}.exercise-card .diagram-scroll{max-width:125mm}.exercise-hint,.exercise-answer{font-size:10pt}}