:root{--ink:#06214a;--muted:#5d718e;--paper:#f5f9ff;--panel:#fff;--line:#d7e5f4;--green:#0b74e8;--green-soft:#eaf4ff;--amber:#69b9ff;--orange:#1d8aff;--blue:#004ea8}*{box-sizing:border-box}body{color:var(--ink);background:var(--paper);margin:0;font-family:Arial,Helvetica,sans-serif}button{font:inherit}.srOnly{clip:rect(0, 0, 0, 0);white-space:nowrap;width:1px;height:1px;position:absolute;overflow:hidden}.shell{align-content:start;gap:18px;min-height:100vh;padding:24px;display:grid}.siteHeader{border:1px solid var(--line);background:var(--panel);border-radius:8px;justify-content:space-between;align-items:center;gap:24px;width:100%;max-width:1440px;margin:0 auto;padding:18px 24px;display:flex}.brandLockup{color:inherit;gap:6px;min-width:0;text-decoration:none;display:grid}.brandLockup:hover,.brandLockup:focus-visible{color:inherit;outline:none}.teachLensBrandImage{object-fit:contain;width:min(300px,52vw);height:auto;display:block}.teachLensLogo.compact{object-fit:contain;width:48px;height:auto;display:block}.siteBrand{min-width:0}.siteBrand h1{font-size:clamp(1.8rem,3vw,3rem);line-height:1}.topNav{flex-wrap:wrap;justify-content:flex-end;align-items:center;gap:8px;display:flex}.topNavGroup{position:relative}.topNavGroup summary{border:1px solid var(--line);min-height:40px;color:var(--muted);cursor:pointer;background:#fff;border-radius:8px;padding:8px 12px;font-weight:800;list-style:none}.topNavGroup summary::-webkit-details-marker{display:none}.topNavGroup summary:after{content:"⌄";color:var(--muted);margin-left:8px;font-size:.9em;display:inline-block}.topNavGroup.active summary{border-color:var(--ink);background:var(--ink);color:#fff}.topNavGroup.active summary:after{color:#fff}.topNavMenu{z-index:20;border:1px solid var(--line);background:#fff;border-radius:8px;gap:6px;width:260px;padding:8px;display:grid;position:absolute;top:calc(100% + 8px);right:0;box-shadow:0 18px 36px #1f293324}.topLessonItem{width:100%;min-height:38px;color:var(--muted);cursor:pointer;text-align:left;background:0 0;border:1px solid #0000;border-radius:8px;align-items:center;padding:8px 10px;font-weight:750;line-height:1.25;text-decoration:none;display:flex}.topLessonItem:hover,.topLessonItem:focus-visible,.topLessonItem.active{border-color:var(--line);background:var(--green-soft);color:var(--ink);outline:none;text-decoration:none}.mobileLessonBrowser{display:none}.siteFooter{border:1px solid var(--line);background:var(--panel);border-radius:8px;justify-content:space-between;align-items:center;gap:24px;width:100%;max-width:1440px;margin:0 auto;padding:18px 24px;display:flex}.footerBrand{gap:4px;min-width:0;display:grid}.footerLogoRow{align-items:center;gap:12px;display:flex}.footerBrand p:last-child{color:var(--muted);margin:0;font-weight:700;line-height:1.45}.footerLinks{flex-wrap:wrap;justify-content:flex-end;gap:10px 18px;display:flex}.footerLinks a{color:var(--blue);text-underline-offset:.2em;font-weight:800;line-height:1.35;text-decoration:underline;text-decoration-thickness:.08em}.footerLinks a:hover,.footerLinks a:focus-visible{color:var(--green);outline:none}.lesson{grid-template-columns:260px minmax(0,1fr);gap:20px;width:100%;max-width:1440px;margin:0 auto;display:grid}.sidebar,.stagePanel{background:var(--panel);border:1px solid var(--line);border-radius:8px}.sidebar{flex-direction:column;gap:24px;min-height:calc(100vh - 144px);padding:24px;display:flex}.eyebrow{color:var(--green);letter-spacing:0;text-transform:uppercase;margin:0 0 8px;font-size:.78rem;font-weight:700}h1,h2{letter-spacing:0;margin:0}h1{font-size:clamp(2rem,4vw,3.5rem);line-height:.95}h2{font-size:clamp(1.55rem,2.8vw,2.6rem);line-height:1.05}.sidebarMenu,.stepList{gap:18px;display:grid}.sidebarHeader{gap:4px;display:grid}.sidebarHeader h2{font-size:1.45rem;line-height:1.1}.sidebarHeader p:last-child{color:var(--muted);margin:4px 0 0;font-weight:700;line-height:1.35}.mobilePickers{display:none}.lessonTabs{gap:18px;display:grid}.lessonCategory,.stepList{gap:8px;display:grid}.lessonCategory h3,.stepList h3,.pageBookmarks h3{color:var(--muted);letter-spacing:0;text-transform:uppercase;margin:0;font-size:.78rem;font-weight:800}.lessonCategoryList,.stepScroller,.pageBookmarks{gap:8px;display:grid}.pageBookmarks a{border:1px solid var(--line);min-height:40px;color:var(--muted);background:#fff;border-radius:8px;align-items:center;padding:8px 10px;font-weight:750;text-decoration:none;display:flex}.pageBookmarks a:hover{border-color:var(--green);background:var(--green-soft);color:var(--ink)}.lessonTab{border:1px solid var(--line);width:100%;min-height:42px;color:var(--muted);cursor:pointer;text-align:left;background:#fff;border-radius:8px;padding:9px 10px;font-weight:700}.lessonTab.active{background:var(--ink);border-color:var(--ink);color:#fff}.stepButton{border:1px solid var(--line);width:100%;min-height:48px;color:var(--ink);cursor:pointer;text-align:left;background:#fff;border-radius:8px;align-items:center;gap:10px;padding:10px;display:flex}.stepButton span{background:#edf1ed;border-radius:50%;flex:none;place-items:center;width:28px;height:28px;font-weight:700;display:inline-grid}.stepButton.active{border-color:var(--green);background:var(--green-soft)}.stepButton.active span{background:var(--green);color:#fff}.stagePanel{grid-template-rows:auto auto auto;align-content:start;gap:16px;min-height:calc(100vh - 144px);padding:24px;display:grid}#lesson-stage,#lesson-step,#lesson-notes{scroll-margin-top:18px}.stageHeader{gap:10px;display:grid}.lessonHero{gap:10px;max-width:980px;display:grid}.lessonEyebrow{background:var(--green-soft);width:fit-content;color:var(--green);letter-spacing:0;text-transform:uppercase;border:1px solid #2f7d6d38;border-radius:999px;margin:0;padding:7px 10px;font-size:.76rem;font-weight:800;line-height:1}.formula{color:var(--blue);white-space:normal;background:#f6fafb;border:1px solid #cfd7dc;border-radius:8px;padding:12px 14px;font-weight:800;line-height:1.35}.formulaBanner{width:100%;max-width:640px;margin-top:2px;font-size:clamp(.98rem,1.3vw,1.12rem)}.diagram{min-height:0}.diagram svg{aspect-ratio:760/430;width:100%;height:auto;max-height:min(54vh,520px);display:block}.mainTriangle polygon,.copyTriangle polygon{stroke:#1f2933;stroke-width:4px;stroke-linejoin:round}.mainTriangle polygon{fill:url(#triangleFill)}.copyTriangle polygon{fill:url(#copyFill)}.copyTriangle{opacity:0;transform-origin:405px 215px;transition:opacity .5s,transform .7s}.diagram[data-step="1"] .copyTriangle{opacity:.92;transform:translate(34px,16px)}.diagram[data-step="2"] .copyTriangle,.diagram[data-step="3"] .copyTriangle{opacity:.92;transform:translate(0)}.parallelogramGuide{opacity:0;transition:opacity .5s}.parallelogramGuide path{fill:#3d6f9114;stroke:var(--blue);stroke-width:3px;stroke-dasharray:12 8}.parallelogramGuide text,.baseLabel,.heightLabel,.halfLabel{fill:var(--ink);font-size:22px;font-weight:800}.diagram[data-step="2"] .parallelogramGuide,.diagram[data-step="3"] .parallelogramGuide{opacity:1}.halfLabel{opacity:0;transition:opacity .4s}.diagram[data-step="3"] .halfLabel{opacity:1}.baseLine,.heightLine,.rightAngle{fill:none;stroke:#1f2933;stroke-width:4px}.heightLine{stroke-dasharray:8 8}.heightLabel{writing-mode:sideways-lr}.sasTriangle{fill:#7fb06938;stroke:#1f2933;stroke-width:4px;stroke-linejoin:round}.side{stroke:#7b8794;stroke-width:8px;stroke-linecap:round;opacity:.35;transition:opacity .25s,stroke .25s,stroke-width .25s}.sideLabel,.vertexLabel{fill:var(--ink);font-size:26px;font-weight:800}.vertexLabel{font-size:24px}.heightGuide,.angleArc,.formulaLine{opacity:0;transition:opacity .25s}.heightGuide line,.heightGuide path{fill:none;stroke:var(--blue);stroke-width:4px;stroke-dasharray:8 8}.heightGuide text{fill:var(--blue);font-size:21px;font-weight:800}.angleArc{fill:none;stroke:var(--orange);stroke-width:9px;stroke-linecap:round}.sasFormulaCard text{fill:var(--ink);font-size:22px;font-weight:800}.sasFormulaCard .formulaLine{fill:var(--blue);font-size:20px}.sasDiagram[data-sas-step="0"] .sideA,.sasDiagram[data-sas-step="0"] .sideB,.sasDiagram[data-sas-step="1"] .sideB,.sasDiagram[data-sas-step="1"] .sideC,.sasDiagram[data-sas-step="2"] .sideA,.sasDiagram[data-sas-step="2"] .sideC{stroke:var(--green);stroke-width:10px;opacity:1}.sasDiagram[data-sas-step="3"] .side{stroke:var(--green);opacity:.8}.sasDiagram[data-sas-step="0"] .angleC,.sasDiagram[data-sas-step="1"] .angleA,.sasDiagram[data-sas-step="2"] .angleB,.sasDiagram[data-sas-step="3"] .angleArc,.sasDiagram[data-sas-step="0"] .formulaC,.sasDiagram[data-sas-step="1"] .formulaA,.sasDiagram[data-sas-step="2"] .formulaB,.sasDiagram[data-sas-step="3"] .formulaAll,.sasDiagram[data-sas-step="0"] .heightFromB,.sasDiagram[data-sas-step="1"] .heightFromC,.sasDiagram[data-sas-step="2"] .heightFromA,.sasDiagram[data-sas-step="3"] .heightGuide{opacity:1}.trigTriangle{fill:#f2b84b2e;stroke:#1f2933;stroke-width:4px;stroke-linejoin:round}.trigSide{stroke:#7b8794;stroke-width:9px;stroke-linecap:round;opacity:.42;transition:opacity .25s,stroke .25s,stroke-width .25s}.trigRightAngle{fill:none;stroke:var(--ink);stroke-width:4px}.thetaArc{fill:none;stroke:var(--orange);stroke-width:8px;stroke-linecap:round}.thetaLabel,.trigSideLabel{fill:var(--ink);font-size:23px;font-weight:800}.oppositeLabel{writing-mode:sideways-lr}.hypotenuseLabel{transform-origin:337px 188px;transform:rotate(-26deg)}.ratioCard text{fill:var(--ink);font-size:22px;font-weight:800}.ratioCard .ratioLine{fill:var(--blue);opacity:0;font-size:20px;transition:opacity .25s}.trigDiagram[data-trig-step="0"] .trigSide{opacity:.82}.trigDiagram[data-trig-step="1"] .trigOpposite,.trigDiagram[data-trig-step="1"] .trigHypotenuse,.trigDiagram[data-trig-step="2"] .trigAdjacent,.trigDiagram[data-trig-step="2"] .trigHypotenuse,.trigDiagram[data-trig-step="3"] .trigOpposite,.trigDiagram[data-trig-step="3"] .trigAdjacent{stroke:var(--green);stroke-width:11px;opacity:1}.trigDiagram[data-trig-step="1"] .ratioSin,.trigDiagram[data-trig-step="2"] .ratioCos,.trigDiagram[data-trig-step="3"] .ratioTan,.trigDiagram[data-trig-step="0"] .ratioAll{opacity:1}.axisLine{stroke:#98a4ad;stroke-width:3px}.unitCircle{fill:#3d6f9114;stroke:var(--ink);stroke-width:4px}.radiusLine,.sineHeight,.cosBase,.sineRightAngle{fill:none;stroke:#7b8794;stroke-width:5px;stroke-linecap:round;transition:opacity .25s,stroke .25s,stroke-width .25s}.sineHeight,.cosBase,.sineRightAngle{opacity:0}.sineHeight{stroke:var(--green);stroke-dasharray:8 8}.cosBase{stroke:var(--blue)}.radianArc,.degreeArc{fill:none;stroke:var(--orange);stroke-width:9px;stroke-linecap:round;opacity:0;transition:opacity .25s}.degreeArc{stroke-width:12px}.circlePoint{fill:var(--orange);stroke:#fff;stroke-width:3px}.unitCircleLabel{fill:var(--ink);font-size:20px;font-weight:800}.sineYLabel,.thetaUnitLabel,.degreeUnitLabel{opacity:0;transition:opacity .25s}.sineValueCard text{fill:var(--ink);font-size:22px;font-weight:800}.sineValueCard .sineValueLine,.sineValueCard .sineAnswerLine{fill:var(--blue);opacity:0;font-size:20px;transition:opacity .25s}.sineValueCard .sineAnswerLine{fill:var(--green);font-size:34px}.sineDerivedDiagram[data-sine-step="0"] .sineIntro,.sineDerivedDiagram[data-sine-step="1"] .sineHeightText,.sineDerivedDiagram[data-sine-step="2"] .sineRadianText,.sineDerivedDiagram[data-sine-step="3"] .sineDegreeText,.sineDerivedDiagram[data-sine-step="1"] .sineHeight,.sineDerivedDiagram[data-sine-step="1"] .cosBase,.sineDerivedDiagram[data-sine-step="1"] .sineRightAngle,.sineDerivedDiagram[data-sine-step="2"] .sineHeight,.sineDerivedDiagram[data-sine-step="2"] .sineRightAngle,.sineDerivedDiagram[data-sine-step="3"] .sineHeight,.sineDerivedDiagram[data-sine-step="3"] .sineRightAngle,.sineDerivedDiagram[data-sine-step="1"] .sineYLabel,.sineDerivedDiagram[data-sine-step="2"] .sineYLabel,.sineDerivedDiagram[data-sine-step="3"] .sineYLabel,.sineDerivedDiagram[data-sine-step="2"] .thetaUnitLabel,.sineDerivedDiagram[data-sine-step="3"] .degreeUnitLabel,.sineDerivedDiagram[data-sine-step="2"] .sineRadianAnswer,.sineDerivedDiagram[data-sine-step="3"] .sineDegreeAnswer,.sineDerivedDiagram[data-sine-step="2"] .radianArc,.sineDerivedDiagram[data-sine-step="3"] .degreeArc{opacity:1}.piCircle{fill:#2f7d6d1a;stroke:var(--ink);stroke-width:4px}.piCenter{fill:var(--ink)}.diameterLine{stroke:var(--blue);stroke-width:7px;stroke-linecap:round;opacity:0;transition:opacity .25s}.diameterLabel,.piLabel{fill:var(--blue);opacity:0;font-size:28px;font-weight:800;transition:opacity .25s}.circumferenceTrace{fill:none;stroke:var(--orange);stroke-width:9px;stroke-linecap:round;stroke-dasharray:754;stroke-dashoffset:754px;opacity:0;transition:stroke-dashoffset .7s,opacity .25s}.unwrappedLine{opacity:0;transition:opacity .25s}.unwrappedLine line,.unwrappedLine path{fill:none;stroke:var(--orange);stroke-width:6px;stroke-linecap:round}.unwrappedLine text{fill:var(--ink);font-size:19px;font-weight:800}.piPolygon{fill:none;stroke:var(--green);stroke-width:5px;stroke-linejoin:round;opacity:0;transition:opacity .25s}.polygonHex{stroke-dasharray:10 8}.polygonDodec{stroke:var(--blue)}.piCard text{fill:var(--ink);font-size:22px;font-weight:800}.piCard .piCardLine,.piCard .piAnswerLine{fill:var(--blue);opacity:0;font-size:20px;transition:opacity .25s}.piCard .piAnswerLine{fill:var(--green);font-size:34px}.piDiagram[data-pi-step="0"] .diameterLine,.piDiagram[data-pi-step="0"] .diameterLabel,.piDiagram[data-pi-step="1"] .diameterLine,.piDiagram[data-pi-step="1"] .diameterLabel,.piDiagram[data-pi-step="2"] .diameterLine,.piDiagram[data-pi-step="2"] .diameterLabel,.piDiagram[data-pi-step="4"] .diameterLine,.piDiagram[data-pi-step="4"] .diameterLabel{opacity:1}.piDiagram[data-pi-step="1"] .circumferenceTrace,.piDiagram[data-pi-step="2"] .circumferenceTrace,.piDiagram[data-pi-step="4"] .circumferenceTrace{opacity:1;stroke-dashoffset:0}.piDiagram[data-pi-step="1"] .unwrappedLine,.piDiagram[data-pi-step="2"] .unwrappedLine,.piDiagram[data-pi-step="3"] .polygonHex,.piDiagram[data-pi-step="3"] .polygonDodec,.piDiagram[data-pi-step="0"] .piMeasureText,.piDiagram[data-pi-step="1"] .piUnwrapText,.piDiagram[data-pi-step="2"] .piRatioText,.piDiagram[data-pi-step="3"] .piPolygonText,.piDiagram[data-pi-step="4"] .piFormulaText,.piDiagram[data-pi-step="2"] .piAnswerLine,.piDiagram[data-pi-step="4"] .piAnswerLine{opacity:1}.circleAreaCircle circle{fill:#2f7d6d24;stroke:var(--ink);stroke-width:4px}.circleAreaCircle line{stroke:var(--blue);stroke-width:5px;stroke-linecap:round}.circleAreaCircle .sliceLine{stroke:var(--orange);stroke-width:3px;opacity:0;transition:opacity .25s}.circleAreaCircle text,.areaRectangleGuide text{fill:var(--ink);font-size:25px;font-weight:800}.wedgeRow{opacity:0;transition:opacity .25s}.wedge{stroke:var(--ink);stroke-width:3px;stroke-linejoin:round}.wedgeUp{fill:#2f7d6d73}.wedgeDown{fill:#f2b84b80}.areaRectangleGuide{opacity:0;transition:opacity .25s}.areaRectangleGuide path,.areaRectangleGuide line{fill:#3d6f9114;stroke:var(--blue);stroke-width:4px;stroke-dasharray:10 8}.circleAreaCard text{fill:var(--ink);font-size:22px;font-weight:800}.circleAreaCard .circleAreaLine,.circleAreaCard .circleAreaAnswer{fill:var(--blue);opacity:0;font-size:20px;transition:opacity .25s}.circleAreaCard .circleAreaAnswer{fill:var(--green);font-size:34px}.circleAreaDiagram[data-circle-area-step="1"] .sliceLine,.circleAreaDiagram[data-circle-area-step="2"] .sliceLine,.circleAreaDiagram[data-circle-area-step="3"] .sliceLine,.circleAreaDiagram[data-circle-area-step="4"] .sliceLine,.circleAreaDiagram[data-circle-area-step="2"] .wedgeRow,.circleAreaDiagram[data-circle-area-step="3"] .wedgeRow,.circleAreaDiagram[data-circle-area-step="4"] .wedgeRow,.circleAreaDiagram[data-circle-area-step="3"] .areaRectangleGuide,.circleAreaDiagram[data-circle-area-step="4"] .areaRectangleGuide,.circleAreaDiagram[data-circle-area-step="0"] .areaCircleText,.circleAreaDiagram[data-circle-area-step="1"] .areaSlicesText,.circleAreaDiagram[data-circle-area-step="2"] .areaRearrangeText,.circleAreaDiagram[data-circle-area-step="3"] .areaHalfText,.circleAreaDiagram[data-circle-area-step="4"] .areaFormulaText,.circleAreaDiagram[data-circle-area-step="4"] .circleAreaAnswer{opacity:1}.sectorCircle{fill:#3d6f9112;stroke:var(--ink);stroke-width:4px}.sectorFill{fill:#2f7d6d38;stroke:var(--green);stroke-width:3px}.sectorRadius,.sectorArc,.sectorAngle{fill:none;stroke:var(--blue);stroke-width:6px;stroke-linecap:round}.sectorArc{stroke:var(--orange);stroke-width:10px}.sectorAngle{stroke:var(--green);stroke-width:5px}.sectorLabel,.sectorCard text{fill:var(--ink);font-size:22px;font-weight:800}.sectorCard .sectorLine,.sectorCard .sectorAnswer{fill:var(--blue);opacity:0;font-size:20px;transition:opacity .25s}.sectorCard .sectorAnswer{fill:var(--green);font-size:32px}.sectorDiagram[data-sector-mode=area][data-sector-step="0"] .sectorAreaIntro,.sectorDiagram[data-sector-mode=area][data-sector-step="1"] .sectorAreaIntro,.sectorDiagram[data-sector-mode=area][data-sector-step="2"] .sectorAreaFormula,.sectorDiagram[data-sector-mode=area][data-sector-step="3"] .sectorAreaRadians,.sectorDiagram[data-sector-mode=perimeter][data-sector-step="0"] .sectorPerimeterIntro,.sectorDiagram[data-sector-mode=perimeter][data-sector-step="1"] .sectorPerimeterArc,.sectorDiagram[data-sector-mode=perimeter][data-sector-step="2"] .sectorPerimeterFormula,.sectorDiagram[data-sector-mode=radian][data-sector-step="0"] .radianIntro,.sectorDiagram[data-sector-mode=radian][data-sector-step="1"] .radianOne,.sectorDiagram[data-sector-mode=radian][data-sector-step="2"] .radianFull,.sectorDiagram[data-sector-mode=radian][data-sector-step="3"] .radianBridge,.sectorDiagram[data-sector-mode=radian] .sectorAnswer,.sectorDiagram[data-sector-mode=area][data-sector-step="3"] .sectorAnswer,.sectorDiagram[data-sector-mode=perimeter][data-sector-step="2"] .sectorAnswer{opacity:1}.sectorDiagram[data-sector-mode=perimeter] .sectorRadius,.sectorDiagram[data-sector-mode=perimeter] .sectorArc,.sectorDiagram[data-sector-mode=radian] .sectorArc,.sectorDiagram[data-sector-mode=radian] .radiusOne{stroke-width:10px}.algebraEquation,.tileLabel,.outsideFactor,.insideTerm{fill:var(--ink);font-size:30px;font-weight:800}.algebraEquation{text-anchor:middle;font-size:28px}.removeEquation,.answerEquation{opacity:0;transition:opacity .25s}.answerEquation{fill:var(--green);font-size:36px}.algebraDiagram[data-algebra-kind=balance] .answerEquation{font-size:34px}.scaleBeam,.scalePost,.scaleBase{fill:none;stroke:var(--ink);stroke-width:7px;stroke-linecap:round}.scalePan path{fill:#3d6f911f;stroke:var(--blue);stroke-width:4px;stroke-linejoin:round}.scalePan text{fill:var(--ink);text-anchor:middle;font-size:27px;font-weight:800}.groupBox{fill:#f2b84b29;stroke:var(--ink);stroke-width:4px}.distributeArrow{fill:none;stroke:var(--orange);stroke-width:6px;stroke-linecap:round;opacity:0;transition:opacity .25s}.tile{stroke:var(--ink);stroke-width:3px}.tileSquare{fill:#2f7d6d59}.tileX{fill:#f2b84b73}.tileUnit{fill:#3d6f9138}.algebraDiagram[data-algebra-step="1"] .removeEquation,.algebraDiagram[data-algebra-step="2"] .removeEquation,.algebraDiagram[data-algebra-step="2"] .answerEquation,.algebraDiagram[data-algebra-kind=distribute][data-algebra-step="1"] .distributeArrow,.algebraDiagram[data-algebra-kind=distribute][data-algebra-step="2"] .distributeArrow{opacity:1}.algebraDiagram[data-algebra-kind=balance][data-algebra-step="2"] .leftPan,.algebraDiagram[data-algebra-kind=balance][data-algebra-step="2"] .rightPan{transform:translateY(-8px)}.algebraDiagram[data-algebra-kind=factor][data-algebra-step="1"] .tileX,.algebraDiagram[data-algebra-kind=factor][data-algebra-step="1"] .tileUnit,.algebraDiagram[data-algebra-kind=factor][data-algebra-step="2"] .tileX,.algebraDiagram[data-algebra-kind=factor][data-algebra-step="2"] .tileUnit{stroke:var(--green);stroke-width:5px}.simAxis,.simGuide{fill:none;stroke:#98a4ad;stroke-width:3px;stroke-linecap:round}.simGuide{stroke-dasharray:7 7;opacity:0;transition:opacity .25s}.simLine{fill:none;stroke-width:7px;stroke-linecap:round;opacity:.72;transition:opacity .25s,stroke-width .25s}.lineOne{stroke:var(--blue)}.lineTwo{stroke:var(--green)}.simPoint{fill:var(--amber);stroke:var(--ink);stroke-width:4px;opacity:0;transform-origin:224px 204px;transition:opacity .25s,transform .25s}.simAxisLabel,.simLineLabel,.simPointLabel,.simCardTitle,.simCardDetail,.simEquation{fill:var(--ink);text-anchor:middle;font-size:20px;font-weight:800}.simLineLabel{fill:var(--blue);font-size:18px}.labelTwo{fill:var(--green)}.simPointLabel{fill:var(--orange);opacity:0;font-size:22px;transition:opacity .25s}.simMethodCard rect{fill:#ffffffb8;stroke:var(--line);stroke-width:3px}.simCardTitle{fill:var(--ink);font-size:25px}.simCardDetail{fill:var(--muted);font-size:18px}.simEquation{fill:var(--blue);font-size:24px}.eqAnswer{fill:var(--green)}.simultaneousDiagram[data-sim-step="1"] .lineOne,.simultaneousDiagram[data-sim-step="2"] .lineTwo{stroke-width:10px;opacity:1}.simultaneousDiagram[data-sim-step="3"] .simPoint,.simultaneousDiagram[data-sim-step="3"] .simGuide,.simultaneousDiagram[data-sim-step="3"] .simPointLabel,.simultaneousDiagram[data-sim-step="4"] .simPoint,.simultaneousDiagram[data-sim-step="4"] .simGuide,.simultaneousDiagram[data-sim-step="4"] .simPointLabel{opacity:1}.simultaneousDiagram[data-sim-step="4"] .simPoint{transform:scale(1.2)}.factorTitle,.factorText,.factorHint,.factorResult{fill:var(--ink);text-anchor:middle;font-size:28px;font-weight:800}.super{baseline-shift:super;font-size:65%}.factorHint,.factorResult,.factorArrow{opacity:0;transition:opacity .25s}.factorHint{fill:var(--blue);font-size:22px}.factorResult{fill:var(--green);font-size:34px}.factorBlock,.squareTile,.groupPair,.completeSquareBox,.completeStrip,.missingCorner{stroke:var(--ink);stroke-width:4px}.sharedFactor,.completeSquareBox{fill:#2f7d6d47}.termBlock,.smallSquare,.completeStrip{fill:#f2b84b66}.bigSquare,.groupPair{fill:#3d6f9124}.missingCorner{fill:#df6b3f2e;stroke-dasharray:9 7}.factorArrow{fill:none;stroke:var(--orange);stroke-width:7px;stroke-linecap:round}.factorMethodDiagram[data-factor-step="1"] .factorHint,.factorMethodDiagram[data-factor-step="2"] .factorHint,.factorMethodDiagram[data-factor-step="3"] .factorHint,.factorMethodDiagram[data-factor-step="1"] .factorArrow,.factorMethodDiagram[data-factor-step="2"] .factorArrow,.factorMethodDiagram[data-factor-step="3"] .factorArrow,.factorMethodDiagram[data-factor-step="2"] .factorResult,.factorMethodDiagram[data-factor-step="3"] .factorResult,.factorMethodDiagram[data-factor-method=complete][data-factor-step="3"] .factorResult{opacity:1}.factorMethodDiagram[data-factor-step="1"] .sharedFactor,.factorMethodDiagram[data-factor-step="2"] .sharedFactor,.factorMethodDiagram[data-factor-step="1"] .smallSquare,.factorMethodDiagram[data-factor-step="2"] .smallSquare,.factorMethodDiagram[data-factor-step="1"] .groupPair,.factorMethodDiagram[data-factor-step="2"] .groupPair,.factorMethodDiagram[data-factor-step="1"] .completeStrip,.factorMethodDiagram[data-factor-step="2"] .completeStrip,.factorMethodDiagram[data-factor-step="3"] .completeStrip{stroke:var(--green);stroke-width:5px}.identityBoard rect{fill:#ffffffb8;stroke:var(--line);stroke-width:3px}.identityExpression,.identityEquals,.identityFactored,.identityCue text{fill:var(--ink);text-anchor:middle;font-size:34px;font-weight:800}.identityEquals{fill:var(--orange);font-size:30px}.identityFactored{fill:var(--green);font-size:32px}.identityCue text{fill:var(--blue);font-size:20px}.identityDiagram[data-identity-family=cubic] .identityExpression,.identityDiagram[data-identity-family=cubic] .identityFactored{font-size:27px}.identityDiagram[data-identity-family=power] .identityExpression,.identityDiagram[data-identity-family=power] .identityFactored{font-size:23px}.lessonText{border-top:1px solid var(--line);padding-top:16px}.lessonText p{max-width:820px;color:var(--muted);margin:14px 0 18px;font-size:1.06rem;line-height:1.55}.progressTrack{background:#e8ece8;border-radius:999px;height:8px;overflow:hidden}.progressTrack div{background:linear-gradient(90deg, var(--green), var(--amber));height:100%;transition:width .25s}.controls{gap:10px;display:flex}.controls button{min-width:92px;min-height:42px;color:var(--ink);cursor:pointer;background:#fff;border:1px solid #bfc9c2;border-radius:8px;font-weight:700}.controls button:last-child{background:var(--ink);color:#fff;border-color:var(--ink)}.controls button:disabled{cursor:not-allowed;opacity:.45}.lessonWriteup{border-top:1px solid var(--line);gap:16px;padding-top:18px;display:grid}.lessonWriteupHeader{gap:8px;max-width:820px;display:grid}.lessonWriteupHeader h3{color:var(--ink);margin:0;font-size:clamp(1.35rem,2.2vw,2rem);line-height:1.1}.lessonWriteupHeader p:last-child{color:var(--muted);margin:0;font-size:1rem;line-height:1.55}.writeupGrid{gap:14px;max-width:860px;display:grid}.writeupStep{border:1px solid var(--line);background:#fff;border-radius:8px;align-content:start;gap:12px;min-width:0;padding:16px;display:grid}.writeupStep h4,.writeupStep p{margin:0}.writeupStep h4{color:var(--ink);font-size:1rem;line-height:1.25}.writeupStep p{color:var(--muted);font-size:.96rem;line-height:1.45}.writeupMathList{gap:8px;display:grid}.writeupMath{color:#245f83;font-variant-numeric:lining-nums tabular-nums;white-space:nowrap;background:#f6fafb;border:1px solid #cfd7dc;border-radius:8px;width:100%;padding:10px 12px;font-family:Arial,Helvetica,sans-serif;font-size:1.04rem;font-weight:760;line-height:1.3;overflow-x:auto}.mathLine{min-height:1.4em;display:inline-block}.mathVar{font-style:italic;font-weight:760}.mathOp{color:#667986;margin:0 .28em;font-weight:500;display:inline-block}.mathLine sup{margin-left:-.12em;font-size:.66em;line-height:1;position:relative;top:-.42em}.mathFraction{vertical-align:middle;grid-template-rows:auto auto;place-items:center;min-width:1.15em;line-height:1;display:inline-grid}.mathFraction>span:first-child{text-align:center;border-bottom:.08em solid;width:100%;padding:0 .16em .13em}.mathFraction>span:last-child{text-align:center;padding:.13em .16em 0}.inlineFraction{font-size:.92em}.mathRoot{vertical-align:middle;align-items:stretch;display:inline-flex}.mathRoot:before{content:"√";font-size:1.3em;line-height:1.08;transform:translateY(.04em)}.mathRoot>span{border-top:.08em solid;padding:.07em .1em 0}@media (max-width:820px){.shell{gap:0;padding:0}.siteHeader{border-top:0;border-left:0;border-right:0;border-radius:0;flex-direction:column;align-items:stretch;gap:12px;padding:14px 12px}.brandLockup{gap:5px}.teachLensBrandImage{width:min(250px,78vw)}.topNav{display:none}.mobileLessonBrowser{display:grid}.mobileLessonBrowser>summary,.mobileLessonCategory>summary{border:1px solid var(--line);min-height:42px;color:var(--ink);cursor:pointer;background:#fff;border-radius:8px;padding:10px 12px;font-weight:800;list-style:none}.mobileLessonBrowser>summary::-webkit-details-marker{display:none}.mobileLessonCategory>summary::-webkit-details-marker{display:none}.mobileLessonBrowser>summary:after,.mobileLessonCategory>summary:after{content:"⌄";float:right;color:var(--muted)}.mobileLessonBrowser[open]>summary,.mobileLessonCategory[open]>summary{border-color:var(--ink);background:var(--ink);color:#fff}.mobileLessonBrowser[open]>summary:after,.mobileLessonCategory[open]>summary:after{color:#fff}.mobileLessonPanel{border:1px solid var(--line);background:#fff;border-radius:8px;gap:8px;margin-top:8px;padding:8px;display:grid}.mobileLessonCategory{gap:8px;display:grid}.mobileLessonCategory>summary{color:var(--muted);background:#f8faf8}.mobileLessonList{gap:6px;padding:0 0 4px;display:grid}.siteFooter{border-bottom:0;border-left:0;border-right:0;border-radius:0;flex-direction:column;align-items:stretch;gap:12px;padding:16px 12px}.footerLinks{justify-content:flex-start}.lesson{grid-template-columns:1fr;gap:0}.sidebar,.stagePanel{border-left:0;border-right:0;border-radius:0;min-height:auto}.sidebar{z-index:10;border-top:0;gap:12px;padding:14px 12px;position:sticky;top:0;box-shadow:0 8px 24px #1f293314}.sidebarHeader{grid-template-columns:minmax(0,1fr)}h1{font-size:1.55rem;line-height:1.05}.desktopMenu{display:none}.mobilePickers{grid-template-columns:1fr;gap:8px;display:grid}.mobilePickers label{gap:5px;min-width:0;display:grid}.mobilePickers span{color:var(--muted);text-transform:uppercase;font-size:.72rem;font-weight:800}.mobilePickers select{border:1px solid var(--line);width:100%;min-height:42px;color:var(--ink);font:inherit;background:#fff;border-radius:8px;padding:8px 32px 8px 10px;font-weight:700}.stagePanel{gap:14px;padding:16px 12px}.formula{white-space:normal}.diagram svg{min-height:300px;max-height:none}}@media (max-width:520px){.mobilePickers{grid-template-columns:1fr}}
