/* OpenDesign Paper / orange editorial. Consolidated from the supplied final index, not the historical override files.
 * The lesson-flow components live in flow.css. Structural diagram rules remain here.
 * Hallmark: genre editorial; system DESIGN.md; macrostructure learning workbench. */
@layer od-layout {:where(.od-stack,.od-row,.od-row-top,.od-cluster,.od-grid,.od-field,.od-stat,.od-cell,.od-tile) > :where(*) {min-width: 0;}
.od-stack   {display: flex;flex-direction: column;gap: var(--od-gap, 8px);}
.od-row     {display: flex;align-items: center;gap: var(--od-gap, 8px);}
.od-row-top {display: flex;align-items: flex-start;gap: var(--od-gap, 8px);}
.od-cluster {display: flex;flex-wrap: wrap;align-items: center;gap: var(--od-gap, 8px);}
.od-fill    {flex: 1 1 0;min-width: 0;}
.od-fixed   {flex: none;}
.od-grid    {display: grid;gap: var(--od-gap, 12px);grid-template-columns: repeat(var(--od-cols, 3), minmax(0, 1fr));}
.od-stat, .od-field, .od-cell {display: grid;gap: var(--od-gap, 2px);}
:where(.od-stat,.od-field,.od-cell) > :where(*) {display: block;}
.od-tile {display: grid;grid-template-rows: auto 1fr;}
:where(.od-tile) > :where(*) {display: block;}
.od-media {display: block;width: 100%;height: auto;aspect-ratio: var(--od-ratio, auto);}
.od-media-cover {object-fit: cover;}
.od-truncate {display: block;max-width: 100%;overflow: hidden;white-space: nowrap;text-overflow: ellipsis;}
.od-clamp-2, .od-clamp-3 {display: -webkit-box;-webkit-box-orient: vertical;overflow: hidden;overflow-wrap: anywhere;}
.od-clamp-2 {-webkit-line-clamp: 2;}
.od-clamp-3 {-webkit-line-clamp: 3;}
.od-lines-2 {min-height: calc(2 * 1.4em);}
.od-nowrap  {white-space: nowrap;}
.od-keep    {word-break: keep-all;overflow-wrap: anywhere;}
.od-screen {display: grid;grid-template-rows: auto minmax(0, 1fr) auto;height: 100%;}
.od-scroll {overflow-y: auto;overscroll-behavior: contain;min-height: 0;}
.od-rail {display: flex;gap: var(--od-gap, 8px);overflow-x: auto;scroll-snap-type: x proximity;scrollbar-width: none;padding-inline: var(--od-rail-pad, 16px);scroll-padding-inline: var(--od-rail-pad, 16px);}
.od-rail::-webkit-scrollbar {display: none;}
:where(.od-rail) > :where(*) {flex: none;scroll-snap-align: start;}
:where(.od-rail) > :where(:last-child) {margin-inline-end: var(--od-rail-pad, 16px);}
.od-spacer {flex: none;visibility: hidden;pointer-events: none;}
.od-touch  {min-width: 44px;min-height: 44px;}}
:root{color-scheme:light;font-synthesis:none;}
:root[data-theme=contrast]{--shadow:none;}
html{scroll-behavior:smooth;}
body{margin:0;}
button,input,textarea,select{font:inherit;}
button,a,input,select,textarea{touch-action:manipulation;}
button{cursor:pointer;}
.skip{position:fixed;top:-100px;left:15px;background:var(--panel);padding:12px;z-index:1000;}
.skip:focus{top:12px;}
button{border:1px solid var(--line);background:var(--panel);color:var(--ink);border-radius:9px;padding:10px 15px;font-weight:600;}
button:hover:not(:disabled){background:var(--soft);border-color:var(--graph-line);}
button.primary,.button.primary{background:var(--accent);color:var(--on-accent);border-color:var(--accent);}
button.primary:hover{filter:brightness(1.08);}
button.ghost{background:transparent;border-color:transparent;}
button.small{padding:6px 10px;font-size:13px;}
button.danger{color:var(--bad);}
button.icon{padding:8px 10px;min-width:38px;}
.button{display:inline-flex;padding:10px 15px;text-decoration:none;border-radius:9px;font-weight:650;border:1px solid var(--line);}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);}
input:not([type=checkbox]):not([type=radio]):not([type=range]),select,textarea{border:1px solid var(--line);background:var(--panel);color:var(--ink);padding:10px 12px;border-radius:8px;max-width:100%;}
input[type=checkbox],input[type=radio]{accent-color:var(--accent);width:18px;height:18px;vertical-align:middle;margin-right:7px;}
textarea{width:100%;min-height:90px;}
.field{display:flex;flex-direction:column;gap:6px;margin-bottom:14px;}
.field>label{font-size:13px;font-weight:700;color:var(--muted);}
.field small{color:var(--muted);}
.inline-fields{display:flex;flex-wrap:wrap;gap:12px;align-items:end;}
.inline-fields .field{flex:1;min-width:100px;}
.check-label{display:inline-flex;gap:4px;align-items:center;margin:5px 12px 5px 0;font-weight:500;}
.checkbox-grid{display:flex;flex-wrap:wrap;gap:10px;}
#shell{display:grid;min-height:100vh;}
.sidebar{position:sticky;top:0;z-index:40;}
.brand{display:flex;align-items:center;color:var(--ink);text-decoration:none;}
.brand-mark{place-items:center;font:24px Georgia,serif;}
.brand small{display:block;color:var(--muted);}
.nav-list{display:flex;flex-direction:column;}
.nav-list a{display:flex;align-items:center;text-decoration:none;font-weight:600;}
.nav-list a svg{height:18px;width:18px;}
.nav-list a:hover{background:var(--soft);}
.side-bottom{color:var(--muted);}
.side-status{display:flex;align-items:center;gap:7px;margin-bottom:7px;}
.status-dot{width:7px;height:7px;border-radius:50%;background:var(--accent);}
.side-bottom .button-row{margin-top:14px;}
.mobile-header{display:none;}
.topbar{display:flex;align-items:center;justify-content:space-between;}
.topbar .meta{display:flex;align-items:center;font-size:12px;color:var(--muted);}
main{margin:0 auto;}
h1{margin:7px 0 14px;}
h2{margin:0 0 17px;}
h3{margin:0 0 12px;}
h4{margin:15px 0 8px;}
p{margin:0 0 15px;}
.eyebrow{font-size:11px;letter-spacing:1.8px;font-weight:750;text-transform:uppercase;color:var(--muted);}
.lede{color:var(--muted);max-width:730px;}
.tiny{font-size:12px;}
.page-heading{display:flex;justify-content:space-between;}
.page-heading .button-row{flex-shrink:0;}
.button-row{display:flex;align-items:center;flex-wrap:wrap;}
.section-line{display:flex;justify-content:space-between;gap:20px;align-items:center;}
.section-line h2{margin:0;}
.section-line a{font-size:13px;}
.grid{display:grid;gap:18px;}
.grid.two{grid-template-columns:repeat(2,minmax(0,1fr));}
.grid.three{grid-template-columns:repeat(3,minmax(0,1fr));}
.grid.four{grid-template-columns:repeat(4,minmax(0,1fr));}
.card.flat{box-shadow:none;}
.card.accent{background:var(--accent);color:var(--on-accent);border-color:var(--accent);}
.card.accent .eyebrow,.card.accent .muted{color:inherit;opacity:.8;}
.card.accent button{background:var(--on-accent);color:var(--accent);border-color:transparent;}
.hero-study{display:grid;grid-template-columns:minmax(0,1fr) 235px;gap:25px;padding:29px 32px;}
.hero-study h2{font-size:28px;max-width:700px;}
.hero-study .step-art{display:flex;flex-direction:column;justify-content:center;gap:12px;border-left:1px solid #ffffff35;padding-left:23px;font-size:13px;}
.step-art .row{display:flex;align-items:center;gap:11px;}
.step-art b{height:26px;width:26px;display:grid;place-items:center;border:1px solid #ffffff88;border-radius:50%;font-size:12px;}
.metric{font-size:29px;font-weight:720;line-height:1.1;margin:13px 0 7px;letter-spacing:-.8px;}
.metric-label{font-size:12px;font-weight:650;color:var(--muted);}
.meter{height:6px;background:var(--soft);border-radius:8px;overflow:hidden;margin:13px 0;}
.meter>span{height:100%;display:block;background:var(--accent);}
.chapter-card{position:relative;text-decoration:none;color:var(--ink);display:block;padding:21px;}
.chapter-card:hover{border-color:var(--accent);background:var(--panel);}
.chapter-card .chapter-num{font-size:11px;font-weight:800;border:1px solid var(--line);padding:4px 7px;border-radius:6px;display:inline-block;margin-bottom:14px;}
.chapter-card h3{font-size:17px;min-height:41px;}
.chapter-meta{display:flex;justify-content:space-between;font-size:12px;color:var(--muted);}
.badge{display:inline-flex;align-items:center;font-size:11px;line-height:1.3;font-weight:700;background:var(--soft);color:var(--muted);gap:5px;white-space:normal;}
.tag-row{display:flex;gap:7px;flex-wrap:wrap;margin:13px 0;}
.notice{padding:15px 18px;background:var(--soft);border:1px solid var(--line);line-height:1.6;margin:17px 0;}
.notice.good{background:var(--accent-soft);color:var(--good);border-color:var(--accent);}
.notice.warn{background:var(--gold-bg);color:var(--gold);}
.notice.bad{background:var(--bad-bg);color:var(--bad);}
.notice p:last-child{margin:0;}
.notice strong{display:block;margin-bottom:5px;}
.empty{padding:30px;text-align:center;color:var(--muted);background:var(--soft);border-radius:12px;}
.list-row{display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);}
.list-row:last-child{border-bottom:0;}
.list-row .subtitle{font-size:12px;color:var(--muted);margin-top:4px;}
.list-row a.title{font-weight:650;text-decoration:none;color:var(--ink);}
.list-row .num{font-variant-numeric:tabular-nums;font-size:12px;color:var(--muted);min-width:38px;}
.list-start{display:flex;align-items:center;gap:15px;}
.filters{display:flex;flex-wrap:wrap;gap:11px;margin:23px 0;}
.filters input{flex:1;min-width:180px;}
.filters select{max-width:240px;}
.chapter-group summary{cursor:pointer;font-size:18px;font-weight:700;list-style:none;padding:20px 24px;display:flex;justify-content:space-between;gap:12px;align-items:center;}
.chapter-group summary::-webkit-details-marker{display:none;}
.chapter-group summary:after{content:"+";font-size:22px;color:var(--muted);}
.chapter-group[open] summary:after{content:"−";}
.lesson-layout{display:grid;grid-template-columns:minmax(0,1fr) 270px;gap:24px;align-items:start;}
.lesson-main{min-width:0;}
.lesson-aside{position:sticky;top:20px;}
.lesson-aside .card{padding:19px;margin-bottom:16px;}
.lesson-aside ul{padding-left:18px;margin:0;font-size:13px;}
.lesson-aside li{margin:7px 0;}
.lesson-tabs{margin-bottom:25px;padding-bottom:0;}
.lesson-tabs button{border:0;background:transparent;border-radius:0;padding:12px 13px;font-size:13px;white-space:nowrap;border-bottom:3px solid transparent;color:var(--muted);}
.lesson-tabs button.active{border-bottom-color:var(--accent);color:var(--accent);}
.lesson-copy{font-family:ui-serif,Georgia,Cambria,"Times New Roman",serif;font-size:19px;line-height:1.8;}
.lesson-copy h3,.lesson-copy h4{font-family:Inter,system-ui,sans-serif;margin-top:25px;}
.lesson-copy p{margin-bottom:20px;}
.lesson-copy li{margin-bottom:12px;}
.lesson-copy table{font-family:Inter,system-ui,sans-serif;font-size:14px;line-height:1.65;}
.intuition{font-size:19px;line-height:1.7;padding:23px;border-left:3px solid var(--accent);background:var(--accent-soft);border-radius:0 10px 10px 0;margin-bottom:24px;font-family:ui-serif,Georgia,serif;}
.formula{font-family:Cambria,"STIX Two Math","DejaVu Serif",serif;font-size:19px;padding:17px 19px;background:var(--soft);border:1px solid var(--line);border-radius:8px;margin:18px 0;line-height:1.85;}
.over{display:inline-block;text-decoration:overline;line-height:1.7;padding-top:1px;}
.method-step{display:flex;gap:13px;padding:14px 0;border-bottom:1px solid var(--line);}
.method-step:last-child{border-bottom:0;}
.method-step>span{flex:none;display:grid;place-items:center;width:27px;height:27px;border-radius:7px;background:var(--accent-soft);color:var(--accent);font-size:12px;font-weight:800;}
.method-step p{margin:0;font-size:15px;line-height:1.7;}
.trap{display:flex;gap:10px;margin:12px 0;color:var(--muted);font-size:14px;}
.trap:before{content:"!";font-weight:800;color:var(--gold);}
.skill-item{padding:9px 0;border-bottom:1px solid var(--line);font-size:12px;}
.skill-item .skill-top{display:flex;justify-content:space-between;gap:8px;margin-bottom:3px;}
.skill-item button{padding:0;border:0;background:transparent;font-size:12px;font-weight:500;text-align:left;color:var(--muted);}
.learn-footer{justify-content:space-between;border-top:1px solid var(--line);}
.recall-card textarea{min-height:180px;}
.source-line{font-size:11px;color:var(--muted);line-height:1.6;margin-top:25px;}
.table-scroll{margin:16px 0;}
table{border-collapse:collapse;width:100%;font-size:14px;}
th,td{padding:10px 12px;text-align:left;border-bottom:1px solid var(--line);}
th{font-size:12px;font-weight:700;color:var(--muted);background:var(--soft);}
tbody tr:last-child td{border-bottom:0;}
.matrix-wrap{display:flex;justify-content:center;margin:14px 0;overflow-x:auto;padding:3px;}
.matrix{width:auto;border-left:2px solid var(--ink);border-right:2px solid var(--ink);border-radius:2px;font-family:Cambria,"DejaVu Serif",serif;font-size:18px;}
.matrix td{border:0;text-align:center;min-width:42px;padding:8px 13px;}
.matrix td.spotlight{background:var(--gold-bg);color:var(--gold);}
.math-svg{display:block;max-height:380px;margin:10px auto;overflow:visible;}
.node-label{font:600 15px system-ui,sans-serif;fill:var(--ink);}
.small-label,.edge-label{font:600 12px system-ui,sans-serif;fill:var(--ink);}
.graph-pair{display:grid;grid-template-columns:1fr 1fr;gap:16px;text-align:center;}
.diagram-area{padding:15px;background:var(--soft);border-radius:10px;margin:16px 0;}
.diagram-area .math-svg{background:var(--panel);border-radius:8px;}
.question-stem{margin:18px 0 22px;}
.question-stem .table-scroll{font-size:15px;}
.question-type{font-size:11px;letter-spacing:1px;text-transform:uppercase;}
.choices{display:flex;flex-direction:column;gap:11px;margin:20px 0;}
.choice{display:flex;align-items:flex-start;text-align:left;border-radius:9px;border:1px solid var(--line);font-weight:450;line-height:1.6;}
.choice .letter{flex:none;width:26px;height:26px;display:grid;place-items:center;border:1px solid var(--line);border-radius:6px;font-size:12px;color:var(--muted);}
.choice.selected{background:var(--accent-soft);border-color:var(--accent);}
.choice.correct{background:var(--accent-soft);}
.choice.wrong{border-color:var(--bad);background:var(--bad-bg);}
.choice.correct .letter{color:var(--good);}
.answer-input{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:19px;width:100%;min-height:53px;}
.answer-help{font-size:12px;color:var(--muted);margin:6px 0 15px;}
.feedback{padding:22px;border-radius:11px;background:var(--soft);border:1px solid var(--line);margin:23px 0;}
.feedback h3{margin-bottom:13px;}
.feedback.good{border-color:var(--good);background:var(--accent-soft);}
.feedback.bad{border-color:var(--bad);background:var(--bad-bg);}
.solution-step{padding:10px 0;display:flex;gap:11px;font-size:15px;line-height:1.65;}
.solution-step>span{color:var(--muted);font-size:11px;flex:none;padding-top:4px;width:18px;}
.answer-box{font-family:Cambria,Georgia,serif;font-size:19px;border:1px solid var(--line);border-radius:7px;padding:13px 15px;background:var(--panel);margin:15px 0;overflow-wrap:anywhere;}
.confidence{align-items:center;font-size:12px;color:var(--muted);flex-wrap:wrap;margin:15px 0;}
.session-grid{display:grid;grid-template-columns:minmax(0,1fr) 225px;align-items:start;}
.session-nav button{font-size:12px;}
.session-nav button.answered{background:var(--accent-soft);color:var(--accent);}
.session-nav button.current{border:2px solid var(--accent);padding:5px 0;}
.session-nav button.flagged:after{content:"•";color:var(--gold);padding-left:2px;}
.session-aside{position:sticky;top:20px;}
.session-aside .card{padding:18px;margin-bottom:15px;}
.time{font-variant-numeric:tabular-nums;font-size:28px;font-weight:700;letter-spacing:-.5px;}
.score-number{font-size:58px;letter-spacing:-2px;font-weight:750;line-height:1.1;}
.review-item{padding:22px;border-bottom:1px solid var(--line);}
.review-item:last-child{border-bottom:0;}
.review-item summary{cursor:pointer;font-size:15px;font-weight:600;}
.review-item .question-stem{font-size:16px;}
.lab-layout{display:grid;grid-template-columns:295px minmax(0,1fr);gap:20px;align-items:start;}
.lab-controls{padding:21px;}
.lab-controls .field{margin-bottom:17px;}
.lab-output{padding:24px;min-height:390px;}
.lab-note{font-size:13px;line-height:1.6;margin:17px 0;color:var(--muted);}
.lab-controls textarea{font-family:ui-monospace,monospace;font-size:14px;min-height:80px;}
.bit-button{font-variant-numeric:tabular-nums;padding:9px 13px;}
.bit-button.on{background:var(--accent);color:var(--on-accent);}
.toggle-grid{display:grid;gap:6px;max-width:300px;margin:15px auto;}
.toggle-grid button{padding:8px;min-width:37px;font-variant-numeric:tabular-nums;}
.toggle-grid .bit-on{background:var(--accent);color:var(--on-accent);border-color:var(--accent);}
.toggle-grid .axis{font-size:12px;font-weight:700;text-align:center;align-self:center;}
.lab-log{background:var(--soft);padding:15px;border-radius:8px;margin:15px 0;font-size:14px;}
.lab-log .queue{font-family:ui-monospace,monospace;font-size:13px;margin-top:8px;}
.proof-line{display:flex;gap:14px;align-items:center;margin:8px 0;padding:14px;background:var(--soft);border-radius:8px;}
.proof-line .line-text{flex:1;font-size:14px;}
.proof-line .line-number{font-size:12px;color:var(--muted);}
.proof-line .line-arrows{display:flex;flex-direction:column;gap:4px;}
.proof-line button{padding:0 8px;line-height:23px;font-size:13px;}
.coverage-cell{white-space:nowrap;}
.citation{font-size:12px;line-height:1.6;color:var(--muted);margin-top:10px;}
.reference-list details{border-bottom:1px solid var(--line);padding:15px 0;}
.reference-list summary{cursor:pointer;font-weight:650;}
.reference-list details p{font-size:14px;margin-top:12px;}
.backup-box{border:1px dashed var(--graph-line);border-radius:10px;padding:24px;text-align:center;}
.search-result{padding:18px 0;border-bottom:1px solid var(--line);}
.notebook-section{padding:18px 0;}
.notebook-section blockquote{padding-left:18px;border-left:3px solid var(--line);}
.modal-backdrop{position:fixed;inset:0;background:#13261dc4;display:flex;align-items:center;justify-content:center;z-index:500;padding:20px;}
.modal{background:var(--panel);border:1px solid var(--line);border-radius:16px;padding:27px;max-width:620px;width:100%;max-height:90vh;overflow:auto;box-shadow:0 25px 90px #0005;}
.modal h2{margin-right:25px;}
.modal .close{float:right;}
.toast{position:fixed;bottom:24px;right:24px;max-width:420px;background:var(--ink);color:var(--bg);padding:15px 20px;border-radius:10px;font-size:14px;box-shadow:0 10px 35px #0002;z-index:600;}
.rule{height:1px;background:var(--line);}
.arrow{margin-left:8px;}
.loading{padding:70px;text-align:center;}
.print-only{display:none;}
.error-banner{display:none;}
.no-script{padding:35px;color:#8a2b24;background:#fff2e9;}
@media(min-width:1500px){main{padding-left:60px;padding-right:60px;}
.topbar{padding-left:60px;padding-right:60px;}}
@media(max-width:1150px){#shell{grid-template-columns:200px 1fr;}
.sidebar{padding-left:12px;padding-right:12px;}
.topbar{padding:0 26px;}
main{padding:30px 26px;}
.lesson-layout{grid-template-columns:minmax(0,1fr) 230px;}
.grid.four{grid-template-columns:repeat(2,1fr);}
.hero-study{grid-template-columns:1fr;}
.hero-study .step-art{display:none;}
.lab-layout{grid-template-columns:245px minmax(0,1fr);}
.session-grid{grid-template-columns:minmax(0,1fr) 185px;}
.lesson-copy{font-size:18px;}
.lesson-tabs button{padding:11px 9px;}}
@media(max-width:960px){.lesson-layout{grid-template-columns:1fr;}
.lesson-aside{position:static;display:grid;grid-template-columns:1fr 1fr;gap:15px;}
.lesson-aside .card{margin:0;}
.grid.three{grid-template-columns:repeat(2,1fr);}
.lab-layout{grid-template-columns:1fr;}
.lab-controls{display:block;}
.lab-controls .control-grid{display:grid;grid-template-columns:1fr 1fr;gap:0 15px;}
.session-grid{grid-template-columns:1fr;}
.session-aside{position:static;display:grid;grid-template-columns:1fr 1fr;gap:15px;}
.session-aside .card{margin:0;}
.page-heading{flex-wrap:wrap;}
.settings-grid{grid-template-columns:1fr;}}
@media(max-width:720px){#shell{display:block;}
.sidebar{display:none;position:fixed;left:0;top:60px;bottom:0;height:calc(100vh - 60px);width:260px;box-shadow:20px 0 80px #10291b44;overflow:auto;}
.sidebar.open{display:flex;}
.sidebar .brand{display:none;}
.mobile-header{display:flex;position:sticky;top:0;height:61px;align-items:center;justify-content:space-between;padding:0 17px;background:var(--panel);border-bottom:1px solid var(--line);z-index:100;}
.mobile-header .brand{font-size:17px;padding:0;gap:8px;}
.mobile-header .brand-mark{height:29px;width:29px;font-size:20px;}
.mobile-header .brand small{display:none;}
.topbar{height:49px;padding:0 20px;}
.topbar .meta .desktop-only{display:none;}
.topbar .crumb{font-size:10px;letter-spacing:1px;}
main{padding:25px 18px 50px;}
h1{font-size:30px;}
.lede{font-size:15px;}
.card{padding:20px;border-radius:12px;}
.hero-study{padding:24px;}
.hero-study h2{font-size:24px;}
.grid.three,.grid.two{grid-template-columns:1fr;}
.grid.four{gap:10px;}
.grid.four .card{padding:16px;}
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.session-nav button{min-width:0;}
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*,*:before,*:after{transition:none!important;animation:none!important;}}
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.card{border:0;padding:0;box-shadow:none;}
.lesson-copy{font-size:12pt;line-height:1.7;}
.intuition{background:#f4f4f4;color:#000;}
.formula{background:#f6f6f6;color:#000;border:1px solid #ccc;white-space:normal;}
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tr,.method-step,.formula{break-inside:avoid;}
h1,h2,h3{break-after:avoid;}
a{color:#000;text-decoration:none;}
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.math-svg text{fill:var(--ink);}
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.question-stem .formula{font-size:16px;}
.proof-block{padding:12px;align-items:flex-start;}}
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.lab-note{overflow-wrap:anywhere;}
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button,.button{align-items:center;justify-content:center;}
button.small{min-height:36px;}
input,textarea,select{min-height:44px;}
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.brand small{text-transform:none;}
.side-bottom a{display:block;color:var(--muted);}
.side-bottom a:hover{color:var(--accent);}
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.page-heading{margin-bottom:25px;}
.page-heading h1{margin-top:0;}
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.card .eyebrow{letter-spacing:.7px;}
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.section-line{margin:30px 0 16px;}
.section-line h2{font-size:22px;}
.section-reference{font-size:13px;font-weight:650;color:var(--accent);}
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.sync-invitation b{font-weight:650;}
.sync-invitation .button{flex-shrink:0;}
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.next-lesson h2{font-size:27px;line-height:1.25;max-width:740px;margin:9px 0 12px;}
.next-lesson p{font-size:15px;color:var(--muted);max-width:690px;}
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.learning-path b{font-size:12px;color:var(--accent);font-variant-numeric:tabular-nums;}
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.roadmap-row:hover{background:var(--accent-soft);}
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.roadmap-topic{display:flex;flex-direction:column;gap:3px;}
.roadmap-topic b{font-size:15px;font-weight:650;}
.roadmap-row small{font-size:12px;color:var(--muted);}
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.saved-sessions h2{font-size:20px;}
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#login-feedback{margin-top:14px;color:var(--bad);}
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.value-chip.on{border-color:var(--accent);color:var(--accent);background:var(--accent-soft);}
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.comparison-strip,.selection-readout,.domain-caption,.frontier-strip{padding:12px 15px;background:var(--panel);border:1px solid var(--line);border-radius:8px;font-size:13px;text-align:center;}
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.logic-flow>div,.term-flow>div{background:var(--panel);border:1px solid var(--line);padding:13px 19px;border-radius:8px;text-align:center;min-width:85px;}
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.quantifier-lines{display:grid;gap:13px;margin:23px 0;}
.quantifier-lines>div{display:grid;grid-template-columns:150px minmax(0,1fr) 35px;gap:10px;align-items:center;padding:13px;background:var(--panel);border:1px solid var(--line);border-radius:8px;}
.quantifier-lines b{font-size:20px;font-family:ui-serif,Georgia,serif;}
.quantifier-lines span{font-size:12px;color:var(--muted);}
.quantifier-lines strong{font-size:25px;color:var(--accent);}
.predicate-tile{padding:14px;font-size:16px;min-width:95px;display:flex;gap:14px;justify-content:space-between;}
.predicate-tile.on{border-color:var(--accent);background:var(--accent-soft);color:var(--accent);}
.predicate-tile b{font-weight:750;}
.proof-board{min-height:290px;}
.premise-strip{background:var(--panel);border:1px solid var(--line);border-left:3px solid var(--accent);padding:14px 18px;display:grid;gap:6px;font-size:18px;font-family:ui-serif,Georgia,serif;}
.proof-chain{list-style:decimal;padding-left:26px;margin:20px 0;display:grid;gap:16px;}
.proof-chain li{padding-left:7px;line-height:1.65;}
.proof-chain li::marker{font-size:12px;font-weight:750;color:var(--accent);}
.proof-chain li>div{font-size:16px;}
.proof-chain small{font-size:12px;color:var(--muted);display:block;margin-top:3px;}
.proof-chain .empty-step{color:var(--muted);font-size:14px;}
.proof-options,.notation-choices{display:grid;gap:10px;}
.proof-option{text-align:left;justify-content:flex-start;font-size:14px;font-weight:500;padding:12px 15px;white-space:normal;background:var(--panel);}
.proof-end{font-size:14px;font-weight:650;color:var(--good);}
.power-set-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;margin:22px 0;}
.subset-tile{padding:17px 8px;background:var(--panel);border:1px solid var(--line);border-radius:8px;text-align:center;font-family:ui-serif,Georgia,serif;font-size:19px;}
.subset-tile.selected{border:2px solid var(--accent);background:var(--accent-soft);color:var(--accent);padding:16px 7px;}
.element-token{min-width:49px;padding:13px;font-size:17px;border-radius:8px;}
.partition-board{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;}
.partition-block{padding:15px 12px;min-height:150px;border:1px solid var(--line);border-radius:9px;background:var(--panel);}
.partition-block h4{font-size:12px;margin:0 0 13px;color:var(--muted);}
.partition-block .element-token{margin:3px;min-width:42px;padding:10px;}
.partition-block.selected{border-color:var(--accent);outline:1px solid var(--accent);}
.partition-block .muted{font-size:12px;line-height:1.5;}
.mapping-grid{display:grid;grid-template-columns:minmax(195px,.8fr) minmax(0,1.2fr);gap:20px;align-items:center;}
.mapping-grid .table-scroll{width:100%;}
.mapping-grid .scene-table td{padding:5px;}
.mapping-grid .scene-svg{min-width:0;}
.mapping-grid .scene-table th{padding:8px;}
.machine-flow{display:flex;gap:16px;align-items:center;justify-content:center;flex-wrap:wrap;margin:30px 0;}
.machine-flow>span{font-size:25px;font-weight:650;}
.machine-flow>div{padding:18px;border:1px solid var(--line);background:var(--panel);border-radius:10px;font-size:13px;text-align:center;min-width:145px;}
.machine-flow strong{display:block;font-size:32px;color:var(--accent);margin-top:9px;}
.log-balance{display:flex;justify-content:center;gap:20px;color:var(--muted);font-size:12px;}
.clause-row{display:flex;gap:15px;align-items:center;justify-content:center;}
.clause{padding:15px;border:1px solid var(--line);background:var(--panel);border-radius:8px;min-width:80px;text-align:center;}
.clause.on{background:var(--signal-bg);border-color:var(--signal);}
.clause span{display:block;font-size:12px;color:var(--muted);}
.clause strong{display:block;font-size:30px;}
.duplicate-wires{display:flex;align-items:center;gap:20px;justify-content:center;margin:30px 0;}
.duplicate-wires>span:not(.value-chip){font-size:12px;color:var(--muted);}
.matrix-product,.system-to-matrix{display:flex;gap:15px;align-items:center;justify-content:center;flex-wrap:wrap;margin:25px 0;}
.matrix-product>b,.system-to-matrix>b{font-size:23px;}
.matrix-frame{display:inline-block;border-left:2px solid var(--ink);border-right:2px solid var(--ink);padding:4px 7px;position:relative;margin:8px 0;max-width:100%;overflow-x:auto;}
.math-matrix{width:auto;border-collapse:collapse;margin:0;font-family:ui-serif,"Cambria Math",Georgia,serif;font-size:20px;}
.math-matrix td{padding:7px 11px;min-width:40px;text-align:center;border:0;background:transparent;white-space:nowrap;}
.math-matrix td.highlight{background:var(--accent-soft);color:var(--accent);}
.math-matrix td.augmented{border-left:1px solid var(--ink);}
.system-equations{font-family:ui-serif,Georgia,serif;font-size:24px;}
.system-equations p{padding:10px 16px;margin:0;}
.highlight{background:var(--accent-soft);color:var(--accent);}
.row-operation{font-size:18px;font-family:ui-serif,Georgia,serif;text-align:center;margin:20px 0;padding:13px;background:var(--panel);border:1px solid var(--line);border-radius:7px;}
.scene-art>.matrix-frame{display:table;margin:15px auto;}
.operation-history{font-size:12px;color:var(--muted);padding-left:26px;margin:15px 0;}
.operation-history li{padding:3px;}
.fraction{display:inline-flex;vertical-align:middle;flex-direction:column;text-align:center;line-height:1.3;margin:0 4px;min-width:23px;}
.fraction>span:first-child{border-bottom:1.5px solid currentColor;padding:0 4px 3px;}
.fraction>span:last-child{padding:3px 4px 0;}
.bound-strip{display:flex;align-items:center;justify-content:center;gap:12px;flex-wrap:wrap;background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:13px;font-size:13px;}
.telescope{display:flex;gap:8px;flex-wrap:wrap;justify-content:center;font-size:17px;font-family:ui-serif,Georgia,serif;margin:20px 0;}
.telescope del{color:var(--muted);text-decoration-color:var(--accent);text-decoration-thickness:2px;}
.relation-pair{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:15px;align-items:center;}
.relation-pair h4{text-align:center;font-size:13px;font-weight:600;margin:10px 0 8px;}
.relation-pair .matrix-frame{display:table;margin:auto;}
.composition-paths{display:grid;gap:10px;text-align:center;font-size:16px;}
.composition-paths>div{border:1px solid var(--line);background:var(--panel);padding:12px;border-radius:7px;}
.composition-paths span{color:var(--accent);}
.composition-paths b{display:block;font-size:12px;margin-top:6px;}
.property-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin:15px 0;}
.property{padding:11px 13px;border:1px solid var(--line);border-radius:7px;background:var(--panel);}
.property b{display:block;font-size:12px;}
.property small{display:block;font-size:11px;color:var(--muted);margin-top:4px;line-height:1.5;}
.property.ok{border-left:3px solid var(--signal);}
.property.not-yet{border-left:3px solid var(--line);}
.property.ok b{color:var(--signal);}
.column-picks{display:flex;gap:8px;flex-wrap:wrap;}
.database-flow{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px;}
.database-flow h4{font-size:13px;font-weight:600;}
.database-flow .scene-table{font-size:13px;}
.database-flow .scene-table th,.database-flow .scene-table td{padding:9px;}
.visit-strip{display:flex;gap:10px;justify-content:center;min-height:55px;align-items:center;margin:12px 0 20px;font-size:13px;color:var(--muted);}
.visit-strip>span{min-width:45px;position:relative;padding:15px 10px 5px;text-align:center;border-bottom:2px solid var(--accent);font-size:22px;font-weight:650;color:var(--accent);}
.visit-strip small{position:absolute;top:0;left:50%;font-size:10px;transform:translateX(-50%);color:var(--muted);font-weight:500;}
.frontier-strip{font-size:12px;margin-top:15px;}
.minimax-readout{display:grid;gap:10px;font-size:13px;text-align:center;background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:17px;}
.minimax-readout strong{font-size:20px;color:var(--accent);}
.code-token{font-family:ui-monospace,monospace;font-size:16px;padding:12px 17px;}
.tree-count{display:flex;align-items:center;justify-content:center;gap:18px;margin:25px 0;}
.tree-count>div{display:grid;text-align:center;gap:5px;}
.tree-count strong{font-size:37px;color:var(--accent);}
.tree-count span{font-size:12px;color:var(--muted);max-width:110px;}
.distribution-arrows{display:flex;gap:16px;justify-content:center;flex-wrap:wrap;margin:20px 0;}
.distribution-arrows>span{padding:17px;background:var(--panel);border:1px solid var(--accent);border-radius:8px;font-size:19px;}
.sigma-symbol{font-size:37px;position:relative;display:inline-block;margin:10px 13px 15px;}
.sigma-symbol sub{position:absolute;top:1.7em;left:50%;transform:translateX(-50%);font-size:11px;line-height:1;white-space:nowrap;}
.sigma-symbol sup{position:absolute;bottom:2.4em;left:50%;transform:translateX(-50%);font-size:12px;line-height:1;}
.sigma-terms{display:flex;align-items:center;justify-content:center;gap:12px;flex-wrap:wrap;margin:30px 0;}
.sigma-terms>div{display:grid;padding:14px;background:var(--panel);border:1px solid var(--line);border-radius:8px;min-width:57px;text-align:center;}
.sigma-terms small{font-size:10px;color:var(--muted);}
.sigma-terms b{font-size:24px;color:var(--accent);}
.timeline-board{display:flex;gap:10px;align-items:stretch;flex-wrap:wrap;justify-content:center;margin:25px 0;}
.timeline-board>div{display:grid;gap:8px;padding:15px 11px;border:1px solid var(--line);border-top:3px solid var(--accent);border-radius:8px;background:var(--panel);max-width:130px;text-align:center;}
.timeline-board small{font-size:11px;color:var(--muted);}
.timeline-board strong{font-size:24px;}
.timeline-board span{font-size:10px;color:var(--muted);}
.timeline-board b{font-size:15px;color:var(--accent);}
.choices button{font-size:15px;min-height:54px;}
.lesson-copy p{line-height:1.8;}
.solution-step{border-radius:7px;}
.question-stem .over,.scene-art .over{white-space:nowrap;}
.over{text-decoration-thickness:1.3px;text-decoration-skip-ink:none;}
@media(min-width:1550px){.activity-layout{grid-template-columns:minmax(0,1fr) 285px;}
.activity-stage{padding:28px 35px;}
.activity-coach{padding:28px;}
.scene-svg{max-height:385px;}}
@media(max-width:1150px){#shell{grid-template-columns:185px minmax(0,1fr);}
main{padding:26px 25px 55px;}
.topbar{padding:0 25px;}
.activity-layout{grid-template-columns:minmax(0,1fr) 225px;}
.activity-stage{padding:20px 17px;}
.activity-coach{padding:22px 17px;}
.mapping-grid{grid-template-columns:1fr;}
.mapping-grid>.scene-svg{max-height:255px;}
.next-lesson{grid-template-columns:minmax(0,1fr) 175px;gap:24px;}
.learning-path{padding-left:20px;}
.database-flow{grid-template-columns:1fr;}
.lesson-tabs a{padding:13px 10px;font-size:13px;}
.lesson-tabs .notes-tab{font-size:11px;}
.quantifier-lines>div{grid-template-columns:minmax(120px,1fr) 30px;}
.quantifier-lines span{grid-column:1;grid-row:auto;}
.quantifier-lines strong{grid-column:2;grid-row:1/3;}
.quantifier-lines b{font-size:19px;}}
@media(max-width:900px){#shell{display:block;}
.sidebar{position:fixed;left:-230px;width:215px;transition:left .18s;box-shadow:8px 0 30px #15233c18;}
.sidebar.open{left:0;}
.mobile-header{display:flex;align-items:center;gap:10px;}
.topbar{height:60px;padding:0 20px;}
.mobile-header .brand{padding:0;font-size:17px;}
.mobile-header .brand-mark{height:30px;width:30px;font-size:19px;}
.mobile-header .brand small{display:none;}
.topbar>.crumb{display:none;}
.topbar .meta{gap:0;}
.topbar .meta>a:not(.save-status-button){display:none;}
main{padding:24px 23px 50px;max-width:1050px;}
.activity-layout{grid-template-columns:minmax(0,1fr) 245px;}
.mapping-grid{grid-template-columns:minmax(160px,.9fr) minmax(0,1.1fr);}
.next-lesson{grid-template-columns:minmax(0,1fr) 190px;}
.settings-grid{grid-template-columns:1fr 1fr;}
.topbar .crumb{letter-spacing:0;}}
@media(max-width:760px){.activity-layout{display:flex;flex-direction:column;gap:0;padding:19px;}
.activity-stage{order:2;border:1px solid var(--line);border-radius:8px;padding:18px 14px;margin:15px 0 18px;}
.activity-coach{display:contents;}
.activity-coach h3{order:0;margin:0 0 7px;font-size:14px;}
.activity-coach>p:not(.tiny){order:1;font-size:14px;margin:0;}
.activity-coach>.activity-check{order:3;width:100%;min-height:47px;}
.activity-feedback{order:4;}
.activity-coach>.text-button{order:5;align-self:center;}
.activity-coach>.tiny{order:6;margin:8px 0 0;}
.activity-header{padding:17px 19px;align-items:flex-start;}
.activity-header h2{font-size:18px;}
.guided-label{font-size:10px;max-width:125px;}
.scene-controls{gap:10px;margin-bottom:17px;}
.scene-readout{font-size:12px;margin-top:18px;padding-top:14px;}
.scene-equation{font-size:23px;}
.scene-svg{max-height:305px;}
.mapping-grid{grid-template-columns:minmax(150px,.85fr) minmax(0,1.15fr);gap:10px;}
.property-grid{grid-template-columns:repeat(2,minmax(0,1fr));}
.lesson-resources{grid-template-columns:1fr;}
.lesson-resources>details{padding:15px 18px;}
.lesson-resources summary>span{display:inline;padding-left:10px;}
.lesson-tabs{margin-bottom:18px;}
.lesson-tabs .notes-tab{margin-left:0;}
.lesson-tabs a{padding:13px 11px;}
.lesson-heading .page-heading{gap:12px;}
.lesson-heading .button{font-size:12px;padding:8px 10px;min-height:38px;}
.lesson-heading h1{font-size:27px;}
.explanation-disclosure{padding:17px 18px;}
.next-lesson{padding:24px;grid-template-columns:1fr;}
.learning-path{display:flex;flex-wrap:wrap;border:0;border-top:1px solid var(--line);padding:18px 0 0;gap:13px 21px;}
.learning-path span{font-size:12px;gap:9px;}
.progress-ribbon{gap:23px;flex-wrap:wrap;}
.progress-ribbon>a{margin-left:0;flex-basis:100%;font-size:12px;}
.roadmap-row{grid-template-columns:25px minmax(0,1fr) 100px;gap:13px;padding:16px 18px;}
.roadmap-row>span:last-child{display:none;}
.roadmap-topic b{font-size:14px;}
.roadmap-row small{font-size:11px;}
.roadmap-progress small{font-size:10px;}
.source-summary{grid-template-columns:1fr;gap:20px;}
.settings-grid{grid-template-columns:1fr;}
.scene-table th{font-size:11px;}
.source-audit-note{padding:17px;}
.lesson-layout{display:block;}
.lesson-aside{position:static;}
.page-heading .button-row{flex-shrink:1;}
.grid.four{grid-template-columns:repeat(2,minmax(0,1fr));}
.grid.three{grid-template-columns:1fr 1fr;}
.section-pagination{font-size:12px;gap:20px;}}
@media(max-width:500px){main{padding:22px 15px 45px;}
.topbar{padding:0 12px;}
.save-status-button{font-size:10px;max-width:155px;line-height:1.4;}
.topbar .mobile-header .brand{font-size:15px;}
.topbar .mobile-header .brand-mark{display:none;}
.page-heading{display:block;margin-bottom:22px;}
.page-heading .button-row{margin-top:14px;}
.page-heading h1{font-size:28px;}
.lede{font-size:14px;}
.lesson-heading .page-heading{display:flex;margin-bottom:15px;align-items:start;}
.lesson-heading .page-heading .button-row{margin-top:0;}
.lesson-heading .page-heading h1{font-size:25px;}
.lesson-breadcrumb{font-size:11px;}
.sync-invitation{padding:12px;gap:12px;font-size:12px;align-items:start;}
.sync-invitation .button{font-size:11px;padding:8px;min-height:38px;}
.next-lesson{padding:21px;}
.next-lesson h2{font-size:23px;}
.next-lesson p{font-size:13px;}
.next-lesson .button-row>.button,.next-lesson .button-row>button{width:100%;}
.learning-path{gap:12px;}
.learning-path span{font-size:10px;gap:5px;}
.learning-path b{font-size:10px;}
.progress-ribbon{gap:18px;padding:22px 0;}
.progress-ribbon b{font-size:25px;}
.progress-ribbon span{font-size:10px;max-width:92px;}
.roadmap-row{padding:15px 13px;grid-template-columns:20px minmax(0,1fr) 72px;gap:10px;}
.roadmap-topic b{font-size:13px;}
.roadmap-topic small{font-size:10px;line-height:1.4;}
.roadmap-progress small{font-size:9px;white-space:nowrap;}
.roadmap-progress .meter{height:4px;}
.section-line h2{font-size:20px;}
.section-line a{font-size:11px;}
.support-strip{font-size:12px;gap:12px;}
.activity-header{padding:15px;}
.activity-header h2{font-size:17px;}
.guided-label{max-width:94px;font-size:9px;line-height:1.5;}
.activity-layout{padding:15px;}
.activity-stage{padding:16px 10px;}
.scene-controls{gap:8px 10px;}
.scene-controls .pick{font-size:13px;padding:9px 10px;min-width:63px;}
.scene-select{font-size:11px;}
.scene-select input,.scene-select select{font-size:13px;max-width:100%;min-width:0;}
.scene-select input{width:115px;}
.range-control{min-width:117px;font-size:11px;}
.scene-equation{font-size:21px;line-height:1.8;margin-bottom:17px;}
.scene-svg{max-height:275px;}
.scene-table td{padding:5px;}
.scene-table th{padding:7px 5px;font-size:10px;}
.matrix-cell{padding:8px;min-width:42px;min-height:44px;}
.mapping-grid{grid-template-columns:1fr;}
.mapping-grid>.scene-svg{max-height:220px;}
.predicate-tile{min-width:117px;font-size:14px;}
.quantifier-lines>div{grid-template-columns:minmax(0,1fr) 30px;padding:12px;gap:3px;}
.quantifier-lines b{font-size:20px;}
.quantifier-lines span{font-size:11px;}
.quantifier-lines strong{grid-column:2;grid-row:1/3;}
.quantifier-lines{gap:9px;}
.power-set-grid{grid-template-columns:repeat(4,minmax(0,1fr));gap:6px;}
.subset-tile{font-size:14px;padding:13px 3px;}
.subset-tile.selected{padding:12px 2px;}
.partition-board{gap:7px;}
.partition-block{padding:12px 7px;min-height:153px;}
.partition-block .element-token{min-width:42px;padding:9px;margin:3px 0;}
.partition-block h4{font-size:11px;}
.partition-block .muted{font-size:10px;}
.proof-chain{padding-left:22px;}
.proof-chain li>div{font-size:14px;}
.premise-strip{font-size:16px;padding:13px;}
.proof-option{font-size:13px;padding:12px;}
.property-grid{gap:7px;}
.property{padding:10px;}
.property b{font-size:11px;}
.property small{font-size:10px;}
.relation-pair{gap:5px;}
.relation-pair>.scene-svg{max-height:180px;}
.relation-pair h4{font-size:11px;}
.composition-paths{font-size:14px;}
.tree-count{gap:13px;}
.tree-count strong{font-size:31px;}
.tree-count span{font-size:10px;}
.clause-row{gap:9px;}
.clause{min-width:67px;padding:12px 9px;}
.clause span{font-size:10px;}
.clause strong{font-size:25px;}
.machine-flow{gap:11px;}
.machine-flow>div{min-width:110px;font-size:11px;padding:13px;}
.machine-flow strong{font-size:28px;}
.matrix-product{gap:10px;margin:18px 0;}
.math-matrix{font-size:18px;}
.math-matrix td{padding:6px 8px;min-width:32px;}
.matrix-frame{padding:3px 5px;}
.row-operation{font-size:16px;padding:12px;}
.bound-strip{font-size:11px;gap:9px;}
.scene-caption{font-size:11px;}
.duplicate-wires{gap:12px;}
.duplicate-wires>span:not(.value-chip){font-size:10px;}
.grid.two,.grid.three{grid-template-columns:1fr;}
.grid.four{grid-template-columns:1fr 1fr;}
.card{padding:20px;}
.lesson-main.card{padding:19px;}
.skill-detail .list-row{display:block;}
.skill-detail .button-row{margin-top:10px;}
.question-stem{font-size:17px;}
.section-pagination{gap:15px;}
.section-pagination a{font-size:11px;}
.session-layout{display:block;}
.session-side{position:static;}
.session-main{min-width:0;}
.question-navigator{display:flex;flex-wrap:wrap;}
.source-footnote{font-size:11px;}
.activity-feedback .button{max-width:300px;}
.explanation-disclosure .lesson-copy{font-size:15px;}
.learn-footer .button{width:100%;}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;animation:none!important;transition:none!important;}}
@media print{.sidebar,.topbar,.lesson-tabs,.activity-coach button,.scene-controls,.section-pagination,.learn-footer{display:none!important;}
#shell{display:block;}
main{padding:0;}
.activity-layout{display:block;}
.activity-stage{border:0;}
.guided-activity{break-inside:avoid;}
details{display:block;}
.lesson-resources{display:none;}
body{background:white;color:black;}}
.save-status-button{text-decoration:none;}
.topbar .mobile-header{align-items:center;}
.topbar .crumb{margin-right:auto;}
.topbar{gap:14px;}
.brand-mark{flex:0 0 34px;}
.side-bottom{margin-top:auto;}
.sidebar{display:flex;flex-direction:column;}
.nav-list{flex:none;}
.topbar .mobile-header .menu-toggle{padding:8px;min-width:44px;}
.topbar .crumb{min-width:0;}
.lesson-tabs .short-label{display:none;}
@media(max-width:760px){.lesson-tabs{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:0;overflow:visible;margin-bottom:19px;}
.lesson-tabs a{padding:10px 4px;justify-content:center;font-size:12px;gap:6px;}
.lesson-tabs a small{flex-shrink:0;}
.lesson-tabs .notes-tab{grid-column:1/-1;justify-content:flex-end;padding:8px 2px;border-bottom:0;min-height:30px;font-size:11px;}
.lesson-tabs .long-label{display:none;}
.lesson-tabs .short-label{display:inline;}
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@media print{
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#main .review-item{background:var(--dm-sheet);padding:24px;border-bottom:1px solid var(--line);}
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#main .progress-ribbon>div:nth-child(3){color:var(--dm-accent);}
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#main[data-view=coverage]>.card{background:var(--dm-sheet);padding:24px;}
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#main #lab-host :is(svg,canvas){max-width:100%;height:auto;}
#main #lab-host :is(.controls,.lab-controls,.control-row){display:flex;flex-wrap:wrap;gap:8px;}
#main :is(.instruction-audit,.source-summary,.notation-specimens){min-width:0;max-width:100%;}
#main #lab-host :is(.card,.lab-panel,.activity-panel){background:transparent;box-shadow:none;}
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#main .settings-grid .sync-explanation{background:var(--dm-gold);padding:16px;}
#main #cloud-status{font-weight:650;color:var(--dm-accent);}
#main :is(.feedback.good,.guided-feedback.good,.activity-feedback.good,.notice.good){background:var(--dm-green);color:var(--dm-good);border:1px solid var(--dm-good);padding:16px 24px;}
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html body :is(a,button,input,select,textarea,summary):focus-visible{outline:3px solid var(--dm-accent);outline-offset:4px;}
#sidebar .nav-list a[aria-current=page]{background:var(--dm-orange);color:var(--dm-accent);font-weight:700;}
html body select,html body select :is(option,optgroup){background:var(--dm-sheet);color:var(--ink);}
#main :is(input,select,textarea){max-width:100%;min-width:0;font-size:16px;}
#main :is(.button-row,.path-actions,.teaching-navigation){gap:8px;flex-wrap:wrap;}
#main :is(.button-row,.path-actions,.teaching-navigation)>*{max-width:100%;}
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#main :is(button,.button){overflow-wrap:break-word;}
#main :is(.settings-grid,.exam-layout,.session-grid,.notation-specimens){min-width:0;max-width:100%;}
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#main :is(.notice,.feedback,.guided-feedback){overflow-wrap:break-word;}
@media(hover:hover){#main :is(.task-row,.library-list article,.dm-course-row):hover{background:var(--dm-orange);}
#main summary:hover{color:var(--dm-accent);}}
@media(max-width:1024px){#main .instruction-heading{grid-template-columns:minmax(0,1fr);}
#main .instruction-heading .skill-picker{max-width:100%;}
#main .dm-concept-list a{grid-template-columns:minmax(0,1fr);gap:4px;}
#main .dm-concept-list small{text-align:left;}}
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#main :is(.dm-next,.section-orientation,.teaching-explanation.concept-first,.worked-line,.task-row,.review-item,.finish-panel,.step-finish,.settings-grid>.card,.result-summary,.session-grid>.card){padding:16px;}
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#main .chapter-content .dm-concept-list{padding:0;margin:0 0 16px;}
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#main .notation-specimens{grid-template-columns:minmax(0,1fr);}
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#main .task-row{display:flex;flex-direction:column;align-items:stretch;gap:16px;}
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#main .session-context{padding:16px;}
#main .progress-ribbon{gap:16px;padding:16px;}
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#main .worked-line{grid-template-columns:32px minmax(0,1fr);}}
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@media print{#main .session-context{background:transparent;color:inherit;}
#main :is(.dm-next,.task-row,.worked-line,.settings-grid>.card){break-inside:avoid;}}



/* DM1 4.2 · OpenDesign Paper system. Reading workspace + focused tools.
   Hallmark review: custom, design-system: DESIGN.md. Course steps are genuinely ordinal.
   Keep educational content; remove repeated containers and competing navigation. */
:root{--reading-width:75ch;--drawer-shadow:-12px 0 48px #211b1224;--scrim:#211b1280;--focus-ring:var(--accent);--ui-radius:8px;--control-height:44px;--drawer-width:640px;--flow-gap:24px;}
html,body{overflow-x:clip;scrollbar-color:var(--line) var(--bg);}
body{caret-color:var(--accent);}
::selection{background:var(--accent-soft);color:var(--ink);}
body #main:focus{outline:none;}
a,button,input,select,textarea{touch-action:manipulation;}
button,a.button{font-family:var(--body);font-size:16px;min-height:44px;line-height:1.4;}
button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:2px solid var(--focus-ring);outline-offset:4px;}
.text-button,.tool-button{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:44px;background:transparent;color:var(--accent);border:0;box-shadow:none;border-radius:6px;font-size:15px;padding:8px 12px;}
.text-button{text-decoration:underline;text-underline-offset:4px;padding-inline:0;}
.tool-button{border:1px solid var(--line);color:var(--ink);background:var(--panel);}
.primary:not(:disabled),a.button.primary{background:var(--action-fill)!important;color:var(--action-ink)!important;border:1px solid var(--action-fill)!important;box-shadow:none!important;}
button:disabled{cursor:default;opacity:1;color:var(--muted);background:var(--soft);border-color:var(--line);}
@media(hover:hover){.text-button:hover{color:var(--ink);background:transparent;}.tool-button:hover{border-color:var(--accent);background:var(--accent-soft);}}
.support-note,.small-text{color:var(--muted);font-size:14px;line-height:1.6;}
.support-note{margin:8px 0 20px;max-width:75ch;}
#main .path-crumb{display:flex;flex-wrap:wrap;gap:4px 10px;padding:0;margin:0 0 16px;font-size:14px;}
#main .path-crumb>a,#main .path-crumb>span{min-height:36px;}
#main .path-crumb>span:last-child{font-weight:400;flex-basis:auto;}
#main .lesson-workspace,#main .section-workspace,#main .path-workspace{max-width:1040px;margin-inline:auto;min-width:0;}
#main .lesson-heading{margin:0 0 16px;}
#main .lesson-heading h1{font:400 clamp(29px,3.6vw,44px)/1.18 var(--display);font-style:normal;max-width:32ch;margin:0 0 16px;color:var(--ink);text-wrap:balance;}
#main .lesson-position{display:flex;align-items:center;justify-content:space-between;gap:8px 24px;flex-wrap:wrap;color:var(--muted);font:14px/1.5 var(--body);}
#main .lesson-position .text-button{font-size:14px;}







#main .lesson-tools{display:flex;align-items:center;flex-wrap:wrap;gap:8px 12px;padding:16px 0 24px;border:0;font-size:14px;}
#main .lesson-tools .tool-caption{color:var(--muted);font-size:13px;}
.experiment-entry:before{content:"";width:14px;height:14px;display:inline-block;border:1.5px solid currentColor;border-radius:50%;background:radial-gradient(circle,currentColor 0 2px,transparent 2.5px);}
#main .lesson-workspace .teaching-page{max-width:none;padding:32px 40px 0;margin:0;background:var(--panel);border:1px solid var(--line);border-radius:8px;box-shadow:none;}
#main .teaching-page>section,#main .teaching-page>div:not(.lesson-next){max-width:var(--reading-width);margin-inline:auto;}
#main .lesson-workspace .teaching-page>.teaching-explanation.concept-first{background:transparent;border:0;border-radius:0;padding:0;margin:0 0 24px;}
#main .teaching-page .concept-first>h2:first-child,#main .teaching-page h2{color:var(--ink);font:400 27px/1.3 var(--display);margin:0 0 20px;}
#main .teaching-page p,#main .teaching-page .worked-line{font-size:18px;line-height:1.7;}
#main .teaching-page p{margin:0 0 20px;}
#main .teaching-page p.support-note,#main .teaching-page .small-text{font-size:14px;line-height:1.6;}
#main .teaching-page h3{font:600 18px/1.5 var(--body);color:var(--ink);margin:28px 0 12px;}
#main .teaching-page .worked-line{display:grid;grid-template-columns:28px minmax(0,1fr);gap:16px;padding:20px 0;margin:0;border:0;border-top:1px solid var(--line);border-radius:0;background:transparent;}
#main .teaching-page .worked-line>b{font:600 13px/1 var(--body);border:1px solid var(--line);color:var(--muted);background:transparent;}
#main .teaching-page .reason-actions{padding-top:20px;gap:16px;}
#main .teaching-page .reasoning-repair{margin-top:32px;padding:0;border:0;background:transparent;}
#main .teaching-page .inline-experiment{border:0;border-block:1px solid var(--line);border-radius:0;background:transparent;padding:24px 0;margin-block:28px;max-width:none;}
#main .experiment-heading{display:flex;justify-content:space-between;align-items:baseline;gap:12px;margin-bottom:12px;}
#main .teaching-page .experiment-heading h3{margin:0;font:400 24px/1.3 var(--display);}
#main .experiment-heading>span{color:var(--accent);font:600 13px/1.5 var(--body);}
#micro-experiment .micro-experiment{background:transparent;border:0;border-radius:0;padding:0;}
#micro-experiment h3{margin:12px 0;}
#micro-experiment input[type=range]{min-height:44px;}
#micro-experiment .micro-controls{gap:16px;}
#micro-experiment :is(table,svg){max-width:100%;}
#main .more-example-link{border-top:1px solid var(--line);padding-top:16px;margin-block:20px;}
#main .teaching-page .lesson-next{max-width:none;background:transparent;border:0;border-top:1px solid var(--line);border-radius:0;padding:24px 0 16px;margin:32px 0 0;}
#main .lesson-next .finish-status{font:14px/1.6 var(--body);color:var(--muted);margin:0 0 16px;}
#main .lesson-next .teaching-navigation{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;align-items:center;margin:0;padding:0;border:0;}
#main .lesson-next .teaching-navigation>*{white-space:nowrap;min-height:44px;}
#main .lesson-next .lesson-exit{display:flex;align-items:center;flex-wrap:wrap;gap:12px 24px;margin-top:12px;color:var(--muted);font:13px/1.5 var(--body);}
#main .lesson-exit a{display:inline-flex;align-items:center;min-height:44px;font-size:14px;}
#main .lesson-exit>span:last-child{margin-left:auto;}
#main .guided-choices{display:grid;gap:12px;margin-block:20px;}
#main .guided-choices button{font-size:17px;line-height:1.6;text-align:left;white-space:normal;padding:16px 20px;}
#main .guided-choices button:disabled{opacity:1;}
#main .teaching-page .guided-feedback{padding:20px;margin-block:24px;border:1px solid var(--line);border-radius:6px;}
#main .teaching-page .guided-feedback h3{margin-top:0;}
#main .teaching-page .recall-comparison{margin-top:24px;border-top:1px solid var(--line);padding-top:24px;}
#main .teaching-page textarea{width:100%;min-height:144px;line-height:1.65;resize:vertical;}
#main .form-evidence{font-size:15px!important;color:var(--muted);}

#main .lesson-panel{position:fixed;inset:0 0 0 auto;width:min(var(--drawer-width),100%);max-width:100%;height:100dvh;max-height:100dvh;margin:0;padding:0;background:var(--panel);color:var(--ink);border:0;border-left:1px solid var(--line);border-radius:0;box-shadow:var(--drawer-shadow);overflow-y:auto;overscroll-behavior:contain;}
#main .lesson-panel::backdrop{background:var(--scrim);}
#main .lesson-panel.model-panel{width:min(920px,100%);}
#main .panel-head{display:flex;justify-content:space-between;align-items:center;gap:16px;padding:16px 28px;border-bottom:1px solid var(--line);background:var(--panel);position:sticky;top:0;z-index:2;}
#main .panel-head>span{font-size:14px;color:var(--muted);}
#main .panel-close{color:var(--ink);background:transparent;border:1px solid var(--line);padding:8px 16px;}
#main .panel-tabs{display:flex;gap:0;border-bottom:1px solid var(--line);padding:0 28px;}
#main .panel-tabs button{flex:1;min-height:52px;border:0;border-bottom:3px solid transparent;border-radius:0;background:transparent;color:var(--muted);font-weight:400;}
#main .panel-tabs button[aria-current]{border-bottom-color:var(--accent);color:var(--ink);font-weight:600;}
#main .panel-body{padding:28px 32px 48px;font:16px/1.7 var(--body);}
#main .panel-body h2{font:400 28px/1.25 var(--display);margin:0 0 24px;}
#main .panel-body h3{font:600 17px/1.5 var(--body);margin:28px 0 12px;}
#main .panel-body p{margin:0 0 16px;}
#main .panel-body section{background:transparent;border:0;border-radius:0;box-shadow:none;padding:0;}
#main .panel-body .meaning-words{display:block;padding:0;margin:0 0 24px;border:0;background:transparent;}
#main .panel-body .meaning-words h3{margin-top:0;}
#main .panel-body dt{color:var(--ink);font-weight:600;margin-top:18px;}
#main .panel-body dd{margin:4px 0 16px;}
#main .panel-body textarea{width:100%;max-width:100%;font:16px/1.65 var(--body);}
#main .panel-body pre{white-space:pre-wrap;word-break:break-word;}
#main .panel-body .method-reference,#main .panel-body .earlier-reference{border-top:1px solid var(--line);padding-top:4px;margin-top:24px;}
#main .panel-body .more-examples h3{margin-top:8px;}
#main .panel-body .model-workspace{overflow-x:auto;}
#main .panel-body .model-prerequisite{background:var(--soft);padding:16px;margin-block:20px;}
#main .panel-body .model-prerequisite h3{margin:0 0 8px;}
#main .panel-body .model-prerequisite p{margin:0;}
#main .panel-body .activity-card{padding:0;border:0;border-radius:0;background:transparent;}
#main .panel-body .activity-start{background:transparent;border:0;padding:0;}
#main .outline-list{list-style:none;padding:0;margin:0 0 24px;border-top:1px solid var(--line);}
#main .outline-list li{margin:0;border-bottom:1px solid var(--line);}
#main .outline-list a{display:block;padding:16px 12px;text-decoration:none;color:var(--ink);}
#main .outline-list a>span,#main .outline-list a>small{display:block;}
#main .outline-list a>small{color:var(--muted);font-size:13px;margin-top:4px;}
#main .outline-list a.current{background:var(--accent-soft);}
#main .path-search{max-width:580px;margin:24px 0 32px;}
#main .path-search label{display:block;font-size:14px;margin-bottom:8px;}
#main .path-search input{width:100%;height:48px;}
#main .course-chapters,#main .chapter-sections,#main .search-results{padding:0;list-style:none;border-top:1px solid var(--line);margin:24px 0 32px;}
#main .course-chapter-row,#main .chapter-sections li>a{display:grid;grid-template-columns:40px minmax(0,1fr) auto;gap:16px;align-items:center;padding:24px 0;border:0;border-bottom:1px solid var(--line);text-decoration:none;color:var(--ink);background:transparent;box-shadow:none;border-radius:0;}
#main .course-chapter-row .chapter-number,#main .idea-number,#main .section-id{background:transparent!important;color:var(--muted);border:0;font:16px/1.5 var(--body);}
#main .course-chapter-row strong,#main .chapter-sections strong{display:block;font:500 19px/1.4 var(--body);}
#main .course-chapter-row small,#main .chapter-sections small,#main .search-results small{display:block;color:var(--muted);font:14px/1.6 var(--body);margin-top:6px;}
#main .row-end{display:flex;gap:8px;align-items:center;font-size:14px;color:var(--accent);white-space:nowrap;}
#main .row-end svg{height:18px;width:18px;fill:none;stroke:currentColor;stroke-width:1.7;}
#main .chapter-sections li{display:block;border:0;padding:0;margin:0;background:transparent;}
#main .support-path{margin-top:48px;}
#main .support-path h2,#main .chapter-checkpoint h2,#main .section-model-entry h2{font:400 27px/1.3 var(--display);margin:0 0 12px;}
#main .chapter-checkpoint{display:block;border:0;border-top:1px solid var(--line);padding:28px 0;margin-top:32px;background:transparent;}
#main .section-introduction{padding:28px 32px;background:var(--panel);border:1px solid var(--line);border-radius:8px;max-width:none;margin:24px 0 36px;}
#main .section-introduction h2{margin:0 0 16px;font:400 26px/1.3 var(--display);}
#main .section-introduction p{max-width:75ch;font-size:17px;line-height:1.7;margin:0 0 20px;}
#main .outline-heading{margin-top:32px;font:400 27px/1.3 var(--display);}
#main .section-model-entry{border:0;padding:20px 0 32px;display:block;}
#main .section-model-entry p{max-width:68ch;}
#main .search-results li{border-bottom:1px solid var(--line);margin:0;padding:0;}
#main .search-results a{display:block;padding:18px 4px;text-decoration:none;color:var(--ink);}
#main .search-results strong{font-size:18px;}
#main .search-result-count{font-size:14px;color:var(--muted);}
#main .path-actions{display:flex;gap:12px 24px;flex-wrap:wrap;}
#main .path-actions a{display:inline-flex;align-items:center;min-height:44px;}
#main .section-transfer{border-top:1px solid var(--line);padding-top:28px;margin-top:32px;}
#main .transfer-answer{margin-top:20px;}
#main .finish-panel h2{font-size:26px;}
.close-navigation{display:none;}
.navigation-backdrop{display:none;}
body.menu-is-open{overflow-y:hidden;}
@media(hover:hover){#main .course-chapter-row:hover,#main .chapter-sections li>a:hover,#main .outline-list a:hover,#main .search-results a:hover{background:var(--accent-soft);color:var(--ink);}}
@media(min-width:768px){#main .lesson-panel{border-radius:0;}}
@media(min-width:768px) and (max-width:1199px){}
@media(max-width:767px){body #main{padding:24px 20px 48px;}.topbar{padding-inline:20px;}#main .lesson-heading h1{font-size:30px;}#main .lesson-position{gap:0 12px;}#main .lesson-tools{gap:8px;padding:16px 0 20px;}#main .lesson-tools .tool-button{font-size:14px;padding:8px 10px;}#main .lesson-tools .tool-caption{flex-basis:100%;}#main .lesson-workspace .teaching-page{padding:24px 20px 0;}#main .teaching-page p,#main .teaching-page .worked-line{font-size:17px;line-height:1.7;}#main .teaching-page h2,#main .teaching-page .concept-first>h2:first-child{font-size:24px;}#main .teaching-page .worked-line{gap:12px;grid-template-columns:24px minmax(0,1fr);}#main .lesson-next .teaching-navigation{display:flex;flex-direction:column-reverse;align-items:stretch;gap:10px;}#main .lesson-next .teaching-navigation>*{justify-content:center;text-align:center;white-space:nowrap;font-size:15px;padding-inline:10px;}#main .lesson-next .lesson-exit{gap:8px 16px;}#main .lesson-exit>span:last-child{margin-left:auto;}#main .panel-head{padding:12px 20px;}#main .panel-tabs{padding-inline:12px;}#main .panel-body{padding:24px 20px 40px;}#main .panel-body h2{font-size:26px;}#main .course-chapter-row,#main .chapter-sections li>a{grid-template-columns:28px minmax(0,1fr);gap:12px;padding:20px 0;}#main .row-end{display:none;}#main .course-chapter-row strong,#main .chapter-sections strong{font-size:17px;}#main .section-introduction{padding:24px 20px;}#main .path-crumb{font-size:13px;gap:4px 8px;}#main .path-crumb>span:last-child{min-height:28px;}.close-navigation{display:flex;align-self:flex-end;margin:0 0 16px auto;min-height:44px;background:transparent;border:1px solid var(--line);color:var(--ink);padding:8px 12px;font-size:14px;}.sidebar{z-index:60;max-height:100dvh;overflow-y:auto;padding-top:20px;}.sidebar.open{box-shadow:12px 0 48px #211b1224;}.navigation-backdrop.is-visible{display:block;position:fixed;inset:0;z-index:50;background:var(--scrim);border:0;border-radius:0;}#main .panel-body .activity-grid{grid-template-columns:minmax(0,1fr);}}
@media(max-width:374px){body #main{padding-inline:16px;}#main .lesson-workspace .teaching-page{padding-inline:16px;}#main .lesson-heading h1{font-size:28px;}#main .lesson-tools{display:grid;grid-template-columns:minmax(0,1fr);}#main .lesson-tools .tool-button{justify-content:flex-start;}#main .panel-head{padding-inline:16px;}#main .panel-body{padding-inline:16px;}}
@media(prefers-reduced-motion:reduce){.sidebar,#main .lesson-panel,.navigation-backdrop{transition:none;scroll-behavior:auto;}}
@media(forced-colors:active){.primary{background:ButtonFace!important;color:ButtonText!important;border:1px solid ButtonText!important;}.navigation-backdrop.is-visible{background:Canvas;opacity:.5;}}
@media print{#main .lesson-tools,#main .lesson-next,#main .lesson-panel{display:none!important;}#main .lesson-workspace .teaching-page{padding:0;border:0;max-width:none;}#main .teaching-page p{font-size:12pt;}body #main{padding:0;}}
/* Neutralize legacy generated wrapper rules in the explicitly redesigned workspace. */
#main .lesson-workspace .teaching-page{background:var(--panel);border:1px solid var(--line);padding:32px 40px 0;}
#main .lesson-workspace .teaching-explanation.concept-first{border:0;background:transparent;padding:0;}
#main .lesson-workspace .lesson-next.step-finish{border:0;border-top:1px solid var(--line);padding:24px 0 16px;background:transparent;border-radius:0;}

#main .path-workspace .chapter-checkpoint{display:block;border-radius:0;background:transparent;padding:28px 0;}
#main .path-workspace .chapter-checkpoint button{width:auto;white-space:nowrap;}
#main .path-workspace .chapter-checkpoint p{margin:0 0 20px;max-width:70ch;}
@media(max-width:767px){#main .lesson-workspace .teaching-page{padding:24px 20px 0;}#main .lesson-workspace .teaching-explanation.concept-first{padding:0;}#main .lesson-workspace .lesson-next.step-finish{padding:20px 0 12px;}}
@media(max-width:374px){#main .lesson-workspace .teaching-page{padding-inline:16px;}}

/* Release 4.2.1: authoritative route rows and step navigation.
   Their old selectors were removed from design-system.css, not covered up.
   Hallmark · design-system: DESIGN.md · learning workbench / course outline. */
:root{--brand-paper:#f8f1dc;--row-inset:24px;--step-number-size:24px;}
.sidebar .brand{position:relative;display:block;width:100%;height:auto;aspect-ratio:3.2;margin:0 0 28px;padding:0;overflow:hidden;flex:none;letter-spacing:normal;}
.sidebar .brand-logo{position:absolute;display:block;width:100%;height:auto;max-width:none;left:0;top:50%;transform:translateY(-50%);}
:root[data-theme=dark] .sidebar .brand,:root[data-theme=contrast] .sidebar .brand{background:var(--brand-paper);border-radius:var(--ui-radius);}
body.panel-is-open{overflow-y:hidden;}
#main .section-workspace .idea-path{list-style:none;counter-reset:none;padding:0;margin:20px 0 32px;background:var(--dm-sheet,var(--panel));border:1px solid var(--line);border-radius:var(--ui-radius);overflow:clip;}
#main .section-workspace .idea-path>li{display:block;counter-increment:none;margin:0;padding:0;border:0;background:transparent;}
#main .section-workspace .idea-path>li+li{border-top:1px solid var(--line);}
#main .section-workspace .idea-path>li>a{display:grid;grid-template-columns:32px minmax(0,1fr) auto;align-items:center;column-gap:20px;min-height:100px;padding:20px var(--row-inset);margin:0;background:transparent;border:0;border-radius:0;box-shadow:none;color:var(--ink);text-decoration:none;}
#main .section-workspace .idea-number{display:block;align-self:start;padding-top:2px;background:transparent;color:var(--muted);font:400 19px/1.4 var(--display);font-variant-numeric:tabular-nums;}
#main .section-workspace .idea-content{display:block;min-width:0;}
#main .section-workspace .idea-content>strong{display:block;color:var(--ink);font:500 19px/1.4 var(--body);overflow-wrap:anywhere;}
#main .section-workspace .idea-progress{display:flex;flex-wrap:wrap;align-items:baseline;gap:2px 16px;margin-top:8px;color:var(--muted);font:400 14px/1.55 var(--body);font-variant-numeric:tabular-nums;}
#main .section-workspace .idea-progress>span{display:block;}
#main .section-workspace .idea-path .row-end{display:flex;align-items:center;gap:8px;color:var(--muted);font:400 14px/1.4 var(--body);white-space:nowrap;}
#main .section-workspace .idea-path .row-end svg{width:18px;height:18px;flex:none;fill:none;stroke:currentColor;stroke-width:1.7;}
#main .section-workspace .idea-path a:focus-visible{outline:2px solid var(--focus-ring);outline-offset:-4px;background:var(--accent-soft);}
#main .section-workspace .idea-path a:active{background:var(--accent-soft);}
#main .lesson-workspace .instruction-stages{display:flex;gap:0;padding:0;margin:0;min-width:0;border:0;border-bottom:1px solid var(--line);border-radius:0;overflow-x:auto;scrollbar-width:thin;scroll-padding-inline:4px;}
#main .lesson-workspace .instruction-stages>a{display:flex;align-items:center;justify-content:center;flex:1 0 auto;gap:8px;min-height:52px;padding:10px 14px;margin:0;border:0;border-bottom:3px solid transparent;border-radius:0;background:transparent;color:var(--muted);box-shadow:none;font:400 15px/1.4 var(--body);text-decoration:none;white-space:nowrap;}
#main .lesson-workspace .instruction-stages .stage-label{display:inline;flex:initial;width:auto;height:auto;margin:0;padding:0;border:0;border-radius:0;outline:0;box-shadow:none;background:transparent;color:inherit;font:inherit;}
#main .lesson-workspace .instruction-stages .stage-number{display:grid;place-items:center;flex:none;width:var(--step-number-size);height:var(--step-number-size);padding:0;border:1px solid var(--line);border-radius:50%;background:transparent;color:inherit;font:500 12px/1 var(--body);font-variant-numeric:tabular-nums;}
#main .lesson-workspace .instruction-stages>a.active{background:var(--accent-soft);border-bottom-color:var(--accent);color:var(--ink);font-weight:600;}
#main .lesson-workspace .instruction-stages>a.active .stage-number{background:var(--action-fill);border-color:var(--action-ink);color:var(--action-ink);}
#main .lesson-workspace .instruction-stages>a.step-done:not(.active) .stage-number{background:var(--good-bg);border-color:var(--good);color:var(--good);}
#main .lesson-workspace .instruction-stages>a:focus-visible{outline:2px solid var(--focus-ring);outline-offset:-4px;}
#main .lesson-workspace .instruction-stages>a:active{background:var(--accent-soft);}
@media(hover:hover){
 #main .section-workspace .idea-path>li>a:hover,#main .lesson-workspace .instruction-stages>a:not(.active):hover{background:var(--accent-soft);color:var(--ink);}
}
@media(max-width:767px){
 .sidebar .brand{display:block;margin-bottom:20px;}
 body #main{padding-top:20px;}
 #main .lesson-workspace .path-crumb{margin-bottom:10px;gap:2px 8px;line-height:1.45;}
 #main .lesson-workspace .path-crumb>a,#main .lesson-workspace .path-crumb>span{min-height:30px;}
 #main .lesson-heading{margin-bottom:10px;}
 #main .lesson-heading h1{margin-bottom:8px;font-size:30px;line-height:1.2;}
 #main .lesson-position{font-size:13px;gap:0 8px;}
 #main .lesson-position .text-button{min-height:36px;font-size:13px;padding:4px 0;}
 #main .lesson-workspace .instruction-stages{margin-inline:-20px;padding-inline:20px;}
 #main .lesson-workspace .instruction-stages>a{flex:0 0 auto;min-height:48px;padding:8px 12px;font-size:14px;}
 #main .lesson-tools{gap:8px;padding:12px 0 16px;}
 #main .lesson-tools .tool-button{min-height:44px;font-size:14px;padding:8px 10px;}
 #main .lesson-tools .tool-caption{font-size:12px;margin:0;}
 #main .lesson-workspace .teaching-page{padding:20px 0 0;border:0;border-top:1px solid var(--line);border-radius:0;background:transparent;}
 #main .lesson-workspace .teaching-page>section{padding-inline:0;}
 #main .lesson-workspace .teaching-page>.independent-start{padding:24px;}
 #main .lesson-workspace .teaching-page .teaching-explanation{padding:0;}
 #main .lesson-workspace .teaching-page h2,#main .lesson-workspace .concept-first>h2:first-child{margin-bottom:16px;font-size:24px;}
 #main .section-workspace .idea-path>li>a{grid-template-columns:24px minmax(0,1fr) 16px;column-gap:12px;padding:20px 16px;min-height:104px;}
 #main .section-workspace .idea-number{font-size:18px;}
 #main .section-workspace .idea-content>strong{font-size:17px;line-height:1.45;}
 #main .section-workspace .idea-progress{display:block;font-size:13px;line-height:1.55;margin-top:8px;}
 #main .section-workspace .idea-path .row-end{display:flex;}
 #main .section-workspace .idea-path .row-label{display:none;}
 #main .section-workspace .idea-path .row-end svg{width:16px;height:16px;}
}
@media(max-width:374px){
 #main .lesson-workspace .instruction-stages{margin-inline:-16px;padding-inline:16px;}
 #main .lesson-heading h1{font-size:28px;}
 #main .lesson-tools{display:flex;flex-wrap:wrap;}
 #main .lesson-tools .tool-button{font-size:13px;padding-inline:8px;gap:6px;}
 #main .section-workspace .idea-path>li>a{column-gap:10px;padding-inline:12px;}
 #main .section-workspace .idea-content>strong{font-size:16px;}
}
@media(forced-colors:active){
 #main .lesson-workspace .instruction-stages>a.active{border-bottom-color:Highlight;}
 #main .lesson-workspace .instruction-stages>a.active .stage-number{background:Highlight;color:HighlightText;border-color:Highlight;}
 #main .section-workspace .idea-path a:focus-visible{outline-color:Highlight;}
}
@media print{.instruction-stages,.sidebar .brand{display:none!important;}}

/* The reading panel owns its inset; the introduction must not add a second one. */
#main .lesson-workspace .teaching-page>.teaching-explanation.concept-first{padding:0;margin:0 0 24px;}

/* Account, answer entry, and teaching controls. Uses the supplied Paper design tokens. */
/* Keep account tasks in the same reading-width surface as the lessons. */
.account-page{max-width:640px;margin:24px auto 64px;padding:0 8px;}
.account-page h1{font-family:var(--display);font-size:clamp(28px,4vw,40px);font-weight:500;}
.account-page header{margin-bottom:28px;}
.account-page p{line-height:1.65;}
.account-field{display:grid;gap:8px;margin:0 0 20px;}
.account-field>label,.account-page>label{font-weight:600;}
.account-field input{width:100%;min-width:0;}
.password-control{display:flex;align-items:center;gap:8px;}
.password-control input{flex:1;min-width:0;}
.password-control button{flex:none;min-height:44px;}
.field-help{font-size:14px;line-height:1.55;color:var(--muted);margin:0;}
.form-feedback{min-height:24px;font-size:15px;line-height:1.55;margin:12px 0;}
.form-feedback[data-state=error]{color:var(--bad);font-weight:600;}
.account-links{display:flex;flex-wrap:wrap;gap:12px 24px;border-top:1px solid var(--line);padding-top:24px;margin-top:16px;}
.account-links a{display:inline-flex;align-items:center;min-height:44px;}
.account-privacy{color:var(--muted);font-size:14px;margin-top:32px;}
.account-section{border-top:1px solid var(--line);padding-top:28px;margin-top:32px;}
.account-section h2{font-size:24px;margin-bottom:12px;}
.account-confirm{display:flex;align-items:center;gap:8px;margin:24px 0;}
.account-confirm input{flex:none;}
.account-identity{display:flex;gap:16px;align-items:baseline;}
.account-identity dd{margin:0;font-weight:600;overflow-wrap:anywhere;}
#new-recovery-key{min-height:76px;overflow-wrap:anywhere;}
.account-delete{border-top:1px solid var(--line);padding-top:20px;margin-top:32px;}
.account-delete summary{color:var(--bad);padding:12px 0;}
.account-link{font-size:14px;min-height:44px;display:inline-flex;align-items:center;padding:0 12px;white-space:nowrap;text-decoration:none;border-radius:var(--radius);}
.account-link:hover,.account-link:focus-visible{background:var(--soft);}
.topbar .save-status-button{margin-left:auto;margin-right:16px;}
.connection-banner{max-width:980px;margin:16px auto;padding:16px 24px;background:var(--soft);border:1px solid var(--line);}
.connection-banner p{margin:0 0 12px;line-height:1.6;}
.connection-banner[hidden]{display:none;}
.nav-list a{border-top:0;}
.nav-list a:nth-child(5){border-radius:8px;margin-top:0;padding:12px 16px;}
/* Matrix entries are a matrix, not an unexplained text serialization. */
.matrix-entry{max-width:100%;overflow-x:auto;padding:8px 4px;}
.matrix-entry-grid{display:grid;grid-template-columns:repeat(var(--matrix-columns),minmax(64px,1fr));gap:8px;border-inline:2px solid var(--ink);padding:8px 12px;width:min(100%,540px);min-width:max-content;}
.matrix-entry-cell{display:block;min-width:0;}
.matrix-entry-cell input{width:100%;max-width:100px;min-width:56px;text-align:center;}
.matrix-text-toggle{justify-self:start;padding:8px 0;}
.answer-symbols{display:flex;gap:8px;flex-wrap:wrap;}
.answer-symbols button{min-width:48px;min-height:44px;}
.answer-help{font-size:14px;line-height:1.6;color:var(--muted);margin:8px 0;}
.answer-reading{font-variant-numeric:tabular-nums;overflow-x:auto;max-width:100%;line-height:1.6;}
.input-reading-label{display:block;font-size:12px;color:var(--muted);margin-bottom:8px;}
.answer-text-wrap[hidden]{display:none;}
.answer-text-wrap input{width:min(100%,420px);}
button:disabled{cursor:not-allowed;}
@media(max-width:640px){.account-page{margin:8px auto 40px;padding:0;}.topbar .save-status-button{font-size:12px;margin-right:4px;}.account-link{padding:0 8px;}.connection-banner{margin:8px;padding:16px;}.password-control{gap:8px;}.account-page .button-row{gap:8px;}.account-page h1{font-size:32px;}.matrix-entry-grid{grid-template-columns:repeat(var(--matrix-columns),minmax(56px,1fr));gap:4px;padding:8px;}}
/* Explicit inputs and computed outputs; no white-on-paper truth switches. */
.truth-control{border:0;padding:0;margin:0;min-width:0;}
.truth-control legend{font-weight:650;padding:0 0 8px;color:var(--ink);}
.truth-control>div{display:flex;gap:6px;}
.truth-control .truth-choice{min-height:44px;color:var(--ink);background:var(--panel);border:1px solid var(--graph-line);font-size:14px;}
.truth-control .truth-choice.selected{background:var(--accent-soft);color:var(--ink);border-color:var(--accent);box-shadow:inset 0 0 0 1px var(--accent);}
.truth-control .truth-choice:hover{background:var(--soft);}
.scene-controls{gap:16px;align-items:end;}
.logic-reason{line-height:1.7;margin:8px 0 20px;color:var(--ink);}
.logic-flow{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap;padding:8px 0 20px;}
.logic-flow .input-stack,.logic-flow .flow-arrow,.logic-flow .formula-node,.logic-flow .truth-output{border:0;box-shadow:none;background:transparent;padding:4px;}
.logic-flow .input-stack{display:flex;flex-direction:column;gap:8px;}
.logic-flow .value-chip,.logic-flow .value-chip.on{background:transparent;border:0;color:var(--ink);padding:0;font-size:15px;}
.logic-flow .formula-node{font-size:22px;min-width:0;}
.logic-flow .truth-output{display:flex;flex-direction:column;gap:4px;min-width:104px;color:var(--ink);border-radius:0;}
.logic-flow .truth-output span{font:13px var(--body);color:var(--muted);}
.logic-flow .truth-output strong{font:600 18px var(--body);color:var(--ink);}
.selected-truth-row{background:var(--accent-soft);outline:1px solid var(--line);outline-offset:-1px;}
.selected-truth-row .current-row{background:transparent;color:var(--ink);font-weight:750;}
.activity-orientation{max-width:none;margin:0;padding:24px 24px 0;}
.activity-orientation p{line-height:1.65;margin:0 0 14px;max-width:76ch;}
.activity-orientation p strong{font-weight:650;}
.tour-controls{display:flex;align-items:center;flex-wrap:wrap;gap:12px;margin-top:18px;}
.tour-controls span{font-size:13px;color:var(--muted);}
.activity-tour{padding:16px 0;border-block:1px solid var(--line);margin-top:20px;}
.activity-tour[hidden]{display:none;}
.activity-tour .tour-position{font-size:13px;color:var(--muted);margin:0 0 8px;}
.activity-tour p{margin:0 0 16px;}
.activity-meaning{margin-top:24px;border-top:1px solid var(--line);padding-top:20px;}
.activity-meaning h3{font-size:20px;margin-bottom:8px;}
.activity-meaning p{line-height:1.65;}
.activity-coach p{line-height:1.65;}
.activity-coach h3{font-size:22px;}
.explore-page>.page-heading{max-width:74ch;}
.explore-page>.page-heading p{line-height:1.65;}
.scene-art,.activity-stage{min-width:0;}
.activity-header h2{margin:0;}
@media(max-width:640px){.scene-controls{gap:16px 12px;}.truth-control .truth-choice{padding:8px 12px;}.logic-flow{justify-content:flex-start;gap:8px;}.logic-flow .flow-arrow{padding:0;}.logic-flow .formula-node{font-size:20px;}.logic-flow .truth-output{min-width:84px;}.activity-layout{display:flex;flex-direction:column;}.activity-coach{width:auto;}.tour-controls>span{display:none;}.activity-orientation{padding:18px 15px 0;}.tour-controls{margin-top:16px;}.activity-tour .button-row{align-items:start;flex-direction:column;}}
@media(prefers-reduced-motion:reduce){.truth-choice,.account-link{transition:none;}}

/* Release 4.3: database-first entry and readable learning progress. */
[hidden]{display:none!important;}
.topbar .account-link{margin-left:auto;}
.startup-view{max-width:40rem;margin:clamp(40px,12vh,112px) auto;padding:0 12px;}
.startup-view h1{font-family:var(--font-heading,var(--font-display,Georgia,serif));font-size:clamp(26px,4vw,36px);line-height:1.2;}
.startup-view p{max-width:55ch;line-height:1.65;margin-block:20px 24px;color:var(--muted);}
#main .learning-progress{border-block:1px solid var(--line);padding-block:28px;margin-block:32px;background:transparent;}
#main .learning-progress h2{font-size:24px;margin:0 0 8px;}
#main .progress-explainer{font-size:15px;line-height:1.6;color:var(--muted);max-width:65ch;margin:0 0 24px;}
#main .learning-progress dl{margin:0;display:grid;gap:24px;}
#main .progress-row{display:grid;grid-template-columns:minmax(0,1fr) minmax(160px,0.8fr);align-items:center;gap:32px;}
#main .progress-row dt{font-weight:650;font-size:16px;line-height:1.4;}
#main .progress-row dt small{display:block;margin-top:4px;font-size:14px;line-height:1.5;color:var(--muted);font-weight:400;}
#main .progress-row dd{margin:0;display:grid;grid-template-columns:90px minmax(0,1fr);gap:16px;align-items:center;}
#main .progress-count{font-size:15px;white-space:nowrap;font-variant-numeric:tabular-nums;font-weight:650;}
#main .progress-count span{color:var(--muted);font-weight:400;}
#main .progress-row progress{display:block;appearance:none;-webkit-appearance:none;width:100%;height:6px;border:0;border-radius:8px;background:var(--line);overflow:hidden;color:var(--accent);}
#main .progress-row progress::-webkit-progress-bar{background:var(--line);border-radius:8px;}
#main .progress-row progress::-webkit-progress-value{background:var(--accent);border-radius:8px;}
#main .progress-row progress::-moz-progress-bar{background:var(--accent);border-radius:8px;}
#main .progress-row:nth-child(2) progress{color:var(--good);}
#main .progress-row:nth-child(2) progress::-webkit-progress-value{background:var(--good);}
#main .progress-row:nth-child(2) progress::-moz-progress-bar{background:var(--good);}
@media(max-width:767px){
 #sidebar.sidebar{position:fixed;inset:0 auto 0 0;top:0;height:100dvh;max-height:100dvh;width:min(320px,calc(100vw - 40px));max-width:calc(100vw - 40px);z-index:1200;padding-top:max(16px,env(safe-area-inset-top));padding-bottom:max(24px,env(safe-area-inset-bottom));overscroll-behavior:contain;overflow-y:auto;}
 .navigation-backdrop.is-visible{position:fixed;inset:0;z-index:1100;}
 body.menu-is-open{overflow:hidden;}
 #sidebar .brand{margin-bottom:20px;}
 .topbar{min-height:60px;height:auto;align-items:center;}
 .topbar .crumb{white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}
 #main .progress-row{grid-template-columns:minmax(0,1fr);gap:10px;}
 #main .progress-row dd{grid-template-columns:84px minmax(0,1fr);}
 #main .learning-progress{padding-block:24px;}
 #main .learning-progress dl{gap:24px;}
 #main .dm-home-grid>aside{display:none;}
}
@media(prefers-reduced-motion:reduce){#sidebar.sidebar.open{animation:none;}}

/* 4.3 release: the navigation dismiss action remains visible when scrolled. */
@media(max-width:767px){
 #sidebar.sidebar .close-navigation{display:flex!important;align-items:center;justify-content:center;position:sticky;top:0;align-self:flex-end;margin:0 0 12px auto;min-height:44px;min-width:112px;padding:10px 14px;z-index:2;color:var(--ink);background:var(--panel,var(--paper));border:1px solid var(--line);border-radius:8px;white-space:nowrap;}
 #sidebar.sidebar .close-navigation:focus-visible{outline:2px solid var(--accent);outline-offset:2px;}
 #sidebar.sidebar .brand{flex-shrink:0;}
}
.guided-setup{line-height:1.65;margin:0 0 20px;}
.guided-setup p{margin:0 0 12px;}

/* Consolidated in design-system.css. */

/* Account choice before the first independent question set. */
.practice-account-dialog{width:min(560px,calc(100vw - 32px));max-width:none;padding:0;border:1px solid var(--line);border-radius:var(--ui-radius);background:var(--panel);color:var(--ink);box-shadow:0 24px 72px #211b1238;}
.practice-account-dialog::backdrop{background:var(--scrim);}
.practice-account-sheet{padding:28px 30px 26px;}
.practice-account-head{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:12px;}
.practice-account-head .eyebrow{margin:0;color:var(--muted);}
.practice-account-close{flex:none;font-size:14px;padding:6px 0;min-height:36px;}
.practice-account-dialog h2{font:500 clamp(29px,5vw,38px)/1.2 var(--display);margin:0 0 14px;}
.practice-account-lede{font-size:17px;line-height:1.65;max-width:48ch;margin:0 0 24px;}
.practice-account-actions{display:flex;align-items:center;gap:10px;margin-bottom:18px;}
.practice-account-actions button{min-height:44px;}
.practice-account-detail{font-size:14px;line-height:1.6;color:var(--muted);margin:0;}
.practice-account-guest{display:flex;align-items:center;justify-content:space-between;gap:24px;border-top:1px solid var(--line);margin-top:24px;padding-top:22px;}
.practice-account-guest strong{display:block;font-size:15px;margin-bottom:5px;}
.practice-account-guest p{font-size:14px;line-height:1.55;color:var(--muted);margin:0;max-width:31ch;}
.practice-account-guest .text-button{flex:none;white-space:nowrap;}
@media(max-width:560px){.practice-account-dialog{width:calc(100vw - 24px);}.practice-account-sheet{padding:22px 20px 20px;}.practice-account-actions{align-items:stretch;flex-direction:column;}.practice-account-actions button{width:100%;}.practice-account-guest{align-items:flex-start;flex-direction:column;gap:14px;}.practice-account-guest .text-button{justify-content:flex-start;padding-left:0;}}
@media(forced-colors:active){.practice-account-dialog{border:2px solid CanvasText;}.practice-account-dialog::backdrop{background:Canvas;opacity:.65;}}