@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(--graph-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(--graph-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)}.progress-track{--progress-ratio:0;--progress-track-color:var(--line);--progress-fill-color:var(--dm-accent,var(--accent));--progress-border-color:transparent;position:relative;box-sizing:border-box;display:block;inline-size:100%;max-inline-size:100%;block-size:8px;margin:13px 0;padding:0;border:1px solid var(--progress-border-color);border-radius:999px;overflow:hidden;background:var(--progress-track-color);contain:paint}.progress-track__fill{position:absolute;inset-block:0;inset-inline-start:0;display:block;inline-size:100%;block-size:100%;background:var(--progress-fill-color);transform:scaleX(var(--progress-ratio));transform-origin:left center}.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 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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 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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 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