/* Lab version B (lab.html), "pages" layer (see site.css for the layer order). Layout follows the owner's second
prototype: stage tabs, the 3D scene with tools beside a lesson column, then the number lab. Colours, type and
buttons use the site tokens. */
@layer pages {
.lb-body{background:var(--c-paper)}
.lb-hero{padding:var(--space-8) 0 var(--space-6)}
.lb-hero-inner{display:flex;justify-content:space-between;align-items:end;gap:var(--space-7)}
.lb-hero .guide-breadcrumb,.lb-hero .guide-breadcrumb a{color:var(--c-muted)}
.lb-hero h1{margin:var(--space-4) 0 0;font-size:clamp(40px,5.4vw,64px);line-height:1.04;letter-spacing:-.04em;font-weight:700;color:var(--c-ink)}
.lb-hero h1 em{font-family:var(--font-serif);font-weight:400;font-style:italic;color:var(--c-accent-ink)}
.lb-hero-copy{max-width:400px}
.lb-hero-copy p{margin:0 0 var(--space-4);font-size:16px;line-height:1.65;color:var(--c-muted)}
.lb-level{display:inline-flex;padding:4px;border-radius:var(--radius-pill);background:var(--c-white);border:1px solid var(--c-line)}
.lb-level button{border:0;background:transparent;padding:10px 20px;border-radius:var(--radius-pill);font:600 14px/1 var(--font-sans);color:var(--c-ink-soft);cursor:pointer}
.lb-btn{border:1px solid var(--c-line);background:var(--c-white);color:var(--c-ink);border-radius:var(--radius-sm);padding:10px 14px;font:600 13px/1.25 var(--font-sans);cursor:pointer;transition:background var(--motion-quick) var(--ease),border-color var(--motion-quick) var(--ease)}
.lb-btn:hover:not(:disabled){border-color:rgba(38,34,44,.35);background:#fff}
.lb-btn:disabled{opacity:.45;cursor:default}
.lb-btn[aria-pressed="true"]{background:#efe6ee;border-color:rgba(143,54,83,.45)}
.lb-primary{background:var(--c-plum);border-color:var(--c-plum);color:#fff}
.lb-primary:hover:not(:disabled){background:#3a3342;border-color:#3a3342}
.lb-square{min-width:40px;font-size:16px}
.lb-body :is(.lb-btn,.lb-chip,.lb-answer,.lb-stages button,.lb-level button,summary,select,textarea,input):focus-visible{outline:3px solid var(--c-accent);outline-offset:3px}
.lb-kicker,.lb-label{display:block;margin:0 0 var(--space-2);font:600 12px/1.4 var(--font-sans);letter-spacing:.01em;color:var(--c-accent-ink)}
/* Stage tabs */
.lb-stages{display:grid;grid-template-columns:repeat(8,minmax(0,1fr));gap:4px;padding:5px;margin-bottom:var(--space-4);background:var(--c-white);border:1px solid var(--c-line);border-radius:14px}
.lb-stages button{border:0;background:transparent;border-radius:10px;padding:13px 8px;font:600 13px/1.2 var(--font-sans);color:var(--c-muted);white-space:nowrap;cursor:pointer}
.lb-stages button:hover{background:#f4eef0;color:var(--c-ink)}
.lb-stages button[aria-current="step"]{background:var(--c-plum);color:#fff}
/* Scene and lesson */
.lb-grid{display:grid;grid-template-columns:minmax(0,1.72fr) minmax(320px,1fr);gap:var(--space-4);align-items:start}
.lb-scene-shell{border:1px solid var(--c-line);border-radius:var(--radius-lg);overflow:hidden;background:#f3f2ee}
.lb-scene-label{display:flex;align-items:center;gap:8px;padding:16px 20px 0;font:600 12px/1.4 var(--font-sans);color:var(--c-ink-soft)}
.lb-live{width:7px;height:7px;border-radius:50%;background:#4f9a80}
#lb-scene-status{margin-left:auto;font-weight:500;color:var(--c-muted);text-align:right}
.lb-scene{position:relative;aspect-ratio:1.46;min-height:330px;isolation:isolate}
.lb-scene canvas{position:absolute;inset:0;width:100%;height:100%;opacity:0;transition:opacity var(--motion-slow) var(--ease)}
.lb-scene.model-ready canvas{opacity:1}
.lb-poster{position:absolute;inset:0;z-index:-1;width:100%;height:100%;object-fit:contain}
.lb-scene.model-ready .lb-poster{visibility:hidden}
.lb-scene.is-failed .lb-poster{visibility:visible}
.lb-scene.is-failed canvas{display:none}
.lb-fallback{position:absolute;left:16px;right:16px;bottom:0;margin:0;padding:12px;background:#fffffff0;border:1px solid var(--c-line);border-radius:var(--radius-sm);font-size:14px;line-height:1.5}
.lb-tools{display:flex;justify-content:space-between;gap:10px;padding:0 18px 14px}
.lb-tool-group{display:flex;gap:6px;flex-wrap:wrap}
.lb-tools .lb-btn{background:#ffffffd9}
.lb-timeline{display:flex;align-items:center;gap:12px;padding:0 20px 16px;font-size:13px;color:var(--c-muted)}
.lb-timeline label{margin:0;font-weight:600}
.lb-timeline input{flex:1;min-width:0}
.lb-timeline output{min-width:76px;text-align:right;font-variant-numeric:tabular-nums}
.lb-body input[type=range]{accent-color:var(--c-accent);cursor:pointer}
.lb-caption{margin:0;padding:14px 20px;border-top:1px solid var(--c-line);display:flex;justify-content:space-between;gap:16px;font-size:13px;line-height:1.55;color:var(--c-muted)}
.lb-caption span{max-width:260px;text-align:right}
.lb-lesson{display:flex;flex-direction:column;min-height:565px;padding:26px 28px;background:var(--c-white);border:1px solid var(--c-line);border-radius:var(--radius-lg)}
.lb-lesson h2{margin:0 0 var(--space-4);font-size:28px;line-height:1.18;letter-spacing:-.03em;color:var(--c-ink)}
.lb-lesson h2:focus{outline:none}
.lb-intro{margin:0 0 var(--space-5);font-size:15px;line-height:1.7;color:var(--c-ink-soft)}
.lb-analogy{margin:0 0 var(--space-5);padding-left:15px;border-left:3px solid var(--stage-color,var(--c-accent))}
.lb-analogy p,.lb-keep p,.lb-tip p,.lb-expert p{margin:0;font-size:14px;line-height:1.65;color:var(--c-ink-soft)}
.lb-steps{list-style:none;margin:0 0 var(--space-5);padding:0;display:grid;gap:8px}
.lb-steps li{position:relative;padding-left:20px;font-size:14px;line-height:1.6;color:var(--c-ink-soft)}
.lb-steps li::before{content:"";position:absolute;left:2px;top:.62em;width:7px;height:7px;border-radius:50%;background:var(--stage-color,var(--c-accent))}
.lb-expert{padding:var(--space-4) 0 var(--space-5);border-top:1px solid var(--c-line)}
.lb-expert code{display:block;margin-top:var(--space-3);padding:12px;border-radius:var(--radius-sm);background:#f6f2ee;font:13px/1.7 var(--font-mono);color:var(--c-ink);overflow-wrap:anywhere}
.lb-keep{margin-top:auto;padding:15px 16px;border-radius:var(--radius-sm);background:#f3eee9}
.lb-tip{margin-top:var(--space-3);padding:15px 16px;border-radius:var(--radius-sm);background:#f1eaf3}
.lb-lesson-nav{display:flex;justify-content:space-between;gap:10px;margin-top:var(--space-5)}
/* Panels below */
.lb-panel{margin-top:var(--space-7);padding:30px 32px 32px;background:var(--c-white);border:1px solid var(--c-line);border-radius:var(--radius-lg)}
.lb-section{padding-top:var(--space-8)}
.lb-section-head{display:flex;justify-content:space-between;align-items:end;gap:28px;margin-bottom:var(--space-5)}
.lb-section-head h2{margin:0;font-size:clamp(26px,3vw,32px);line-height:1.2;letter-spacing:-.03em;color:var(--c-ink)}
.lb-section-head>p{margin:0;max-width:320px;font-size:14px;line-height:1.6;color:var(--c-muted)}
.lb-model-tag{padding:9px 14px;border:1px solid var(--c-line);border-radius:var(--radius-pill);background:#f6f2ee;font-size:13px;white-space:nowrap;color:var(--c-ink-soft)}
.lb-lead{max-width:780px;margin:0 0 var(--space-5);font-size:15px;line-height:1.7;color:var(--c-muted)}
.lb-input-layout{display:grid;grid-template-columns:minmax(0,1.65fr) minmax(240px,1fr);gap:36px;padding-bottom:var(--space-5)}
.lb-workbench label{display:block;margin-bottom:9px;font:600 13px/1.4 var(--font-sans);color:var(--c-ink)}
.lb-workbench textarea{display:block;width:100%;min-height:91px;resize:vertical;padding:16px;border:1px solid #d9d0d6;border-radius:var(--radius-sm);background:#fbf9f7;font:17px/1.5 var(--font-sans);color:var(--c-ink)}
.lb-examples{display:flex;flex-wrap:wrap;gap:6px;margin-top:10px}
.lb-chip{border:1px solid var(--c-line);background:var(--c-white);border-radius:var(--radius-pill);padding:7px 12px;font:600 13px/1.2 var(--font-sans);color:var(--c-ink-soft);cursor:pointer}
.lb-chip:hover{border-color:rgba(143,54,83,.45);color:var(--c-accent-ink)}
.lb-workbench .lb-sampling label{display:flex;justify-content:space-between}
.lb-sampling input{width:100%;margin:0 0 16px}
.lb-actions{display:flex;flex-wrap:wrap;gap:7px}
.lb-token-head{display:flex;flex-wrap:wrap;justify-content:space-between;gap:4px 10px;margin-bottom:12px;padding-top:19px;border-top:1px solid var(--c-line);font:600 13px/1.4 var(--font-sans);color:var(--c-ink-soft)}
.lb-token-head span:last-child{font-weight:400;color:var(--c-muted)}
.lb-tokens{display:flex;flex-wrap:wrap;gap:6px;max-height:220px;overflow-y:auto;padding:3px}
.lb-token{display:flex;flex-direction:column;gap:4px;min-width:44px;padding:9px 12px;border:1px solid #efd9cf;border-radius:8px;background:#fdf0ea}
.lb-token:nth-child(3n+2){background:#edf6f1;border-color:#d2e6dc}
.lb-token:nth-child(3n){background:#f2eef9;border-color:#e0d8ef}
.lb-token b{max-width:200px;font:500 14px/1.3 var(--font-mono);overflow-wrap:anywhere;color:var(--c-ink)}
.lb-token small{font-size:12px;color:var(--c-muted)}
.lb-token.is-outside{opacity:.45}
.lb-muted{margin:14px 0 0;font-size:14px;line-height:1.6;color:var(--c-muted)}
.lb-inspector-head{display:flex;justify-content:space-between;align-items:center;gap:20px;margin-top:21px;padding:22px 0 16px;border-top:1px solid var(--c-line)}
.lb-inspector-head h3{margin:0;font-size:18px;letter-spacing:-.01em;color:var(--c-ink)}
.lb-selects{display:flex;gap:15px}
.lb-workbench .lb-selects label{display:flex;align-items:center;gap:8px;margin:0;font-weight:500;color:var(--c-muted)}
.lb-selects select{padding:7px 24px 7px 10px;border:1px solid var(--c-line);border-radius:8px;background:#fbf9f7;font-size:14px;color:var(--c-ink)}
.lb-inspector{padding:18px 20px;border:1px solid #ece4de;border-radius:var(--radius-sm);background:#faf7f4;font-size:14px;line-height:1.65;color:var(--c-ink-soft)}
.lb-inspector>p:last-child{margin-bottom:0}
.lb-probs{display:grid;grid-template-columns:1fr 1fr;gap:10px 40px}
.lb-prob{display:grid;grid-template-columns:90px minmax(30px,1fr) 56px;gap:12px;align-items:center;font-size:13px}
.lb-prob code{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font:13px var(--font-mono);color:var(--c-ink)}
.lb-prob>span:last-child{text-align:right;font-variant-numeric:tabular-nums}
.lb-bar{height:10px;border-radius:3px;background:#ece3dd;overflow:hidden}
.lb-bar i{display:block;height:100%;border-radius:3px;background:linear-gradient(90deg,#c0503a,#b5476f)}
.lb-note{margin:16px 0 0;font-size:13px;line-height:1.65;color:var(--c-muted)}
.lb-matrix-scroll{max-height:400px;overflow:auto;border-radius:6px}
.lb-matrix{border-collapse:separate;border-spacing:3px;font:12px var(--font-mono);font-variant-numeric:tabular-nums}
.lb-matrix th{max-width:100px;padding:6px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-weight:400;color:var(--c-ink-soft)}
.lb-matrix thead th{position:sticky;top:0;z-index:1;background:#faf7f4}
.lb-matrix tbody th{position:sticky;left:0;z-index:1;background:#faf7f4;text-align:left}
.lb-matrix td{--cell-alpha:0;min-width:44px;padding:8px 5px;border-radius:3px;text-align:center;color:#22302a;background:rgba(79,154,128,var(--cell-alpha))}
.lb-matrix td.neg{background:rgba(192,80,58,var(--cell-alpha))}
.lb-context-note{padding:10px 13px;border-radius:6px;background:#fbeee0;color:#7a4f22}
.lb-metrics{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;padding:10px 0 16px}
.lb-metrics div{display:flex;flex-direction:column;gap:6px}
.lb-metrics b{font-size:28px;font-weight:650;letter-spacing:-.03em;color:var(--c-ink)}
.lb-metrics span{font-size:13px;color:var(--c-muted)}
.lb-training{display:grid;grid-template-columns:1fr 1fr;gap:32px;margin-top:22px;padding-top:24px;border-top:1px solid var(--c-line)}
.lb-training h3{margin:0 0 10px;font-size:18px}
.lb-training p{font-size:14px;line-height:1.65;color:var(--c-muted)}
.lb-training .lb-metrics{grid-template-columns:1fr 1fr}
.lb-questions{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}
.lb-question{padding:22px;background:var(--c-white);border:1px solid var(--c-line);border-radius:14px}
.lb-question h3{margin:0 0 var(--space-4);font-size:17px;line-height:1.45;letter-spacing:-.01em;color:var(--c-ink)}
.lb-answer{display:block;width:100%;margin-top:6px;padding:10px 12px;border:1px solid var(--c-line);border-radius:10px;background:#fbf9f7;text-align:left;font:500 14px/1.5 var(--font-sans);color:var(--c-ink);cursor:pointer}
.lb-answer:hover{border-color:rgba(38,34,44,.3)}
.lb-answer.is-correct{border-color:#4f9a80;background:#e9f5ef}
.lb-answer.is-wrong{border-color:#c0503a;background:#fbeeea}
.lb-feedback{margin:14px 0 0;font-size:14px;line-height:1.6;color:var(--c-ink-soft)}
.lb-feedback:empty{display:none}
.lb-search{display:flex;align-items:center;gap:12px;margin:0;font:600 13px var(--font-sans);color:var(--c-muted)}
.lb-search input{min-width:220px;padding:11px 14px;border:1px solid var(--c-line);border-radius:10px;background:var(--c-white);font-size:14px}
.lb-glossary{display:grid;grid-template-columns:repeat(3,1fr);align-items:start;gap:9px}
.lb-glossary details{border:1px solid var(--c-line);border-radius:12px;background:var(--c-white)}
.lb-glossary summary{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:15px 18px;font:600 14px var(--font-sans);color:var(--c-ink);cursor:pointer;list-style:none}
.lb-glossary summary::-webkit-details-marker{display:none}
.lb-glossary summary::after{content:"+";color:var(--c-muted);transition:transform var(--motion-quick) var(--ease)}
.lb-glossary details[open] summary::after{transform:rotate(45deg)}
.lb-glossary details p{margin:0;padding:0 18px 16px;font-size:14px;line-height:1.65;color:var(--c-muted)}
.lb-sources{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.lb-sources a{padding:22px;background:var(--c-white);border:1px solid var(--c-line);border-radius:14px;color:var(--c-ink);text-decoration:none;transition:border-color var(--motion-quick) var(--ease)}
.lb-sources a:hover{border-color:rgba(143,54,83,.45)}
.lb-sources span{font-size:13px;color:var(--c-muted)}
.lb-sources h3{margin:12px 0 8px;font-size:16px;line-height:1.4}
.lb-sources p{margin:0;font-size:14px;line-height:1.6;color:var(--c-muted)}
.lb-body main{padding-bottom:var(--space-8)}
@media(min-width:1450px){.lb-scene{aspect-ratio:1.52}}
@media(max-width:1100px){
.lb-grid{grid-template-columns:minmax(0,1.4fr) minmax(300px,1fr)}
.lb-scene{aspect-ratio:auto;height:460px;min-height:0}
.lb-caption{display:block}.lb-caption span{display:block;max-width:none;margin-top:4px;text-align:left}
.lb-tools{padding:0 12px 14px}
.lb-stages button{font-size:12px}
.lb-questions,.lb-sources,.lb-glossary{grid-template-columns:1fr 1fr}
}
@media(max-width:780px){
.lb-hero{padding:var(--space-6) 0 var(--space-5)}
.lb-hero-inner{display:block}.lb-hero-copy{max-width:none;margin-top:var(--space-4)}
.lb-stages{display:flex;overflow-x:auto;scrollbar-width:thin}
.lb-stages button{flex-shrink:0;padding:12px 14px}
.lb-grid{grid-template-columns:1fr}
.lb-scene{height:380px}
.lb-tools{flex-wrap:wrap;justify-content:center}
.lb-tool-group{justify-content:center}
.lb-lesson{min-height:0;padding:24px 20px}
.lb-lesson h2{font-size:26px}
.lb-panel{padding:24px 18px}
.lb-section-head{display:block}.lb-section-head>p{margin-top:12px;max-width:none}
.lb-model-tag{display:inline-block;margin-top:14px;white-space:normal}
.lb-input-layout{grid-template-columns:1fr;gap:24px}
.lb-probs{grid-template-columns:1fr}
.lb-prob{grid-template-columns:80px 1fr 52px}
.lb-inspector{padding:16px}
.lb-inspector-head{align-items:start}
.lb-selects{flex-direction:column;gap:8px}
.lb-training{grid-template-columns:1fr;gap:12px}
.lb-search{margin-top:var(--space-4)}.lb-search input{flex:1;min-width:0}
.lb-questions,.lb-sources,.lb-glossary{grid-template-columns:1fr}
.lb-metrics b{font-size:24px}
}
/* Labels and tips on the model, carried over from the homepage lesson. JS places each label above its part. */
.lb-pins{position:absolute;inset:0;pointer-events:none;overflow:hidden;z-index:2}
.lb-pin{position:absolute;left:0;top:0;margin:0;padding:5px 8px;pointer-events:auto;cursor:pointer;white-space:nowrap;
font:600 12px/1.2 var(--font-mono);color:#3a3440;background:#fbf8f2eb;border:1px solid #c9c0c6;border-left:3px solid var(--pin,#c9c0c6);
border-radius:4px;box-shadow:0 2px 12px rgba(51,42,48,.1);transition:background var(--motion-quick) var(--ease),color var(--motion-quick) var(--ease)}
.lb-pin:hover{border-color:#8f8590;box-shadow:0 4px 16px rgba(51,42,48,.18)}
.lb-pin.is-selected{background:var(--c-plum);color:#fff;border-color:var(--c-plum);border-left-color:var(--pin)}
.lb-pin.is-sub{background:#2f2a35;color:#faf5eb;border-color:#2f2a35;border-left-color:var(--pin)}
.lb-pin.is-off,.lb-scene:not(.model-ready) .lb-pins{visibility:hidden}
.lb-pin:focus-visible{outline:3px solid var(--c-accent);outline-offset:2px}
.lb-tip{position:absolute;top:0;left:0;z-index:6;width:min(290px,calc(100% - 20px));padding:14px 16px;border-radius:14px;
background:rgba(255,253,250,.97);border:1px solid rgba(38,34,44,.12);box-shadow:0 18px 40px -20px rgba(70,44,62,.6);color:var(--c-ink)}
.lb-tip[hidden]{display:none}
.lb-tip-title{display:block;margin:0 26px 6px 0;font-size:15px;font-weight:700}
.lb-tip-text{margin:0 0 12px;font-size:14px;line-height:1.55;color:var(--c-ink-soft)}
.lb-tip-go{display:inline-flex;align-items:center;min-height:38px;padding:0 14px;border:0;border-radius:var(--radius-pill);background:var(--grad-accent);color:#fff;font:600 13px var(--font-sans);cursor:pointer}
.lb-tip-close{position:absolute;top:6px;right:6px;width:30px;height:30px;border:0;border-radius:50%;background:transparent;color:var(--c-muted);font-size:20px;line-height:1;cursor:pointer}
.lb-tip-close:hover{background:rgba(38,34,44,.07)}
.lb-tip :is(.lb-tip-go,.lb-tip-close):focus-visible{outline:3px solid var(--c-accent);outline-offset:2px}
@media(max-width:780px){.lb-pin{padding:4px 6px}}
}