/* Linear Regression page: visual-first course layout. */
body.lr-page { --lr-surface: color-mix(in srgb, var(--bg-card) 88%, transparent); }
.lr-page .model-layout { max-width: 1240px; grid-template-columns: 1fr; }
.lr-page .model-sidebar, .lr-page #sidebar-toggle { display: none; }
.lr-page #main-content { max-width: 1120px; width: 100%; margin: 0 auto; }
.lr-page .model-hero { min-height: 430px; grid-template-columns: 1.15fr .85fr; gap: 3rem; padding: 4.5rem 3.5rem; border-radius: 1.5rem; background: radial-gradient(circle at 82% 20%, color-mix(in srgb, var(--accent-secondary) 10%, transparent), transparent 34%), linear-gradient(135deg, color-mix(in srgb, var(--accent-primary) 8%, var(--bg-card)), var(--bg-card)); }
.lr-page .model-title { font-size: clamp(3rem, 6vw, 5.3rem); text-transform: none; letter-spacing: -.06em; }
.lr-page .model-title em { color: inherit; background: none; -webkit-text-fill-color: currentColor; }
.lr-page .model-subtitle { max-width: 570px; font-size: clamp(1.05rem, 2vw, 1.28rem); line-height: 1.7; }
.lr-page .hero-badges { gap: .45rem; }
.lr-page .hero-badges .badge { text-transform: none; letter-spacing: .01em; font-size: .74rem; }
.lr-page .hero-actions { margin-top: 1.8rem; }
.lr-page .model-dna-card { overflow: hidden; padding: 0; background: var(--lr-surface); }
.lr-hero-graphic { padding: 1rem 1rem .7rem; border-bottom: 1px solid var(--border-subtle); background: color-mix(in srgb, var(--bg-secondary) 55%, transparent); }
.lr-hero-graphic svg { display: block; width: 100%; height: auto; }
.lr-hero-line { stroke-dasharray: 700; stroke-dashoffset: 700; animation: lr-line-draw 1.8s .3s cubic-bezier(.16,1,.3,1) forwards; }
.lr-hero-point { opacity: 0; animation: lr-point-in .45s var(--delay) ease-out forwards; }
.lr-page .model-dna-card > .dna-header, .lr-page .model-dna-card > .dna-grid, .lr-page .model-dna-card > .row-link { margin-left: 1.35rem; margin-right: 1.35rem; }
.lr-page .model-dna-card > .dna-header { margin-top: 1.2rem; }
.lr-page .model-dna-card > .row-link { margin-bottom: 1.2rem; }
.lr-page .progress-wrap { max-width: 760px; margin: 1.2rem auto 0; }
.lr-page #model-toc { position: sticky; top: calc(var(--nav-h) + .65rem); z-index: 20; display: flex; gap: .4rem; overflow-x: auto; padding: .45rem; margin: 1.4rem 0 0; border: 1px solid var(--border-subtle); border-radius: .85rem; background: color-mix(in srgb, var(--bg-primary) 86%, transparent); backdrop-filter: blur(14px); scrollbar-width: none; }
.lr-page #model-toc::-webkit-scrollbar { display: none; }
.lr-page #model-toc a { flex: 0 0 auto; padding: .6rem .8rem; border: 0; background: transparent; border-radius: .55rem; font: 700 .72rem var(--font-mono); white-space: nowrap; color: var(--text-muted); }
.lr-page #model-toc a:hover, .lr-page #model-toc a.active { background: var(--bg-soft); color: var(--accent-secondary); }
.lr-page #model-toc .toc-n { color: var(--accent-primary); }
.lr-block { margin: 5.5rem 0; scroll-margin-top: calc(var(--nav-h) + 4rem); }
.lr-block h2 { max-width: 760px; margin: .35rem 0 1rem; font-size: clamp(2rem, 4vw, 3rem); line-height: 1.08; letter-spacing: -.045em; }
.lr-kicker, .lr-card-label { color: var(--accent-secondary); font: 700 .7rem var(--font-mono); letter-spacing: .15em; text-transform: uppercase; }
.lr-lead { max-width: 700px; color: var(--text-secondary); font-size: 1.08rem; line-height: 1.75; }
.lr-understand-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 2rem; }
.lr-story-card, .lr-worked-example, .lr-compare > div { padding: 1.35rem; border: 1px solid var(--border-subtle); border-radius: 1rem; background: var(--lr-surface); }
.lr-story-card { min-height: 190px; position: relative; overflow: hidden; }
.lr-story-card::after { content: ''; position: absolute; width: 140px; height: 140px; right: -85px; bottom: -90px; border-radius: 50%; background: var(--accent-secondary); filter: blur(42px); opacity: .1; }
.lr-card-number { display: block; margin-bottom: 1.8rem; color: var(--accent-primary); font: 700 .8rem var(--font-mono); }
.lr-story-card h3, .lr-worked-example h3 { margin-bottom: .45rem; font-size: 1.05rem; }
.lr-story-card p { color: var(--text-secondary); font-size: .88rem; line-height: 1.65; }
.lr-question-card { display: grid; gap: .45rem; margin-top: 1rem; padding: 1.2rem 1.35rem; border-left: 3px solid var(--accent-primary); background: var(--bg-soft); }
.lr-question-card span { color: var(--accent-primary); font: 700 .68rem var(--font-mono); letter-spacing: .12em; }
.lr-question-card strong { max-width: 720px; font-size: 1rem; }
.lr-section-heading { display: flex; justify-content: space-between; align-items: end; gap: 1.5rem; }
.lr-section-heading p { color: var(--text-secondary); max-width: 650px; }
.lr-live-pill { flex: none; padding: .45rem .65rem; border: 1px solid var(--border-accent); border-radius: 999px; color: var(--accent-secondary); font: 700 .66rem var(--font-mono); }
.lr-live-pill i { display: inline-block; width: .45rem; height: .45rem; margin-right: .35rem; border-radius: 50%; background: var(--accent-secondary); box-shadow: 0 0 0 5px color-mix(in srgb, var(--accent-secondary) 15%, transparent); }
.lr-playground { display: grid; grid-template-columns: minmax(0, 1.75fr) minmax(245px, .65fr); gap: 1rem; margin-top: 1.7rem; padding: 1rem; border: 1px solid var(--border-accent); border-radius: 1.25rem; background: var(--lr-surface); box-shadow: var(--shadow-card); }
.lr-plot-wrap { position: relative; min-width: 0; border-radius: .9rem; overflow: hidden; background: var(--bg-secondary); }
.lr-canvas { display: block; width: 100%; height: 420px; touch-action: none; cursor: crosshair; }
.lr-plot-help { position: absolute; left: 1rem; bottom: .8rem; padding: .3rem .55rem; border-radius: .4rem; background: color-mix(in srgb, var(--bg-primary) 82%, transparent); color: var(--text-muted); font: .68rem var(--font-mono); }
.lr-controls { display: grid; align-content: start; gap: 1rem; padding: 1.1rem; border-left: 1px solid var(--border-subtle); }
.lr-control-heading { display: grid; gap: .25rem; padding-bottom: .35rem; border-bottom: 1px solid var(--border-subtle); }
.lr-control-heading span { color: var(--accent-secondary); font: 700 .67rem var(--font-mono); letter-spacing: .12em; }
.lr-control-heading strong { font-size: 1.1rem; }
.lr-range { display: grid; gap: .55rem; color: var(--text-secondary); font-size: .86rem; }
.lr-range span { display: flex; justify-content: space-between; gap: .5rem; }
.lr-range b { color: var(--accent-primary); font-family: var(--font-mono); }
.lr-range input { accent-color: var(--accent-primary); }
.lr-toggle { display: flex; gap: .6rem; align-items: center; color: var(--text-secondary); font-size: .86rem; cursor: pointer; }
.lr-toggle input { width: 1rem; height: 1rem; accent-color: var(--accent-primary); }
.lr-live-stats { display: grid; grid-template-columns: 1fr 1fr; gap: .5rem; }
.lr-live-stats .viz-stats { display: contents; }
.lr-live-stats .viz-stats > div { padding: .55rem; border: 1px solid var(--border-subtle); border-radius: .55rem; background: var(--bg-secondary); }
.lr-live-stats .stat-label { display: block; color: var(--text-muted); font: .63rem var(--font-mono); text-transform: uppercase; }
.lr-live-stats .stat-value { display: block; margin-top: .2rem; color: var(--accent-secondary); font: 700 .9rem var(--font-mono); }
.lr-control-actions { display: flex; gap: .5rem; }
.lr-button { flex: 1; padding: .65rem .7rem; border: 1px solid var(--border-subtle); border-radius: .55rem; background: var(--bg-secondary); color: var(--text-primary); font-weight: 700; cursor: pointer; transition: transform .2s ease, border-color .2s ease, background .2s ease; }
.lr-button:hover { transform: translateY(-2px); border-color: var(--accent-secondary); background: var(--bg-soft); }
.lr-button-primary { border-color: transparent; background: var(--accent-gradient); color: #12212c; }
.lr-concept-flow, .lr-pipeline { display: flex; align-items: stretch; gap: .5rem; margin-top: 1.7rem; }
.lr-concept-flow article, .lr-pipeline article { flex: 1; padding: 1rem; border: 1px solid var(--border-subtle); border-radius: .8rem; background: var(--lr-surface); }
.lr-concept-flow article span, .lr-pipeline article span { display: block; margin-bottom: 1.4rem; color: var(--accent-primary); font: .7rem var(--font-mono); }
.lr-concept-flow article strong, .lr-pipeline article strong { display: block; font-size: .9rem; }
.lr-concept-flow article p { margin-top: .3rem; color: var(--text-muted); font-size: .78rem; }
.lr-concept-flow > b, .lr-pipeline > b { align-self: center; color: var(--accent-primary); font-size: 1.3rem; }
.lr-one-line { margin-top: 1.2rem; color: var(--text-secondary); font-size: 1rem; }
.lr-equation-card { margin-top: 1.6rem; padding: 2rem; border: 1px solid var(--border-accent); border-radius: 1.1rem; background: linear-gradient(135deg, color-mix(in srgb, var(--accent-primary) 8%, var(--bg-card)), var(--bg-card)); text-align: center; }
.lr-equation { font: 800 clamp(2.2rem, 5vw, 4.2rem) var(--font-mono); letter-spacing: -.08em; }
.lr-equation span { display: inline-block; padding: 0 .12em; border-radius: .2em; transition: background .2s ease, color .2s ease; }
.lr-equation span.focused { background: var(--accent-primary); color: #12212c; }
.lr-equation-card p { margin-top: .8rem; color: var(--text-muted); font-size: .78rem; }
.lr-symbol-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: .7rem; margin-top: .8rem; }
.lr-symbol-card { display: grid; gap: .3rem; padding: 1rem; border: 1px solid var(--border-subtle); border-radius: .8rem; background: var(--lr-surface); color: var(--text-primary); text-align: left; cursor: pointer; transition: transform .2s ease, border-color .2s ease, background .2s ease; }
.lr-symbol-card:hover, .lr-symbol-card.active { transform: translateY(-3px); border-color: var(--accent-primary); background: var(--bg-soft); }
.lr-symbol-card strong { font: 800 1.5rem var(--font-mono); color: var(--accent-secondary); }
.lr-symbol-card span { color: var(--text-muted); font-size: .78rem; }
.lr-disclosure { margin-top: .7rem; border: 1px solid var(--border-subtle); border-radius: .75rem; background: var(--lr-surface); }
.lr-disclosure summary { display: flex; justify-content: space-between; padding: 1rem 1.1rem; cursor: pointer; font-weight: 700; list-style: none; }
.lr-disclosure summary::-webkit-details-marker { display: none; }
.lr-disclosure summary span { color: var(--accent-primary); font: 1.1rem var(--font-mono); }
.lr-disclosure[open] summary span { transform: rotate(45deg); }
.lr-disclosure-body { padding: 0 1.1rem 1.1rem; color: var(--text-secondary); font-size: .92rem; line-height: 1.75; }
.lr-pipeline article { min-height: 130px; }
.lr-pipeline article small { display: block; margin-top: .9rem; color: var(--text-muted); font: .72rem var(--font-mono); }
.lr-loss-card { display: grid; grid-template-columns: .7fr 1.3fr; gap: 1rem; align-items: center; margin-top: 1rem; padding: 1rem 1.3rem; border: 1px solid var(--border-subtle); border-radius: .9rem; background: var(--lr-surface); }
.lr-loss-card strong { display: block; margin-top: .3rem; }
.lr-loss-card svg { width: 100%; }
.lr-practice-grid { display: grid; grid-template-columns: 1.15fr .85fr; gap: 1rem; margin-top: 1.5rem; }
.lr-worked-example { padding: 1.5rem; }
.lr-worked-example table { width: 100%; margin: 1rem 0; border-collapse: collapse; font: .82rem var(--font-mono); }
.lr-worked-example th, .lr-worked-example td { padding: .45rem .6rem; border-bottom: 1px solid var(--border-subtle); text-align: left; }
.lr-worked-example th { color: var(--accent-secondary); }
.lr-steps { display: grid; gap: .5rem; padding-left: 1.2rem; color: var(--text-secondary); font-size: .88rem; }
.lr-result { display: grid; gap: .3rem; margin-top: 1.2rem; padding: 1rem; border-radius: .7rem; background: var(--bg-soft); color: var(--accent-primary); font: 800 1.35rem var(--font-mono); }
.lr-result small { color: var(--text-secondary); font: .76rem var(--font-sans); }
.lr-compare { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-top: 1.5rem; }
.lr-compare > div:first-child { border-top: 3px solid var(--status-success); }
.lr-compare > div:last-child { border-top: 3px solid var(--status-warning); }
.lr-compare h3 { margin-bottom: .8rem; font-size: 1rem; }
.lr-compare p { padding: .4rem 0; color: var(--text-secondary); font-size: .86rem; }
.lr-app-grid, .lr-metric-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: .7rem; margin-top: 1rem; }
.lr-app-grid article, .lr-metric-card { display: grid; gap: .25rem; padding: 1rem; border: 1px solid var(--border-subtle); border-radius: .8rem; background: var(--lr-surface); text-align: left; }
.lr-app-grid article span { color: var(--accent-primary); font-size: 1.3rem; }
.lr-app-grid article strong { font-size: .9rem; }
.lr-app-grid article small, .lr-metric-card span { color: var(--text-muted); font-size: .75rem; }
.lr-metric-card { color: var(--text-primary); cursor: pointer; transition: transform .2s ease, border-color .2s ease; }
.lr-metric-card:hover, .lr-metric-card.open { transform: translateY(-3px); border-color: var(--accent-primary); }
.lr-metric-card strong { color: var(--accent-secondary); font: 800 1.3rem var(--font-mono); }
.lr-metric-card em { display: none; color: var(--accent-primary); font-size: .7rem; font-style: normal; }
.lr-metric-card.open em { display: block; }
.lr-recap { margin-top: 1.5rem; padding: 1.4rem; border: 1px solid var(--border-accent); border-radius: 1rem; background: linear-gradient(120deg, color-mix(in srgb, var(--accent-secondary) 7%, var(--bg-card)), var(--bg-card)); }
.lr-recap-flow { display: flex; flex-wrap: wrap; align-items: center; gap: .5rem; margin: 1rem 0; color: var(--text-secondary); font-weight: 700; }
.lr-recap-flow span { padding: .45rem .65rem; border-radius: .45rem; background: var(--bg-soft); }
.lr-recap-flow b { color: var(--accent-primary); }
.lr-recap p { max-width: 720px; color: var(--text-secondary); }
.lr-full-notes { margin: 2rem 0 4rem; border: 1px solid var(--border-subtle); border-radius: 1rem; background: var(--lr-surface); }
.lr-full-notes summary { padding: 1rem 1.2rem; cursor: pointer; color: var(--accent-secondary); font-weight: 700; }
.lr-full-notes .section-block { margin: 1rem 1.2rem 2rem; }
.lr-full-notes .section-block:first-of-type { margin-top: 1.2rem; }
.lr-full-notes #prev-next { margin: 1.2rem; }
@keyframes lr-line-draw { to { stroke-dashoffset: 0; } }
@keyframes lr-point-in { from { opacity: 0; transform: scale(.2); } to { opacity: 1; transform: scale(1); } }
@media (max-width: 850px) { .lr-page .model-hero { grid-template-columns: 1fr; padding: 3rem 1.5rem; } .lr-page .model-dna-card { max-width: 560px; } .lr-playground, .lr-practice-grid { grid-template-columns: 1fr; } .lr-controls { border-left: 0; border-top: 1px solid var(--border-subtle); } .lr-canvas { height: 360px; } .lr-pipeline { flex-wrap: wrap; } .lr-pipeline article { min-width: 28%; } }
@media (max-width: 600px) { .lr-block { margin: 4rem 0; } .lr-understand-grid, .lr-compare { grid-template-columns: 1fr; } .lr-symbol-grid, .lr-app-grid, .lr-metric-grid { grid-template-columns: repeat(2, 1fr); } .lr-concept-flow { display: grid; grid-template-columns: 1fr 1fr; } .lr-concept-flow > b { display: none; } .lr-canvas { height: 300px; } .lr-live-pill { display: none; } .lr-loss-card { grid-template-columns: 1fr; } .lr-recap-flow { align-items: flex-start; flex-direction: column; } .lr-recap-flow b { transform: rotate(90deg); margin-left: .7rem; } }
@media (prefers-reduced-motion: reduce) { .lr-hero-line, .lr-hero-point { animation: none; opacity: 1; stroke-dashoffset: 0; } }