/* Extends the existing mechanical hub with a narrow article column. */
.lesson-page .lesson-layout{display:grid;grid-template-columns:15rem minmax(0,1fr);gap:var(--ab-space-8);align-items:start}
.lesson-page .lesson-toc{position:sticky;top:var(--ab-space-6);max-height:calc(100dvh - 3rem);overflow:auto;padding:var(--ab-space-4)}
.lesson-page .lesson-toc ol{padding-left:var(--ab-space-6);margin-bottom:0}
.lesson-page .lesson-toc a{display:inline-block;padding-block:var(--ab-space-2);line-height:1.5}
.lesson-page .lesson-body{min-width:0;max-width:var(--ab-content-reading)}
.lesson-page .lesson-section{padding-block:var(--ab-space-8);scroll-margin-top:var(--ab-space-6)}
.lesson-page .lesson-section h3{font-size:var(--ab-type-h3);margin-top:var(--ab-space-8)}
.lesson-page .lesson-section p,.lesson-page .lesson-section li{font-size:1rem;line-height:var(--ab-leading-body)}
.lesson-page .lesson-section ul,.lesson-page .lesson-section ol{padding-left:var(--ab-space-6)}
.lesson-page .lesson-equation{font-family:var(--ab-font-mono);padding:var(--ab-space-4);background:var(--ab-surface);border-left:3px solid var(--ab-control-line);overflow-wrap:anywhere;line-height:1.9}
.lesson-page .equation-inline{font-family:var(--ab-font-mono)}
.lesson-page .table-wrap{margin-block:var(--ab-space-6);border:1px solid var(--ab-control-line);border-radius:var(--ab-radius-sm)}
.lesson-page table{min-width:30rem;font-size:var(--ab-type-sm)}
.lesson-page th,.lesson-page td{color:var(--ab-text);background:var(--ab-surface);line-height:1.6}
.lesson-page caption{padding:var(--ab-space-3);margin:0}
.lesson-page .lesson-figure{margin:var(--ab-space-8) 0;border:1px solid var(--ab-control-line);border-radius:var(--ab-radius-md);background:var(--ab-surface)}
.lesson-page .diagram-scroll{overflow:auto}
.lesson-page .lesson-figure svg{display:block;width:100%;min-width:38rem;height:auto}
.lesson-page .diagram-ink{stroke:var(--ab-domain-mechanical-text);stroke-width:2;fill:none;stroke-linejoin:round;stroke-linecap:round}
.lesson-page .diagram-ink text{fill:var(--ab-text);stroke:none;font-family:var(--ab-font-body);font-size:22px}
.lesson-page .diagram-dash{stroke-dasharray:8 6}
.lesson-page figcaption{font-size:var(--ab-type-sm);line-height:1.6;padding:var(--ab-space-4);border-top:1px solid var(--ab-line);color:var(--ab-text-muted)}
.lesson-page #mistakes,.lesson-page #field{border-left:3px solid var(--ab-control-line);padding-left:var(--ab-space-6);margin-block:var(--ab-space-6);background:var(--ab-surface)}
.lesson-page .review-details p{padding-top:var(--ab-space-4)}
.lesson-page .lesson-section:target{scroll-margin-top:var(--ab-space-6)}
.lesson-page #resources li{margin-bottom:var(--ab-space-6)}
@media(max-width:60rem){.lesson-page .lesson-layout{grid-template-columns:1fr}.lesson-page .lesson-toc{position:static;max-height:none}.lesson-page .lesson-toc ol{columns:2}.lesson-page .lesson-body{max-width:none}}
@media(max-width:36rem){.lesson-page .lesson-toc ol{columns:1}.lesson-page #mistakes,.lesson-page #field{padding-left:var(--ab-space-4)}}
@media print{.lesson-page .lesson-toc,.lesson-page [data-lesson-theme]{display:none!important}.lesson-page .lesson-layout{display:block}.lesson-page .lesson-body{max-width:none}.lesson-page .lesson-figure svg{min-width:0}.lesson-page .diagram-scroll,.lesson-page .table-wrap{overflow:visible}.lesson-page table{min-width:0}.lesson-page .diagram-ink{stroke:var(--ab-text)}.lesson-page .lesson-equation,.lesson-page .lesson-figure{break-inside:avoid}}

/* Article layout repair: contain legacy navigation, typography and spacing rules. */
.lesson-page .hub-container{width:100%;max-width:var(--ab-content-wide);margin-inline:auto}
.lesson-page .page-breadcrumb{align-items:center;gap:.5rem .75rem;line-height:1.5}
.lesson-page .hub-hero{padding-block:var(--ab-space-8) var(--ab-space-12)}
.subject-page .lesson-page .hub-hero h1{max-width:24ch;margin:0 0 var(--ab-space-6);font-size:var(--ab-type-h1);line-height:1.15;letter-spacing:-.025em;text-wrap:pretty;overflow-wrap:normal}
.lesson-page .hub-hero .lead{max-width:65ch;margin-bottom:var(--ab-space-6)}
.lesson-page .hub-toolbar{align-items:center;gap:1rem 2rem}
.lesson-page .hub-toolbar .theme-control{display:flex;align-items:center;gap:.5rem;margin:0}
.lesson-page .meta{justify-content:flex-start;align-items:center;gap:.75rem 1rem;margin-bottom:var(--ab-space-6);font-size:var(--ab-type-sm);color:var(--ab-text-muted)}
.lesson-page .lesson-layout{grid-template-columns:minmax(12rem,15rem) minmax(0,1fr);padding-block:var(--ab-space-8) var(--ab-space-12)}
.lesson-page nav.lesson-toc{display:block;width:100%;min-width:0;color:var(--ab-text);font-size:var(--ab-type-sm)}
.lesson-page .lesson-toc>strong{display:block;margin-bottom:var(--ab-space-3)}
.lesson-page .lesson-toc ol{margin:0;padding-left:1.25rem;columns:1}
.lesson-page .lesson-toc li{padding-left:.25rem;margin:0;break-inside:avoid}
.lesson-page .lesson-toc a{display:block;padding:.5rem 0;overflow-wrap:break-word}
.lesson-page .lesson-body{width:100%;max-width:none}
.lesson-page .lesson-section{padding:var(--ab-space-8) 0;margin:0;max-width:100%;scroll-margin-top:2rem}
.lesson-page .lesson-section:first-child{padding-top:0}
.lesson-page .lesson-section h2{font-size:clamp(1.5rem,1.25rem + .8vw,2rem);line-height:1.25;letter-spacing:-.02em;text-wrap:pretty;overflow-wrap:normal;margin-bottom:var(--ab-space-6)}
.lesson-page .lesson-section h3{font-size:1.25rem;line-height:1.35;letter-spacing:-.01em;margin:var(--ab-space-6) 0 var(--ab-space-3)}
.lesson-page .lesson-section p{max-width:65ch;margin:0 0 var(--ab-space-4)}
.lesson-page .lesson-section em{color:inherit;font-style:italic}
.lesson-page .lesson-section ul,.lesson-page .lesson-section ol{margin-block:var(--ab-space-4) var(--ab-space-6);padding-left:1.5rem}
.lesson-page .lesson-section li{padding-left:.25rem;margin-bottom:var(--ab-space-3)}
.lesson-page .lesson-section>:last-child{margin-bottom:0}
.lesson-page .lesson-equation{margin-block:var(--ab-space-6);font-size:clamp(.875rem,.83rem + .2vw,1rem);font-variant-numeric:tabular-nums;border-radius:0 var(--ab-radius-sm) var(--ab-radius-sm) 0;line-height:1.9}
.lesson-page sub,.lesson-page sup{font-size:.75em;line-height:0;position:relative;vertical-align:baseline}
.lesson-page sub{bottom:-.25em}.lesson-page sup{top:-.5em}
.lesson-page table{table-layout:auto;min-width:30rem}
.lesson-page th,.lesson-page td{padding:.875rem 1rem;vertical-align:top;font-size:var(--ab-type-sm);overflow-wrap:normal;word-break:normal}
.lesson-page th{background:var(--ab-surface-raised)}
.lesson-page caption{padding:1rem;text-align:left;line-height:1.6}
.lesson-page .lesson-figure{margin-block:var(--ab-space-6);max-width:100%}
.lesson-page #mistakes,.lesson-page #field{padding:var(--ab-space-6);margin-block:var(--ab-space-6);border:1px solid var(--ab-line);border-left:3px solid var(--ab-control-line);border-radius:var(--ab-radius-sm)}
.lesson-page .review-details summary{align-items:flex-start;line-height:1.6}
.lesson-page .review-details summary::before{flex:0 0 1rem}
.lesson-page .actions{align-items:stretch;gap:var(--ab-space-3)}
.lesson-page .actions .button{margin:0;text-align:left;justify-content:flex-start;flex:1 1 14rem}
.lesson-page .lesson-section a:not(.button){text-decoration:underline;text-underline-offset:.2em}
body:has(.lesson-page)>header,body:has(.lesson-page)>footer{padding-inline:max(clamp(1rem,4vw,2rem),calc((100% - 68rem)/2));gap:1.5rem}
body:has(.lesson-page)>footer{flex-wrap:wrap}
body:has(.lesson-page)>header .brand small{font-size:.75rem;letter-spacing:.08em}
@media(max-width:60rem){
 .lesson-page .lesson-layout{grid-template-columns:minmax(0,1fr);gap:var(--ab-space-8)}
 .lesson-page .lesson-body{max-width:65ch;margin-inline:auto}
 .lesson-page .lesson-toc{position:static;max-width:65ch;margin-inline:auto;max-height:none}
 .lesson-page .lesson-toc ol{columns:2;column-gap:2rem}
 body:has(.lesson-page)>header nav{display:flex;flex-wrap:wrap;width:100%;order:3;gap:.5rem 1.25rem}
 body:has(.lesson-page)>header nav>a,body:has(.lesson-page)>header nav summary{display:inline-flex;align-items:center;min-height:2.75rem}
 body:has(.lesson-page)>header nav details>div{left:0;right:auto;top:100%;max-width:calc(100vw - 2rem)}
}
@media(max-width:36rem){
 .lesson-page .lesson-toc ol{columns:1}
 .lesson-page .hub-toolbar{align-items:flex-start;flex-direction:column}
 .lesson-page .hub-hero{padding-block:var(--ab-space-8)}
 .lesson-page .lesson-section{padding-block:var(--ab-space-6)}
 .lesson-page #mistakes,.lesson-page #field{padding:var(--ab-space-4)}
 .lesson-page .meta{gap:.5rem .75rem}
 .lesson-page .verification-badge{width:fit-content}
}
@media print{
 body:has(.lesson-page)>header,body:has(.lesson-page)>footer,.lesson-page .page-breadcrumb{display:none!important}
 .lesson-page .hub-container{width:100%;max-width:none;padding:0}
 .lesson-page .hub-hero,.lesson-page .lesson-section{padding:1rem 0}
 .lesson-page .hub-hero h1{font-size:24pt!important}
 .lesson-page .lesson-layout{display:block;padding:0}
 .lesson-page .lesson-body{max-width:none}
 .lesson-page .lesson-section h2{font-size:16pt;break-after:avoid}
 .lesson-page .lesson-section h3{break-after:avoid}
 .lesson-page .lesson-section p{orphans:3;widows:3}
 .lesson-page .table-wrap{overflow:visible}.lesson-page table{min-width:0}
 .lesson-page tr{break-inside:avoid}.lesson-page thead{display:table-header-group}
}