/* One shared layout for generated lessons. Never add selectors for a lesson ID. */
:root{
 --font-sans:"Be Vietnam Pro",system-ui,sans-serif;--bg-page:#f8fafc;--bg-surface:#fff;--bg-surface-soft:#f1f5f9;--text-main:#0f172a;--text-secondary:#334155;--text-muted:#52647b;--border-color:#dbe3ed;--primary:#0056d2;--primary-hover:#0043a4;--primary-light:#e6f0ff;--success:#047857;--success-bg:#ecfdf5;--danger:#b91c1c;--danger-bg:#fef2f2;
 --page-width:920px;--page-gutter:24px;--card-padding:24px;--section-gap:28px;--card-radius:12px;--header-clearance:110px;--audio-bar-clearance:100px;
}
[data-theme="dark"]{--bg-page:#0f172a;--bg-surface:#172235;--bg-surface-soft:#202e43;--text-main:#f1f5f9;--text-secondary:#d4dfed;--text-muted:#a5b7ce;--border-color:#3b4c63;--primary:#8cb9ff;--primary-hover:#b6d2ff;--primary-light:#233c61;--success:#6ee7b7;--success-bg:#123e35;--danger:#fca5a5;--danger-bg:#4b2630}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:var(--header-clearance)}
body{margin:0;background:var(--bg-page);color:var(--text-main);font:400 16px/1.7 var(--font-sans)}
button,input,select,textarea{font:inherit}button,a,input,summary{touch-action:manipulation}
button{cursor:pointer}a{color:var(--primary);text-underline-offset:3px}a:hover{color:var(--primary-hover)}
button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible,[tabindex]:focus-visible{outline:3px solid var(--primary);outline-offset:3px}
[hidden]{display:none!important}
h1,h2,h3,h4{font-weight:700;line-height:1.4;overflow-wrap:normal;word-break:normal;text-wrap:wrap}
.lesson-title,.section-title-text{ text-wrap:pretty }
p{margin:0 0 14px}p:last-child{margin-bottom:0}ul,ol{padding-inline-start:24px;margin:10px 0 16px}li+li{margin-top:6px}
.skip-link{position:fixed;top:8px;left:12px;transform:translateY(-150%);z-index:1000;background:var(--bg-surface);padding:12px}
.skip-link:focus{transform:none}
.site-header{position:sticky;top:0;z-index:40;background:var(--bg-surface);border-bottom:1px solid var(--border-color)}
.site-header-inner{max-width:1200px;margin:auto;padding:8px var(--page-gutter);display:flex;align-items:center;gap:12px;min-height:64px}
.site-brand{display:flex;align-items:center;gap:8px;min-width:0;font-size:18px;font-weight:700;white-space:nowrap;text-decoration:none}
.logo-icon{font-size:23px}.site-actions{margin-left:auto;display:flex;align-items:center;gap:12px}
.toc-toggle,.theme-toggle-btn,#closeToc{width:44px;height:44px;flex:0 0 44px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface-soft);color:var(--text-main);display:grid;place-items:center;padding:0}
.route-link{display:inline-flex;align-items:center;gap:5px;min-height:44px;text-decoration:none;font-size:14px;font-weight:600;white-space:nowrap}
.section-progress-bar{position:sticky;top:var(--site-header-height,64px);z-index:39;display:flex;justify-content:safe center;gap:4px;padding:6px 12px;overflow-x:auto;background:var(--bg-surface);border-bottom:1px solid var(--border-color)}
.section-progress-bar a{flex:0 0 44px;min-height:44px;display:grid;place-items:center;font-size:12px;font-weight:600;text-decoration:none;border-radius:6px;color:var(--text-secondary)}
.section-progress-bar a.active{background:var(--primary-light);color:var(--primary)}
.lesson-toc{position:fixed;z-index:60;top:12px;left:12px;width:min(360px,calc(100vw - 24px));max-height:calc(100dvh - 24px);overflow:auto;background:var(--bg-surface);border:1px solid var(--border-color);border-radius:12px;padding:16px;box-shadow:0 8px 28px #0003}
.toc-header{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:12px}
.lesson-toc a{display:block;padding:10px 8px;min-height:44px;text-decoration:none;border-radius:6px}.lesson-toc a:hover{background:var(--bg-surface-soft)}
.article-wrapper{padding:24px var(--page-gutter) 0}.article-container{max-width:var(--page-width);margin-inline:auto;text-align:justify;text-justify:inter-word;text-align-last:auto}
/* Justify lesson prose through the shared shell; keep the final line natural. */
.article-container :is(p,li,figcaption,.quiz-q-prompt,.explanation-content,.warmup-opt,.warmup-option,.quiz-opt-btn>span:last-child,.station-choice>span){text-align:justify;text-justify:inter-word;text-align-last:start}
.quiz-opt-btn>span:last-child,.station-choice>span{flex:1;min-width:0}
.lesson-hero{padding:0 0 24px;margin:0;border-bottom:1px solid var(--border-color)}
.lesson-breadcrumb{display:flex;flex-wrap:wrap;align-items:center;gap:8px;font-size:13px;margin-bottom:10px;color:var(--text-muted)}
.lesson-meta{display:flex;flex-wrap:wrap;gap:6px 16px;font-size:13px;color:var(--text-muted);margin-bottom:10px}
.lesson-title{font-size:clamp(1.375rem,1rem + 1vw,1.75rem);line-height:1.4;margin:0 0 12px;max-width:none;letter-spacing:0}
.lesson-description{max-width:70ch;color:var(--text-secondary);margin-bottom:10px}
.lesson-share{display:flex;flex-wrap:wrap;gap:6px 20px;font-size:13px}.lesson-share a{display:inline-flex;align-items:center;min-height:32px}
.article-body>section{margin-top:var(--section-gap);scroll-margin-top:var(--header-clearance)}
.section-title{display:flex;align-items:baseline;gap:8px;font-size:clamp(1.25rem,1.06rem + .55vw,1.5rem);margin:0 0 16px;padding:0;max-width:none}
.section-title-number,.section-number{flex:0 0 auto;color:var(--primary)}.section-title-text{flex:1;min-width:0}
.lesson-card,.warmup-card,.lab-card,.station-card,.lesson-summary,.lesson-resources,.lesson-cta,.faq-card,.example-block,.lesson-objectives,.objectives-card,.lesson-prerequisites,.prerequisites-card{padding:var(--card-padding);background:var(--bg-surface);border:1px solid var(--border-color);border-radius:var(--card-radius);margin:16px 0}
.objectives-grid,.lesson-intro-grid{display:grid;grid-template-columns:1.2fr 1fr;gap:16px}.objectives-grid>*,.lesson-intro-grid>*{margin:0;min-width:0}
h3{font-size:18px;margin:0 0 12px}h4{font-size:16px;margin:14px 0 8px}
.callout{padding:18px 20px;margin:16px 0;border:1px solid var(--border-color);border-left:4px solid var(--primary);border-radius:8px;background:var(--bg-surface)}
.callout-warning{border-left-color:var(--danger)}.callout-tip{border-left-color:var(--success)}
.callout-title{margin:0 0 8px;font-size:17px}.callout p{color:var(--text-secondary)}
.example-block .example-prompt{font-weight:500}.example-answer{padding-top:10px;border-top:1px solid var(--border-color)}
.math-block,.katex-display{max-width:100%;overflow-x:auto;overflow-y:hidden;padding-block:8px}
.katex{font-size:1.08em}.katex-display>.katex{white-space:nowrap;max-width:none}
.warmup-options{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin:14px 0}
.warmup-option,.btn,.btn-outline,.btn-check-answer,.station-actions button,.resource-download{min-height:44px;padding:10px 14px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface);color:var(--text-main);font-weight:600;line-height:1.55;text-align:left;text-decoration:none}
.warmup-option:hover,.btn:hover,.btn-outline:hover{border-color:var(--primary);background:var(--primary-light)}
.warmup-feedback{border-left:3px solid var(--primary);padding:10px 14px;background:var(--bg-surface-soft);margin-top:12px}
.warmup-option.correct{border-color:var(--success);background:var(--success-bg)}.warmup-option.wrong{border-color:var(--danger);background:var(--danger-bg)}
.lab-header{display:block}.lab-title{width:100%;font-size:18px;margin:0 0 8px}.lab-description{color:var(--text-secondary)}
.lab-controls{display:flex;flex-wrap:wrap;gap:8px;margin:14px 0}
.lab-controls button[aria-pressed="true"]{border-color:var(--primary);background:var(--primary-light);color:var(--primary)}
.lab-controls label{display:flex;align-items:center;gap:8px;flex-wrap:wrap}.lab-controls input{max-width:100%;min-width:0;width:180px;padding:9px 12px;border:1px solid var(--border-color);border-radius:8px;color:var(--text-main);background:var(--bg-surface)}
.lesson-figure{margin:16px 0;min-width:0}.figure-stage{position:relative;width:100%;min-width:0;background:var(--bg-surface-soft);border:1px solid var(--border-color);border-radius:10px}
.figure-stage canvas,.figure-stage svg{display:block;max-width:100%;width:100%;height:auto}
.geometry-stage{height:340px;touch-action:pan-y}.geometry-stage canvas{height:100%;touch-action:none}
.figure-caption,figcaption{margin-top:10px;font-size:14px;line-height:1.65;color:var(--text-secondary)}
.figure-label{position:absolute;z-index:2;pointer-events:none;font-size:14px;font-weight:700;line-height:1.4;padding:2px 5px;color:var(--text-main);background:var(--bg-surface);border-radius:4px}
.figure-static{padding:12px}.geometry-fallback{font-size:14px;margin:8px 0 0}.figure-status{padding:8px 12px;font-size:14px;color:var(--text-secondary);min-height:40px}
.place-value-output{padding:16px;overflow-x:auto}.place-value-table{border-collapse:collapse;width:100%;min-width:540px;text-align:center}.place-value-table th,.place-value-table td{border:1px solid var(--border-color);padding:10px;font-variant-numeric:tabular-nums}.place-value-expanded{margin:12px 0 0;white-space:normal;overflow-wrap:anywhere}
.station-heading{display:flex;align-items:baseline;gap:10px;flex-wrap:wrap}.station-level{font-size:12px;color:var(--text-muted)}.station-actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}
details{margin:10px 0}summary{cursor:pointer;font-weight:600;min-height:44px;padding:8px 0}details>div,details>p{padding-top:8px}
.station-card details{border-top:1px solid var(--border-color);padding-top:6px}
.lesson-cta a,.resource-download{display:inline-flex;align-items:center;gap:8px;min-height:44px;color:var(--primary);border-color:var(--primary);margin:8px 0}
.lesson-cta .affiliate-disclosure{color:var(--text-muted);font-size:13px}
.lesson-resources .resource-status{font-size:14px;color:var(--text-muted);margin-top:10px}
.faq-card{margin:10px 0}.faq-card summary{font-size:16px;padding:0;display:list-item}
.site-footer{max-width:var(--page-width);margin:32px auto 0;padding:24px var(--page-gutter) calc(var(--audio-bar-clearance) + 24px);text-align:center;color:var(--text-secondary)}
.footer-brand{font-size:18px;font-weight:700;color:var(--primary);margin-bottom:4px}.footer-slogan{font-size:14px;margin:0 0 16px}
.footer-copyright{padding-top:16px;border-top:1px solid var(--border-color);font-size:13px;line-height:1.8}.footer-copyright p{margin:0 0 4px}
.keep-phrase{display:inline-block;white-space:nowrap;max-width:100%}
.quiz-header-bar{display:flex;flex-direction:column;gap:16px;padding:0 0 18px;border-bottom:1px solid var(--border-color);margin-bottom:20px}.quiz-header-title{font-size:20px;margin:0 0 6px}.quiz-header-description{font-size:14px;color:var(--text-muted)}
.quiz-mode-toolbar{display:flex;flex-wrap:wrap;align-items:center;gap:12px;justify-content:space-between}
.quiz-mode-pills{display:flex;flex-wrap:wrap;gap:8px}.quiz-mode-pill{min-height:44px;padding:9px 12px;background:var(--bg-surface);color:var(--text-secondary);border:1px solid var(--border-color);border-radius:8px;font-weight:600;font-size:14px}
.quiz-mode-pill.active{background:var(--primary-light);color:var(--primary);border-color:var(--primary)}
.quiz-timer{display:flex;align-items:center;gap:6px;padding:8px 12px;border-radius:8px;background:var(--danger-bg);color:var(--danger);font-weight:700;font-variant-numeric:tabular-nums;white-space:nowrap}
.quiz-timer[hidden]{display:none}#quizTimerText{white-space:nowrap}.timer-warning{outline:2px solid #d97706}.timer-urgent{outline:2px solid var(--danger)}
.quiz-part-block{margin:24px 0}.quiz-part-header{display:flex;flex-direction:column;align-items:flex-start;gap:8px;margin-bottom:14px}
.quiz-part-title{font-size:17px;margin:0}.quiz-part-badge{font-size:12px;color:var(--text-secondary);padding:5px 10px;background:var(--bg-surface-soft);border-radius:6px;line-height:1.8}
.quiz-q-item{margin:14px 0;padding:18px;border:1px solid var(--border-color);border-radius:10px;background:var(--bg-surface)}
.quiz-q-prompt{margin-bottom:12px;line-height:1.75}.quiz-options-grid{display:grid;grid-template-columns:1fr;gap:8px}
.quiz-opt-btn{width:100%;display:flex;align-items:baseline;gap:10px;padding:10px 12px;min-height:44px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface);color:var(--text-main);text-align:left;line-height:1.65}
.opt-letter{font-weight:700;flex:0 0 auto}.quiz-opt-btn.selected{border-color:var(--primary);background:var(--primary-light)}.quiz-opt-btn.correct{border-color:var(--success);background:var(--success-bg)}.quiz-opt-btn.wrong{border-color:var(--danger);background:var(--danger-bg)}
.quiz-check-row{margin-top:12px}.btn-check-answer{display:inline-flex;align-items:center;flex-wrap:wrap;gap:4px;background:var(--primary-light);border-color:var(--primary);color:var(--primary);font-size:14px}
.quiz-action-bar{margin-top:24px;display:flex}.quiz-action-bar .btn-check-answer{justify-content:center;text-align:center}
.quiz-explanation-box{display:none;padding:14px 16px;margin-top:14px;background:var(--bg-surface-soft);border:1px solid var(--border-color);border-radius:8px}
.quiz-explanation-box.show{display:block}.explanation-title{font-weight:700;margin-bottom:8px}.title-correct{color:var(--success)}.title-wrong{color:var(--danger)}
.quiz-tf-table-scroll{max-width:100%;overflow-x:auto}.quiz-tf-table{width:100%;border-collapse:collapse;table-layout:fixed;min-width:0;font-size:14px}
.quiz-tf-table th,.quiz-tf-table td{border:1px solid var(--border-color);padding:10px;vertical-align:top}.quiz-tf-table th{background:var(--bg-surface-soft);text-align:left}.quiz-tf-table .col-choice{width:52px;text-align:center;padding:4px}
.tf-radio-label{position:relative;display:flex;align-items:center;justify-content:center;gap:2px;min-height:44px;border:1px solid transparent;border-radius:6px;cursor:pointer}.tf-radio-input{margin:0;accent-color:var(--primary);width:17px;height:17px}
.selected-true,.selected-false{background:var(--primary-light)}.answer-key-true{border-color:var(--success)}.answer-key-false{border-color:var(--danger)}
.quiz-short-row{display:flex;flex-wrap:wrap;align-items:center;gap:10px}.quiz-short-label{font-weight:600;width:100%}.quiz-short-input{width:180px;max-width:100%;min-width:0;min-height:44px;padding:8px 12px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface);color:var(--text-main)}.quiz-short-input.correct{border-color:var(--success)}.quiz-short-input.wrong{border-color:var(--danger)}.quiz-unit{font-size:14px;color:var(--text-muted)}
.quiz-result-summary{display:none;margin-top:24px}.quiz-result-summary.show{display:block}.quiz-result-card{background:var(--primary-light);color:var(--text-main);border-radius:12px;padding:24px;text-align:center;border:1px solid var(--primary)}.quiz-result-card h3{font-size:20px}.quiz-score{font-size:42px;line-height:1.3;font-weight:700;margin:12px 0}.quiz-score-unit{font-size:20px}
.diagnostic-report-card{padding:20px;border:1px solid var(--border-color);border-radius:12px;margin-top:16px;background:var(--bg-surface)}
.diagnostic-coach-header{display:flex;align-items:flex-start;gap:12px;margin-bottom:16px}.coach-avatar{font-size:28px;flex:0 0 auto}.coach-title{font-weight:700;font-size:17px;margin-bottom:8px}.coach-quote{font-size:14px;color:var(--text-secondary)}.diagnostic-warning,.diagnostic-item-title{color:var(--danger);font-weight:600}.diagnostic-weakness-item{margin-top:12px;padding:14px;background:var(--bg-surface-soft);border-radius:8px}.diagnostic-item-description{font-size:14px;margin-top:6px}
.btn-jump-review{border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface);color:var(--primary);min-height:44px;padding:9px 12px;margin-top:10px;text-align:left;font-weight:600;line-height:1.6}.diagnostic-success{padding:14px;border-radius:8px;background:var(--success-bg);color:var(--success)}
.smart-audio-bar{position:fixed;z-index:45;bottom:0;left:0;right:0;padding:10px max(16px,env(safe-area-inset-left)) calc(10px + env(safe-area-inset-bottom));border-top:1px solid var(--border-color);background:var(--bg-surface);display:flex;align-items:center;justify-content:center;gap:20px;flex-wrap:wrap}
.audio-bar-left,.audio-bar-right{display:flex;align-items:center;gap:8px;min-width:0}.audio-bar-left{flex:1;max-width:700px}.audio-bar-right{flex:0 0 auto}
.narrator-nav-btn,.audio-play-btn,.speed-badge-btn{min-width:44px;min-height:44px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface-soft);color:var(--text-main);padding:8px;font-weight:600;line-height:1.4}.audio-play-btn{background:var(--primary-light);color:var(--primary)}
.audio-info-col{min-width:0;flex:1}.audio-title-status{font-size:13px;font-weight:600}.audio-sub-hint{font-size:11px;color:var(--text-muted);line-height:1.5;margin-top:2px}
.autoscroll-toggle-label{display:flex;align-items:center;gap:6px;font-size:12px;min-height:44px}.autoscroll-toggle-label input{accent-color:var(--primary)}
.narrator-progress-wrap{height:3px;background:var(--border-color);margin-top:6px;border-radius:2px}.narrator-progress-fill{height:100%;width:0;background:var(--primary)}
.narrator-error-message{width:100%;font-size:13px;color:var(--danger);max-width:920px}.narrator-onboard-tooltip{display:none}.karaoke-word.active{background:var(--primary-light);color:var(--primary)}
.lesson-resume{position:fixed;z-index:46;bottom:var(--audio-bar-clearance);left:16px;right:16px;max-width:580px;margin:auto;background:var(--bg-surface);border:1px solid var(--primary);border-radius:12px;padding:16px}.lesson-resume p{font-size:14px;margin-bottom:10px}.resume-actions{display:flex;gap:8px;flex-wrap:wrap}.resume-actions button{min-height:44px;padding:8px 14px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface-soft);color:var(--text-main)}
.thayan-toast{position:fixed;bottom:var(--audio-bar-clearance);left:16px;right:16px;z-index:90;background:var(--text-main);color:var(--bg-surface);padding:14px;border-radius:8px;display:none}.thayan-toast.show{display:block}
.thayan-modal-overlay{position:fixed;inset:0;z-index:100;background:#0008;display:grid;place-items:center;padding:16px}.thayan-modal-card{background:var(--bg-surface);border-radius:12px;padding:24px;max-width:480px;max-height:90dvh;overflow:auto}.thayan-modal-overlay input{max-width:100%;padding:10px;border:1px solid var(--border-color);color:var(--text-main);background:var(--bg-surface)}
@media(min-width:768px){.quiz-options-grid.two-cols{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:640px){
 :root{--page-gutter:16px;--card-padding:18px;--section-gap:24px}
 .site-header-inner{gap:8px;padding:7px 12px;min-height:60px}.site-brand{gap:5px;font-size:15px}.logo-icon{font-size:20px}.site-actions{gap:6px}.route-link{font-size:13px}
 .section-progress-bar{gap:2px;justify-content:safe center;padding:4px 12px}
 .article-wrapper{padding-top:18px}.lesson-hero{padding-bottom:18px}.lesson-title{font-size:20px;margin-bottom:10px}.lesson-breadcrumb{font-size:12px;gap:6px;margin-bottom:8px}.lesson-meta{font-size:12px;gap:4px 12px;margin-bottom:8px}
 .lesson-description{font-size:15px;line-height:1.65}.section-title{font-size:20px;margin-bottom:14px}
 .objectives-grid,.lesson-intro-grid{grid-template-columns:1fr}.warmup-options{grid-template-columns:1fr}
 .lab-title{font-size:18px}.lab-controls{gap:8px}.lab-controls button{font-size:14px;flex:1 1 auto}
 .geometry-stage{height:280px}.quiz-q-item{padding:14px}.quiz-tf-table{font-size:13px}.quiz-tf-table td,.quiz-tf-table th{padding:8px}.quiz-tf-table .col-choice{width:46px;padding:1px}.tf-radio-label{gap:0;flex-direction:column;padding:2px}
 .quiz-result-card{padding:18px}.quiz-score{font-size:36px}
 .smart-audio-bar{gap:6px 12px;padding:8px 12px calc(8px + env(safe-area-inset-bottom));justify-content:space-between}.audio-bar-left{gap:5px}.audio-bar-right{gap:5px}.audio-sub-hint{display:none}.autoscroll-toggle-label{display:none}.audio-title-status{font-size:11px;line-height:1.5}.audio-info-col{margin-left:3px}
 .narrator-nav-btn,.audio-play-btn,.speed-badge-btn{min-width:44px;min-height:44px;padding:6px}
 .site-footer{margin-top:24px}.footer-copyright{font-size:12px}
}
@media(max-width:350px){.site-header-inner{gap:5px;padding-inline:8px}.site-brand{font-size:14px;gap:3px}.site-actions{gap:4px}.route-link{font-size:12px}.logo-icon{font-size:18px}.audio-title-status{font-size:10px}.audio-bar-left{gap:3px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}

/* Aliases match the single renderer and keep spacing owned by the shell. */
.lesson-callout{padding:18px 20px;margin:16px 0;border:1px solid var(--border-color);border-left:4px solid var(--primary);border-radius:8px;background:var(--bg-surface)}
.lesson-callout.callout-warning{border-left-color:var(--danger)}.lesson-callout.callout-tip{border-left-color:var(--success)}
.lesson-example,.warmup-box,.lesson-self-check,.lesson-shop-cta{padding:var(--card-padding);margin:16px 0;background:var(--bg-surface);border:1px solid var(--border-color);border-radius:var(--card-radius)}
.warmup-opt,.lab-control-btn{min-height:44px;padding:10px 14px;border:1px solid var(--border-color);border-radius:8px;background:var(--bg-surface);color:var(--text-main);font-weight:600;line-height:1.6;text-align:left}
.warmup-opt:hover,.lab-control-btn:hover{border-color:var(--primary);background:var(--primary-light)}
.warmup-opt.correct{border-color:var(--success);background:var(--success-bg)}.warmup-opt.wrong{border-color:var(--danger);background:var(--danger-bg)}
.warmup-feedback:empty{display:none}.lab-feedback{font-size:14px;color:var(--text-secondary);margin-top:10px}
.resource-btn,.lesson-shop-cta>a{display:inline-flex;align-items:center;min-height:44px;padding:10px 14px;margin:8px 0;border:1px solid var(--primary);border-radius:8px;color:var(--primary);background:var(--primary-light);font-weight:600;text-decoration:none;line-height:1.6}
.lesson-shop-cta>p{font-size:13px;color:var(--text-muted)}
.faq-item{padding:16px var(--card-padding);margin:10px 0;background:var(--bg-surface);border:1px solid var(--border-color);border-radius:var(--card-radius)}
.station-answer-form{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin:14px 0}
.station-answer-form>label{width:100%;font-weight:600}.station-answer-form fieldset{width:100%;min-width:0;margin:0;padding:12px;border:1px solid var(--border-color);border-radius:8px}
.station-answer-form legend{font-size:14px;padding:0 6px}.station-choice{display:flex;align-items:center;gap:8px;min-height:44px;padding:8px 10px;border:1px solid var(--border-color);border-radius:6px;margin:6px 0;background:var(--bg-surface)}
.station-choice input{width:18px;height:18px;flex:0 0 auto;accent-color:var(--primary)}
.station-feedback{font-size:14px;margin:10px 0;padding:10px 12px;background:var(--bg-surface-soft);border-radius:8px}.station-feedback:empty{display:none}.station-feedback.correct{color:var(--success);background:var(--success-bg)}.station-feedback.wrong{color:var(--danger);background:var(--danger-bg)}
.place-value-expanded{padding:0 16px 16px}
@media(max-width:640px){.warmup-opt,.lab-control-btn{font-size:14px}}

/* Persistent heading hierarchy: colour and borders supplement the written labels. */
.lesson-title,.section-title,.article-body h3{color:var(--primary)}
.lesson-callout h3,.callout-title{color:var(--primary)}
.lesson-callout.callout-warning{background:var(--danger-bg)}
.lesson-callout.callout-warning h3{color:var(--danger)}
.lesson-callout.callout-tip{background:var(--success-bg)}
.lesson-callout.callout-tip h3{color:var(--success)}
.lesson-callout.callout-definition{background:var(--primary-light)}