:root{font-family:ui-rounded,'Trebuchet MS',Arial,sans-serif;color:#163d46;background:#f4f7f2;line-height:1.55}*{box-sizing:border-box}body{margin:0}header{display:flex;justify-content:space-between;gap:20px;align-items:center;padding:22px max(5%,calc((100% - 1080px)/2));background:#fff;border-bottom:1px solid #d5e1dd}a{color:#125f67}.brand{font-weight:800;text-decoration:none}main{max-width:1080px;margin:36px auto;padding:0 24px}h1{font-size:clamp(2rem,5vw,3.6rem);line-height:1.1;letter-spacing:-.04em}h2{font-size:1.7rem;line-height:1.25}h3{margin-top:0}.eyebrow{font-size:.8rem;letter-spacing:.15em;font-weight:bold;text-transform:uppercase;color:#48675e}.hero{padding:30px 0 36px;max-width:770px}.lead{font-size:1.3rem}.card,article{padding:28px;background:white;border:1px solid #d6e2db;border-radius:20px;margin:18px 0;box-shadow:0 6px 0 #e7ede5}.pilot{display:grid;grid-template-columns:1fr 1fr;gap:32px;align-items:center}.tag{display:inline-block;border-radius:30px;background:#e4f1c9;padding:5px 12px;font-size:.8rem;font-weight:bold}button,.button{font:inherit;cursor:pointer;border:2px solid #c1d3ce;background:white;color:#163d46;border-radius:12px;padding:12px 18px;min-height:48px;margin:5px 6px 5px 0;display:inline-block;text-decoration:none}button:hover,.button:hover{border-color:#14736f;background:#edf7f3}.primary{background:#176a64;color:white;border-color:#176a64}button:disabled{opacity:.55;cursor:default}button[aria-pressed=true]{background:#d8eddf;border-color:#176a64}button:focus-visible,a:focus-visible,input:focus-visible{outline:4px solid #df981c;outline-offset:4px}.choices{display:grid;gap:10px;margin:22px 0}.choices label{border:2px solid #d6e2db;padding:14px;border-radius:12px;display:flex;align-items:center;gap:12px;cursor:pointer}.choices label:has(input:checked){border-color:#176a64;background:#ecf6ee}input{width:22px;height:22px;flex-shrink:0}.feedback{padding:14px;background:#edf4e7;border-radius:10px;min-height:28px}.layout{display:grid;grid-template-columns:220px 1fr;gap:28px}nav button{display:block;width:100%;text-align:left;margin-bottom:8px}nav .active{background:#d8eddf;border-color:#176a64}.twins{display:grid;grid-template-columns:1fr 1fr;gap:16px}svg{width:100%;height:auto;max-height:340px;background:#f5f7ee;border-radius:16px}.state{font-weight:bold;display:flex;flex-wrap:wrap;gap:16px}small,.muted{color:#4b665f}.safety{border-left:5px solid #d49e3c;padding:16px 22px;background:#fff8e8;border-radius:8px}footer{max-width:1080px;padding:24px;margin:40px auto;font-size:.85rem;color:#52675f}#storage{max-width:1032px;margin:12px auto}.preview{background:#ffedac;padding:18px;position:sticky;top:0;z-index:2}dl{display:grid;grid-template-columns:minmax(130px,1fr) 2fr;gap:10px}dt{font-weight:bold}dd{margin:0;overflow-wrap:anywhere}.badge{padding:20px;background:#e4f1c9;border-radius:16px;font-weight:bold}progress{width:100%;accent-color:#176a64}details{padding:14px;border-bottom:1px solid #d6e2db}summary{cursor:pointer;font-weight:bold}.trace-buttons{display:flex;flex-wrap:wrap}.trace-buttons button{min-width:66px} @media(max-width:700px){.layout,.pilot,.twins{grid-template-columns:1fr}nav{display:flex;overflow:auto;gap:8px}nav button{width:auto;min-width:118px}main{padding:0 16px;margin-top:20px}.card,article{padding:20px}header{padding:16px;align-items:flex-start}.brand{max-width:210px}dl{grid-template-columns:1fr}h1{font-size:2.4rem}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}

/* Student hierarchy: the picture and the current action come first. */
header{flex-wrap:wrap}
.site-links{display:flex;flex-wrap:wrap;gap:8px 18px;align-items:center}
.site-links a{display:inline-flex;align-items:center;min-height:48px}
.prototype-note{max-width:1032px;margin:16px auto;padding:12px 16px;background:#fff8e8;border-left:4px solid #a87922;border-radius:6px;font-size:.9rem}
main,article,.student-page .twins>section{min-width:0}
button,.button,.choices label,legend{overflow-wrap:anywhere}
@media(max-width:700px){.prototype-note{margin:12px 16px}.site-links{width:100%}}
[hidden]{display:none!important}
.sr-only{position:absolute!important;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap;border:0}
.student-page{max-width:1240px}
.student-page .hero{padding:0 0 12px;max-width:none}
.student-page .hero h1{font-size:clamp(2rem,4vw,3rem);margin:0 0 12px}
.student-page .lead{margin:0;font-size:1.2rem}
.student-page .layout{display:block}
.student-page .activity-card{padding:24px 32px;margin-top:12px}
.student-page .activity-heading{display:flex;align-items:center;gap:14px;margin-bottom:20px}
.student-page .activity-heading h2{margin:0;font-size:1.8rem}
.student-page .activity-heading .eyebrow{margin-left:auto;font-size:.72rem}
.student-page .step-number{display:grid;place-items:center;background:#176a64;color:#fff;width:48px;height:48px;flex-shrink:0;border-radius:50%;font-size:1.3rem;font-weight:bold}
.student-page .step-menu{padding:0;border:1px solid #c1d3ce;background:#fff;border-radius:12px}
.student-page .step-menu>summary{padding:12px 18px}
.student-page .step-menu>summary span{float:right}
.student-page .step-menu nav{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));padding:12px;gap:8px;overflow:visible}
.student-page nav button{margin:0;min-width:0}
.student-page svg{display:block;width:100%;height:auto;max-height:none;border-radius:20px}
.student-page .model-stage{width:100%;margin:8px auto 18px}
.student-page .model-stage>svg{aspect-ratio:520/300}
.student-page .model-stage>small{display:block;font-size:.76rem;margin-top:8px}
.student-page .model-stage>.state{margin:12px 0 4px;gap:8px;align-items:center;font-size:1rem}
.student-page .state>span{padding:6px 12px;background:#e8efea;border:1px solid #cadbd1;border-radius:30px}
.student-page .state .lamp-status{font-size:1.12rem;border:2px solid #526b61;display:inline-flex;align-items:center;gap:6px}
.student-page .state .is-on{background:#ffe7a2;color:#493511;border-color:#927327}
.student-page .state .is-off{background:#fff;color:#163d46}
.student-page .state .is-hidden{background:#f1eee4;color:#163d46}
.student-page .path-guide{margin-top:6px;font-size:.85rem}
.student-page button{min-height:56px;padding:14px 24px;font-size:1.05rem;font-weight:600}
.student-page button.primary{min-height:64px;font-size:1.18rem;padding:16px 30px}
.student-page button.primary:hover{background:#10534f;color:#fff;border-color:#10534f}
.student-page .model-controls{display:flex;align-items:center;flex-wrap:wrap;gap:10px;margin:10px 0 18px}
.student-page .model-controls button{margin:0;flex:1;min-width:150px}
.student-page #reset-model,.student-page #trace-reset{flex:0 1 auto;font-size:.95rem;min-width:120px}
.student-page .action-prompt{font-size:1.25rem;font-weight:700;margin:12px 0 18px}
.student-page .activity-navigation{display:flex;justify-content:space-between;align-items:center;border-top:1px solid #d6e2db;margin-top:24px;padding-top:16px;gap:12px}
.student-page .activity-navigation button{margin:0}
.student-page .learn-panel{border:1px solid #cfddd5;border-radius:12px;margin:14px 0;padding:0;background:#f8faf6}
.student-page .learn-panel>summary{padding:12px 16px;min-height:48px;color:#205c57}
.student-page .learn-panel>p,.student-page .learn-panel>dl,.student-page .learn-panel>ul{margin:14px 20px}
.student-page .learn-panel p{max-width:70ch}
.student-page .choices{border:0;padding:0;margin:20px 0 12px;grid-template-columns:1fr 1fr;gap:12px;min-width:0}
.student-page .choices legend{font-size:1.35rem;line-height:1.35;font-weight:700;width:100%;margin-bottom:18px;padding:0}
.student-page .choices label{font-size:1.1rem;min-height:76px;padding:18px;background:#fff;border-color:#b8cec5}
.student-page .choices input{width:25px;height:25px;accent-color:#176a64}
.student-page .choices label:has(input:checked){background:#e5f1e7;border:3px solid #176a64;padding:17px}
.student-page .answer-action{display:flex;justify-content:flex-end;margin-top:12px}
.student-page .feedback{margin:14px 0 0;padding:14px 18px;min-height:0;font-weight:600}
.student-page .feedback:empty,.student-page .hint-text:empty{display:none}
.student-page .feedback button{display:inline-block;margin-left:12px;background:#fff}
.student-page .hint-text{background:#fff7df;border-left:4px solid #a88225;padding:14px 18px}
.student-page .pilot{display:block;padding:24px 32px}
.student-page .pilot-heading{display:flex;align-items:center;gap:18px;margin-bottom:16px}
.student-page .pilot-heading h2{margin:0;font-size:1.6rem}
.student-page .pilot-heading .tag{white-space:nowrap}
.student-page .pilot .model-stage{max-width:900px}
.student-page .home-action{display:flex;align-items:center;justify-content:space-between;gap:16px}
.student-page .home-action button{min-width:220px}
.student-page .progress-chip{display:inline-block;background:#e8efea;border-radius:24px;padding:6px 12px;font-size:.9rem;font-weight:600;color:#234e48}
.student-page .observation-choices{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.student-page .observation-choices button{display:flex;align-items:center;gap:18px;text-align:left;min-height:100px;margin:0;font-size:1.2rem}
.student-page .choice-symbol{font-size:2.2rem;line-height:1;width:48px;text-align:center;flex-shrink:0}
.student-page .activity-symbol{display:grid;place-items:center;width:120px;height:120px;border:3px solid #7da49a;background:#eaf3e8;border-radius:50%;margin:20px auto;font-size:4rem;font-weight:700;color:#23564f}
.student-page .trace-buttons{gap:10px;margin:14px 0}
.student-page .trace-buttons button{flex:1;min-width:66px;min-height:72px;margin:0;font-size:1.5rem}
.student-page .trace-buttons button[aria-pressed=true]{border-width:4px;text-decoration:underline;text-underline-offset:5px}
.student-page .trace-status{padding:14px 18px;background:#eaf3e8;border-radius:12px;font-weight:700}
.student-page .twins{gap:24px}
.student-page .twins h3{font-size:1.2rem;margin:0 0 10px}
.student-page .twins .state{font-size:.85rem;gap:5px}
.student-page .twins .state>span{padding:4px 8px}
.student-page .twins .state .lamp-status{font-size:1rem}
.student-page .uncertain-panel{padding:16px;background:#fff7e5;border:2px solid #9b7b31;border-radius:20px;text-align:center;margin:16px 0;font-size:1.2rem;font-weight:600}
.student-page .uncertain-panel p{margin:8px 0}
.student-page .question-marker{display:flex;align-items:center;gap:18px;font-weight:700;font-size:1.2rem}
.student-page .question-marker .progress-chip{margin-left:auto}
.student-page .question-icon{display:grid;place-items:center;width:80px;height:80px;border-radius:20px;background:#e4efde;font-size:2.8rem;color:#20564e}
.student-page .question-navigation{display:flex;justify-content:space-between;flex-wrap:wrap;gap:8px;margin:12px 0}
.student-page .reflection-prompts details{border:2px solid #c1d3ce;border-radius:16px;padding:0;margin:12px 0;background:#fff}
.student-page .reflection-prompts summary{padding:20px;min-height:64px;font-size:1.2rem}
.student-page .reflection-prompts details[open]{border-color:#176a64;background:#edf5e9}
.student-page .reflection-prompts p{font-size:1.35rem;margin:8px 20px 24px}
.student-page .score-cards{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin:24px 0}
.student-page .score-cards>div{display:flex;flex-direction:column;align-items:center;gap:8px;padding:24px 16px;background:#edf4e7;border:2px solid #aec5b5;border-radius:20px;text-align:center}
.student-page .score-cards strong{font-size:3rem;line-height:1.2}
.student-page .badge{padding:24px;text-align:center;font-size:1.6rem}
.safety-compact{padding:14px 18px;margin-top:20px;font-size:.9rem}
.safety-visible{display:flex;gap:12px;align-items:center}
.safety-visible>span{font-size:1.5rem;flex-shrink:0}
.safety-visible p{margin:2px 0;font-weight:600}
.safety-compact>details{padding:8px 0 0;border:0}
.safety-compact summary{min-height:44px;display:list-item;padding:8px 0}
#storage{padding:0 16px}
#storage .storage-alert{padding:12px 16px;background:#fff2ce;border:1px solid #9b7b31;border-radius:10px;margin:8px 0;font-weight:bold;color:#473912}
#storage details{padding:0 12px;background:#fffaf0;border:1px solid #d9cda4;border-radius:10px}
#storage summary{padding:12px 0;min-height:48px}
summary:focus-visible{outline:4px solid #b66b00;outline-offset:4px;border-radius:6px}
@media(max-width:700px){
 .student-page .activity-card,.student-page .pilot{padding:18px 14px}
 .student-page .activity-heading{gap:10px;margin-bottom:14px}
 .student-page .activity-heading .eyebrow{display:none}
 .student-page .activity-heading h2{font-size:1.5rem}
 .student-page .step-number{width:40px;height:40px}
 .student-page .step-menu nav{grid-template-columns:1fr 1fr;display:grid}
 .student-page .pilot-heading{display:block}
 .student-page .pilot-heading h2{font-size:1.4rem;margin-top:12px}
 .student-page .model-stage{margin:10px 0 16px}
 .student-page .model-stage>.state{font-size:.85rem;gap:5px}
 .student-page .state>span{padding:4px 8px}
 .student-page .state .lamp-status{font-size:1rem}
 .student-page .choices{grid-template-columns:1fr;gap:10px}
 .student-page .choices legend{font-size:1.15rem}
 .student-page .choices label{padding:14px;min-height:64px;font-size:1rem}
 .student-page .choices label:has(input:checked){padding:13px}
 .student-page .model-controls button{min-width:0;flex:1 1 40%;padding:12px;font-size:1rem}
 .student-page #reset-model,.student-page #trace-reset{flex-basis:100%;min-height:48px}
 .student-page .home-action{flex-direction:column;align-items:stretch;gap:8px}
 .student-page .home-action button,.student-page .answer-action button{width:100%;min-width:0}
 .student-page .home-action .progress-chip{text-align:center;align-self:center}
 .student-page .observation-choices{grid-template-columns:1fr}
 .student-page .observation-choices button{min-height:78px;font-size:1.05rem}
 .student-page .activity-symbol{width:88px;height:88px;font-size:3rem}
 .student-page .trace-buttons{display:grid;grid-template-columns:repeat(3,1fr)}
 .student-page .trace-buttons button{min-width:0;min-height:64px}
 .student-page .twins{grid-template-columns:1fr;gap:20px}
 .student-page .question-marker{font-size:1rem;gap:10px;flex-wrap:wrap}
 .student-page .question-icon{width:56px;height:56px;font-size:2rem}
 .student-page .question-marker .progress-chip{margin-left:0}
 .student-page .question-navigation>button{flex:1;min-width:0;font-size:.95rem;padding:12px}
 .student-page .question-navigation>button.primary{font-size:1rem}
 .student-page .score-cards{gap:10px}
 .student-page .score-cards strong{font-size:2.2rem}
 .student-page .score-cards>div{padding:18px 8px;font-size:.9rem}
 .student-page .feedback button{display:block;margin:12px 0 0;width:100%}
 .student-page .action-prompt{font-size:1.1rem}
}
@media(min-width:701px){.student-page #prediction-model{max-width:960px}.student-page #diagram,.student-page #trace-diagram{max-width:1050px}}
/* Keep the picture large while leaving room for the current action. */
@media(min-width:701px){
 .student-page .model-stage>svg{height:min(43vh,420px);min-height:250px;aspect-ratio:auto}
 .student-page .twins .model-stage>svg{height:auto;min-height:0;aspect-ratio:480/260}
 .student-page .pilot .model-stage>svg{height:min(40vh,390px);min-height:240px}
}
@media(max-width:700px){.student-page .model-stage>svg{aspect-ratio:480/260}}
/* Generic object pictures: no branded parts or schematic symbols. */
.student-page .pictorial-circuit{background:#f8f7ec}
.student-page .parts-reminder{max-width:1000px;margin:12px auto 20px}
.student-page .parts-reminder>svg,.student-page .uncertain-panel>svg{width:100%;height:auto;max-height:none;aspect-ratio:800/220;background:#fff}
.student-page .parts-reminder>small,.student-page .uncertain-panel>small{display:block;font-size:.76rem;margin-top:6px;font-weight:normal}
.student-page .quiz-picture{max-width:900px}
.student-page .model-stage>svg.pictorial-circuit{aspect-ratio:770/405}
@media(min-width:701px){
 .student-page .model-stage>svg.pictorial-circuit{aspect-ratio:auto}
 .student-page .twins .model-stage>svg.pictorial-circuit{aspect-ratio:770/405}
}
@media(max-width:700px){
 .student-page .parts-reminder>svg,.student-page .uncertain-panel>svg{min-height:110px}
 .student-page .quiz-picture{margin-bottom:14px}
}