@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Manrope:wght@400;500;600;700;800&display=swap');
:root{color-scheme:light;--ink:#22342d;--muted:#72796e;--paper:#f7f7f0;--line:#dce0d5;--green:#315e48;--orange:#d78443;--blue:#4c9daa;--purple:#8581b5;--yellow:#c1a64d;font-family:'DM Sans',system-ui,sans-serif;background:var(--paper);color:var(--ink)}
*{box-sizing:border-box}body{margin:0}button,input{font:inherit}button{cursor:pointer}button,a,input,summary{touch-action:manipulation}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:2px solid var(--green);outline-offset:4px}button{color:inherit}a{color:inherit}button:disabled{cursor:default;opacity:.35}button{border:0}button:active{transform:translateY(1px)}.skip{position:absolute;left:20px;top:-100px;z-index:10;background:var(--paper);padding:10px}.skip:focus{top:10px}.masthead{height:88px;margin:0 44px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);gap:20px}.brand{text-decoration:none;font-weight:800;letter-spacing:.08em;font-size:15px;display:flex;align-items:center;gap:12px;white-space:nowrap}.brand-mark{background:var(--green);color:var(--paper);height:34px;width:34px;border-radius:50%;display:grid;place-items:center;font-size:30px;font-weight:400;line-height:1}.slash{color:#99a497;margin:0 4px}.project-label{font-size:10px;letter-spacing:.13em;color:var(--muted);font-weight:600}.project-label span{margin-left:22px;color:var(--green)}nav{display:flex;align-items:center;gap:25px}.text-button{background:transparent;font-size:12px;padding:6px 0}.tour-button{background:var(--green);color:var(--paper);padding:12px 17px;border-radius:5px;font-size:12px;display:flex;align-items:center;gap:12px;font-weight:600}.tour-button:hover{background:#244a38}main{padding:0 44px}.intro{display:flex;align-items:center;justify-content:space-between;padding:32px 0 28px;gap:30px}.eyebrow{font-size:10px;letter-spacing:.13em;font-weight:600;color:var(--muted);display:flex;align-items:center;gap:7px}.status-dot{width:5px;height:5px;border-radius:50%;display:inline-block;background:var(--green);flex-shrink:0}h1{font-family:'Manrope',sans-serif;font-size:clamp(24px,2.4vw,36px);letter-spacing:-.045em;line-height:1.28;font-weight:600;margin:9px 0 0}h1 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button{background:transparent;border-radius:3px;font-size:10px;padding:8px 10px}.view-switch button[aria-pressed=true]{background:var(--green);color:var(--paper)}.camera-tools{display:flex;gap:5px}.camera-tools button{height:31px;width:33px;background:rgba(247,247,240,.95);border:1px solid #d5ddcf;border-radius:5px;font-size:17px;display:grid;place-items:center}.scene-bottom{position:absolute;bottom:0;left:0;right:0;border-top:1px solid #d3ddce;min-height:65px;display:flex;justify-content:space-between;align-items:center;padding:12px 20px;gap:10px;background:#e5ecdf}.flow-switch{display:flex;align-items:center;flex-wrap:wrap;gap:3px}.flow-switch button{font-size:10px;background:transparent;display:flex;align-items:center;gap:5px;border-radius:3px;padding:7px 8px}.flow-switch button[aria-pressed=true]{background:#d4dfcc;font-weight:600}.swatch{display:inline-block;width:6px;height:6px;border-radius:50%}.fuel{background:var(--orange)}.electric{background:var(--yellow)}.cooling{background:var(--blue)}.data{background:var(--purple)}.orbit-hint{font-size:9px;color:#7d8b78;white-space:nowrap}.lesson{padding:24px 24px 18px;display:flex;flex-direction:column;background:var(--paper);border-left:1px solid var(--line);min-width:0}.lesson-top{display:flex;align-items:center;justify-content:space-between;gap:8px;font-size:8px;letter-spacing:.06em;color:var(--muted)}.concept-badge{font-size:7px;letter-spacing:.05em;padding:4px 5px;background:#eaece2;border-radius:2px;white-space:nowrap}.chapter-dots{display:flex;gap:5px;margin:20px 0 18px}.chapter-dots button{flex:1;height:5px;background:#dfe3d7;padding:0;border-radius:2px;position:relative}.chapter-dots button:before{content:'';position:absolute;inset:-7px 0}.chapter-dots 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0;font-size:10px;color:var(--green);display:flex;gap:12px;align-items:center}.lesson-nav #prev-system{font-size:18px;min-width:20px}.lesson-nav #tour-pause{font-size:9px}.tour-progress{margin-bottom:15px}.tour-progress>div:first-child{font-size:8px;display:flex;justify-content:space-between;color:var(--muted);letter-spacing:.04em;margin-bottom:5px}.tour-track{height:3px;background:#e2e6da}.tour-track>div{height:100%;background:var(--green);width:0}.assumptions{display:grid;grid-template-columns:1.05fr 1fr 1fr 1fr;margin-top:30px;padding:4px 0 28px;gap:28px}.assumptions-title h2{font-family:'Manrope',sans-serif;font-size:22px;font-weight:500;line-height:1.25;letter-spacing:-.04em;margin:9px 0}.assumptions-title>p{color:var(--muted);font-size:11px;line-height:1.7;margin:0}.assumptions-title .text-button{font-size:10px;color:var(--green);margin-top:12px}.assumption-field{border-left:1px solid 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24px;font-size:9px;color:#8a9383;display:flex;justify-content:space-between;gap:20px;align-items:center}footer button{background:transparent;color:#687e5e;font-size:9px;display:flex;gap:15px;align-items:center}dialog{border:1px solid var(--line);background:var(--paper);color:var(--ink);max-width:800px;width:calc(100% - 40px);max-height:85vh;border-radius:10px;padding:30px;box-shadow:0 30px 100px #122b2a33}dialog::backdrop{background:#183b2f66;backdrop-filter:blur(5px)}.dialog-header{display:flex;justify-content:space-between;align-items:flex-start;gap:20px}.dialog-header h2{font-family:'Manrope',sans-serif;font-size:28px;letter-spacing:-.04em;line-height:1.2;font-weight:500}.dialog-header button{background:#e7ecdf;border-radius:50%;width:32px;height:32px;flex-shrink:0;font-size:24px}.dialog-intro{font-size:13px;line-height:1.7;color:var(--muted);margin:0 0 25px}.ledger-row{border-top:1px solid var(--line);display:grid;grid-template-columns:85px 155px 1fr;gap:15px;padding:17px 0;align-items:start}.ledger-row .type{font-size:9px;background:#e7ecdf;padding:5px 7px;border-radius:3px;justify-self:start}.ledger-row h3{font-size:12px;font-weight:500;margin:3px 0}.ledger-row p{font-size:11px;line-height:1.7;margin:0;color:var(--muted)}.ledger-row a{color:var(--green)}.research-next{background:#e9eddf;padding:18px;margin-top:20px;border-radius:5px}.research-next h3{font-size:14px;margin:0 0 8px;font-weight:500}.research-next p{font-size:12px;line-height:1.7;margin:0;color:#6e7c60}.dialog-footnote{font-size:10px;line-height:1.7;color:var(--muted);margin-bottom:0}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}button[hidden],div[hidden]{display:none}
@media(min-width:1500px){main,.masthead{max-width:1540px;margin-left:auto;margin-right:auto}main{padding:0 50px}.masthead{padding:0 50px}.world-panel{min-height:640px}.explorer{grid-template-columns:minmax(0,1fr) 350px}.lesson{padding:30px}.lesson h2{font-size:32px}.lesson-summary{font-size:14px}.system-steps li{font-size:12px}}
@media(max-width:1100px){.masthead{margin:0 24px}.project-label{display:none}main{padding:0 24px}.intro>p{display:none}.explorer{grid-template-columns:minmax(0,1fr) 280px}.lesson{padding:20px}.world-panel{min-height:560px}.orbit-hint{display:none}.assumptions{gap:18px}.assumption-field{padding-left:18px}.field-heading{flex-wrap:wrap;gap:5px}.field-heading output{font-size:18px}.assumptions-title h2{font-size:20px}}
@media(max-width:760px){.masthead{height:72px;margin:0 18px}.brand{font-size:12px;gap:8px}.brand-mark{height:27px;width:27px;font-size:25px}nav{gap:12px}nav>.text-button{display:none}.tour-button{font-size:10px;padding:10px 12px;gap:8px}main{padding:0 18px}.intro{padding:24px 0 21px}h1{font-size:25px;max-width:450px}.eyebrow{font-size:8px}.explorer{grid-template-columns:1fr}.world-panel{min-height:460px}.lesson{border-left:0;border-top:1px solid var(--line);padding:22px}.lesson h2{max-width:none;font-size:25px}.lesson-summary{margin-bottom:18px}.system-steps{gap:10px;margin-bottom:20px}.system-steps li{font-size:12px}.lesson-metric{margin-top:0}.chapter-dots{margin:16px 0}.lesson-source{font-size:10px}.lesson-top{font-size:9px}.concept-badge{font-size:8px}.learn-more summary{font-size:12px}.lesson-nav button{min-height:32px;font-size:12px}.lesson-nav{font-size:10px}.assumptions{grid-template-columns:repeat(3,minmax(0,1fr));gap:18px;margin-top:25px}.assumptions-title{grid-column:1/-1}.assumptions-title h2{margin:7px 0;font-size:22px}.assumptions-title .text-button{margin-top:5px}.assumption-field{padding-left:12px}.assumption-field:first-of-type{border-left:0;padding-left:0}.field-heading label{font-size:10px}.field-heading output{font-size:20px}.field-heading{align-items:flex-start;flex-direction:column;gap:8px}.range-ends{font-size:7px;margin-bottom:18px}.result-label{font-size:9px;flex-direction:column;align-items:flex-start;gap:5px;min-height:28px}.result{font-size:25px}.result small{font-size:10px}.assumption-field p{font-size:9px}.scene-note{font-size:7px}.hotspot{font-size:9px;padding:6px}.scene-bottom{padding:12px}.scene-tools{left:12px;right:12px}.view-switch button{padding:8px;font-size:9px}.flow-switch button{font-size:9px;padding:7px 6px}footer{align-items:flex-start;font-size:8px;line-height:1.7}footer button{font-size:9px;text-align:right}.ledger-row{grid-template-columns:80px 1fr;gap:8px}.ledger-row p{grid-column:1/-1}.dialog-header h2{font-size:24px}dialog{padding:22px}.scene-top{left:14px;right:14px}}
@media(max-width:420px){.world-panel{min-height:400px}.assumptions{grid-template-columns:1fr;gap:22px}.assumption-field{border-left:0;border-top:1px solid var(--line);padding:18px 0 0}.field-heading{flex-direction:row;align-items:center}.range-ends{font-size:9px}.result-label{flex-direction:row;min-height:0;font-size:11px}.result{font-size:30px}.assumption-field p{font-size:11px}.state-label{font-size:8px}.scene-note{display:none}.scene-tag{font-size:8px}.hotspot{font-size:8px;gap:4px;padding:6px 5px}h1{font-size:23px}.scene-tools{bottom:84px}.view-switch button{font-size:8px;padding:8px 6px}.camera-tools button{width:28px}.brand{font-size:10px}.tour-button{font-size:9px}.lesson-nav button{min-height:38px}.scene-bottom{min-height:69px}.flow-switch button{font-size:9px}.system-steps li{font-size:12px}}
@media(pointer:coarse){.hotspot{padding:10px 7px}.view-switch button,.flow-switch button{min-height:32px}.camera-tools button{height:36px;width:36px}.chapter-dots button:before{inset:-10px 0}.text-button{min-height:36px}input[type=range]{height:28px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}