:root{font-family:"Segoe UI",Arial,sans-serif;color:#eaf0e5;background:#102e35;--gold:#ebd29b;--muted:#b4c8c7;--line:#cadbd629;color-scheme:dark}*{box-sizing:border-box}body{margin:0;min-width:320px}h1,h2,h3,p{margin:0}h1,h2,h3{font-family:Cambria,"Times New Roman",serif;font-weight:400}a{color:inherit;text-decoration:none}button,input,select{font:inherit}button,a,input,select{touch-action:manipulation}button{cursor:pointer;color:inherit}button:disabled{cursor:default;opacity:.55}button:focus-visible,a:focus-visible,select:focus-visible,input:focus-visible{outline:3px solid var(--gold);outline-offset:4px}button:hover{filter:brightness(1.1)}.proof-skip{position:fixed;top:-100px;left:15px;background:#eee5d3;color:#17363b;padding:16px;z-index:20;opacity:0}.proof-skip:focus{top:12px;opacity:1}.proof-header{height:90px;padding:0 max(5%,calc((100% - 1440px)/2));border-bottom:1px solid 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.2s}#proof-status.visible{opacity:1}
@media(min-width:1500px){main{padding-inline:30px}.proof-header{padding-inline:max(30px,calc((100% - 1380px)/2))}}
@media(max-width:1100px){.proof-layout{grid-template-columns:minmax(0,.9fr) minmax(0,1.1fr);gap:20px}.proof-header{padding-inline:4%}main{padding-inline:4%}.mission-heading h1{font-size:45px}.mission-heading>div>p:last-child{max-width:550px}.mission-progress{width:195px;padding-left:22px}.geometry-panel{position:static}.proof-step{padding:19px 17px}.step-heading>h3{font-size:20px}.premise{font-size:13px}.drop-field select{font-size:12px}.panel-label{padding-inline:18px}.figure-controls,details{padding-inline:19px}}
@media(max-width:800px){main{padding:32px 5% 45px}.proof-header{padding-inline:5%;gap:20px;height:80px}.proof-brand{font-size:27px}.proof-brand>small{font-size:7px;letter-spacing:1.5px}.back-link{font-size:12px}.proof-header>.quiet{font-size:12px}.mission-heading{align-items:flex-start}.mission-heading h1{font-size:42px}.mission-heading>div>p:last-child{font-size:14px}.mission-progress{width:155px;padding-left:20px}.mission-progress>strong{font-size:30px}.mission-progress>span{font-size:8px;line-height:1.7}.proof-layout{grid-template-columns:1fr;gap:32px}.geometry-panel .geometry{max-width:700px;margin:auto}.geometry-panel{display:grid;grid-template-columns:1fr 1fr}.geometry-panel>.panel-label,.geometry-panel>.geometry{grid-column:1/-1;width:100%}.figure-controls{grid-column:1}.problem{grid-column:2;grid-row:3/5;border-left:1px solid var(--line)}.measurements{grid-column:1}.reasoning-panel>h2{font-size:34px}.direction-key{flex-direction:row;gap:20px;flex-wrap:wrap}.proof-step{padding:23px}.drop-field select{font-size:14px}.premise{font-size:14px}.step-heading>h3{font-size:24px}#bank-cards{grid-template-columns:repeat(2,minmax(0,1fr))}.idea-card{font-size:14px}.card-bank h2{font-size:30px}.eyebrow{font-size:10px}}
@media(max-width:520px){.proof-header{height:78px;gap:15px;padding-inline:5%}.proof-brand{font-size:25px}.proof-brand>small{font-size:6px;letter-spacing:1px}.back-link{font-size:11px}.proof-header>.quiet{font-size:11px;padding:8px 0}.proof-header>.quiet>span{display:none}main{padding-top:28px}.mission-heading{display:block;margin-bottom:26px}.mission-heading h1{font-size:39px;margin-top:12px}.mission-heading>div>p:last-child{font-size:13px;line-height:1.8}.mission-progress{border:0;padding:0;margin-top:20px;width:100%;display:grid;grid-template-columns:90px 1fr;align-items:center;gap:5px 10px}.mission-progress>strong{font-size:26px;grid-row:span 2}.mission-progress>span{font-size:8px;margin:0;letter-spacing:1px}.mission-progress progress{height:4px}.geometry-panel{display:block;border-radius:7px}.panel-label{padding:12px 17px}.panel-label>span{font-size:9px;letter-spacing:.8px}.geometry{padding:0}.point text{font-size:25px}.figure-legend{font-size:12px}.figure-controls,details{padding:17px}.problem{border-left:0}.figure-controls>label:first-child,.check-label{font-size:12px}details p{font-size:13px}details .micro{font-size:11px}summary{font-size:13px}.reasoning-panel>.panel-label{padding:10px 16px}.reasoning-panel>h2{font-size:29px;margin-top:24px}.direction-key{flex-direction:column;gap:8px;padding:13px}.direction-key>span{font-size:11px}.goal-node{padding:19px}.goal-node>strong{font-size:32px}.goal-node>span{font-size:11px}.branch-intro{font-size:12px}.proof-step{padding:18px 15px}.step-heading{gap:10px}.step-heading>h3{font-size:22px}.step-heading>span{font-size:11px;padding:5px}.premise{font-size:13px}.drop-field{padding:10px}.drop-field label{font-size:8px}.drop-field select{font-size:12px;min-height:46px;padding-left:8px}.step-controls{gap:10px;justify-content:space-between}.gold-button{font-size:12px;padding:11px 13px}.gold-button>span{margin-left:8px}.hint-button{font-size:11px;padding-inline:2px}.step-feedback,.step-feedback p,.hint{font-size:12px}.dependencies{gap:8px}.dependencies>small{width:100%;font-size:8px}.dependencies a{font-size:11px}.given-label{font-size:10px}.card-bank{margin-top:35px;padding-top:26px}.card-bank h2{font-size:29px}.card-bank>div>p:not(.eyebrow){font-size:13px}.bank-tabs{gap:8px}.bank-tabs button{font-size:12px;padding:12px 14px}#bank-cards{grid-template-columns:1fr;gap:10px}.idea-card{font-size:14px;min-height:60px}#selected-card{font-size:12px}.completion{padding:23px}.completion h2{font-size:28px}.completion p{font-size:13px}.completion small{font-size:10px}footer{font-size:10px;align-items:flex-start;line-height:1.7;padding:22px 5%}footer>a{white-space:nowrap}dialog{padding:32px 22px;border-radius:7px}dialog h2{font-size:28px}dialog p,dialog li{font-size:13px}dialog .eyebrow{font-size:9px;letter-spacing:1px}dialog .solution li{line-height:2}.dialog-actions{flex-direction:column}.dialog-actions button{min-height:44px}#proof-status{font-size:12px;padding:12px 16px}.fraction{margin-inline:3px}}
@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}
.inference-arrow{width:max-content;max-width:95%;justify-content:center}.inference-arrow>span{font-size:10px;letter-spacing:0;line-height:1.3}.inline-bank{padding:14px 0 0;border:0}.inline-bank>summary{font-size:12px;color:var(--gold)}.inline-bank>p{font-size:11px;color:#aabfb9;margin:14px 0 9px}.inline-bank-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px}.inline-bank .idea-card{font-size:12px;padding:10px;min-height:50px;line-height:1.5}.inline-bank .fraction{margin-inline:2px}@media(max-width:520px){.inline-bank .idea-card{font-size:11px}.inference-arrow>span{font-size:9px}}
