:root{--ink:#183544;--muted:#526773;--blue:#164e72;--teal:#09645d;--line:#c9d6dc;--paper:#fff;--wash:#f0f5f7;--error:#a13224}*{box-sizing:border-box}body{margin:0;background:var(--wash);color:var(--ink);font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;font-size:17px;line-height:1.6}button,input,select{font:inherit}button,a,input,select,summary{-webkit-tap-highlight-color:transparent}button{min-height:48px;padding:10px 17px;border:1px solid #aebfc8;border-radius:10px;background:white;color:var(--ink);cursor:pointer;font-weight:650}button:hover{background:#edf4f7}button.primary{background:var(--blue);border-color:var(--blue);color:white}button.primary:hover{background:#103d59}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid #b96816;outline-offset:3px}input,select{padding:10px;border:1.5px solid #9cafba;border-radius:8px;background:white;color:var(--ink);min-height:48px;max-width:100%;font-size:18px}input{width:130px}input[aria-invalid=true]{border-color:var(--error)}[hidden]{display:none!important}.top{max-width:1280px;margin:auto;padding:22px 32px;display:flex;justify-content:space-between;gap:20px;align-items:center;border-bottom:1px solid var(--line)}.brand{text-decoration:none;font-weight:800;color:var(--ink);letter-spacing:-.4px}.brand span{display:block;font-size:13px;letter-spacing:1px;text-transform:uppercase;font-weight:500;color:var(--muted)}.lesson{font-size:14px;color:var(--muted)}main{max-width:1280px;margin:auto;padding:30px 32px}.intro{margin-bottom:25px}.eyebrow{font-size:12px;font-weight:750;letter-spacing:1.6px;color:var(--teal);margin:0 0 8px}h1{font-size:clamp(28px,4vw,42px);letter-spacing:-1.4px;line-height:1.15;margin:0 0 12px}h2{font-size:clamp(25px,3vw,32px);line-height:1.2;letter-spacing:-.8px;margin:0 0 20px}h2:focus{outline:none}p{margin:0 0 18px}.intro p:last-child{color:var(--muted);margin:0}.steps{display:grid;grid-template-columns:repeat(5,1fr);gap:8px;margin-bottom:24px}.steps button{display:flex;gap:9px;align-items:center;text-align:left;background:transparent;border-color:transparent;font-size:15px;padding:10px}.steps b{border:1px solid #9cb1bc;border-radius:50%;width:29px;height:29px;flex-shrink:0;text-align:center;line-height:27px}.steps button[aria-current=step]{background:var(--ink);color:white}.steps button[aria-current=step] b{border-color:#a8cbd8}.workspace{display:grid;grid-template-columns:minmax(0,1.05fr) minmax(0,1fr);gap:24px;align-items:start}.panel{background:white;padding:30px;border:1px solid var(--line);border-radius:16px}.task{padding:14px 18px;background:#edf5fa;border-radius:8px}.task strong{font-size:25px;margin-left:10px;white-space:nowrap}.machine{display:flex;align-items:center;justify-content:space-between;gap:7px;margin:22px 0 26px;text-align:center}.machine div{flex:1;padding:13px 5px;border:1px solid var(--line);border-radius:12px}.machine small{display:block;font-size:13px}.machine strong{font-size:30px;line-height:1.4}.machine .rule{background:#e5f4f1;border-color:#afd3cb}.try{border-top:1px solid var(--line);padding-top:20px}label{display:block;margin-bottom:10px;font-weight:600}.actions{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin:12px 0}.next{margin-top:22px}.feedback:empty{display:none}.feedback{padding:12px 15px;border-left:3px solid var(--blue);background:#edf5fa;margin-top:14px}.feedback.good{border-color:var(--teal);background:#eaf6f1}.feedback.error{border-color:var(--error);background:#fff0ec}.small,.provided{font-size:14px;color:var(--muted)}.provided{display:block}details{margin-top:20px;border-top:1px solid var(--line);padding-top:16px}summary{cursor:pointer;font-weight:650;padding:4px 0;min-height:44px}details p:first-of-type{margin-top:12px}table{border-collapse:collapse;width:100%;margin:18px 0}caption{text-align:left;font-weight:700;margin-bottom:10px}th,td{text-align:left;padding:12px 8px;border-bottom:1px solid var(--line);vertical-align:top}thead th{font-size:14px;color:var(--muted)}td input{width:100%;min-width:65px}td:last-child{width:36%}.cell-feedback{display:block;font-size:14px;margin-top:5px}.note{border-left:4px solid var(--teal);background:#edf7f4;padding:16px 18px;margin:20px 0}.note b{display:block}.point-picker{display:flex;gap:8px;flex-wrap:wrap;margin:20px 0}.point-picker button{flex:1;white-space:nowrap}.point-picker button[aria-pressed=true]{background:var(--ink);color:white}.coord-fields{display:flex;gap:16px;flex-wrap:wrap}.coord-fields label{flex:1;min-width:110px}.coord-fields input,.coord-fields select{display:block;width:100%;margin-top:5px}.visual{background:white;border:1px solid var(--line);border-radius:16px;padding:22px;position:sticky;top:20px;min-width:0}.visual-heading{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:12px}.visual-heading strong{font-size:22px}.visual-heading .eyebrow{margin:0}#graph{width:100%;overflow:auto}#graph svg{display:block;width:100%;height:auto}#graph.big svg{min-width:700px}#graph-caption{font-size:15px;color:var(--muted);margin:12px 0 0}#plot-tools{margin-top:16px}#plot-tools .small{margin-top:10px}.paper-steps{padding-left:25px}.paper-steps li{padding-left:4px;margin-bottom:16px}footer{padding:28px 0;color:var(--muted);font-size:14px}footer details{max-width:750px}footer a{color:var(--blue)}#print-page{display:none}
@media(max-width:850px){.top{padding:18px 20px}main{padding:24px 20px}.workspace{gap:16px;grid-template-columns:1fr}.visual{position:static}.panel{padding:24px}.steps button{flex-direction:column;gap:5px;text-align:center;font-size:13px;padding:9px 4px}.steps{gap:3px}.visual{max-width:700px;width:100%;justify-self:center}}@media(max-width:400px){main{padding:20px 12px}.top{padding:16px 12px}.lesson{max-width:110px;text-align:right}.panel{padding:20px 16px}.visual{padding:14px}.steps button{font-size:12px}th,td{padding:10px 4px}.task strong{display:block;margin:4px 0 0}}
button,input,select,summary{touch-action:manipulation}
.panel{min-width:0;width:100%}
@media(max-width:850px){.panel>.visual{border:0;border-radius:0;padding:0;margin:24px 0}.panel>.visual #plot-tools{margin-bottom:20px}}
@media print{@page{size:A4;margin:16mm}body{background:white;color:#000;font-size:12pt}body>header,body>main,noscript{display:none!important}#print-page{display:block}#print-page h1{font-size:23pt;letter-spacing:0}#print-page h2{font-size:16pt;letter-spacing:0;margin:20px 0 10px}#print-page table{margin:10px 0}#print-page svg{display:block;width:125mm;height:125mm;margin:0 auto}#print-page .print-answer{break-before:page}#print-page p{margin-bottom:10px}#print-page tr{height:13mm}#print-page .print-meta{font-size:10pt}#print-page section{break-inside:avoid}}