:root{color-scheme:light;--ink:#172f3d;--muted:#59707c;--paper:#f6f4ed;--line:#d7ddd7;--accent:#126054;--soft:#e7eeea}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:24px}body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.7 system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}a{color:inherit;text-underline-offset:4px}button,summary,a{-webkit-tap-highlight-color:transparent}a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid #cf8150;outline-offset:5px}.skip{position:fixed;top:-100px;left:20px;background:#fff;padding:12px;z-index:5}.skip:focus{top:12px}.topbar,main,footer{width:min(1200px,calc(100% - 80px));margin:auto}.topbar{min-height:100px;display:flex;align-items:center;gap:28px;border-bottom:1px solid var(--line)}.brand{display:block;font-weight:900;font-size:34px;line-height:1;text-decoration:none;letter-spacing:-2px}.brand span{display:block;font-size:8px;letter-spacing:1.7px;margin-top:7px}.topbar>span{font-size:11px;letter-spacing:1.6px;color:var(--muted);flex:1}.topbar>a:last-child{font-size:13px}.hero{display:grid;grid-template-columns:1.25fr 1fr;gap:80px;padding:80px 0 70px;align-items:center}.eyebrow{font-size:11px;font-weight:750;letter-spacing:2px;color:var(--accent)}h1{font-size:clamp(44px,5vw,70px);line-height:1.05;letter-spacing:-3px;margin:20px 0 25px;font-weight:750}h1 em{font-style:normal;color:var(--accent)}.lead{font-size:19px;color:var(--muted);max-width:540px;line-height:1.65}.hero-actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:30px}.hero-actions a{font-size:13px;font-weight:700;text-decoration:none;padding:14px 18px;border:1px solid var(--accent);border-radius:4px}.primary{background:var(--accent);color:#fff}.primary span{margin-left:18px}.mission-map{display:grid;grid-template-columns:1fr 1fr;border:1px solid var(--line);border-radius:4px;background:#fdfcf7}.mission-map>div{padding:24px}.mission-map>div:nth-child(odd){border-right:1px solid var(--line)}.mission-map>div:nth-child(-n+2){border-bottom:1px solid var(--line)}.mission-map span{display:block;color:#839a8e;font-size:13px}.mission-map strong{display:block;font-size:25px;margin:12px 0 4px;font-weight:650;letter-spacing:-.6px}.mission-map p{font-size:13px;line-height:1.6;color:var(--muted);margin:0}.prepare{border-top:1px solid var(--line);border-bottom:1px solid var(--line);display:grid;grid-template-columns:270px 1fr;gap:45px;padding:30px 0;margin-bottom:60px}.prepare h2{font-size:20px;line-height:1.4;margin-top:7px}.prepare p{margin-top:0;color:var(--muted);font-size:14px}.workbook{display:grid;grid-template-columns:270px minmax(0,1fr);gap:45px;align-items:start}.workbook aside{position:sticky;top:24px}.workbook aside h2{font-size:26px;line-height:1.3;letter-spacing:-.7px;margin:12px 0 25px}.workbook nav{display:grid;gap:2px}.workbook nav a{display:flex;gap:14px;text-decoration:none;font-size:13px;line-height:1.5;padding:10px 0;border-bottom:1px solid var(--line)}.workbook nav a:hover{color:var(--accent)}.workbook nav span{font-size:11px;color:var(--muted);min-width:18px}.download-link{font-size:13px;display:inline-block;margin:25px 0}.lesson{border-top:1px solid var(--line);scroll-margin-top:24px;background:#fdfcf7}.lesson:last-child{border-bottom:1px solid var(--line)}.lesson>summary{display:grid;grid-template-columns:32px 1fr 20px;gap:15px;align-items:baseline;list-style:none;cursor:pointer;padding:24px;font-size:19px;font-weight:650;line-height:1.5}.lesson>summary::-webkit-details-marker{display:none}.lesson-no{font-size:12px;color:var(--accent);font-weight:750}.expand{font-size:22px;font-weight:400;color:var(--accent)}.lesson[open] .expand{transform:rotate(45deg)}.lesson-body{padding:0 28px 35px}.objective{font-size:17px;color:var(--accent);border-left:2px solid #95b3a3;padding-left:18px;margin:8px 0 30px}.lesson-body section{padding:16px 0}.lesson-body h3{font-size:22px;line-height:1.4;letter-spacing:-.5px;margin:12px 0 16px}.lesson-body h4{font-size:16px;line-height:1.5;margin:12px 0}.lesson-body p,.lesson-body li{font-size:14px;line-height:1.85}.lesson-body ul,.lesson-body ol{padding-left:22px}.code{position:relative;margin:16px 0;background:#172f3d;border-radius:5px;color:#f1f5ef;overflow:hidden}.code pre{padding:44px 20px 20px;margin:0;overflow:auto;white-space:pre;font:13px/1.8 ui-monospace,SFMono-Regular,Consolas,monospace}.copy{position:absolute;right:8px;top:6px;border:1px solid #526673;border-radius:3px;background:#263e4b;color:#e7efee;font-size:11px;padding:5px 10px;cursor:pointer;min-height:28px}summary{cursor:pointer;font-size:13px;color:var(--accent);font-weight:650;padding:10px 0}.table-wrap{overflow-x:auto;margin:16px 0}table{border-collapse:collapse;min-width:100%;font-size:12px;text-align:left}td,th{padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top;min-width:110px}th{background:var(--soft);font-weight:650}.practice-grid{display:grid;grid-template-columns:minmax(0,1fr);gap:14px}.practice{min-width:0;padding:18px;border:1px solid var(--line);border-radius:4px;background:#fff}.practice h4{margin-top:0}.write-prompt{color:var(--muted);border-left:2px solid #a7b9ae;padding-left:12px}.practice small{overflow-wrap:anywhere;font-size:10px;color:var(--muted)}.robot-lab{margin-top:14px;padding:22px!important;background:var(--soft);border-radius:4px}.caption{font-size:12px!important;color:var(--muted)}.references{margin:70px 0 45px;border-top:1px solid var(--line);padding:30px 0;max-width:100%}.references h2{font-size:20px}.references p,.references li{font-size:13px;color:var(--muted)}footer{padding:24px 0 40px;border-top:1px solid var(--line);display:flex;justify-content:space-between;gap:25px;font-size:12px;color:var(--muted)}.copy-status{position:fixed;bottom:20px;left:50%;transform:translateX(-50%);background:var(--ink);color:white;padding:8px 16px;border-radius:4px;font-size:13px;pointer-events:none;opacity:0}.copy-status.show{opacity:1}
@media(max-width:900px){.topbar,main,footer{width:calc(100% - 40px)}.hero{gap:28px;padding:50px 0}.prepare,.workbook{grid-template-columns:210px minmax(0,1fr);gap:25px}.mission-map>div{padding:18px}.hero-actions{gap:10px}.hero-actions a{padding:12px}}
@media(max-width:650px){.topbar{min-height:85px;gap:15px}.topbar>span{display:none}.topbar>a:last-child{margin-left:auto;font-size:12px}.hero{grid-template-columns:1fr;gap:35px;padding:40px 0}h1{font-size:49px;letter-spacing:-2px}.lead{font-size:17px}.mission-map{grid-template-columns:1fr 1fr}.mission-map>div{padding:16px}.mission-map strong{font-size:23px;margin-top:5px}.prepare,.workbook{display:block}.prepare{padding:20px 0;margin-bottom:32px}.prepare h2{margin-bottom:14px}.workbook aside{position:static}.workbook aside h2{font-size:24px;max-width:260px}.workbook nav{grid-template-columns:1fr 1fr;gap:0 15px;margin-bottom:18px}.workbook nav a{font-size:11px;gap:8px;align-items:center}.lesson>summary{padding:20px 12px;grid-template-columns:23px 1fr 16px;gap:10px;font-size:16px}.lesson-body{padding:0 15px 24px}.objective{font-size:15px}.lesson-body h3{font-size:20px}.code pre{font-size:12px;padding-left:14px;padding-right:14px}.practice{padding:13px}.robot-lab{padding:15px!important}.references{margin-top:35px}footer{flex-direction:column;gap:10px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
@media print{body{background:white}.topbar,.hero-actions,.workbook aside,.copy,.download-link,footer{display:none}.hero,.workbook,.prepare{display:block}main{width:100%}.lesson-body{padding:0}.lesson{break-before:page}details:not([open])>.lesson-body{display:block}.code{background:#f4f4f4;color:#111}.code pre{white-space:pre-wrap;padding:12px}.lesson>summary{padding-left:0}.mission-map{display:none}}
.lesson-links{display:flex;justify-content:space-between;gap:18px;border-top:1px solid var(--line);padding-top:18px;margin-top:24px;font-size:13px;font-weight:650}
/* Language controls stay available throughout a long lesson. */
html{scroll-behavior:auto;scroll-padding-top:125px}.topbar{position:sticky;top:0;z-index:10;background:var(--paper);gap:20px}.other-course{font-size:13px}.language-switch{display:flex;gap:2px;padding:3px;border:1px solid var(--line);border-radius:6px;flex:none}.language-switch a{display:grid;place-items:center;min-width:44px;min-height:38px;padding:5px 8px;border-radius:3px;font-size:12px;font-weight:750;text-decoration:none}.language-switch a[aria-current=page]{background:var(--accent);color:#fff}html[lang=ko] .lesson-body p,html[lang=ko] .lesson-body li{word-break:keep-all;overflow-wrap:anywhere}html[lang=ko] h1{letter-spacing:-2px}
@media(max-width:650px){.topbar{display:grid;grid-template-columns:auto 1fr;gap:8px 14px;padding:12px 0;min-height:100px}.language-switch{justify-self:end}.topbar>.other-course{grid-column:1/-1;justify-self:end;margin-left:0;font-size:11px}.topbar>.brand{grid-column:1;grid-row:1}.topbar>.language-switch{grid-column:2;grid-row:1}html[lang=ko] h1{font-size:43px;letter-spacing:-2px;overflow-wrap:anywhere}}
@media print{.topbar{display:none}}
html[lang=ko] p{word-break:keep-all;overflow-wrap:anywhere}
/* Hairline figure and concept diagrams share the workbook's paper and ink. */
.hero{gap:52px}.robot-figure{margin:0;min-width:0;border:1px solid var(--line);border-radius:8px;background:#fdfcf7;overflow:hidden}.hairline-stage{width:100%;aspect-ratio:5/4;--hairline-plate:#fdfcf7;--hairline-hi:#126054;--hairline-edge:#365747;--hairline-mid:#7d9387;--hairline-lo:#bdcbbf;--hairline-stroke:1.3}.hairline-stage>svg{display:block;width:100%;height:100%}.robot-figure figcaption{padding:0 24px 20px}.robot-figure h2{font-size:20px;line-height:1.4;margin:0}.robot-figure figcaption>p{font-size:13px;color:var(--muted);margin:8px 0}.motion-toggle,.diagram-controls button{font:inherit;font-size:12px;font-weight:650;padding:8px 13px;min-height:44px;border:1px solid #a9bdb0;border-radius:5px;color:var(--accent);background:#fdfcf7;cursor:pointer}.motion-toggle:hover,.diagram-controls button:hover{background:var(--soft)}.mission-map{grid-template-columns:repeat(4,minmax(0,1fr));margin:0 0 45px}.mission-map>div:nth-child(n){border:0;border-right:1px solid var(--line);padding:20px 24px}.mission-map>div:last-child{border-right:0}.mission-map strong{font-size:21px;margin:3px 0}.lesson-diagram{margin:22px 0 30px;padding:22px;border:1px solid #bdcbbf;border-radius:6px;background:#f0f4ef;min-width:0}.lesson-diagram figcaption h4{font-size:20px;letter-spacing:-.5px;margin:8px 0}.lesson-diagram figcaption>p{color:#405e4e;font-size:13px;margin:8px 0 20px}.diagram-steps{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin:0;padding:0!important;list-style:none}.diagram-steps>li{position:relative;border:1px solid #c6d3c8;background:#fdfcf7;border-radius:5px;padding:14px;min-width:0;box-shadow:inset 3px 0 0 transparent}.diagram-number{display:block;font:11px ui-monospace,monospace;letter-spacing:1px;color:#657e6d;margin-bottom:6px}.diagram-steps strong{display:block;font-size:14px;line-height:1.4}.diagram-steps p{margin:7px 0 0;font-size:12px;line-height:1.65;color:#4f6959;overflow-wrap:anywhere}.diagram-steps>li.is-current{border-color:var(--accent);box-shadow:inset 3px 0 0 var(--accent)}.diagram-controls{display:flex;flex-wrap:wrap;gap:7px;align-items:center;padding-top:16px}.diagram-controls[hidden]{display:none}.diagram-position{margin-left:auto;font:12px ui-monospace,monospace;color:var(--accent)}.diagram-note{color:var(--muted);font-size:11px!important;line-height:1.65!important;margin:14px 0 0!important}.route-scene,.error-scene{display:block;width:100%;max-height:220px;margin:0 auto 18px;color:var(--accent);overflow:visible}.route-scene rect,.error-scene rect{fill:#fdfcf7;stroke:#b0c4b5;stroke-width:1.5}.route-scene rect.is-current,.error-scene .is-current rect{fill:#dbe9df;stroke:var(--accent);stroke-width:2.5}.route-guide{stroke:#728f7a;stroke-width:2;stroke-dasharray:6 5;fill:none}.route-dot{fill:var(--accent);stroke:#fdfcf7;stroke-width:3}.error-scene text{font:18px ui-monospace,monospace;text-anchor:middle;fill:#365747}.bar-axis{stroke:#879f8d;stroke-width:1.2}.diagram-poll .diagram-number{width:25px;height:25px;border:1px solid #bdcbbf;border-radius:50%;display:grid;place-items:center}.diagram-gate .diagram-steps>li:nth-child(3){border-style:double}.diagram-gate .diagram-steps>li:last-child{border-style:dashed}.diagram-record .diagram-steps>li,.diagram-list .diagram-steps>li{display:grid;grid-template-columns:28px minmax(0,1fr);column-gap:8px}.diagram-record .diagram-number,.diagram-list .diagram-number{grid-row:1/3}.diagram-record p,.diagram-list p{grid-column:2}.diagram-flow .diagram-steps>li:not(:last-child)::after{content:'↓';position:absolute;right:12px;bottom:8px;color:#8ba394;font-size:16px}.diagram-flow .diagram-steps>li{padding-right:25px}.lesson-diagram[data-state=playing] .diagram-position::before{content:'● ';color:var(--accent);font-size:9px}
body[data-motion=on] .route-dot{transition:transform 700ms cubic-bezier(.32,.72,0,1)}body[data-motion=on] .diagram-steps>li,body[data-motion=on] .route-scene rect,body[data-motion=on] .error-scene rect{transition:border-color 350ms,box-shadow 350ms,fill 350ms,stroke 350ms}
@media(min-width:1000px){.diagram-square .diagram-visual,.diagram-grid .diagram-visual{display:grid;grid-template-columns:220px minmax(0,1fr);gap:16px;align-items:center}.diagram-square .route-scene,.diagram-grid .route-scene{margin:0}.diagram-square .diagram-steps,.diagram-grid .diagram-steps{gap:8px}.diagram-square .diagram-steps>li,.diagram-grid .diagram-steps>li{padding:10px}}
@media(max-width:900px){.hero{gap:25px}.robot-figure figcaption{padding:0 17px 18px}.mission-map>div:nth-child(n){padding:16px}.lesson-diagram{padding:17px}.diagram-steps>li{padding:12px}}
@media(max-width:650px){.robot-figure{max-width:440px;width:100%;justify-self:center}.hairline-stage{max-height:320px}.mission-map{grid-template-columns:repeat(2,minmax(0,1fr));margin-bottom:30px}.mission-map>div:nth-child(n){border-right:0;border-bottom:1px solid var(--line)}.mission-map>div:nth-child(odd){border-right:1px solid var(--line)}.mission-map>div:nth-last-child(-n+2){border-bottom:0}.lesson-diagram{padding:15px;margin:20px 0}.diagram-steps{grid-template-columns:minmax(0,1fr);gap:8px}.diagram-steps>li{padding:12px}.diagram-steps strong{font-size:14px}.diagram-steps p{font-size:12px}.diagram-controls button{padding:7px 10px;font-size:11px}.diagram-position{font-size:11px}.route-scene{max-height:180px}.diagram-flow .diagram-steps>li:not(:last-child)::after{bottom:-15px;right:20px;z-index:1;background:#f0f4ef;line-height:20px}.robot-figure h2{font-size:20px}}
@media print{.robot-figure,.diagram-controls{display:none!important}.mission-map{display:none}.lesson-diagram{break-inside:avoid;background:white}.diagram-steps>li{box-shadow:none!important;border-color:#aaa!important}.route-dot{transition:none!important}}