:root{color-scheme:light;--paper:#f4f3ed;--panel:#fffef9;--ink:#183c3b;--muted:#58706c;--line:#ccd7cd;--teal:#226b72;--orange:#bd6831;--red:#9b3029;--hit:#f8dfcf;--clear:#dce8de;--focus:#0a53ad}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:17px/1.6 system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}main{max-width:1176px;margin:auto;padding:48px 28px 26px}h1,h2,h3,p{margin:0}h1{font-size:clamp(38px,5.4vw,64px);line-height:1.06;letter-spacing:-.035em;font-weight:700;margin:16px 0 22px}h2{font-size:26px;line-height:1.25;letter-spacing:-.018em}h3{font-size:19px;line-height:1.35}.eyebrow{color:var(--muted);font-size:12px;letter-spacing:.13em;font-weight:750}.intro{max-width:780px;margin-bottom:36px}.lede{font-size:19px;max-width:720px;color:#365652}.lesson{display:grid;grid-template-columns:minmax(0,1.65fr) minmax(300px,1fr);gap:22px}.diagram-panel,.observations{min-width:0}.diagram-panel{background:var(--panel);border:1px solid var(--line);border-radius:18px;padding:24px}.diagram-heading{display:flex;align-items:baseline;justify-content:space-between;gap:12px}.diagram-heading h2{font-size:22px}.diagram-heading>span{font-size:13px;color:var(--muted)}svg{display:block;width:100%;height:auto;margin:12px 0 4px;overflow:visible}svg text{font-family:inherit}.axis{fill:none;stroke:#77928a;stroke-width:1.5}.grid{fill:none;stroke:#e4e9e1;stroke-width:1}.axis-label{font-size:13px;fill:#536e68}.hinge-label{font-size:12px}.tip-path{fill:none;stroke:#a7b8ae;stroke-width:1.5;stroke-dasharray:3 7}.path-label{font-size:12px;fill:#637c74}.ghost{fill:#e7efeb;fill-opacity:.35;stroke:#85a59b;stroke-width:1.8;stroke-dasharray:7 5}.pose-label{font-size:13px;fill:#557a70}.leaf{fill:#8dbcb8;fill-opacity:.85;stroke:var(--teal);stroke-width:2.8;stroke-linejoin:round}.leaf.is-hit{stroke:var(--red);stroke-width:3.2}.obstacle{fill:#edc192;fill-opacity:.8;stroke:var(--orange);stroke-width:2}.obstacle-label{font-size:12px;fill:#76411e;font-weight:650}.hinge{fill:#fffdf5;stroke:var(--teal);stroke-width:2.5}.hinge-core{fill:var(--ink)}.angle-badge{fill:var(--teal);font-size:35px;font-weight:650}.diagram-caption{color:var(--muted);font-size:13px;line-height:1.5;padding:0 6px}.angle-control{border-top:1px solid var(--line);margin-top:22px;padding-top:18px}.control-label{display:flex;justify-content:space-between;align-items:baseline;font-weight:650}.control-label output{font-size:25px;font-variant-numeric:tabular-nums}input[type=range]{width:100%;margin:13px 0 5px;height:26px;accent-color:var(--teal);cursor:pointer}.small{font-size:13px;color:var(--muted);line-height:1.5}.angle-presets{display:flex;gap:8px;margin-top:16px}button{font:inherit;color:var(--ink);border:1px solid #9db5a9;background:#fffdf6;border-radius:9px;padding:10px 12px;cursor:pointer;min-height:44px}button:hover{background:#e6eee5}button[aria-pressed=true]{background:var(--ink);color:#fffef4;border-color:var(--ink)}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid var(--focus);outline-offset:4px}.angle-presets button{flex:1;font-size:14px}.angle-presets span{font-weight:700;margin-left:8px}.observations{display:flex;flex-direction:column;gap:14px}.current-state{padding:23px;background:#e2ece2;border:1px solid #b9ccbb;border-radius:16px;min-height:128px}.current-state.is-hit{background:#f8e2d4;border-color:#d8ab8e}.result{font-size:30px;line-height:1.2;font-weight:700;margin:9px 0 5px}.obstacle-control{padding:16px 18px 15px;border:1px solid var(--line);border-radius:14px;min-width:0;margin:0;background:#eeeee5}.obstacle-control legend{padding:0 6px;font-size:15px;font-weight:650}.obstacle-presets{display:flex;gap:8px;margin:10px 0}.obstacle-presets button{flex:1;font-size:13px;padding:8px}.check-card{background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:19px}.check-method{font-size:12px;color:var(--muted);margin:2px 0 12px}.check-result{font-size:19px;line-height:1.4;font-weight:700;margin-bottom:5px}.check-card .warning{color:var(--red)}.sweep-track{height:17px;position:relative;margin-top:19px}#sample-cells{display:flex;height:100%;border:1px solid #8faa96;border-radius:3px;overflow:hidden}#sample-cells span{flex:1;min-width:0;background:#d7e6db}#sample-cells .hit{background:#a34532}#sample-cursor{position:absolute;height:27px;width:3px;background:var(--ink);top:-5px;transform:translateX(-50%);box-shadow:0 0 0 1px var(--panel)}.track-labels{display:flex;justify-content:space-between;font-size:11px;color:var(--muted);margin-top:3px}.track-key{font-size:11px;color:var(--muted);display:flex;align-items:center;flex-wrap:wrap;gap:6px;margin-top:9px}.key-dot{display:inline-block;width:9px;height:9px;border-radius:2px}.clear-dot{background:#d7e6db;border:1px solid #8faa96}.hit-dot{background:#a34532;margin-left:9px}.explanation{display:grid;grid-template-columns:1.2fr 1fr;gap:50px;margin-top:48px}.explanation h2{margin:10px 0 16px}.explanation p+p,.practical-note p{margin-top:13px}.practical-note{border-left:2px solid #b9cdbd;padding-left:25px;margin-top:27px;font-size:15px}.limits{margin-top:36px;background:#e9ece2;border:1px solid #c6d1c1;border-radius:12px;padding:23px 26px}.limits h2{font-size:19px;margin-bottom:10px}.limits p{font-size:14px}.limits p+p{margin-top:10px}.download{display:flex;gap:28px;align-items:center;justify-content:space-between;border-top:1px solid var(--line);margin-top:38px;padding-top:30px}.download h2{font-size:22px;margin-bottom:8px}.download p{font-size:14px;color:var(--muted);max-width:620px}.download-button{display:inline-flex;gap:14px;align-items:center;white-space:nowrap;padding:13px 18px;border-radius:8px;background:var(--ink);color:#fffdf5;text-decoration:none;font-size:14px;font-weight:650;min-height:48px}.download-button:hover{background:#28605a}.offline-note{border-top:1px solid var(--line);margin-top:30px;padding-top:25px;color:var(--muted);font-size:14px}footer{font-size:12px;color:var(--muted);margin-top:30px;max-width:800px}.no-script{padding:18px;border:2px solid var(--red);margin-top:15px}[hidden]{display:none!important}
@media(max-width:800px){main{padding:28px 18px 22px}.intro{margin-bottom:27px}.lesson{grid-template-columns:1fr}.diagram-panel{padding:19px}.observations{display:grid;grid-template-columns:1fr 1fr;gap:12px}.current-state{min-height:0}.explanation{grid-template-columns:1fr;gap:21px;margin-top:33px}.practical-note{margin-top:0}.download{align-items:flex-start;flex-direction:column;gap:18px}.diagram-heading{flex-wrap:wrap;gap:5px}.check-card{padding:17px}.result{font-size:26px}}
@media(max-width:490px){h1{font-size:39px}.lede{font-size:17px}.observations{grid-template-columns:1fr}.angle-presets span{display:block;margin-left:0}.angle-presets button{padding:8px}.limits{padding:19px}.diagram-panel{padding:16px}.diagram-heading h2{font-size:20px}.diagram-heading>span{font-size:12px}.axis-label,.pose-label,.obstacle-label{font-size:20px}.path-label{display:none}.angle-badge{font-size:42px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}
@media print{body{background:white}main{padding:0}.lesson{display:block}.observations{display:grid;grid-template-columns:1fr 1fr;margin-top:15px}.angle-control,.obstacle-control,.download{display:none}.diagram-panel{break-inside:avoid}.explanation{display:block}.practical-note{margin-top:18px}.limits{break-inside:avoid}}

.site-nav{display:flex;align-items:center;justify-content:space-between;gap:18px;max-width:1200px;margin:0 auto;padding:24px 26px 0;font-size:13px}.site-nav a{color:var(--ink)}.site-brand{font-weight:750;letter-spacing:.08em;text-decoration:none}.site-brand span{color:var(--muted);font-size:11px}.skip-link{position:absolute;left:14px;top:-80px;padding:12px;background:#fff;z-index:10}.skip-link:focus{top:10px}.practical-note a,footer a{color:var(--teal)}@media(max-width:490px){.site-nav{padding:20px 18px 0;align-items:flex-start}.site-brand span{display:block;margin-top:4px}.site-nav>a:last-child{max-width:110px;text-align:right}}
