/* Chapter 03: demand-driven preview, ordinary page scrolling. */
.length-overview{margin:0;border:1px solid var(--line);border-radius:13px;overflow:hidden;background:var(--surface)}
.length-overview img{display:block;width:100%;height:auto}.length-overview figcaption{display:grid;gap:8px;padding:20px 24px;color:var(--muted);font-size:14px;line-height:1.7}.length-overview figcaption strong{color:var(--ink);font:600 20px/1.4 var(--display)}
.length-lab-shell{border:1px solid var(--line);border-radius:14px;overflow:hidden;background:var(--surface)}
.length-workbench{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(390px,1fr);align-items:start}
.length-preview{min-width:0;background:#090f17}.length-stage{position:relative;aspect-ratio:8/5;background:#090f17}
.length-stage canvas,.length-stage>img{display:block;width:100%;height:100%;object-fit:contain}
.length-stage:has(>img:not([hidden]))>canvas{display:none}.length-stage canvas{touch-action:pan-y pinch-zoom;cursor:crosshair}.length-stage canvas:focus-visible{outline-offset:-3px}
.length-stage [hidden]{display:none!important}.length-legend{display:flex;flex-wrap:wrap;gap:10px 18px;padding:15px 20px;border-top:1px solid var(--line);font:400 10px/1.6 var(--mono);color:var(--muted)}
.length-legend span{display:inline-flex;align-items:center;gap:8px}.length-legend i{width:10px;height:10px;display:inline-block;border-radius:50%;flex:none}
.length-center-color{background:#f5f5f5}.length-probe-color{border:2px solid #ffad59}.length-shape-color{background:#4ce0e3}
.length-view-note,.length-fallback-message{padding:0 20px;color:var(--dim);font-size:11px;line-height:1.7;margin:0 0 18px}.length-fallback-message{color:var(--muted);padding-top:16px}
.length-controls{min-width:0;padding:20px;border-left:1px solid var(--line)}
.length-view-control{display:flex;align-items:center;gap:10px;flex-wrap:wrap}.length-view-control>label{font:500 15px/1.5 var(--display)}
.length-view-control select{flex:1;min-width:100px;max-width:100%;background:#0b111b;border:1px solid var(--line);border-radius:7px;color:var(--ink);padding:9px;font:400 11px/1.5 var(--mono)}
.length-view-control button,.length-preset-buttons button{border-radius:7px;padding:8px 10px;font-size:10px;min-height:36px}
.length-shape-controls{padding-block:10px 14px;border-bottom:1px solid var(--line)}
.length-shape-controls>p{color:var(--dim);font-size:10px;line-height:1.65;margin:12px 0 0}
.length-input-row{display:grid;grid-template-columns:76px minmax(0,1fr) 67px;gap:8px;align-items:center;margin-top:9px}
.length-input-row label{font:400 10px/1.5 var(--mono);color:var(--muted)}
.length-input-row input[type=range]{min-width:0;width:100%;margin:0;min-height:30px;accent-color:#4ce0e3}
.length-input-row input[type=number]{width:100%;min-width:0;border:1px solid var(--line);background:#0b111b;color:var(--ink);border-radius:6px;padding:7px 4px;font:400 11px/1.5 var(--mono);font-variant-numeric:tabular-nums}
.length-point-controls{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px;margin-top:17px}
.length-point-controls fieldset{min-width:0;padding:0;border:0;margin:0}.length-point-controls legend{padding:0;color:var(--ink);font:500 15px/1.5 var(--display)}
.length-point-controls .length-input-row{grid-template-columns:10px minmax(0,1fr) 61px;gap:5px}.length-point-controls fieldset:last-child input[type=range]{accent-color:#ffad59}
.length-preset-buttons{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px}
#length-shader-status{font:400 10px/1.7 var(--mono);color:var(--accent);margin:15px 0 0;min-height:34px}
.length-readouts{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:18px 20px;padding:22px;border-block:1px solid var(--line);margin:0;background:#0b111b}
.length-readouts>div{min-width:0}.length-readouts dt{color:var(--dim);font:400 10px/1.6 var(--mono);margin:0 0 6px}.length-readouts dd{margin:0;color:var(--ink);font:400 14px/1.6 var(--mono);font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.length-geometry-note{padding:14px 22px;margin:0;border-bottom:1px solid var(--line);min-height:69px;font-size:12px;line-height:1.7;color:var(--muted)}
.length-readout-note,.length-control-help{padding:0 22px;font-size:12px;line-height:1.75;color:var(--muted);margin:16px 0}.length-readout-note{color:var(--dim);font-size:11px}
#length-error{white-space:pre-wrap;overflow-wrap:anywhere;color:#ffb6a4;background:#291717;padding:16px;border-radius:8px;font-size:12px}.length-lab-section .code-panel{min-width:0}
@media(max-width:900px){.length-workbench{grid-template-columns:1fr}.length-stage{max-width:800px;margin-inline:auto}.length-controls{border-left:0;border-top:1px solid var(--line)}.length-point-controls{gap:30px}.length-input-row{grid-template-columns:85px minmax(0,1fr) 78px}.length-point-controls .length-input-row{grid-template-columns:14px minmax(0,1fr) 72px;gap:8px}.length-preview{padding-bottom:1px}}
@media(max-width:580px){.length-stage{aspect-ratio:1}.length-controls{padding:18px}.length-point-controls{grid-template-columns:1fr;gap:18px}.length-input-row{grid-template-columns:73px minmax(0,1fr) 72px;gap:6px}.length-point-controls .length-input-row{grid-template-columns:14px minmax(0,1fr) 72px;gap:10px}.length-readouts{grid-template-columns:repeat(2,minmax(0,1fr));gap:17px;padding:18px}.length-legend{padding:14px 18px;gap:10px 18px}.length-view-note,.length-fallback-message,.length-geometry-note,.length-readout-note,.length-control-help{padding-inline:18px}.length-geometry-note{min-height:89px}}