:root{--bg:#f3f4ef;--paper:#fff;--ink:#18333d;--muted:#6b7f84;--teal:#00867e;--border:#dce3de;--dark:#12323e;--mint:#dff3ed;--a:#13a4a4;--b:#df9751;--c:#9673b8}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font:15px/1.6 "PingFang SC","Microsoft YaHei",system-ui,sans-serif}a{color:inherit;text-decoration:none}button,input,select{font:inherit}button{cursor:pointer;border:1px solid var(--border);background:#fff;color:var(--ink);padding:9px 14px;border-radius:8px;transition:background .15s,border-color .15s}button:hover{background:#edf6f1;border-color:#84b9ac}button:disabled{opacity:.35;cursor:default}.primary{background:var(--dark);border-color:var(--dark);color:#fff;min-width:143px}.primary:hover{background:#236052;color:white}.primary span{color:#87e1cc;margin-right:5px}button:focus-visible,a:focus-visible,select:focus-visible,summary:focus-visible,input:focus-visible{outline:3px solid #00a99c;outline-offset:3px}h1,h2,h3,p{margin:0}.topbar{height:82px;padding:0 max(28px,calc((100vw - 1536px)/2));border-bottom:1px solid var(--border);display:flex;align-items:center;justify-content:space-between;background:#fff}.brand{display:flex;align-items:center;gap:13px;font-size:11px;letter-spacing:1.6px;font-weight:700}.brand small{display:block;font-size:11px;letter-spacing:2px;font-weight:400;color:var(--muted);margin-top:3px}.brandmark{width:43px;height:43px;background:var(--dark);color:white;border-radius:10px;display:grid;grid-template-columns:repeat(3,auto);align-items:center;justify-content:center;font:italic 19px Georgia;letter-spacing:0}.brandmark span{color:#8bdcc5}.toplinks{display:flex;align-items:center;gap:28px;font-size:12px}.edition{font:11px ui-monospace,monospace;color:var(--muted);letter-spacing:1px}.toplinks a:hover{color:var(--teal)}main{max-width:1536px;margin:auto;padding:0 28px}.intro{padding:39px 0 31px;display:flex;align-items:flex-end;justify-content:space-between;gap:20px}.eyebrow{font:600 10px/1.4 system-ui,sans-serif;letter-spacing:1.6px;color:var(--teal)}.status-dot{display:inline-block;width:6px;height:6px;background:var(--teal);border-radius:50%;margin-right:9px;vertical-align:1px}h1{font-size:clamp(29px,3.1vw,43px);letter-spacing:-1.2px;line-height:1.4;margin:9px 0 7px;font-weight:650}h1 span{color:var(--teal);margin-left:6px}.intro p{color:var(--muted);font-size:14px}.intro-note{display:flex;flex-direction:column;align-items:flex-end;gap:6px;font-size:12px;color:var(--muted)}.intro-note b{font-size:14px;color:var(--ink);font-weight:500}.smalltag{border:1px solid #c6d9cf;border-radius:20px;color:#52776c;padding:3px 12px;font-size:10px;margin-top:3px}.player{border:1px solid var(--border);border-radius:16px;background:white;box-shadow:0 12px 38px #294c3710;overflow:hidden}.toolbar{display:flex;align-items:center;gap:9px;padding:17px 22px 9px}.toolbar button{font-size:12px}.chapter-controls{display:flex;gap:4px;margin-left:6px}.chapter-controls button{padding:8px 13px}.speed-label{font-size:11px;color:var(--muted);margin-left:9px;display:flex;align-items:center;gap:7px}select{border:1px solid var(--border);border-radius:7px;background:white;padding:7px;color:var(--ink);font-size:12px}.clock{margin-left:auto;font:500 14px ui-monospace,monospace;white-space:nowrap}.clock span{font-size:11px;color:var(--muted)}.fullscreen{margin-left:8px}.timeline{padding:0 23px 12px;display:flex;align-items:center;gap:18px}.timeline input{flex:1;min-width:0;height:4px;accent-color:var(--teal);cursor:pointer}.timeline span{font-size:10px;color:var(--muted)}.chapters{display:grid;grid-template-columns:repeat(8,1fr);gap:0;border-top:1px solid var(--border);border-bottom:1px solid var(--border);background:#fbfcf9;padding:0 14px}.chapters button{border:0;border-radius:0;padding:14px 7px;background:transparent;text-align:left;font-size:11px;color:var(--muted);position:relative;white-space:nowrap}.chapters button .num{font:10px ui-monospace,monospace;margin-right:6px;color:#93a9a1}.chapters button[aria-current="step"]{color:#006e64;background:#edf7f2;font-weight:600}.chapters button[aria-current="step"]:after{content:"";position:absolute;bottom:-1px;height:3px;background:var(--teal);left:7px;right:7px}.chapters button.done .num{color:var(--teal)}.stage-layout{display:grid;grid-template-columns:minmax(0,1fr) 310px}.visual{min-width:0;background:#f7faf8;border-right:1px solid var(--border)}.visual-head{padding:23px 26px 12px;display:flex;align-items:center;justify-content:space-between;gap:10px}.visual-head h2{font-size:20px;font-weight:550;margin-top:7px}.mode{background:#e5f0eb;border:1px solid #ccdcd3;border-radius:5px;padding:4px 10px;font-size:10px;color:#567567;white-space:nowrap}#scene{width:100%;display:block;aspect-ratio:1200/580;background:#f7faf8}#scene text{font-family:"PingFang SC","Microsoft YaHei",system-ui,sans-serif;fill:#233e48;font-size:18px}#scene .s{font-size:15px;fill:#758a8e}#scene .xs{font-size:13px;fill:#758a8e}#scene .h{font-size:23px;font-weight:600;fill:#163b45}#scene .white{fill:#e4f8f3}#scene .mono{font-family:ui-monospace,monospace}#scene .teal{fill:#00867e}.scene-legend{display:flex;flex-wrap:wrap;gap:10px 20px;padding:14px 24px;border-top:1px solid #e5ebe6;font-size:10px;color:var(--muted)}.scene-legend i{width:7px;height:7px;display:inline-block;background:var(--color);border-radius:50%;margin-right:6px}.legend-note{margin-left:auto}.lesson{padding:25px 25px 15px;display:flex;flex-direction:column;background:white}.lesson-header{display:flex;justify-content:space-between;color:var(--muted);font:9px/1.5 ui-monospace,monospace;letter-spacing:1px}.lesson-header span:first-child{color:var(--teal)}.lesson h2{font-size:23px;line-height:1.4;margin-top:18px;letter-spacing:-.3px}.lesson .key{margin-top:12px;font-size:13px;color:#50676d;line-height:1.85}.caption{font-size:14px;line-height:1.9;border-left:3px solid var(--teal);padding:9px 0 9px 14px;margin:20px 0;min-height:115px;color:#24464c}.insight{background:#eff6ef;border:1px solid #e1e9dc;border-radius:9px;padding:12px 14px}.insight>span{font-size:10px;color:#598568;font-weight:600}.insight p{font-size:12px;line-height:1.8;margin-top:5px}.terms{margin-top:18px}.tiny-label{font:9px system-ui,sans-serif;letter-spacing:1.1px;color:#8a9b97}.terms>div{display:flex;gap:6px;flex-wrap:wrap;margin-top:7px}.terms em{font-style:normal;font-size:10px;background:#f5f6f2;border:1px solid #e7eae3;padding:3px 7px;border-radius:5px}.notice{font-size:10px;color:#718781;margin-top:auto;padding-top:18px;line-height:1.7}.graphs{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:0;border-top:1px solid var(--border)}.chart{padding:20px 22px 15px;min-width:0;border-right:1px solid var(--border)}.chart:last-child{border-right:0}.chart-head{display:flex;align-items:center;justify-content:space-between;gap:5px}.chart h3{font-size:13px;font-weight:600;margin:4px 0 9px;display:flex;flex-wrap:wrap;gap:4px 9px}.chart h3 span{font-weight:400;font-size:9px;color:#759187;align-self:center}.chart-badge{font:10px ui-monospace,monospace;color:#69887a;border:1px solid #dce6dc;border-radius:5px;padding:4px 7px}.chart canvas{width:100%;height:190px;display:block}.chart p{font-size:10px;color:var(--muted);line-height:1.7;min-height:32px;margin-top:8px}.completion{padding:30px;background:#eaf4ed;border-top:1px solid var(--border)}.completion h2{font-size:25px;margin-top:8px}.summary-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:25px;margin:18px 0}.summary-grid p{font-size:12px;color:#5c756b}.summary-grid b{display:block;color:#26513e;margin-bottom:5px}.reading{display:grid;grid-template-columns:1fr 1.1fr;gap:40px;padding:38px 10px 33px;align-items:center}.reading h2{font-size:23px;font-weight:500;margin-top:9px}.reading p{font-size:12px;color:var(--muted);line-height:1.9}.reading b{color:#365951;font-weight:500}.references{border-top:1px solid var(--border);border-bottom:1px solid var(--border)}summary{cursor:pointer;padding:20px 10px;font-size:12px;list-style:none;display:flex;justify-content:space-between}summary span{color:var(--muted);font-size:10px}.reference-body{display:grid;grid-template-columns:1fr 1.5fr;gap:45px;padding:5px 10px 25px;font-size:12px;color:#627b71;line-height:1.9}.reference-body h3{font-size:13px;color:var(--ink);margin:0 0 10px}.reference-body a{color:var(--teal);text-decoration:underline;text-underline-offset:3px}.reference-body p{margin:7px 0 14px}footer{display:flex;justify-content:space-between;padding:22px 10px 30px;font-size:9px;color:#84978e;letter-spacing:1px}.foot-dot{margin:0 12px}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.nojs{padding:20px;background:white}#lab:fullscreen{max-width:none;background:var(--bg);padding:18px 30px;overflow:auto}#lab:fullscreen .intro{padding-top:10px}#lab:fullscreen .reading,#lab:fullscreen .references,#lab:fullscreen footer{display:none}[hidden]{display:none!important}
@media(min-width:1550px){.lesson{padding:28px 28px}.stage-layout{grid-template-columns:minmax(0,1fr) 330px}.caption{min-height:120px}.lesson h2{font-size:25px}.lesson .key{font-size:14px}}
@media(max-width:1150px){main{padding:0 18px}.stage-layout{grid-template-columns:minmax(0,1fr) 270px}.lesson{padding:20px}.lesson h2{font-size:20px}.lesson .key{font-size:12px}.caption{font-size:12px;min-height:95px;margin:15px 0}.terms{margin-top:12px}.notice{font-size:9px}.chapters{padding:0 5px}.chapters button{font-size:10px;padding:12px 5px}.chapters button .num{margin-right:3px}.chart{padding:15px}.chart canvas{height:170px}.visual-head{padding:20px}.visual-head h2{font-size:17px}}
@media(max-width:850px){.topbar{height:70px;padding:0 20px}.edition{display:none}.toplinks{gap:15px}.toplinks a{font-size:10px}.intro{padding:27px 0 23px}.intro-note{display:none}.intro p{font-size:12px}.stage-layout{grid-template-columns:1fr}.visual{border-right:0}.lesson{border-top:1px solid var(--border);display:grid;grid-template-columns:1fr 1fr;gap:8px 24px;padding:20px 24px}.lesson-header{grid-column:1/-1}.lesson h2{margin-top:3px}.lesson .key{grid-column:1}.caption{grid-column:2;grid-row:2/4;margin:0;min-height:0}.insight{grid-column:1}.terms{grid-column:2;grid-row:4;margin:0}.notice{grid-column:1/-1;padding-top:3px;margin-top:0}.scene-legend{font-size:9px;padding:12px 20px}.graphs{grid-template-columns:1fr 1fr}.chart:last-child{grid-column:1/-1;border-top:1px solid var(--border)}.chart:nth-child(2){border-right:0}.chart:last-child canvas{height:165px}.chapters{display:flex;overflow-x:auto;padding:0 10px;scrollbar-width:thin}.chapters button{flex:none;padding:14px 12px;font-size:11px}.reading{gap:25px}.reading h2{font-size:20px}}
@media(max-width:550px){main{padding:0 10px}.topbar{padding:0 15px;height:65px}.toplinks a:first-of-type{display:none}.brand{font-size:9px;gap:9px}.brand small{font-size:9px}.brandmark{height:36px;width:36px;font-size:16px}.intro{padding:25px 8px 20px}.eyebrow{font-size:8px;letter-spacing:1.1px}h1{font-size:30px;letter-spacing:-1px}.intro p{font-size:11px;max-width:300px}.player{border-radius:12px}.toolbar{gap:6px;padding:13px 12px 11px;flex-wrap:wrap}.toolbar .primary{min-width:128px}.toolbar button{font-size:11px;padding:8px 10px}.chapter-controls{margin-left:auto}.speed-label{margin-left:0;margin-top:3px;font-size:10px}.clock{margin-left:auto;font-size:12px}.fullscreen{margin-left:4px}.timeline{padding:0 13px 12px;flex-wrap:wrap;gap:8px}.timeline input{flex-basis:100%}.timeline span{font-size:8px}.chapters button{padding:12px 10px;font-size:10px}.visual-head{padding:17px 16px 10px}.visual-head h2{font-size:16px;margin-top:5px}.mode{font-size:8px;padding:3px 6px}#scene{aspect-ratio:720/590}.scene-legend{gap:7px 12px;padding:10px 15px;font-size:8px}.legend-note{flex-basis:100%;margin:0}.lesson{display:flex;padding:18px;gap:0}.lesson-header{font-size:9px}.lesson h2{margin-top:11px;font-size:22px}.lesson .key{font-size:12px;margin-top:8px}.caption{margin:13px 0;font-size:13px;min-height:60px;padding-left:12px}.insight{padding:10px 12px}.terms{margin-top:11px}.notice{padding-top:12px;font-size:9px}.graphs{grid-template-columns:1fr}.chart,.chart:nth-child(2){border-right:0;border-bottom:1px solid var(--border);padding:17px}.chart:last-child{grid-column:auto;border-bottom:0;border-top:0}.chart canvas,.chart:last-child canvas{height:190px}.reading{grid-template-columns:1fr;padding:30px 8px;gap:15px}.reading h2{font-size:21px}.reference-body{grid-template-columns:1fr;gap:14px;padding:0 8px 15px}summary{font-size:11px;padding:18px 8px}.completion{padding:24px 18px}.completion h2{font-size:23px}.summary-grid{grid-template-columns:1fr;gap:14px}.summary-grid p{font-size:12px}footer{font-size:8px;gap:12px;padding:20px 8px}#lab:fullscreen{padding:10px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}button{transition:none}}
/* Keep the instrument and three signal panels visible together on desktop. */
@media(min-width:851px){.topbar{height:68px}.intro{padding-top:22px;padding-bottom:21px}h1{font-size:36px;margin-top:6px;margin-bottom:5px}.toolbar{padding-top:13px}.chapters button{padding-top:12px;padding-bottom:12px}.visual-head{padding-top:18px;padding-bottom:8px}#scene{height:340px;aspect-ratio:auto}.chart canvas{height:160px}.chart{padding-top:15px;padding-bottom:12px}}
@media(min-width:851px) and (max-height:940px){.intro{padding-top:15px;padding-bottom:15px}h1{font-size:30px}.intro .eyebrow{font-size:9px}#scene{height:285px}.lesson{padding-top:18px;padding-bottom:12px}.lesson h2{margin-top:12px;font-size:20px}.caption{margin:12px 0;min-height:80px}.terms{margin-top:12px}.chart canvas{height:140px}}