:root{--ink:#18373c;--muted:#647b80;--teal:#0f766e;--teal-dark:#095c57;--mint:#e7f5f0;--line:#dce8e5;--paper:#f7faf9;--white:#fff;--blue:#276bb0;--orange:#b66a30;--radius:20px;font-family:Inter,"PingFang SC","Microsoft YaHei",system-ui,sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none}*{box-sizing:border-box}body{margin:0;font-size:16px;line-height:1.65}a{color:inherit;text-decoration:none}button,input,textarea,select{font:inherit}button,a,input,select,textarea{-webkit-tap-highlight-color:transparent}button{cursor:pointer}button:disabled{cursor:default;opacity:.42}button,a,input,textarea,select{touch-action:manipulation}:focus-visible{outline:3px solid #009f92;outline-offset:4px}button{border:0}svg{display:block;max-width:100%}[hidden]{display:none!important}.site-header{background:rgba(255,255,255,.94);border-bottom:1px solid var(--line)}.header-inner{max-width:1264px;margin:auto;padding:23px 36px;display:flex;align-items:center;gap:54px}.brand{display:flex;gap:12px;align-items:center;font-size:21px;font-weight:750;letter-spacing:.04em}.brand-symbol{display:grid;place-items:center;background:var(--teal);width:43px;height:43px;color:white;border-radius:13px;font-size:35px;line-height:1}.brand small{display:block;font-size:10px;letter-spacing:.17em;font-weight:600;line-height:1.2;color:var(--muted)}nav{display:flex;gap:34px;margin-left:auto}nav a{font-size:15px;color:var(--muted);position:relative;padding:7px 0}nav a[aria-current=page]{color:var(--teal);font-weight:700}.site-header nav a[aria-current=page]:after{content:"";position:absolute;bottom:-24px;height:3px;background:var(--teal);left:0;right:0}.festival{font-size:12px;padding:6px 12px;border:1px solid var(--line);border-radius:6px;color:var(--muted);letter-spacing:.08em}#note-count:not(:empty){font-size:11px;background:var(--mint);border-radius:50%;margin-left:6px;padding:2px 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21px}.tag{font-size:12px;letter-spacing:.06em;color:var(--accent);font-weight:650}.card-copy h3{font-size:24px;margin:7px 0 8px;letter-spacing:.015em}.card-copy p{font-size:15px;color:var(--muted);margin:0;min-height:50px;line-height:1.7}.card-bottom{border-top:1px solid var(--line);margin-top:22px;padding-top:15px;display:flex;justify-content:space-between;align-items:center;font-size:12px;color:var(--muted)}.card-bottom strong{font-weight:650;font-size:14px;color:var(--accent)}.card-bottom strong span{margin-left:9px;font-size:18px}.how-to{margin:34px 0 51px;display:flex;align-items:center;gap:36px;padding:24px 28px;border:1px solid var(--line);border-radius:14px;background:#eff6f3}.how-to h2{font-size:16px;max-width:110px;margin:0;line-height:1.6}.how-to ol{display:flex;padding:0;margin:0;list-style:none;flex:1;justify-content:space-between;gap:25px}.how-to li{display:flex;gap:11px;align-items:center}.how-to li>b{color:#4d8b7f;font-family:monospace;font-size:14px;border:1px solid #bcdbd1;border-radius:50%;width:30px;height:30px;display:grid;place-items:center}.how-to strong{display:block;font-size:14px;font-weight:650}.how-to span{font-size:12px;color:var(--muted)}.site-footer{max-width:1192px;margin:auto;padding:22px 0 24px;border-top:1px solid var(--line);display:flex;justify-content:space-between;gap:20px;color:var(--muted);font-size:12px}.site-footer i{font-style:normal;margin:0 10px;color:#9ab1ab}.site-footer a{text-decoration:underline;text-underline-offset:3px}.skip-link{position:fixed;left:20px;top:-80px;padding:10px 20px;background:white;z-index:100}.skip-link:focus{top:10px}.noscript{padding:30px}.breadcrumb{display:flex;align-items:center;gap:12px;font-size:13px;color:var(--muted);padding:27px 0 18px}.breadcrumb a:hover{color:var(--teal)}.lab-heading{display:flex;justify-content:space-between;gap:24px;align-items:center;margin-bottom:26px}.lab-heading h1{font-size:32px;line-height:1.3;margin:4px 0 6px;letter-spacing:-.02em}.lab-heading p{margin:0;color:var(--muted);font-size:15px}.lab-topic-nav{display:flex;border:1px solid var(--line);border-radius:10px;padding:4px;background:white;flex-shrink:0}.lab-topic-nav a{font-size:13px;padding:7px 13px;border-radius:7px;color:var(--muted)}.lab-topic-nav a[aria-current=page]{color:var(--teal);background:var(--mint);font-weight:650}.experiment{border:1px solid var(--line);border-radius:20px;overflow:hidden;background:white}.experiment-top{padding:16px 22px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;gap:15px;align-items:center}.experiment-top strong{font-size:14px;display:flex;align-items:center;gap:9px}.experiment-top strong:before{content:"";width:7px;height:7px;border-radius:50%;background:var(--accent)}.sim-label{font-size:12px;color:var(--muted);background:var(--paper);border:1px solid var(--line);border-radius:5px;padding:3px 8px}.experiment-grid{display:grid;grid-template-columns:minmax(0,1fr) 325px}.visual-panel{min-width:0;background:radial-gradient(#bfd7d155 .8px,transparent .8px),#f4f9f7;background-size:17px 17px;display:flex;flex-direction:column;justify-content:space-between}.stage-wrap{position:relative;min-width:0;padding:10px 12px 0}.stage-wrap svg{width:100%;height:auto;max-height:385px}.stage-wrap svg text{font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif}.stage-caption{margin:0 22px 17px;display:flex;justify-content:space-between;gap:15px;align-items:center;color:var(--muted);font-size:12px}.stage-caption strong{font-weight:600;color:var(--accent)}.control-panel{padding:23px 23px 24px;border-left:1px solid var(--line);display:flex;flex-direction:column;gap:20px}.control-title{font-size:12px;color:var(--muted);letter-spacing:.1em;display:flex;align-items:center;justify-content:space-between}.reset-params{font-size:12px;color:var(--teal);background:none;padding:0}.control-group label{font-size:14px;font-weight:600;display:flex;justify-content:space-between;align-items:center;margin-bottom:11px}.control-group output{font-size:14px;color:var(--accent);font-weight:700}.control-group select{width:100%;padding:10px 11px;border:1px solid var(--line);border-radius:8px;background:white;color:var(--ink);font-size:14px}.range-ends{display:flex;justify-content:space-between;color:var(--muted);font-size:12px;margin-top:3px}input[type=range]{width:100%;margin:0;accent-color:var(--accent);cursor:pointer;height:24px}.check-control{display:flex;align-items:center;gap:10px;font-size:14px}.check-control input{accent-color:var(--teal);width:18px;height:18px}.param-insight{padding-top:17px;border-top:1px solid var(--line);margin-top:auto}.param-insight strong{font-size:13px;font-weight:650;display:block;margin-bottom:6px;color:var(--accent)}.param-insight p{font-size:14px;line-height:1.75;margin:0;color:var(--muted)}.player{padding:16px 20px;border-top:1px solid var(--line);display:flex;align-items:center;gap:11px;flex-wrap:wrap}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border:1px solid var(--line);background:white;color:var(--ink);border-radius:8px;font-size:14px;font-weight:550;min-height:40px;padding:8px 15px;transition:background .15s}.btn:hover:not(:disabled){background:var(--mint)}.btn-primary{color:white;border-color:var(--teal);background:var(--teal)}.btn-primary:hover:not(:disabled){background:var(--teal-dark)}.btn svg{width:16px;height:16px}.player-speed{margin-left:auto;display:flex;gap:8px;align-items:center;font-size:13px;color:var(--muted)}.player-speed select{color:var(--ink);background:white;border:1px solid var(--line);border-radius:6px;padding:6px}.time{font-family:monospace;color:var(--muted);font-size:12px;min-width:80px}.timeline{display:flex;gap:4px;padding:0 20px 18px}.timeline button{height:6px;border-radius:4px;padding:0;background:#e7eeec;flex:1;position:relative;overflow:hidden}.timeline button:before{content:"";position:absolute;inset:0 auto 0 0;width:var(--progress,0%);background:var(--accent)}.steps{display:grid;grid-template-columns:repeat(var(--steps),minmax(0,1fr));gap:10px;margin:22px 0}.step-button{display:flex;align-items:center;justify-content:center;gap:10px;border:1px solid var(--line);padding:12px 8px;border-radius:9px;background:white;color:var(--muted);font-size:14px}.step-button b{font-size:12px;width:24px;height:24px;border:1px solid var(--line);border-radius:50%;display:grid;place-items:center;font-weight:500;flex-shrink:0}.step-button[aria-current=step]{background:var(--mint);border-color:#a8d3c6;color:var(--teal);font-weight:650}.step-button[aria-current=step] b{background:var(--teal);color:white;border-color:var(--teal)}.explanation{display:grid;grid-template-columns:200px 1fr;gap:30px;padding:6px 0 29px}.explanation .eyebrow{font-size:11px}.explanation h2{font-size:23px;margin:7px 0}.explanation p{margin:4px 0;font-size:16px;line-height:1.85}.watch-for{color:var(--teal);font-size:14px!important;margin-top:8px!important}.learning-bottom{display:grid;grid-template-columns:1fr 1fr;gap:22px;margin:6px 0 30px}.learning-card{border:1px solid var(--line);border-radius:15px;background:white;padding:25px}.learning-card .section-kicker{font-size:11px;letter-spacing:.13em;color:var(--muted)}.learning-card h2{font-size:19px;margin:5px 0 15px}.quiz-question{font-size:15px;margin:0 0 15px;font-weight:600}.quiz-options{display:grid;gap:8px}.quiz-option{display:flex;align-items:center;gap:10px;text-align:left;font-size:14px;line-height:1.5;background:var(--paper);border:1px solid var(--line);border-radius:8px;padding:10px 12px;color:var(--ink)}.quiz-option span{font-size:12px;flex-shrink:0;color:var(--muted);width:21px;height:21px;display:grid;place-items:center;background:white;border-radius:4px}.quiz-option:hover{border-color:#83b9ac}.quiz-option.correct{background:#e7f5ee;border-color:#59a384}.quiz-option.incorrect{background:#fff2ec;border-color:#dca27e}.quiz-feedback{font-size:14px;margin:14px 0 0;line-height:1.7;color:var(--teal)}.quiz-feedback.wrong{color:#9a4d2b}.notes-hint{font-size:13px;color:var(--muted);margin:0 0 12px}.notes-textarea{resize:vertical;width:100%;min-height:150px;border:1px solid var(--line);border-radius:9px;padding:12px;color:var(--ink);line-height:1.75;font-size:14px;background:var(--paper)}.notes-textarea::placeholder{color:#7d9395}.notes-bottom{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:12px}.save-status{font-size:12px;color:var(--muted);line-height:1.5}.note-counter{font-size:11px;color:var(--muted);text-align:right}.source-details{margin:0 0 35px;border-top:1px solid var(--line);padding-top:15px;color:var(--muted);font-size:13px}.source-details summary{cursor:pointer}.source-details p{margin:10px 0}.source-details a{text-decoration:underline;text-underline-offset:3px;color:var(--teal);margin-right:20px}.notebook-header{padding:45px 0 25px}.notebook-header h1{font-size:36px;margin:9px 0}.notebook-header p{color:var(--muted);font-size:15px}.notebook-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:22px;margin-bottom:45px}.notebook-card{background:white;border:1px solid var(--line);padding:25px;border-radius:15px;display:flex;flex-direction:column;min-height:280px}.notebook-card h2{font-size:21px;margin:8px 0 13px}.notebook-card p{white-space:pre-wrap;overflow-wrap:anywhere;font-size:14px;color:var(--muted);flex:1}.notebook-card time{font-size:12px;color:var(--muted);display:block;margin-bottom:16px}.empty-note{font-style:normal;color:#849999!important}.notebook-card .btn{align-self:flex-start}.storage-warning{font-size:14px;color:#9a4d2b}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}.finish-tip{font-size:12px;color:var(--teal);margin-left:4px}
@media(min-width:1450px){.home-intro{padding-top:72px;padding-bottom:55px}.card-scene{height:245px}.how-to{margin-top:38px}}@media(max-width:1000px){.header-inner{gap:25px}.festival{display:none}.intro-aside{display:none}.card-copy{padding:18px}.card-copy h3{font-size:22px}.card-scene{height:185px}.experiment-grid{grid-template-columns:minmax(0,1fr) 285px}.control-panel{padding:18px}.lab-topic-nav a{padding:7px 9px}.how-to{gap:22px}.how-to ol{gap:15px}.how-to li>b{display:none}.explanation{grid-template-columns:170px 1fr;gap:20px}.site-footer{margin:0 36px}}@media(max-width:740px){.header-inner{padding:18px 20px;gap:12px}.brand{font-size:18px;gap:9px}.brand small{font-size:8px}.brand-symbol{width:36px;height:36px;border-radius:10px;font-size:30px}nav{gap:19px}nav a{font-size:13px}.site-header nav a[aria-current=page]:after{bottom:-20px}main{padding:0 20px}.home-intro{padding:36px 0 28px}.home-intro h1{font-size:39px;margin:16px 0 14px}.home-intro p{font-size:15px}.eyebrow{font-size:11px}.section-line span{font-size:11px}.topics-grid{grid-template-columns:1fr;gap:20px}.card-scene{height:225px}.card-copy{padding:21px 23px}.card-copy h3{font-size:25px}.card-copy p{min-height:0}.card-bottom{margin-top:18px}.how-to{display:block;padding:22px;margin:25px 0 33px}.how-to h2{max-width:none;font-size:16px;margin-bottom:18px}.how-to ol{display:grid;gap:15px}.how-to li{gap:14px}.how-to li>b{display:grid}.how-to strong{display:inline;margin-right:10px}.site-footer{margin:0 20px;display:block;padding:20px 0;font-size:11px}.site-footer>span{display:block;margin:5px 0}.breadcrumb{padding:20px 0 14px}.lab-heading{display:block;margin-bottom:20px}.lab-heading h1{font-size:29px}.lab-heading p{font-size:14px}.lab-topic-nav{width:max-content;max-width:100%;margin-top:18px}.lab-topic-nav a{font-size:12px;padding:6px 10px}.experiment-top{padding:13px 15px}.experiment-grid{grid-template-columns:1fr}.stage-wrap{padding:12px 4px 0}.stage-wrap svg{min-height:220px}.stage-caption{font-size:10px;margin:0 13px 14px}.control-panel{border-left:0;border-top:1px solid var(--line);gap:15px;padding:19px}.param-insight{padding-top:12px}.control-group label{margin-bottom:5px}.player{padding:13px;gap:8px}.player .btn{font-size:12px;padding:7px 10px;min-height:38px}.player-speed{font-size:12px;margin-left:0}.time{margin-left:auto;min-width:68px;font-size:11px}.timeline{padding:0 13px 15px}.steps{gap:5px;margin:16px 0}.step-button{flex-direction:column;gap:6px;font-size:11px;padding:9px 2px}.step-button b{width:21px;height:21px;font-size:10px}.explanation{grid-template-columns:1fr;gap:0;padding:5px 0 20px}.explanation h2{font-size:22px;margin-bottom:5px}.explanation p{font-size:15px}.learning-bottom{grid-template-columns:1fr;gap:17px}.learning-card{padding:21px}.notebook-grid{grid-template-columns:1fr}.notebook-header{padding-top:30px}.notebook-header h1{font-size:31px}.notebook-card{min-height:250px}.finish-tip{width:100%}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}

.btn{white-space:nowrap;flex-shrink:0}.save-status{min-width:0}.lab-topic-nav{gap:0}.lab-topic-nav a{position:static}.lab-topic-nav a:after{display:none}

.visual-panel{position:relative}.zoom-scene{position:absolute;right:15px;top:10px;z-index:1;font-size:12px;color:var(--muted);padding:4px 8px;border:1px solid var(--line);border-radius:5px;background:#fff9}.zoom-scene:hover{color:var(--teal);background:white}.diagram-dialog{border:1px solid var(--line);border-radius:16px;padding:0;width:min(94vw,1050px);max-width:1050px;background:var(--paper);color:var(--ink)}.diagram-dialog::backdrop{background:#153b3b88}.diagram-dialog-header{padding:18px 22px;display:flex;justify-content:space-between;gap:16px;align-items:center;background:white;border-bottom:1px solid var(--line)}.diagram-dialog h2{margin:0;font-size:18px}.diagram-dialog p{margin:5px 0 0;font-size:13px;color:var(--muted)}.diagram-scroll{overflow-x:auto;padding:18px 10px}.diagram-scroll>div{min-width:680px}.diagram-scroll svg{width:100%}.diagram-scroll svg text{font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif}@media(max-width:740px){.zoom-scene{font-size:12px;right:11px;top:8px}.stage-wrap{padding-top:32px}.diagram-dialog-header{padding:15px}.diagram-dialog-header h2{font-size:16px}.diagram-dialog-header p{font-size:12px}.diagram-dialog{width:96vw}.stage-caption{min-height:26px}}

/* A single transport controls animation and speech. */
.sound-toggle{margin-left:auto}.sound-toggle[aria-pressed=true]{background:#e6eeeb;color:#526b65}.audio-status{font-size:13px;color:var(--muted);margin:10px 0 16px}.audio-status:empty{display:none}.lab-heading{flex-wrap:wrap}.lab-topic-nav{flex-wrap:wrap}.topics-grid{align-items:stretch}.card-copy p{min-height:4.5em}@media(max-width:980px){.lab-topic-nav a{padding:8px 12px}}@media(max-width:740px){.lab-topic-nav{gap:4px}.lab-topic-nav a{font-size:12px;padding:6px 10px}.player .sound-toggle{margin-left:auto}.player .time{margin-left:0}}