:root{color-scheme:light;--bg:#fff;--surface:#fff;--soft:#f7f9fc;--ink:#1b2637;--muted:#68758a;--line:#e3e8f0;--grid:#edf0f5;--blue:#3568e8;--blue-light:#edf3ff;--reference:#97a2b4;--success:#267a61;--warning:#a7681d;--danger:#c34545;--radius:16px;--shadow:0 10px 35px rgba(26,49,85,.035)}
*{box-sizing:border-box}
[hidden]{display:none!important}
html{scroll-behavior:smooth;scroll-padding-top:98px}
body{margin:0;background:var(--bg);color:var(--ink);font-family:"Microsoft YaHei","PingFang SC","Noto Sans CJK SC",-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;font-size:14px;line-height:1.65;-webkit-font-smoothing:antialiased}
button,input,select,textarea{font:inherit}
button,a,input,select{-webkit-tap-highlight-color:transparent}
a{color:var(--blue);text-decoration:none}
a:hover{text-decoration:underline;text-underline-offset:4px}
button{cursor:pointer}
button:disabled{cursor:not-allowed;opacity:.42}
button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid #3568e84d;outline-offset:3px}
::selection{background:#dce7ff;color:#183d98}
#site-header{position:sticky;top:0;z-index:30;background:#fffffff5;border-bottom:1px solid var(--line);backdrop-filter:blur(12px)}
.site-header-inner{max-width:1392px;min-height:78px;margin:auto;padding:0 40px;display:flex;align-items:center;justify-content:space-between;gap:32px}
.site-brand{display:inline-flex;align-items:center;gap:12px;flex-shrink:0;color:var(--ink);text-decoration:none!important}
.site-mark{display:flex;width:36px;height:36px;align-items:center;justify-content:center;background:var(--blue-light);border-radius:11px;color:var(--blue)}
.site-brand strong{font-size:17px;letter-spacing:.5px;font-weight:650;display:block}
.site-brand small{display:block;font-size:10px;letter-spacing:1.5px;color:var(--muted);line-height:1.6}
.site-nav{display:flex;align-items:center;align-self:stretch;gap:26px}
.site-nav a{position:relative;display:flex;align-items:center;gap:9px;color:var(--muted);white-space:nowrap;font-weight:500;text-decoration:none;font-size:14px}
.site-nav a span{font-size:11px;letter-spacing:.4px;color:#a3adbd}
.site-nav a[aria-current=page]{color:var(--blue);font-weight:650}
.site-nav a[aria-current=page]:after{content:"";height:3px;border-radius:3px 3px 0 0;position:absolute;bottom:0;left:0;right:0;background:var(--blue)}
.site-nav a:hover{color:var(--blue)}
.header-label{color:#8a95a6;font-size:11px;letter-spacing:.7px;white-space:nowrap}
.page-shell{max-width:1392px;margin:0 auto;padding:42px 40px 54px}
.page-heading{position:relative;margin:0 0 25px}
.page-heading h1{margin-bottom:0}
.eyebrow{margin:0 0 10px;color:var(--blue);font-size:11px;font-weight:650;letter-spacing:2px;text-transform:uppercase}
h1,h2,h3,p{margin-top:0}
h1{font-size:34px;line-height:1.35;letter-spacing:.6px;font-weight:650;margin-bottom:12px}
h2{font-size:18px;line-height:1.5;font-weight:650;margin-bottom:12px}
h3{font-size:15px;font-weight:650;margin-bottom:10px}
.lede{font-size:14px;line-height:1.9;color:var(--muted);max-width:900px;margin:0}
.page-number{position:absolute;top:-9px;right:0;font-size:62px;font-weight:300;line-height:1.1;color:#e8edf5;letter-spacing:-4px}
.experiment-layout{display:grid;grid-template-columns:292px minmax(0,1fr);gap:22px;align-items:start}
.control-panel,.plot-panel,.info-panel,.secondary-panel{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);min-width:0;box-shadow:var(--shadow)}
.control-panel{padding:22px;position:sticky;top:100px}
.plot-panel{overflow:hidden}
.panel-heading{padding:20px 24px 14px;display:flex;align-items:flex-start;justify-content:space-between;gap:14px}
.panel-heading h2,.panel-heading h3{margin-bottom:3px}
.panel-heading p{margin:0;font-size:12px;color:var(--muted);line-height:1.7}
.panel-heading small{color:var(--muted);font-size:11px}
.control-panel>.panel-heading{padding:0 0 16px;border-bottom:1px solid var(--line);margin-bottom:19px}
.control-panel h2{font-size:15px}
.control-group{margin-bottom:21px}
.control-group:last-child{margin-bottom:0}
.control-label{display:flex;align-items:center;justify-content:space-between;gap:10px;font-size:12px;color:var(--ink);margin-bottom:10px;font-weight:600}
.control-label output{font-variant-numeric:tabular-nums;color:var(--blue);font-weight:650}
label small,.control-group>small,.control-help{display:block;color:var(--muted);font-size:11px;line-height:1.75;margin-top:7px;font-weight:400}
input[type=range]{width:100%;height:5px;accent-color:var(--blue);cursor:pointer;margin:8px 0 6px;display:block}
input[type=number],select{border:1px solid #dce3ed;border-radius:8px;padding:7px 9px;background:#fff;color:var(--ink);min-width:0}
input[type=number]{font-variant-numeric:tabular-nums;width:83px;text-align:right}
select{width:100%;height:37px;font-size:12px}
input[type=checkbox]{accent-color:var(--blue);width:15px;height:15px;vertical-align:middle;margin:0 7px 0 0;cursor:pointer}
.range-control{width:100%}
.range-ends,.range-labels{display:flex;justify-content:space-between;color:#8b96a7;font-size:10px;margin-top:2px}
.number-row,.parameter-row{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:7px}
.segmented{display:flex;flex-wrap:wrap;gap:6px}
.segmented button,.preset-button,.preset-btn{padding:7px 9px;border:1px solid var(--line);border-radius:7px;background:#fff;color:var(--muted);font-size:11px;line-height:1.6;transition:background .15s,border-color .15s}
.segmented button:hover,.preset-button:hover,.preset-btn:hover{border-color:#b4c8f7;color:var(--blue)}
.segmented .active,.preset-button.active,.preset-btn.active,.segmented [aria-pressed=true]{background:var(--blue-light);border-color:#b9cdf9;color:#2858cc}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:7px;border:1px solid var(--line);border-radius:8px;padding:8px 12px;min-height:36px;font-weight:550;font-size:12px;background:white;color:var(--ink);text-decoration:none!important;line-height:1.5;transition:background .15s,box-shadow .15s}
.btn:hover{background:#f6f8fc;border-color:#ccd6e6}
.btn-primary{background:var(--blue);color:white;border-color:var(--blue)}
.btn-primary:hover{background:#2958cc;color:#fff;border-color:#2958cc}
.btn-secondary{background:#fff;border-color:#dce3ed;color:#526078}
.btn-small{padding:5px 9px;min-height:29px;font-size:11px}
.btn-row,.actions,.button-row{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.btn-row>.btn,.button-row>.btn{flex:1}
.btn-block{width:100%}
.divider{height:1px;background:var(--line);margin:21px 0}
.formula{border:1px solid #e8edf5;border-radius:9px;background:#f7f9fc;padding:12px 14px;font-family:"Cambria Math",Cambria,"Microsoft YaHei",serif;font-size:15px;line-height:1.8;overflow-wrap:anywhere;color:#35445c}
.formula small{font-family:"Microsoft YaHei",sans-serif;font-size:10px;color:var(--muted)}
.formula sub,.formula sup{font-size:.73em}
.chart-wrap{width:100%;min-width:0;position:relative;padding:0 12px 12px;overflow:hidden}
.chart-wrap svg{display:block;width:100%;height:auto;overflow:visible;touch-action:pan-y}
.chart-wrap svg text{font-family:"Microsoft YaHei","PingFang SC",sans-serif;font-variant-numeric:tabular-nums}
.chart-wrap svg [data-draggable],.chart-wrap svg .draggable{cursor:grab;touch-action:none}
.chart-wrap svg .draggable:active{cursor:grabbing}
.legend{display:flex;align-items:center;flex-wrap:wrap;gap:16px;font-size:11px;color:var(--muted);line-height:1.8}
.plot-panel>.legend,.chart-legend{padding:0 25px 19px}
.legend>span{display:inline-flex;align-items:center;gap:6px}
.legend-dot{display:inline-block;width:8px;height:8px;border-radius:50%;background:var(--legend-color,var(--blue));vertical-align:middle;margin-right:5px}
.legend-dot.gray,.legend-dot.reference{background:var(--reference)}
.legend-line{display:inline-block;width:19px;height:0;border-top:2px solid var(--blue);vertical-align:middle;margin-right:5px}
.legend-line.gray,.legend-line.reference{border-color:var(--reference)}
.legend-line.dashed{border-top-style:dashed}
.metrics-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin-top:16px}
.metric-card{border:1px solid var(--line);border-radius:11px;background:#fff;padding:16px 18px;min-width:0}
.metric-label{display:block;font-size:11px;color:var(--muted);line-height:1.6;margin-bottom:9px}
.metric-value{display:block;font-size:26px;line-height:1.3;color:var(--ink);font-weight:600;font-variant-numeric:tabular-nums;letter-spacing:-.5px}
.metric-value small,.metric-value .unit{font-size:12px;font-weight:400;letter-spacing:0;margin-left:4px;color:var(--muted)}
.metric-value>span{font-size:12px;font-weight:400;letter-spacing:0;margin-left:4px;color:var(--muted)}
.metric-hint{display:block;font-size:10px;color:#8a95a6;margin-top:7px;line-height:1.8}
.metric-hint:empty{display:none}
.metric-card.primary .metric-value,.metric-value.blue{color:var(--blue)}
.insight{padding:16px 19px;background:#f3f7ff;border:1px solid #e3ecff;border-radius:10px;color:#3d577e;font-size:12px;line-height:1.9;margin-top:16px}
.insight p:last-child{margin-bottom:0}
.insight strong{color:#264e99;font-weight:650}
.insight.warning{background:#fff9ed;border-color:#f5e6c4;color:#8e6626}
.insight.danger{background:#fff4f3;border-color:#f7d9d6;color:#a2423b}
.section-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:22px;margin-top:24px;align-items:start}
.section-grid>.info-panel,.section-grid>.secondary-panel{padding:22px 24px}
.note{color:var(--muted);font-size:12px;line-height:1.9}
.note:last-child{margin-bottom:0}
.pill{display:inline-flex;align-items:center;gap:5px;white-space:nowrap;font-size:10px;padding:3px 8px;border-radius:20px;background:var(--blue-light);color:#3562c2;font-weight:550}
.pill.success{background:#edf8f1;color:var(--success)}
.pill.warning{background:#fff5e4;color:var(--warning)}
.pill.danger{background:#fff0ef;color:var(--danger)}
.small{font-size:11px}.muted{color:var(--muted)}.mono{font-family:Consolas,"SFMono-Regular",monospace;font-variant-numeric:tabular-nums}.hidden{display:none!important}
.check-row,.toggle-row{display:flex;gap:8px;align-items:center;font-size:12px;margin:10px 0}
.check-row input,.toggle-row input{flex-shrink:0}
.key-values{display:grid;grid-template-columns:auto 1fr;gap:7px 16px;font-size:12px;margin:0}
.key-values dt{color:var(--muted)}.key-values dd{margin:0;text-align:right;font-variant-numeric:tabular-nums}
.reading-list,.step-list{padding-left:18px;color:var(--muted);font-size:12px;line-height:1.9;margin:12px 0 0}
.reading-list li,.step-list li{padding-left:4px;margin-bottom:6px}
.equation-row{font-family:"Cambria Math",Cambria,serif;font-size:16px;line-height:1.8;overflow-wrap:anywhere}
.page-links{display:flex;justify-content:space-between;gap:16px;padding:28px 0 0;margin-top:27px;border-top:1px solid var(--line)}
.page-links a{font-size:12px;color:#526684;text-decoration:none}
.page-links a:hover{color:var(--blue)}
#site-footer{border-top:1px solid var(--line);color:#8a95a6;font-size:10px}
.site-footer-inner{max-width:1392px;margin:auto;padding:22px 40px 26px;display:flex;justify-content:space-between;gap:20px;letter-spacing:.3px}
.toast{position:fixed;z-index:100;bottom:28px;left:50%;transform:translateX(-50%);background:#24344c;color:#fff;padding:11px 20px;border-radius:9px;font-size:12px;box-shadow:0 8px 24px #14223820;max-width:90vw;pointer-events:none}
details.method{margin-top:24px;border:1px solid var(--line);border-radius:10px;padding:12px 18px;color:var(--muted);font-size:11px;line-height:1.9}
details.method summary{cursor:pointer;color:#526078;font-weight:550}
details.method p{margin:12px 0 0}
.time-actions,.frequency-actions{display:flex;gap:8px;flex-wrap:wrap}
.time-actions .btn{flex:1;padding:8px;font-size:11px}
.time-questions{padding:19px 23px 10px;color:var(--muted);font-size:12px}
.time-questions p{line-height:1.9;margin-bottom:18px}
#timePoleReadout{margin:0;padding:0 23px 20px}
#timeInsight{margin:0 22px}
.time-method,.frequency-method{margin-top:24px;border:1px solid var(--line);border-radius:10px;padding:12px 18px;color:var(--muted);font-size:11px;line-height:1.9}
.time-method summary,.frequency-method summary{cursor:pointer;color:#526078;font-weight:550}
.time-method p,.frequency-method p{margin:12px 0 0}
.time-secondary>.time-method{margin-top:0;align-self:start}
.control-panel .formula{margin-bottom:22px}
.control-group .note{margin:6px 0 0;font-size:10px;line-height:1.85}
.frequency-number-row{display:flex;justify-content:space-between;align-items:center;gap:10px}
.frequency-number-row input[type=number]{width:82px}
.frequency-check-row{display:inline-flex;align-items:center;gap:8px;font-size:12px;cursor:pointer}
.frequency-check-row input{margin:0}
.frequency-small-formula{font-size:16px}
.frequency-presets{display:grid;gap:8px}
.frequency-presets .btn{justify-content:flex-start;padding:9px 12px}
.frequency-disabled{opacity:.5}
.frequency-legend{display:flex;flex-wrap:wrap;gap:16px;align-items:center;padding:0 25px 19px;font-size:11px;color:var(--muted)}
.frequency-legend>span{display:inline-flex;align-items:center;gap:7px}
.frequency-metrics{margin:0 22px 22px}
.frequency-metrics{grid-template-columns:repeat(3,minmax(0,1fr))}
.frequency-metrics.frequency-has-lead{grid-template-columns:repeat(4,minmax(0,1fr))}
.frequency-metrics .metric-value{overflow-wrap:anywhere}
.frequency-metrics .metric-card{box-shadow:none;padding:13px 12px;border-radius:9px}
.frequency-metrics .metric-value{font-size:23px}
.frequency-number-row label{color:var(--muted);font-size:11px}
.frequency-explanations p:last-child{color:var(--muted);font-size:12px;line-height:1.9;margin-bottom:0}
.note-panel{padding:22px 24px;background:#fff;border:1px solid var(--line);border-radius:var(--radius)}
@media(min-width:1600px){.page-shell{padding-top:49px}}
@media(max-width:1100px){.site-header-inner,.page-shell{padding-left:26px;padding-right:26px}.site-nav{gap:20px}.header-label{display:none}.experiment-layout{grid-template-columns:264px minmax(0,1fr);gap:17px}.control-panel{padding:18px}.panel-heading{padding:17px 19px 12px}.metrics-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.metric-value{font-size:24px}.site-footer-inner{padding-left:26px;padding-right:26px}}
@media(max-width:760px){.site-header-inner{min-height:auto;flex-wrap:wrap;gap:0;padding:16px 20px 0}.site-brand strong{font-size:16px}.site-mark{width:33px;height:33px}.site-brand small{font-size:9px}.site-nav{width:100%;min-height:51px;justify-content:space-between;gap:12px;margin-top:8px}.site-nav a{font-size:12px;gap:5px}.site-nav a span{font-size:9px}.page-shell{padding:27px 17px 36px}.page-heading{padding-right:48px;margin-bottom:23px}.page-number{font-size:44px;top:-2px;letter-spacing:-2px}h1{font-size:27px;letter-spacing:0}.lede{font-size:12px;line-height:1.9}.eyebrow{font-size:10px;letter-spacing:1.1px}.experiment-layout{grid-template-columns:minmax(0,1fr);gap:17px}.control-panel{position:static;padding:18px}.control-panel .control-group{margin-bottom:17px}.control-panel>.panel-heading{margin-bottom:16px}.panel-heading{padding:17px 16px 11px}.panel-heading h2{font-size:15px}.panel-heading p{font-size:10px}.chart-wrap{padding:0 4px 7px}.plot-panel>.legend{padding:0 17px 15px}.legend{font-size:10px;gap:11px}.metrics-grid{gap:9px;margin-top:13px}.metric-card{padding:13px 14px}.metric-value{font-size:24px}.metric-label{font-size:10px;margin-bottom:7px}.metric-hint{font-size:10px}.section-grid{grid-template-columns:minmax(0,1fr);gap:16px;margin-top:17px}.section-grid>.info-panel,.section-grid>.secondary-panel{padding:18px}.site-footer-inner{padding:19px 20px;flex-wrap:wrap;gap:6px}.insight{font-size:11px;padding:13px 15px}.formula{font-size:14px}.page-links{padding-top:20px;margin-top:22px}.page-links a{font-size:11px}.control-label{font-size:12px}.site-nav a[aria-current=page]:after{height:2px}.btn{font-size:11px}.page-heading .pill{font-size:9px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{transition:none!important}}
@media(max-width:1100px){.frequency-metrics.frequency-has-lead{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:760px){.frequency-metrics{grid-template-columns:repeat(2,minmax(0,1fr))}.frequency-metrics .metric-value{font-size:21px}.frequency-metrics{margin:0 14px 15px}}

/* Academic typography: local system fonts; no external font service. */
:root{--academic-text:"Times New Roman","SimSun",serif;--academic-heading:"SimHei","Noto Sans CJK SC",sans-serif;--academic-math:"Cambria Math","Times New Roman","SimSun",serif;--radius:6px;--shadow:none}
body{font-family:var(--academic-text);font-size:16px}
h1,h2,h3,.site-brand strong{font-family:var(--academic-heading);font-weight:500;letter-spacing:0}
h1{font-size:29px}h2{font-size:18px}h3{font-size:16px}
.site-brand strong{font-size:18px}.site-mark{border-radius:4px;background:#f1f5fb}
.site-nav a{font-size:15px;font-weight:400}.site-nav a[aria-current=page]{font-weight:400}
.page-shell{padding-top:30px}.page-heading{margin-bottom:13px}
.control-panel h2{font-size:17px}.control-label{font-size:14px;font-weight:400}
button,input,select,textarea{font-family:var(--academic-text)}
.btn{font-size:14px;font-weight:400;border-radius:4px}.segmented button,.preset-button,.preset-btn{font-size:13px;border-radius:4px;font-weight:400}
input[type=number],select{border-radius:4px;font-size:15px}
.formula,.root-formula,.root-live-equation,.equation-row,math{font-family:var(--academic-math)}
.formula{font-size:18px;border-radius:4px;background:#fafbfd}
.metric-card{border-radius:4px}.metric-label{font-size:13px}.metric-value{font-family:var(--academic-math);font-weight:400;font-size:27px;letter-spacing:0}.metric-hint{font-size:12px}
.legend,.root-legend,.frequency-legend{font-size:13px}.note{font-size:14px}
svg text{font-family:var(--academic-math)!important;font-weight:400}
.pill{font-family:var(--academic-text);font-size:12px;font-weight:400;border-radius:3px}
.chart-wrap svg text{font-family:var(--academic-math)!important}
.time-method,.frequency-method,details.method{font-family:var(--academic-text);font-size:14px;border-radius:4px}
.time-method summary,.frequency-method summary,details.method summary{font-family:var(--academic-text);font-size:14px;font-weight:400}
.root-pole-list span{font-family:var(--academic-math);font-size:17px;border-radius:3px}
.system-context{display:grid;grid-template-columns:minmax(0,1fr) 260px;align-items:center;gap:36px;padding:0 16px 15px;margin-bottom:22px;border-bottom:1px solid var(--line)}
.feedback-diagram{min-width:0}.feedback-diagram svg{display:block;width:100%;max-width:600px;height:auto;margin:0 auto}
.feedback-diagram math{font-family:var(--academic-math);font-size:27px}
.feedback-relations h2{font-size:16px;margin:0 0 12px;color:#43546b}
.feedback-relations>math{font-size:23px;display:block;text-align:left;margin:11px 0}
#feedback-plant{font-family:var(--academic-math)}
.system-context svg text{font-family:var(--academic-math)!important}
.system-context #feedback-plant math{font-size:28px}
.feedback-equation{margin:10px 0;text-align:left}
.feedback-equation math{font-size:23px}
@media(max-width:1100px){.system-context{grid-template-columns:minmax(0,1fr) 205px;gap:18px;padding-left:0;padding-right:0}.feedback-relations>math{font-size:21px}}
@media(max-width:760px){.page-shell{padding-top:22px}.page-heading{margin-bottom:12px}h1{font-size:26px}.system-context{grid-template-columns:minmax(0,1fr);gap:4px;padding-bottom:11px;margin-bottom:17px}.feedback-relations{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}.feedback-relations h2{margin:0;font-size:13px}.feedback-relations>math{font-size:18px;margin:4px 0}.feedback-diagram svg{max-width:600px}.site-nav a{font-size:13px}.metric-value{font-size:25px}.control-label{font-size:14px}.btn{font-size:13px}.legend,.root-legend,.frequency-legend{font-size:12px}.metric-label{font-size:12px}}
@media(max-width:760px){.feedback-equation{margin:4px 0}.feedback-equation math{font-size:18px}}