/* M02K07 · Group velocity */
.group-chapter{padding-top:74px;padding-bottom:50px}.k07-header{display:grid;grid-template-columns:minmax(0,1.4fr) minmax(280px,.6fr);gap:34px;align-items:end}.k07-header h2{margin:.12em 0 .22em;font-size:clamp(3.2rem,7vw,6.8rem);line-height:.9;letter-spacing:-.055em}.k07-header h2 em{font-weight:400;color:var(--accent)}.k07-header .lead{max-width:820px}.k07-index{padding:24px;border:1px solid var(--line);border-radius:var(--radius);background:linear-gradient(145deg,color-mix(in srgb,var(--accent) 10%,var(--panel)),var(--panel));box-shadow:var(--shadow)}.k07-index>span{display:block;color:var(--accent);font-size:.75rem;text-transform:uppercase;letter-spacing:.13em}.k07-index>strong{display:block;margin:10px 0;font-family:"Cambria Math","STIX Two Math",Georgia,serif;font-size:clamp(1.8rem,3vw,2.7rem);font-weight:500}.k07-index p{margin:0;color:var(--muted);font-size:.88rem}
.group-beat-section,.group-packet-section,.group-interpretation{padding-top:58px;padding-bottom:58px}.group-beat-grid{display:grid;grid-template-columns:1.35fr 1fr 1fr;gap:12px}.group-beat-card,.group-geometry-card,.group-packet-card,.group-interpret-card{padding:23px;border:1px solid var(--line);border-radius:var(--radius-sm);background:var(--panel)}.group-beat-card.primary,.group-packet-card.primary{background:linear-gradient(145deg,color-mix(in srgb,var(--accent) 9%,var(--panel)),var(--panel));border-color:color-mix(in srgb,var(--accent) 30%,var(--line))}.group-beat-card>span,.group-packet-card>span{color:var(--accent);font-size:.73rem;text-transform:uppercase;letter-spacing:.11em}.group-beat-card strong,.group-packet-card strong{display:block;margin:10px 0 7px}.group-beat-card p,.group-packet-card p,.group-geometry-card p,.group-interpret-card p{margin:12px 0 0;color:var(--muted);font-size:.86rem}.group-beat-card .equation,.group-packet-card .equation{margin-top:14px}.group-beat-card.primary .equation{font-size:.91rem}
.group-geometry-section{padding:58px 0;background:color-mix(in srgb,var(--panel) 45%,transparent);border-block:1px solid var(--line)}.group-geometry-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.group-geometry-card>strong{display:block;margin:10px 0}.group-geometry-card.key{border-color:color-mix(in srgb,var(--accent) 42%,var(--line));background:linear-gradient(145deg,color-mix(in srgb,var(--accent) 8%,var(--panel)),var(--panel))}.group-geometry-card .equation{margin-top:13px}
.group-packet-grid{display:grid;grid-template-columns:1.25fr 1fr 1fr;gap:12px}.group-packet-card.boundary{border-style:dashed}.group-lab-section{padding:62px 0;background:linear-gradient(180deg,color-mix(in srgb,var(--panel) 36%,transparent),transparent 24%,transparent 76%,color-mix(in srgb,var(--panel) 32%,transparent));border-block:1px solid var(--line)}.group-lab-shell{display:grid;grid-template-columns:minmax(235px,290px) minmax(0,1fr);gap:16px;align-items:start}.group-controls{position:sticky;top:88px;display:grid;gap:14px;padding:18px;border:1px solid var(--line);border-radius:var(--radius);background:var(--panel);box-shadow:var(--shadow)}.group-preset-row{display:grid;grid-template-columns:repeat(3,1fr);gap:7px}.group-preset-row button{min-height:36px;padding:7px;border:1px solid var(--line);border-radius:9px;background:var(--panel-2);color:var(--muted);font:inherit;font-size:.72rem;cursor:pointer}.group-preset-row button:hover,.group-preset-row button:focus-visible{border-color:var(--accent);color:var(--text)}.group-main{display:grid;gap:12px;min-width:0}.group-panel{border:1px solid var(--line);border-radius:var(--radius);background:var(--panel);overflow:hidden}.group-panel-head{display:flex;justify-content:space-between;gap:16px;align-items:center;padding:16px 18px;border-bottom:1px solid var(--line)}.group-panel-head>div>span{display:block;color:var(--muted);font-size:.72rem;text-transform:uppercase;letter-spacing:.1em}.group-panel-head>div>strong{display:block;margin-top:4px}.group-status{display:flex;align-items:center;gap:7px;color:var(--muted);font-size:.74rem}.group-status i{width:8px;height:8px;border-radius:50%;background:var(--accent-3);box-shadow:0 0 12px color-mix(in srgb,var(--accent-3) 70%,transparent)}.group-packet-svg,.group-dispersion-svg{display:block;width:100%;height:auto;background:radial-gradient(circle at 50% 25%,color-mix(in srgb,var(--accent) 5%,transparent),transparent 48%)}.group-axis,.group-disp-axis{stroke:var(--line-strong);stroke-width:1}.group-wave{fill:none;stroke:var(--accent);stroke-width:2.2;stroke-linejoin:round;stroke-linecap:round}.group-envelope{fill:none;stroke:var(--muted);stroke-width:1.4;stroke-dasharray:7 6;opacity:.9}.group-envelope-center{stroke:var(--accent-3);stroke-width:1.5;stroke-dasharray:5 5}.group-phase-marker{stroke:var(--warm);stroke-width:1.5;stroke-dasharray:3 5}.group-center-dot{fill:var(--accent-3);stroke:var(--bg);stroke-width:2}.group-phase-dot{fill:var(--warm);stroke:var(--bg);stroke-width:2}.group-svg-label,.group-svg-phase,.group-disp-label,.group-disp-phase,.group-disp-group{font:600 13px/1.2 Inter,system-ui,sans-serif}.group-svg-label,.group-disp-group{fill:var(--accent-3)}.group-svg-phase,.group-disp-phase{fill:var(--warm)}.group-disp-label{fill:var(--text)}.group-svg-muted{fill:var(--muted);font:12px/1.2 Inter,system-ui,sans-serif}.group-telemetry{display:grid;grid-template-columns:repeat(6,1fr);border-top:1px solid var(--line)}.group-telemetry>div{padding:13px 11px;border-right:1px solid var(--line);min-width:0}.group-telemetry>div:last-child{border-right:0}.group-telemetry span{display:block;color:var(--muted);font-size:.68rem;line-height:1.25}.group-telemetry strong{display:block;margin-top:5px;font-size:.84rem;font-variant-numeric:tabular-nums;white-space:nowrap}.group-detail-grid{display:grid;grid-template-columns:minmax(0,1.25fr) minmax(250px,.75fr);gap:12px}.dispersion-panel{min-width:0}.group-phase-ray{stroke:var(--warm);stroke-width:2}.group-tangent{stroke:var(--accent-3);stroke-width:3}.group-kpoint{fill:var(--text);stroke:var(--bg);stroke-width:2}.group-band{fill:color-mix(in srgb,var(--accent) 28%,transparent)}.group-slope-readout{display:grid;grid-template-columns:1fr 1fr;border-top:1px solid var(--line)}.group-slope-readout>div{padding:13px 16px}.group-slope-readout>div+div{border-left:1px solid var(--line)}.group-slope-readout span{display:block;color:var(--muted);font-size:.72rem}.group-slope-readout strong{display:block;margin-top:5px;font-variant-numeric:tabular-nums}.group-reading-card{padding:22px}.group-reading-card h3{margin:8px 0 16px}.group-slip{padding:14px;border:1px solid var(--line);border-radius:12px;background:var(--panel-2)}.group-slip span{display:block;color:var(--muted);font-family:"Cambria Math","STIX Two Math",Georgia,serif}.group-slip strong{display:block;margin-top:5px;font-size:1.35rem;font-variant-numeric:tabular-nums}.group-reading-card p{color:var(--muted);font-size:.88rem}.group-validity{margin-top:16px;padding-top:14px;border-top:1px solid var(--line);color:var(--muted);font-size:.76rem}.group-validity b{color:var(--text)}
.group-interpret-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.group-interpret-card>span{color:var(--accent);font-family:"Cambria Math","STIX Two Math",Georgia,serif;font-size:1.45rem}.group-interpret-card strong{display:block;margin:10px 0 8px}.group-interpret-card.key{border-color:color-mix(in srgb,var(--accent) 38%,var(--line))}.group-next{margin-top:10px}
@media(max-width:1120px){.group-lab-shell{grid-template-columns:1fr}.group-controls{position:static;grid-template-columns:repeat(2,minmax(0,1fr))}.group-preset-row,.group-controls .lab-actions{align-self:end}.group-telemetry{grid-template-columns:repeat(3,1fr)}.group-telemetry>div:nth-child(3){border-right:0}.group-telemetry>div:nth-child(-n+3){border-bottom:1px solid var(--line)}}
@media(max-width:980px){.k07-header{grid-template-columns:1fr}.k07-index{max-width:680px}.group-beat-grid,.group-packet-grid{grid-template-columns:1fr 1fr}.group-beat-card.primary,.group-packet-card.primary{grid-column:1/-1}.group-geometry-grid,.group-interpret-grid{grid-template-columns:1fr 1fr}.group-geometry-card:last-child,.group-interpret-card:last-child{grid-column:1/-1}.group-detail-grid{grid-template-columns:1fr}}
@media(max-width:680px){.group-chapter{padding-top:56px;padding-bottom:42px}.k07-header h2{font-size:clamp(2.5rem,13vw,4.6rem)}.group-beat-section,.group-geometry-section,.group-packet-section,.group-lab-section,.group-interpretation{padding-top:48px;padding-bottom:52px}.group-beat-grid,.group-packet-grid,.group-geometry-grid,.group-interpret-grid{grid-template-columns:1fr}.group-beat-card.primary,.group-packet-card.primary,.group-geometry-card:last-child,.group-interpret-card:last-child{grid-column:auto}.group-controls{grid-template-columns:1fr}.group-telemetry{grid-template-columns:1fr 1fr}.group-telemetry>div{border-bottom:1px solid var(--line)}.group-telemetry>div:nth-child(odd){border-right:1px solid var(--line)}.group-telemetry>div:nth-child(even){border-right:0}.group-telemetry>div:nth-last-child(-n+2){border-bottom:0}.group-panel-head{align-items:flex-start}.group-packet-svg{min-height:270px}.group-svg-label,.group-svg-phase{font-size:16px}.group-dispersion-svg{min-height:260px}}
@media(max-width:420px){.group-chapter{padding-top:48px}.group-beat-card,.group-geometry-card,.group-packet-card,.group-interpret-card{padding:20px}.group-preset-row{grid-template-columns:1fr}.group-packet-svg{min-height:250px}.group-telemetry>div{padding:11px 9px}.group-telemetry strong{font-size:.78rem}.group-svg-label,.group-svg-phase{font-size:34px}.group-svg-muted{font-size:28px}.group-disp-phase,.group-disp-group,.group-disp-label{font-size:24px}.group-dispersion-svg{min-height:250px}}
@media(max-width:360px){.k07-header h2{font-size:2.25rem;overflow-wrap:anywhere}.group-telemetry strong{font-size:.73rem}.group-slope-readout{grid-template-columns:1fr}.group-slope-readout>div+div{border-left:0;border-top:1px solid var(--line)}}