.damping-chapter { margin-top:96px; }
.damping-index {
  background:linear-gradient(145deg,color-mix(in srgb,var(--accent-2) 7%,var(--panel)),var(--panel));
}
.damping-index::after { border-color:color-mix(in srgb,var(--accent-2) 28%,transparent); }

.damping-model-grid,
.damping-regime-grid,
.damping-timescale-grid,
.damping-cross-grid {
  display:grid;
  gap:12px;
}
.damping-model-grid { grid-template-columns:repeat(3,minmax(0,1fr)); }
.damping-regime-grid { grid-template-columns:repeat(3,minmax(0,1fr)); }
.damping-timescale-grid { grid-template-columns:repeat(3,minmax(0,1fr)); }
.damping-cross-grid { grid-template-columns:repeat(4,minmax(0,1fr)); }

.damping-model-grid article,
.regime-card,
.damping-timescale-grid article,
.damping-cross-grid article {
  min-width:0;
  padding:24px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.damping-model-grid h3,
.regime-card h3 { margin:14px 0 8px; }
.damping-model-grid p,
.regime-card p,
.damping-timescale-grid p,
.damping-cross-grid p { margin:9px 0 0; color:var(--muted); font-size:.84rem; }

.regime-card { position:relative; overflow:hidden; }
.regime-card::before {
  content:"";
  position:absolute;
  inset:0 auto 0 0;
  width:3px;
}
.regime-card.under::before { background:var(--accent); }
.regime-card.critical::before { background:var(--accent-3); }
.regime-card.over::before { background:var(--accent-2); }
.regime-tag {
  display:inline-flex;
  padding:5px 8px;
  border:1px solid var(--line-strong);
  border-radius:999px;
  color:var(--muted);
  font-size:.68rem;
  font-weight:850;
}

.dissipation-derivation {
  display:grid;
  grid-template-columns:minmax(0,.8fr) auto minmax(0,1.1fr) auto minmax(0,1.1fr);
  gap:12px;
  align-items:stretch;
}
.dissipation-derivation article {
  display:grid;
  align-content:center;
  padding:24px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.dissipation-result {
  background:linear-gradient(145deg,color-mix(in srgb,var(--accent-2) 6%,var(--panel)),var(--panel)) !important;
}
.dissipation-note {
  margin:14px 0 0;
  padding:18px 20px;
  border-left:3px solid var(--accent-2);
  background:color-mix(in srgb,var(--accent-2) 5%,transparent);
  color:var(--muted);
}

.damping-lab-section {
  background:
    radial-gradient(circle at 18% 15%,color-mix(in srgb,var(--accent-2) 7%,transparent),transparent 31%),
    linear-gradient(180deg,color-mix(in srgb,var(--accent) 3%,transparent),transparent 25%);
}
.damping-lab {
  display:grid;
  grid-template-columns:275px minmax(0,1fr);
  gap:12px;
  align-items:start;
}
.damping-controls {
  position:sticky;
  top:calc(var(--header-h) + 16px);
  display:grid;
  gap:21px;
  padding:22px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel-solid);
}
.damping-actions { display:grid; grid-template-columns:1fr 1fr; gap:8px; }
.damping-main { min-width:0; display:grid; gap:12px; }

.damping-metrics {
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  overflow:hidden;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.damping-metrics article {
  min-width:0;
  padding:15px 16px;
  border-right:1px solid var(--line);
}
.damping-metrics article:last-child { border-right:0; }
.damping-metrics span { display:block; color:var(--muted); font-size:.66rem; font-weight:740; }
.damping-metrics strong { display:inline-block; margin-top:5px; font-size:1.06rem; font-variant-numeric:tabular-nums; }
.damping-metrics small { margin-left:4px; color:var(--muted); font-size:.58rem; }
.regime-readout { color:var(--accent); }

.damping-visual-grid {
  display:grid;
  grid-template-columns:minmax(0,1.45fr) minmax(300px,.55fr);
  gap:12px;
}
.damping-bottom-grid {
  display:grid;
  grid-template-columns:minmax(0,1.3fr) minmax(300px,.7fr);
  gap:12px;
}
.damping-time-panel,
.damping-phase-panel,
.damping-energy-panel { margin:0; }
.damping-time-panel figcaption,
.damping-phase-panel figcaption,
.damping-energy-panel figcaption {
  display:block;
  padding:18px 20px;
  border-bottom:1px solid var(--line);
}
.damping-time-panel figcaption span,
.damping-phase-panel figcaption span,
.damping-energy-panel figcaption span {
  display:block;
  color:var(--muted);
  font-size:.68rem;
  font-weight:750;
  letter-spacing:.06em;
  text-transform:uppercase;
}
.damping-time-panel figcaption strong,
.damping-phase-panel figcaption strong,
.damping-energy-panel figcaption strong { display:block; margin-top:3px; font-size:.92rem; }

.damping-time-panel svg,
.damping-phase-panel svg,
.damping-energy-panel svg { width:100%; min-height:290px; }

.damping-trace {
  fill:none;
  vector-effect:non-scaling-stroke;
  stroke-linecap:round;
  stroke-linejoin:round;
}
.damping-trace.response { stroke:var(--accent); stroke-width:3.2; }
.damping-trace.envelope {
  stroke:var(--accent-2);
  stroke-width:1.4;
  stroke-dasharray:6 6;
  opacity:.8;
}
.damping-time-marker-line,
.damping-energy-marker-line {
  stroke:var(--line-strong);
  stroke-width:1;
  stroke-dasharray:4 5;
}
.damping-time-marker,
.damping-phase-marker,
.damping-energy-marker {
  fill:var(--text);
  stroke:var(--bg);
  stroke-width:2;
}

.damping-phase-trace {
  fill:none;
  stroke:var(--accent-2);
  stroke-width:2.4;
  vector-effect:non-scaling-stroke;
}
.phase-regime-note,
.time-response-note {
  margin:0;
  padding:0 20px 18px;
  color:var(--muted);
  font-size:.74rem;
}

.damping-energy-trace {
  fill:none;
  stroke:var(--accent-3);
  stroke-width:3;
  vector-effect:non-scaling-stroke;
}

.damping-state-grid {
  display:grid;
  grid-template-columns:1fr 1fr;
  border-bottom:1px solid var(--line);
}
.damping-state-grid > div {
  display:grid;
  grid-template-columns:auto 1fr auto;
  gap:6px;
  align-items:baseline;
  min-width:0;
  padding:13px 14px;
  border-right:1px solid var(--line);
  border-bottom:1px solid var(--line);
}
.damping-state-grid > div:nth-child(2n) { border-right:0; }
.damping-state-grid > div:nth-last-child(-n+2) { border-bottom:0; }
.damping-state-grid span { color:var(--accent-2); font-size:.68rem; font-weight:850; }
.damping-state-grid strong { justify-self:end; min-width:0; font-size:.82rem; font-variant-numeric:tabular-nums; }
.damping-state-grid small { color:var(--muted); font-size:.56rem; }

.damping-regime-scale {
  display:grid;
  grid-template-columns:auto 1fr auto;
  gap:10px;
  align-items:center;
  padding:20px;
}
.damping-regime-scale > span {
  color:var(--muted);
  font-size:.65rem;
  text-transform:uppercase;
  letter-spacing:.04em;
}
.regime-scale-track {
  position:relative;
  height:9px;
  border-radius:999px;
  background:linear-gradient(90deg,
    color-mix(in srgb,var(--accent) 58%,var(--line)),
    color-mix(in srgb,var(--accent-3) 62%,var(--line)) 50%,
    color-mix(in srgb,var(--accent-2) 62%,var(--line)));
}
.regime-scale-marker {
  position:absolute;
  top:50%;
  left:20%;
  width:15px;
  height:15px;
  border:2px solid var(--bg);
  border-radius:50%;
  background:var(--text);
  transform:translate(-50%,-50%);
}
.critical-marker {
  position:absolute;
  top:-4px;
  bottom:-4px;
  left:50%;
  width:1px;
  background:var(--text);
  opacity:.55;
}
.damping-state > p {
  margin:0;
  padding:0 20px 20px;
  color:var(--muted);
  font-size:.75rem;
}

.damping-timescale-grid .equation { margin-top:9px; }
.damping-cross-grid article > span {
  color:var(--accent);
  font-size:.68rem;
  font-weight:850;
  letter-spacing:.06em;
  text-transform:uppercase;
}
.damping-cross-grid strong { display:block; margin-top:8px; }

@media (max-width:1080px) {
  .damping-visual-grid,
  .damping-bottom-grid { grid-template-columns:1fr; }
  .damping-phase-panel {
    display:grid;
    grid-template-columns:minmax(0,1fr) minmax(220px,.4fr);
    align-items:center;
  }
  .damping-phase-panel figcaption { grid-column:1/-1; }
  .phase-regime-note { padding:20px; }
}
@media (max-width:980px) {
  .damping-model-grid,
  .damping-regime-grid,
  .damping-timescale-grid { grid-template-columns:1fr 1fr; }
  .damping-model-grid > :last-child,
  .damping-regime-grid > :last-child,
  .damping-timescale-grid > :last-child { grid-column:1/-1; }
  .dissipation-derivation { grid-template-columns:1fr; }
  .derivation-arrow { transform:rotate(90deg); min-height:22px; }
  .damping-lab { grid-template-columns:1fr; }
  .damping-controls { position:static; grid-template-columns:1fr 1fr; }
  .damping-actions { align-self:end; }
  .damping-cross-grid { grid-template-columns:1fr 1fr; }
}
@media (max-width:720px) {
  .damping-chapter { margin-top:58px; }
  .damping-model-grid,
  .damping-regime-grid,
  .damping-timescale-grid,
  .damping-cross-grid { grid-template-columns:1fr; }
  .damping-model-grid > :last-child,
  .damping-regime-grid > :last-child,
  .damping-timescale-grid > :last-child { grid-column:auto; }
  .damping-controls { grid-template-columns:1fr; }
  .damping-metrics { grid-template-columns:1fr 1fr; }
  .damping-metrics article:nth-child(2) { border-right:0; }
  .damping-metrics article:nth-child(-n+2) { border-bottom:1px solid var(--line); }
  .damping-phase-panel { display:block; }
  .damping-state-grid { grid-template-columns:1fr; }
  .damping-state-grid > div { border-right:0; border-bottom:1px solid var(--line); }
  .damping-state-grid > div:last-child { border-bottom:0; }
  .damping-time-panel svg,
  .damping-phase-panel svg,
  .damping-energy-panel svg { min-height:250px; }
}