.phase-chapter { margin-top:96px; }
.phase-index {
  background:linear-gradient(145deg,color-mix(in srgb,var(--accent) 7%,var(--panel)),var(--panel));
}
.phase-index::after { border-color:color-mix(in srgb,var(--accent) 26%,transparent); }

.phase-equation-card {
  display:grid;
  grid-template-columns:minmax(0,1.1fr) minmax(300px,.9fr);
  gap:12px;
  margin-bottom:12px;
}
.phase-master-equation,
.phase-equation-key {
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.phase-master-equation {
  min-height:150px;
  padding:28px;
  font-size:clamp(1.5rem,3.4vw,2.5rem);
}
.phase-equation-key {
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:1px;
  overflow:hidden;
  background:var(--line);
}
.phase-equation-key span {
  display:flex;
  align-items:center;
  gap:10px;
  padding:18px;
  background:var(--panel-solid);
  color:var(--muted);
  font-size:.8rem;
}
.phase-equation-key b {
  color:var(--accent);
  font-family:"Cambria Math","STIX Two Math",Georgia,serif;
  font-size:1.25rem;
}

.quantity-grid {
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:12px;
}
.quantity-grid article {
  min-width:0;
  padding:24px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.quantity-symbol {
  color:var(--accent-2);
  font-family:"Cambria Math","STIX Two Math",Georgia,serif;
  font-size:2rem;
}
.quantity-grid h3 { margin:10px 0 8px; }
.quantity-grid p { min-height:92px; margin:0; color:var(--muted); font-size:.84rem; }
.quantity-grid .equation { min-height:64px; margin-top:16px; }
.quantity-grid small { display:block; margin-top:8px; color:var(--muted); font-size:.66rem; }

.relation-band {
  display:grid;
  grid-template-columns:minmax(0,1fr) auto minmax(0,1fr) auto minmax(0,1fr);
  gap:12px;
  align-items:stretch;
}
.relation-band article {
  padding:24px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.relation-band article > span {
  color:var(--muted);
  font-size:.7rem;
  font-weight:800;
  letter-spacing:.05em;
  text-transform:uppercase;
}
.relation-band p { margin:10px 0 0; color:var(--muted); font-size:.82rem; }
.relation-arrow {
  display:grid;
  place-items:center;
  color:var(--accent);
  font-size:1.45rem;
}

.phase-lab-section {
  background:
    radial-gradient(circle at 80% 20%,color-mix(in srgb,var(--accent) 7%,transparent),transparent 34%),
    linear-gradient(180deg,color-mix(in srgb,var(--accent-2) 3%,transparent),transparent 24%);
}
.phase-lab {
  display:grid;
  grid-template-columns:270px minmax(0,1fr);
  gap:12px;
  align-items:start;
}
.phase-controls {
  position:sticky;
  top:calc(var(--header-h) + 16px);
  display:grid;
  gap:22px;
  padding:22px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel-solid);
}
.phase-actions { display:grid; grid-template-columns:1fr 1fr; gap:8px; }
.phase-main { min-width:0; display:grid; gap:12px; }
.phase-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);
}
.phase-metrics article {
  min-width:0;
  padding:15px 16px;
  border-right:1px solid var(--line);
}
.phase-metrics article:last-child { border-right:0; }
.phase-metrics span { display:block; color:var(--muted); font-size:.66rem; font-weight:740; }
.phase-metrics strong { display:inline-block; margin-top:5px; font-size:1.08rem; font-variant-numeric:tabular-nums; }
.phase-metrics small { margin-left:4px; color:var(--muted); font-size:.6rem; }

.phase-visual-grid {
  display:grid;
  grid-template-columns:minmax(0,1.55fr) minmax(300px,.65fr);
  gap:12px;
}
.phase-wave-panel,
.phasor-panel { margin:0; }
.phase-wave-panel figcaption,
.phasor-panel figcaption {
  display:block;
  padding:18px 20px;
  border-bottom:1px solid var(--line);
}
.phase-wave-panel figcaption span,
.phasor-panel figcaption span {
  display:block;
  color:var(--muted);
  font-size:.68rem;
  font-weight:750;
  letter-spacing:.06em;
  text-transform:uppercase;
}
.phase-wave-panel figcaption strong,
.phasor-panel figcaption strong { display:block; margin-top:3px; font-size:.92rem; }

.phase-wave-svg { width:100%; min-height:320px; }
.pp-wave-trace {
  fill:none;
  stroke:var(--accent);
  stroke-width:3.2;
  stroke-linecap:round;
  stroke-linejoin:round;
  vector-effect:non-scaling-stroke;
}
.pp-time-line {
  stroke:var(--line-strong);
  stroke-width:1;
  stroke-dasharray:4 5;
}
.pp-time-marker {
  fill:var(--text);
  stroke:var(--bg);
  stroke-width:2;
}
.pp-amplitude-guide,
.pp-period-line,
.pp-period-tick {
  stroke:var(--accent-2);
  stroke-width:1.4;
  vector-effect:non-scaling-stroke;
}
.pp-amplitude-arrow {
  fill:none;
  stroke:var(--accent-2);
  stroke-width:2;
  marker-end:none;
}
.pp-dimension-label {
  fill:var(--accent-2);
  font-size:12px;
  font-weight:800;
}
.plot-note { padding:0 20px 18px; }

.phasor-svg { width:100%; min-height:320px; }
.phasor-ring {
  fill:none;
  stroke:var(--line-strong);
  stroke-width:1.3;
}
.phasor-axis {
  stroke:var(--line);
  stroke-width:1;
}
.phasor-vector {
  stroke:var(--accent);
  stroke-width:3.2;
  stroke-linecap:round;
}
.phasor-component {
  stroke:var(--accent-2);
  stroke-width:2.4;
  stroke-linecap:round;
}
.phasor-projection {
  stroke:var(--accent-2);
  stroke-width:1.6;
  stroke-dasharray:5 4;
  opacity:.85;
}
.phasor-point {
  fill:var(--text);
  stroke:var(--bg);
  stroke-width:2;
}
.phasor-arc {
  fill:none;
  stroke:var(--accent-3);
  stroke-width:2;
}
.phasor-theta {
  fill:var(--accent-3);
  font-size:14px;
  font-weight:850;
}
.phasor-cardinal,
.phasor-x-label {
  fill:var(--muted);
  font-size:11px;
}
.phasor-readout {
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:14px;
  padding:0 20px 18px;
  color:var(--muted);
  font-size:.76rem;
}
.phasor-readout strong {
  color:var(--text);
  font-variant-numeric:tabular-nums;
}

.initial-condition-grid {
  display:grid;
  grid-template-columns:minmax(0,1.25fr) minmax(240px,.75fr);
  gap:12px;
}
.initial-condition-grid article {
  padding:24px;
  border:1px solid var(--line);
  border-radius:var(--radius-sm);
  background:var(--panel);
}
.initial-condition-main {
  grid-row:span 2;
  display:flex;
  flex-direction:column;
  justify-content:center;
}
.initial-condition-grid p { color:var(--muted); font-size:.84rem; }
.initial-condition-grid .equation { overflow-x:auto; }

.precision-grid {
  display:grid;
  grid-template-columns:repeat(4,minmax(0,1fr));
  gap:12px;
}
.precision-grid article {
  padding:22px;
  border-top:1px solid var(--line-strong);
}
.precision-grid strong { color:var(--accent); font-size:.8rem; }
.precision-grid p { margin:10px 0 0; color:var(--muted); font-size:.82rem; }

@media (max-width:1080px) {
  .quantity-grid { grid-template-columns:1fr 1fr; }
  .quantity-grid p { min-height:70px; }
  .phase-visual-grid { grid-template-columns:1fr; }
  .phasor-panel { display:grid; grid-template-columns:minmax(0,1fr) minmax(220px,.45fr); align-items:center; }
  .phasor-panel figcaption { grid-column:1/-1; }
  .phasor-readout { display:grid; align-content:center; padding:24px; }
  .precision-grid { grid-template-columns:1fr 1fr; }
}
@media (max-width:980px) {
  .phase-equation-card { grid-template-columns:1fr; }
  .relation-band { grid-template-columns:1fr; }
  .relation-arrow { transform:rotate(90deg); min-height:24px; }
  .phase-lab { grid-template-columns:1fr; }
  .phase-controls { position:static; grid-template-columns:1fr 1fr; }
  .phase-actions { align-self:end; }
}
@media (max-width:720px) {
  .phase-chapter { margin-top:58px; }
  .quantity-grid,
  .precision-grid,
  .initial-condition-grid { grid-template-columns:1fr; }
  .quantity-grid p { min-height:0; }
  .initial-condition-main { grid-row:auto; }
  .phase-controls { grid-template-columns:1fr; }
  .phase-equation-key { grid-template-columns:1fr; }
  .phase-metrics { grid-template-columns:1fr 1fr; }
  .phase-metrics article:nth-child(2) { border-right:0; }
  .phase-metrics article:nth-child(-n+2) { border-bottom:1px solid var(--line); }
  .phasor-panel { display:block; }
  .phase-wave-svg,
  .phasor-svg { min-height:270px; }
}