/* Lecture 03: analytical inverse kinematics of a 3R positioning robot. */
.lecture-03 .slide-kicker {
  margin: 0 0 0.3rem;
  color: var(--epfl-red);
  font-size: var(--font-small);
  font-weight: 800;
  letter-spacing: 0.09em;
  text-transform: uppercase;
}

.lecture-03 .slide-title {
  margin-bottom: 0.3rem;
  font-size: clamp(2rem, 3vw, 3.45rem);
}

.lecture-03 .slide-subtitle {
  max-width: 86ch;
  margin: 0 0 var(--vgap-sm);
  color: var(--muted);
  font-size: clamp(1rem, 1.25vw, 1.4rem);
  line-height: 1.34;
}

.lecture-03 .lecture-promise {
  max-width: 68ch;
  margin: var(--vgap-md) auto 0;
  padding-top: var(--vgap-sm);
  border-top: 1px solid var(--line);
  color: var(--muted);
}

.lecture-03 .equation {
  margin-block: clamp(0.45rem, 1.2vh, 1rem);
}

.lecture-03 .equation.compact { font-size: clamp(0.9rem, 1.25vw, 1.35rem); }
.lecture-03 .equation.micro { font-size: clamp(0.78rem, 1.04vw, 1.1rem); }

.ik-callout,
.ik-takeaway,
.ik-question {
  padding: 0.5rem 0.7rem;
  border-left: 3px solid var(--epfl-red);
  background: color-mix(in srgb, var(--epfl-red) 4%, white);
  line-height: 1.35;
}

.ik-takeaway { margin-top: var(--vgap-sm); color: var(--muted); }
.ik-question { border-left-color: var(--science-blue); background: #f7f9fc; }

.method-path {
  flex: 1;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1rem;
  align-items: center;
}

.method-card {
  min-height: 15rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-top: 5px solid var(--black);
  background: var(--white);
}

.method-card:last-child { border-top-color: var(--epfl-red); }
.method-card .method-number { color: var(--epfl-red); font-size: var(--font-h3); font-weight: 800; }
.method-card h3 { margin: 0.4rem 0; font-size: var(--font-h3); }
.method-bridge { color: var(--muted); font-size: var(--font-h3); font-weight: 700; }

.dh-table,
.branch-table {
  width: 100%;
  border-collapse: collapse;
  font-variant-numeric: tabular-nums;
}

.dh-table th,
.dh-table td,
.branch-table th,
.branch-table td {
  padding: 0.48rem 0.62rem;
  border-bottom: 1px solid var(--line);
  text-align: center;
}

.dh-table th,
.branch-table th { border-bottom: 3px solid var(--black); }
.dh-table tbody tr:nth-child(2),
.branch-table tbody tr:nth-child(2n) { background: #fafafa; }

.symbol-grid,
.step-grid,
.circle-counts,
.comparison-grid {
  display: grid;
  gap: 0.65rem;
}

.symbol-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.step-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.circle-counts { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.comparison-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); flex: 1; }

.symbol-card,
.step-card,
.count-card,
.comparison-card {
  min-width: 0;
  padding: 0.65rem;
  border-top: 4px solid var(--black);
  background: #fafafa;
}

.step-card:nth-child(2),
.count-card:nth-child(2),
.comparison-card:last-child { border-top-color: var(--epfl-red); }
.symbol-card p,
.step-card p,
.count-card p,
.comparison-card p { margin: 0.3rem 0 0; }
.step-card strong { color: var(--epfl-red); font-size: 1.15em; }

.derivation-stack {
  display: grid;
  gap: 0.5rem;
  align-content: center;
}

.derivation-row {
  display: grid;
  grid-template-columns: 3.2rem minmax(0, 1fr);
  gap: 0.7rem;
  align-items: start;
}

.derivation-row .tag {
  color: var(--epfl-red);
  font-size: 1.35em;
  font-weight: 800;
}

.derivation-row p { margin: 0; }

.boxed-result {
  padding: 0.65rem;
  border: 2px solid var(--black);
  background: var(--white);
}

.quartic-flow {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  gap: 0.5rem;
  align-items: center;
  margin: var(--vgap-sm) 0;
}

.quartic-flow > div:not(.flow-arrow) {
  min-height: 7.5rem;
  padding: 0.65rem;
  border-top: 4px solid var(--black);
  background: #fafafa;
  text-align: center;
}

.quartic-flow > div:nth-child(3) { border-top-color: var(--epfl-red); }
.flow-arrow { color: var(--muted); font-size: var(--font-h3); }

.degeneracy-grid {
  flex: 1;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
}

.degeneracy-card {
  padding: 0.9rem;
  border: 1px solid var(--line);
  border-top: 5px solid var(--epfl-red);
}

.degeneracy-card h3 { margin: 0 0 0.45rem; font-size: var(--font-h3); }

.geometry-stage {
  width: 100%;
  height: 100%;
  min-height: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line);
  background: #fcfcfc;
}

.geometry-stage svg { width: 100%; height: 100%; max-height: 62vh; }
.geometry-stage text { font-family: Arial, Helvetica, sans-serif; fill: var(--ink); }
.geometry-stage .muted-line { stroke: #999; }
.geometry-stage .strong-line { stroke: #111; }
.geometry-stage .accent-line { stroke: #f00; }
.geometry-stage .blue-line { stroke: #3f6ea8; }
.geometry-stage .dash { stroke-dasharray: 7 6; }

.pk-formula {
  padding: 0.6rem;
  border: 1px solid var(--line);
  border-left: 4px solid var(--epfl-red);
  background: #fafafa;
}

.pk-formula .equation { margin-block: 0.35rem; }

.condition-list {
  display: grid;
  gap: 0.45rem;
}

.condition-list > div {
  display: grid;
  grid-template-columns: 6.7rem minmax(0, 1fr);
  gap: 0.55rem;
  padding: 0.45rem 0.55rem;
  border-bottom: 1px solid var(--line);
}

.condition-list strong { color: var(--epfl-red); }

.branch-tree {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  gap: 0.55rem;
  align-items: stretch;
}

.branch-node {
  padding: 0.7rem;
  border: 1px solid var(--line);
  border-top: 4px solid var(--black);
  background: #fafafa;
}

.branch-node:nth-of-type(2) { border-top-color: var(--epfl-red); }
.branch-node p { margin-bottom: 0; }

.source-note {
  /* margin-top: 1 rem; */
  margin: 0.1rem;
  color: var(--muted);
  font-size: clamp(0.62rem, 0.72vw, 0.78rem);
  /* outline: 2px dotted green; */
  max-width: none;
}

/* Lecture-specific Three.js application scenes. */
.ik3r-application {
  flex: 1;
  min-height: 0;
  display: grid;
  grid-template-columns: minmax(0, 1.65fr) minmax(20rem, .75fr);
  gap: .7rem;
}

.ik3r-application.is-wide {
  grid-template-columns: minmax(0, 1.8fr) minmax(18rem, .62fr);
}

.ik3r-demo {
  position: relative;
  width: 100%;
  height: 100%;
  min-height: 0;
  overflow: hidden;
  border: 1px solid var(--line);
  background: #fcfcfc;
}

.ik3r-canvas {
  position: absolute;
  inset: 0;
}

.ik3r-canvas canvas {
  display: block;
  width: 100%;
  height: 100%;
  cursor: grab;
}

.ik3r-canvas canvas:active { cursor: grabbing; }

.ik3r-note {
  position: absolute;
  left: .55rem;
  right: .55rem;
  bottom: .5rem;
  z-index: 2;
  max-width: none;
  margin: 0;
  padding: .32rem .48rem;
  border-left: 3px solid var(--epfl-red);
  background: rgba(255,255,255,.92);
  color: var(--muted);
  font-size: clamp(.68rem, .82vw, .9rem);
  line-height: 1.3;
  pointer-events: none;
}

.ik3r-note.is-error { color: var(--epfl-red); }
.ik3r-controls {
  position: absolute;
  right: .55rem;
  top: .55rem;
  z-index: 3;
  display: flex;
  align-items: center;
  gap: .35rem;
  padding: .28rem .4rem;
  border: 1px solid rgba(0, 0, 0, .12);
  background: rgba(255, 255, 255, .94);
  font-size: clamp(.68rem, .78vw, .86rem);
}

.ik3r-control-label,
.ik3r-label-toggle {
  color: var(--muted);
  font-weight: 700;
}

.ik3r-label-toggle {
  display: inline-flex;
  align-items: center;
  gap: .3rem;
  cursor: pointer;
}

.ik3r-label-toggle input { margin: 0; }

.ik3r-state-toggle {
  display: inline-flex;
  align-items: center;
  gap: .22rem;
  color: var(--muted);
  font-weight: 700;
  cursor: pointer;
}

.ik3r-state-toggle input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.ik3r-switch-track {
  position: relative;
  width: 1.65rem;
  height: .9rem;
  border-radius: 1rem;
  background: #b9bec4;
  transition: background .15s ease;
}

.ik3r-switch-track::after {
  content: '';
  position: absolute;
  top: .12rem;
  left: .12rem;
  width: .66rem;
  height: .66rem;
  border-radius: 50%;
  background: #fff;
  box-shadow: 0 1px 2px rgba(0, 0, 0, .28);
  transition: transform .15s ease;
}

.ik3r-state-toggle input:checked + .ik3r-switch-track { background: var(--epfl-red); }
.ik3r-state-toggle input:checked + .ik3r-switch-track::after { transform: translateX(.75rem); }
.ik3r-state-toggle input:focus-visible + .ik3r-switch-track { outline: 2px solid #2775ff; outline-offset: 2px; }

.ik3r-slider-control {
  display: inline-grid;
  grid-template-columns: auto 4.6rem 2.4rem;
  align-items: center;
  gap: .2rem;
  color: var(--muted);
  font-weight: 700;
}

.ik3r-slider-control input { width: 4.6rem; }
.ik3r-slider-control output { font-variant-numeric: tabular-nums; text-align: right; }

.is-cga-interactive .ik3r-controls {
  left: .55rem;
  right: .55rem;
  flex-wrap: wrap;
  justify-content: flex-end;
  row-gap: .18rem;
}

.is-cga-interactive .ik3r-slider-control {
  grid-template-columns: auto 3.8rem 2.25rem;
}

.is-cga-interactive .ik3r-slider-control input { width: 3.8rem; }

.ik3r-label-select {
  min-width: 5.2rem;
  padding: .14rem .25rem;
  border: 1px solid var(--line);
  background: var(--white);
  color: var(--ink);
  font: inherit;
}

.custom3r-numeric-card {
  min-width: 0;
  padding: .75rem;
  border: 1px solid var(--line);
  border-top: 4px solid var(--black);
  background: var(--white);
  align-self: stretch;
}

.custom3r-numeric-card.accent { border-top-color: var(--epfl-red); }
.custom3r-numeric-card h3 { margin: 0 0 .5rem; font-size: clamp(1.25rem, 1.65vw, 1.8rem); }
.custom3r-numeric-card p { margin: .35rem 0; }
.custom3r-numeric-card .equation { margin-block: .45rem; }

.numeric-sequence {
  display: grid;
  gap: .42rem;
}

.numeric-sequence > div {
  padding: .42rem .5rem;
  border-bottom: 1px solid var(--line);
}

.numeric-sequence strong {
  display: inline-block;
  min-width: 4.7rem;
  color: var(--epfl-red);
}

.ik3r-mini {
  min-height: 34vh;
  margin-top: .45rem;
}

.ik3r-full {
  flex: 1;
  min-height: 0;
}

@media (max-width: 900px) {
  .circle-counts { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .step-grid { grid-template-columns: 1fr; }
  .quartic-flow,
  .branch-tree { grid-template-columns: 1fr; }
  .flow-arrow { display: none; }
  .ik3r-application,
  .ik3r-application.is-wide { grid-template-columns: 1fr; }
}