.page-shell {
  max-width: var(--max-width);
  margin: 0 auto;
  padding-inline: var(--page-gutter);
}

.foundations-hero {
  padding-top: clamp(60px, 9vh, 112px);
  padding-bottom: clamp(48px, 7vh, 80px);
}

.foundations-hero .page-title {
  max-width: 16ch;
}

.lab-section {
  padding-top: var(--space-8);
  padding-bottom: var(--space-9);
  border-top: 1px solid var(--line);
}

.section-head {
  margin-bottom: var(--space-6);
}

.section-head-row {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: var(--space-5);
}

.section-title {
  font-size: clamp(28px, 3.2vw, 44px);
  letter-spacing: -0.02em;
}

.section-lede {
  max-width: 62ch;
  margin: calc(-1 * var(--space-4)) 0 var(--space-5);
  color: var(--ink-2);
  font-size: 14.5px;
}

.lab-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.18fr) minmax(320px, 0.82fr);
  gap: clamp(28px, 4vw, 56px);
  align-items: start;
}

.lab-grid-reverse {
  grid-template-columns: minmax(320px, 0.82fr) minmax(0, 1.18fr);
}

.lab-visual {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  padding: var(--space-4);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--surface);
  box-shadow: var(--shadow-card);
}

.lab-controls {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  padding-top: var(--space-2);
}

.lab-kicker {
  color: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.14em;
}

.lab-title {
  margin-top: -8px;
  font-size: clamp(24px, 2.4vw, 32px);
  letter-spacing: -0.02em;
}

.lab-copy {
  color: var(--ink-2);
  font-size: 14px;
  line-height: 1.65;
}

.bezier-host {
  min-height: 0;
}

.bezier-readout {
  align-self: flex-start;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: var(--r-xs);
  background: var(--surface-2);
  color: var(--ink-2);
  font-family: var(--font-mono);
  font-size: 11.5px;
}

.preset-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.preset-chip {
  padding: 7px 12px;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  background: var(--surface);
  color: var(--ink-2);
  font-size: 12px;
  transition: color var(--dur-2), border-color var(--dur-2), background-color var(--dur-2);
}

.preset-chip:hover {
  border-color: var(--line-strong);
  color: var(--ink);
}

.bezier-preview {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.bezier-legend {
  display: flex;
  gap: 16px;
  color: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 10px;
}

.bezier-legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.legend-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.legend-curve {
  background: var(--accent);
}

.legend-linear {
  background: var(--ink-3);
}

.bezier-preview-track {
  position: relative;
  height: 44px;
  border-radius: var(--r-sm);
  background: var(--surface-3);
  overflow: hidden;
}

.bezier-preview-line {
  position: absolute;
  top: 50%;
  left: 12px;
  right: 12px;
  height: 1px;
  background: var(--line-strong);
}

.bezier-dot {
  position: absolute;
  top: 50%;
  left: 11px;
  width: 20px;
  height: 20px;
  margin-top: -10px;
  border-radius: 50%;
  will-change: transform;
}

.bezier-dot-curve {
  z-index: 2;
  background: var(--accent);
  box-shadow: 0 4px 12px rgba(0, 113, 227, 0.3);
}

.bezier-dot-linear {
  width: 12px;
  height: 12px;
  margin-top: -6px;
  background: var(--ink-3);
  opacity: 0.55;
}

.lab-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.lab-button {
  padding: 10px 16px;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  background: var(--surface);
  color: var(--ink);
  font-size: 13px;
  transition: transform var(--dur-2) var(--ease-out), border-color var(--dur-2), box-shadow var(--dur-2);
}

.lab-button:hover {
  border-color: var(--line-strong);
}

.lab-button:active {
  transform: scale(0.97);
}

.lab-button-primary {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.lab-slider {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.lab-slider-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
}

.lab-value {
  color: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.spring-graph {
  display: block;
  width: 100%;
  height: auto;
  border-radius: var(--r-sm);
}

.spring-graph-bg {
  fill: var(--surface-3);
}

.spring-grid line {
  stroke: var(--line);
  stroke-dasharray: 3 4;
}

.spring-target {
  stroke: var(--accent);
  stroke-width: 1.5;
  stroke-dasharray: 5 5;
  opacity: 0.55;
}

.spring-curve {
  fill: none;
  stroke: var(--accent);
  stroke-width: 2.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.spring-axis-labels text {
  fill: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 10px;
}

.spring-demo {
  display: flex;
  align-items: center;
  min-height: 64px;
  padding: 12px;
  border-radius: var(--r-sm);
  background: var(--surface-2);
  border: 1px solid var(--line);
}

.spring-track {
  position: relative;
  width: 100%;
  height: 40px;
  border-radius: var(--r-pill);
  background: var(--surface-3);
}

.spring-target-marker {
  position: absolute;
  top: 50%;
  right: 18px;
  width: 2px;
  height: 20px;
  margin-top: -10px;
  border-radius: 1px;
  background: var(--accent);
  opacity: 0.5;
}

.spring-puck {
  position: absolute;
  top: 50%;
  left: 3px;
  width: 34px;
  height: 34px;
  margin-top: -17px;
  border-radius: 50%;
  background: linear-gradient(145deg, #ffffff, #d9d9e0);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.2);
  will-change: transform;
}

.spring-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  padding-top: 4px;
  color: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 10.5px;
}

.meta-value {
  color: var(--ink);
  font-weight: 500;
}

.duration-grid {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 12px;
}

.duration-card {
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--surface);
  cursor: pointer;
  transition: border-color var(--dur-2), box-shadow var(--dur-2), transform var(--dur-2) var(--ease-out);
}

.duration-card:hover,
.duration-card:focus-visible {
  border-color: transparent;
  box-shadow: var(--shadow-card);
  transform: translateY(-2px);
}

.duration-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 14px;
}

.duration-head strong {
  font-size: 18px;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}

.duration-head span {
  color: var(--ink-3);
  font-size: 11px;
}

.duration-track {
  position: relative;
  height: 26px;
  border-radius: var(--r-pill);
  background: var(--surface-3);
  overflow: hidden;
}

.duration-dot {
  position: absolute;
  top: 50%;
  left: 3px;
  width: 20px;
  height: 20px;
  margin-top: -10px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 3px 10px rgba(0, 113, 227, 0.3);
}

.duration-card.is-playing .duration-dot {
  animation: duration-run var(--dur) var(--ease-out) both;
}

@keyframes duration-run {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(var(--duration-travel, 0px));
  }
}

.duration-detail {
  margin-top: 12px;
  color: var(--ink-3);
  font-size: 11.5px;
  line-height: 1.5;
}

.principle-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.principle-card {
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--surface);
}

.principle-card:first-child {
  grid-column: span 2;
  background: var(--ink);
  color: #fff;
}

.principle-card:first-child p {
  color: rgba(255, 255, 255, 0.66);
}

.principle-number {
  display: block;
  margin-bottom: 16px;
  color: var(--ink-3);
  font-family: var(--font-mono);
  font-size: 10.5px;
}

.principle-card:first-child .principle-number {
  color: rgba(255, 255, 255, 0.5);
}

.principle-card h3 {
  margin-bottom: 8px;
  font-size: 18px;
}

.principle-card p {
  color: var(--ink-2);
  font-size: 13.5px;
  line-height: 1.65;
}

@media (max-width: 1100px) {
  .duration-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 900px) {
  .lab-grid,
  .lab-grid-reverse {
    grid-template-columns: 1fr;
  }

  .principle-grid {
    grid-template-columns: 1fr 1fr;
  }

  .principle-card:first-child {
    grid-column: span 2;
  }
}

@media (max-width: 620px) {
  .duration-grid,
  .principle-grid {
    grid-template-columns: 1fr;
  }

  .principle-card:first-child {
    grid-column: auto;
  }

  .section-head-row {
    flex-direction: column;
    align-items: start;
  }
}

@media (prefers-reduced-motion: reduce) {
  .duration-card.is-playing .duration-dot {
    animation-duration: 200ms;
  }
}