:root {
  --bg: #ffffff;
  --ink: #0f172a;
  --muted: #516173;
  --line: #e4ebf2;
  --accent: #0a84ff;
  --term-heading-h: 24px;
  --mini-label-h: 25px;
  --panel-op-w: 30px;
  --brain-h: clamp(112px, 10.2vw, 138px);
  --prevalence-brain-h: var(--brain-h);
  --matrix-size: clamp(112px, 9.6vw, 132px);
  --scatter-extra: 10px;
  --scatter-h: clamp(142px, 13.4vw, 190px);
  --equation-brain-w: clamp(150px, 12.5vw, 166px);
  --mini-size: clamp(92px, 8.8vw, 122px);
  --scatter-size: calc(var(--matrix-size) + var(--scatter-extra));
  --mini-brain-h: clamp(92px, 8vw, 116px);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Avenir Next", "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.page {
  width: min(1500px, calc(100% - 28px));
  margin: 0 auto;
  padding: 10px 0 18px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.topbar {
  display: flex;
  align-items: end;
  min-height: 44px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line);
}

.selector-shell {
  display: flex;
  align-items: center;
  gap: 10px;
  max-width: 690px;
}

.selector-label {
  display: grid;
  grid-template-columns: auto minmax(300px, 320px);
  gap: 10px;
  align-items: center;
  color: #0757b8;
  font-size: 0.86rem;
  font-weight: 500;
}

select {
  min-height: 34px;
  width: 100%;
  border: 1px solid rgba(10, 132, 255, 0.36);
  border-radius: 10px;
  padding: 5px 34px 5px 11px;
  background: linear-gradient(180deg, #0a84ff 0%, #0872e3 100%);
  color: #ffffff;
  font: inherit;
  font-weight: 500;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.24), 0 4px 12px rgba(10, 132, 255, 0.16);
}

select option {
  background: #ffffff;
  color: var(--ink);
}

select option:disabled {
  color: #8da0b4;
}

.download-button {
  min-height: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 5px 13px;
  border: 1px solid #0a84ff;
  border-radius: 10px;
  background: #ffffff;
  color: #0a84ff;
  font: inherit;
  font-size: 0.86rem;
  font-weight: 500;
  line-height: 1;
  text-decoration: none;
  white-space: nowrap;
  box-shadow: 0 4px 12px rgba(10, 132, 255, 0.18);
}

.download-button[aria-disabled="true"] {
  opacity: 0.55;
  pointer-events: none;
}

h2,
p {
  margin-top: 0;
}

h2 {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
  font-size: clamp(0.98rem, 1.12vw, 1.16rem);
  font-weight: 500;
  letter-spacing: 0;
  line-height: 1.12;
}

h2 > span:last-child {
  min-height: 26px;
  display: inline;
}

sub {
  font-size: 0.72em;
  line-height: 0;
  vertical-align: -0.32em;
}

.math-token {
  white-space: nowrap;
}

.math-sub {
  display: inline-block;
  margin-left: 0.02em;
  font-size: 0.56em;
  line-height: 0;
  transform: translateY(0.58em);
}

.step-badge {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  display: inline-grid;
  place-items: center;
  border-radius: 7px;
  background: #0a84ff;
  color: #ffffff;
  font-size: 0.9rem;
  font-weight: 700;
  line-height: 1;
  box-shadow: 0 6px 18px rgba(10, 132, 255, 0.18);
}

.story-section,
.derivation {
  border-top: 1px solid var(--line);
  padding: 14px 0 0;
  background: transparent;
}

.overview-section {
  border-top: 0;
  padding-top: 0;
}

.story-stack {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.overview-grid {
  display: grid;
  grid-template-columns:
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--panel-op-w)
    var(--equation-brain-w);
  gap: 8px;
  align-items: center;
  justify-content: start;
}

.overview-inputs {
  grid-column: 1 / 4;
  display: grid;
  gap: 16px;
}

.overview-row {
  display: grid;
  grid-template-columns: var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w);
  gap: 8px;
  align-items: center;
  justify-content: start;
}

.flow-arrow {
  color: #06122d;
  font-size: clamp(1.7rem, 2.5vw, 2.6rem);
  font-weight: 600;
  line-height: 1;
  text-align: center;
}

.output-arrow {
  display: inline-block;
  justify-self: center;
  font-size: clamp(1.75rem, 2.35vw, 2.65rem);
  transform: scaleX(1.25);
  transform-origin: center;
}

.output-arrow-wrap {
  grid-column: 4;
  display: grid;
  gap: 0;
  justify-items: center;
  justify-self: center;
  align-content: center;
  padding-left: 0;
}

.arrow-label {
  margin-bottom: -8px;
  color: #182b3e;
  font-size: 0.72rem;
  font-weight: 500;
  line-height: 1.04;
  text-align: center;
  transform: translateX(6px);
  white-space: nowrap;
}

.prevalence-term {
  width: var(--equation-brain-w);
}

.overview-matrix {
  width: var(--equation-brain-w);
}

.overview-matrix .term-heading {
  width: var(--matrix-size);
  margin-bottom: -6px;
  margin-left: 28px;
  transform: translateY(6px);
}

.prevalence-term .term-heading {
  margin-bottom: 23px;
  transform: translateY(14px);
}

.reference-term {
  grid-column: 5;
  width: var(--equation-brain-w);
  justify-self: center;
}

.equation {
  display: grid;
  gap: 8px;
  align-items: start;
  grid-template-columns:
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--panel-op-w)
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--scatter-size);
  justify-content: start;
}

.equation-with-scatter {
  grid-template-columns: minmax(0, 1fr) 28px minmax(0, 1fr) minmax(240px, 0.82fr);
}

.equation-specificity > .scatter-term,
.equation-mean > .scatter-term {
  grid-column: 7;
}

.control-mini-grid > .scatter-term {
  grid-column: 5;
}

.term,
.matrix-term {
  min-width: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  padding: 0;
}

.term-heading {
  min-height: var(--term-heading-h);
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 8px;
  color: #182b3e;
  font-size: 0.82rem;
  font-weight: 500;
  line-height: 1.14;
  text-align: center;
}

.term > .term-heading span {
  transform: none;
}

.term-heading strong {
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 500;
  text-align: right;
  line-height: 1.14;
}

.term-meta {
  margin: 0 0 4px;
  color: #17213a;
  font-size: 0.74rem;
  font-weight: 650;
  line-height: 1.2;
  text-align: center;
}

.brain-plot {
  width: 100%;
  height: var(--brain-h);
}

.prevalence-brain {
  height: var(--prevalence-brain-h);
}

.reference-brain {
  height: var(--brain-h);
}

.canvas-brain-plot {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0;
  align-items: center;
}

.brain-canvas {
  display: block;
  width: 100%;
  height: 100%;
  cursor: grab;
  touch-action: none;
}

.brain-canvas.is-dragging {
  cursor: grabbing;
}

.brain-scale {
  display: none;
  width: 28px;
  height: 56%;
  min-height: 54px;
  max-height: 132px;
  justify-self: center;
  grid-template-columns: 7px 8px 13px;
  grid-template-rows: 1fr;
  gap: 1px;
  align-items: stretch;
}

.brain-scale-title {
  align-self: center;
  color: #334155;
  font-size: 0.56rem;
  font-weight: 500;
  line-height: 1;
  text-align: center;
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  white-space: nowrap;
}

.brain-scale-bar {
  border: 1px solid #cbd5e1;
  border-radius: 2px;
}

.brain-scale-ticks {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  color: #334155;
  font-size: 0.56rem;
  font-weight: 520;
  line-height: 1;
  white-space: nowrap;
}

.brain-empty-message {
  position: absolute;
  left: 8px;
  right: 34px;
  top: 42%;
  transform: translateY(-50%);
  padding: 5px 7px;
  border: 1px solid #d6e0ea;
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.84);
  color: #334155;
  font-size: 0.72rem;
  font-weight: 500;
  line-height: 1.12;
  text-align: center;
}

.brain-empty-message[hidden] {
  display: none;
}

.matrix-plot {
  width: calc(var(--matrix-size) + 28px);
  height: calc(var(--matrix-size) + 16px);
  aspect-ratio: 1 / 1;
  margin: 0 auto;
}

.matrix-with-strip {
  display: grid;
  grid-template-columns: 22px var(--matrix-size);
  gap: 6px;
  align-items: end;
  aspect-ratio: auto;
}

.row-strip-wrap {
  height: calc(var(--matrix-size) + 16px);
  display: grid;
  grid-template-rows: 16px var(--matrix-size);
  gap: 0;
  align-items: stretch;
}

.row-strip-label {
  color: #182b3e;
  font-size: 0.72rem;
  font-weight: 500;
  line-height: 1;
  text-align: center;
}

.row-strip-canvas,
.matrix-canvas {
  display: block;
}

.row-strip-canvas {
  width: 22px;
  height: var(--matrix-size);
}

.matrix-canvas {
  width: 100%;
  height: var(--matrix-size);
}

.scatter-plot {
  width: var(--scatter-size);
  height: var(--scatter-size);
  max-width: 100%;
  aspect-ratio: 1 / 1;
  margin: 0 auto;
}

.scatter-term {
  display: grid;
  place-items: center;
  height: var(--brain-h);
  margin-top: var(--term-heading-h);
}

.operator {
  height: var(--brain-h);
  display: grid;
  place-items: center;
  align-self: start;
  justify-self: center;
  margin-top: var(--term-heading-h);
  color: #0f172a;
  font-size: clamp(1.4rem, 1.9vw, 2.1rem);
  font-weight: 560;
  line-height: 1;
}

.operator.small {
  font-size: clamp(1.2rem, 1.6vw, 1.75rem);
}

.formula {
  min-height: 18px;
  margin: -5px 0 0;
  color: #223443;
  font-size: 0.76rem;
  line-height: 1.18;
  text-align: center;
  transform: translateX(-16px);
  overflow: visible;
  white-space: nowrap;
}

.metric-line,
.identity-line {
  margin: 6px 0 0;
  color: #223443;
  font-size: 0.8rem;
  font-weight: 700;
  line-height: 1.18;
  text-align: center;
}

.identity-line {
  text-align: left;
  padding-left: 3px;
}

.mini-label {
  min-height: var(--mini-label-h);
  margin-bottom: 5px;
  color: #223443;
  font-size: 0.82rem;
  font-weight: 500;
  line-height: 1.14;
  text-align: center;
}

.mini-matrix {
  width: var(--mini-size);
  height: var(--mini-size);
  aspect-ratio: 1 / 1;
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
  margin: 0 auto;
}

.mini-matrix-term {
  width: var(--equation-brain-w);
  min-width: 0;
}

.mini-matrix .matrix-canvas {
  border: 0;
}

.centered-grid {
  display: grid;
  grid-template-columns:
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--panel-op-w)
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--panel-op-w)
    var(--equation-brain-w);
  gap: 8px;
  align-items: start;
  justify-content: start;
}

.combined-grid {
  display: grid;
  grid-template-columns: minmax(360px, 0.78fr) minmax(0, 1.42fr);
  gap: 20px;
  align-items: start;
}

.control-mini-grid {
  display: grid;
  grid-template-columns:
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--panel-op-w)
    var(--equation-brain-w) var(--panel-op-w) var(--equation-brain-w) var(--scatter-size);
  gap: 8px;
  align-items: start;
  justify-content: start;
}

.control-mini-grid > .operator,
.control-mini-grid > .scatter-term {
  height: var(--mini-brain-h);
}

.control-mini-grid > .scatter-term {
  height: var(--scatter-size);
  margin-top: calc(var(--term-heading-h) + (var(--mini-brain-h) - var(--scatter-size)) / 2);
}

.centered-grid > .operator {
  height: var(--mini-size);
  margin-top: calc(var(--mini-label-h) + 5px);
}

.centered-grid > .scatter-arrow {
  height: var(--brain-h);
  margin-top: var(--term-heading-h);
}

.centered-grid > .term,
.centered-grid > .scatter-term {
  grid-column: auto;
}

.mini-term {
  padding: 0;
}

.mini-term .term-heading {
  min-height: var(--term-heading-h);
  font-size: 0.82rem;
}

.mini-brain {
  height: var(--mini-brain-h);
}

.mini-scatter {
  width: var(--scatter-size);
  height: var(--scatter-size);
}

.derivation {
  padding: 8px 12px;
}

.derivation p {
  margin: 0;
  color: #334155;
  font-size: 0.82rem;
  font-weight: 600;
  line-height: 1.28;
}

.loading-indicator {
  position: fixed;
  top: 8px;
  right: 10px;
  z-index: 40;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.96);
  color: #223443;
  font-size: 0.75rem;
}

.loading-indicator.hidden {
  display: none;
}

.spinner {
  width: 12px;
  height: 12px;
  border: 2px solid #cbd5e1;
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@media (max-width: 1180px) {
  :root {
    --brain-h: 128px;
    --prevalence-brain-h: 92px;
    --matrix-size: 122px;
    --scatter-h: 158px;
    --scatter-size: calc(var(--matrix-size) + var(--scatter-extra));
  }
}

@media (max-width: 900px) {
  :root {
    --brain-h: 150px;
    --prevalence-brain-h: 126px;
    --matrix-size: min(58vw, 190px);
    --equation-brain-w: min(74vw, 260px);
    --mini-size: min(48vw, 160px);
    --scatter-size: calc(var(--matrix-size) + var(--scatter-extra));
    --mini-brain-h: 130px;
  }

  .overview-grid,
  .overview-row,
  .combined-grid,
  .control-mini-grid,
  .centered-grid {
    grid-template-columns: 1fr;
    justify-items: center;
  }

  .overview-inputs,
  .output-arrow-wrap,
  .reference-term {
    grid-column: auto;
  }

  .output-arrow-wrap {
    justify-self: center;
    padding-left: 0;
  }

  .equation-specificity,
  .equation-mean {
    grid-template-columns: 1fr;
    justify-items: center;
  }

  .equation-with-scatter,
  .control-mini-grid {
    grid-template-columns: 1fr;
    justify-items: center;
  }

  .equation-specificity > .scatter-term,
  .equation-mean > .scatter-term,
  .control-mini-grid > .scatter-term {
    grid-column: auto;
  }

  .operator,
  .operator.small {
    height: auto;
    min-height: 28px;
    display: grid;
    place-items: center;
    margin: 0;
    padding-top: 0;
    transform: none;
  }

  .flow-arrow,
  .output-arrow,
  .centered-to-brain-arrow,
  .scatter-arrow {
    transform: rotate(90deg);
  }

  .centered-to-brain-arrow,
  .centered-grid > .scatter-arrow {
    height: auto;
    margin: 0;
  }

  .scatter-term {
    height: auto;
    margin-top: 0;
    padding-top: 0;
  }

  .term,
  .prevalence-term,
  .reference-term,
  .overview-matrix,
  .mini-term {
    width: 100%;
    max-width: 300px;
    justify-self: center;
  }
}

@media (max-width: 700px) {
  :root {
    --brain-h: 144px;
    --prevalence-brain-h: 118px;
    --matrix-size: min(64vw, 210px);
    --equation-brain-w: min(88vw, 300px);
    --mini-size: min(68vw, 210px);
    --scatter-size: calc(var(--matrix-size) + var(--scatter-extra));
    --mini-brain-h: 126px;
  }

  .page {
    width: min(100% - 18px, 520px);
    gap: 14px;
    padding-top: 8px;
  }

  .topbar,
  .selector-shell {
    width: 100%;
  }

  .selector-shell {
    flex-wrap: wrap;
    align-items: stretch;
  }

  .selector-label {
    width: 100%;
    grid-template-columns: 1fr;
    gap: 6px;
  }

  .download-button {
    width: 100%;
  }

  h2 {
    gap: 8px;
    align-items: flex-start;
    font-size: 0.98rem;
    line-height: 1.18;
  }

  h2 > span:last-child {
    min-height: 22px;
    align-items: flex-start;
  }

  .step-badge {
    width: 23px;
    height: 23px;
    border-radius: 6px;
    font-size: 0.78rem;
  }

  .overview-row,
  .overview-grid,
  .equation-specificity,
  .equation-with-scatter,
  .equation-mean,
  .control-mini-grid {
    grid-template-columns: 1fr;
  }

  .overview-inputs {
    gap: 18px;
  }

  .overview-row {
    gap: 5px;
  }

  .output-arrow-wrap {
    gap: 0;
  }

  .term-heading {
    font-size: 0.8rem;
  }

  .overview-matrix .term-heading,
  .prevalence-term .term-heading {
    width: auto;
    margin: 0 0 5px;
    transform: none;
  }

  .matrix-plot {
    width: calc(var(--matrix-size) + 28px);
  }

  .story-stack {
    gap: 18px;
  }

  .mini-label {
    margin-bottom: 4px;
  }
}