:root {
  --serif: 'Source Serif 4', Georgia, serif;
  --sans: 'Manrope', 'SF Pro Display', -apple-system, BlinkMacSystemFont, sans-serif;
  --mono: 'IBM Plex Mono', 'SFMono-Regular', monospace;

  --bg: #f6f3ed;
  --paper: #fffdf9;
  --paper-soft: #f9f6f0;
  --ink: #202733;
  --muted: #626d79;
  --line: rgba(32, 39, 51, 0.12);
  --line-strong: rgba(32, 39, 51, 0.18);
  --blue: #3c68cf;
  --coral: #d35b43;
  --teal: #1e7770;
  --gold: #b48939;
  --shadow: 0 10px 28px rgba(32, 39, 51, 0.06);
}

*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.14rem;
  line-height: 1.72;
  background: linear-gradient(180deg, #f8f5f0 0%, #f3efe7 100%);
  -webkit-font-smoothing: antialiased;
}

.progress-bar {
  position: fixed;
  inset: 0 0 auto;
  height: 3px;
  z-index: 50;
}

.progress-bar__fill {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--teal), var(--blue));
}

.article {
  max-width: 1160px;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 5rem;
}

.back-link,
.primary-link,
.ghost-link,
.toolbar-button,
.mode-chip,
.rule-chip,
.dataset-chip,
.toc__link {
  font-family: var(--sans);
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9rem;
}

.back-link:hover,
.back-link:focus-visible,
.toc__link:hover,
.toc__link:focus-visible {
  color: var(--ink);
}

.hero {
  padding: 0.5rem 0 2rem;
}

.hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(300px, 0.9fr);
  gap: 1.25rem;
  margin-top: 1.4rem;
  align-items: start;
}

.hero__copy,
.hero-card,
.interactive-figure,
.diagram-board,
.code-panel,
.aside,
.takeaway-card,
.ledger,
.module-copy,
.batch-panel,
.compare-card,
.stat-card,
.summary-card,
.rule-card,
.rule-spotlight,
.module-list__item,
.stage-pill,
.equation-card {
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--paper);
  box-shadow: var(--shadow);
}

.hero__copy,
.hero-card,
.ledger,
.module-copy,
.batch-panel,
.rule-spotlight,
.takeaway-card,
.code-panel,
.aside,
.compare-card {
  padding: 1.3rem 1.4rem;
}

.kicker,
.eyebrow,
.hero-card__eyebrow,
.code-panel__eyebrow,
.note-label,
.diagram-kicker,
.guide__label {
  margin: 0;
  font-family: var(--sans);
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--muted);
}

.hero h1 {
  margin: 0.45rem 0 0.9rem;
  max-width: 10ch;
  font-size: clamp(3.1rem, 7vw, 5.2rem);
  line-height: 0.95;
  font-weight: 700;
  letter-spacing: -0.045em;
}

.abstract {
  max-width: 34ch;
  margin: 0 0 0.9rem;
  font-size: 1.18rem;
  color: var(--ink);
}

.abstract--secondary {
  color: var(--muted);
  font-size: 1.02rem;
}

.hero__meta,
.hero__actions,
.hero-notes,
.summary-strip,
.scrubber-row,
.dataset-switcher {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
}

.hero__meta {
  margin-top: 1.1rem;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.88rem;
}

.hero__actions {
  margin-top: 1.15rem;
}

.primary-link,
.ghost-link,
.toolbar-button,
.mode-chip,
.rule-chip,
.dataset-chip {
  appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  padding: 0.78rem 1.05rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--paper);
  color: var(--ink);
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
  transition: border-color 160ms ease, background 160ms ease, color 160ms ease, transform 160ms ease;
}

.primary-link,
.toolbar-button--accent,
.mode-chip.is-active,
.rule-chip.is-active,
.dataset-chip.is-active {
  background: var(--ink);
  border-color: var(--ink);
  color: #fff;
}

.primary-link:hover,
.ghost-link:hover,
.toolbar-button:hover,
.mode-chip:hover,
.rule-chip:hover,
.dataset-chip:hover {
  transform: translateY(-1px);
}

.hero-card__formula {
  margin: 1rem 0;
  padding: 0.9rem 1rem;
  border-radius: 18px;
  background: var(--paper-soft);
  border: 1px solid var(--line);
}

.hero-card__copy {
  margin: 0;
  font-size: 1rem;
  color: var(--ink);
}

.hero-notes {
  flex-direction: column;
  margin-top: 1rem;
  gap: 0.8rem;
}

.hero-notes div {
  padding-top: 0.8rem;
  border-top: 1px solid var(--line);
}

.note-label {
  display: block;
  margin-bottom: 0.25rem;
}

.toc {
  position: sticky;
  top: 0.75rem;
  z-index: 20;
  margin: 1.6rem 0 2.8rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(255, 253, 249, 0.94);
  box-shadow: 0 10px 24px rgba(32, 39, 51, 0.05);
}

.toc ul {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.55rem 0.9rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.toc__link {
  display: block;
  text-decoration: none;
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.35;
}

.toc__link.is-active {
  color: var(--ink);
  font-weight: 800;
}

section {
  margin-top: 4.2rem;
  scroll-margin-top: 5.8rem;
}

section h2 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 4.5vw, 3rem);
  line-height: 1.02;
  font-weight: 700;
  letter-spacing: -0.04em;
}

.num {
  color: var(--muted);
  margin-right: 0.28em;
}

section h3 {
  margin: 0.25rem 0 0.6rem;
  font-size: 1.3rem;
  font-weight: 700;
  line-height: 1.18;
}

p {
  max-width: 66ch;
  margin: 0 0 1rem;
}

code,
pre {
  font-family: var(--mono);
}

code {
  padding: 0.08em 0.35em;
  border-radius: 0.45rem;
  background: rgba(32, 39, 51, 0.06);
  font-size: 0.88em;
}

pre {
  margin: 0;
  overflow-x: auto;
  font-size: 0.92rem;
  line-height: 1.62;
  white-space: pre-wrap;
}

.math-block {
  margin: 1rem 0;
  overflow-x: auto;
}

.katex-display {
  margin: 0 !important;
}

.compare-grid,
.takeaway-grid,
.rule-grid {
  display: grid;
  gap: 1rem;
}

.compare-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin-top: 1.4rem;
}

.compare-card--highlight {
  border-color: rgba(60, 104, 207, 0.28);
  background: #fbfcff;
}

.diagram-board,
.interactive-figure {
  margin: 1.6rem 0 0;
  overflow: hidden;
}

.flow-diagram,
#graphSvg,
#moduleSvg,
#batchSvg {
  width: 100%;
  display: block;
}

.diagram-board {
  padding: 1rem;
}

.diagram-node {
  fill: #ffffff;
  stroke: #ccd5e0;
  stroke-width: 2;
}

.diagram-node--loss {
  fill: #fff4f0;
}

.diagram-label,
.node-label {
  font-family: var(--sans);
  font-weight: 800;
  fill: var(--ink);
}

.diagram-label {
  font-size: 18px;
}

.diagram-sub,
.diagram-copy,
.node-sub,
.edge-label {
  font-family: var(--sans);
  fill: var(--muted);
}

.diagram-sub,
.node-sub,
.edge-label {
  font-size: 12px;
}

.diagram-copy {
  font-size: 14px;
}

.diagram-kicker--coral {
  fill: var(--coral);
}

.legend-pill {
  stroke: none;
}

.legend-pill--blue {
  fill: rgba(60, 104, 207, 0.12);
}

.legend-pill--coral {
  fill: rgba(211, 91, 67, 0.14);
}

.legend-text {
  font-family: var(--mono);
  font-size: 12px;
  fill: var(--ink);
}

.flow-arrow {
  fill: none;
  stroke-linecap: round;
  stroke-width: 4;
}

.flow-arrow--forward {
  stroke: var(--blue);
}

.flow-arrow--backward {
  stroke: var(--coral);
}

.aside,
.code-panel {
  margin-top: 1.2rem;
}

.aside {
  background: var(--paper-soft);
  color: var(--muted);
}

.aside strong {
  color: var(--ink);
}

.figure-controls,
.figure-toolbar,
.scrubber-label {
  font-family: var(--sans);
}

.figure-controls,
.figure-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.65rem;
  padding: 1rem 1.1rem;
  background: var(--paper-soft);
  border-bottom: 1px solid var(--line);
}

.figure-controls--wrap {
  justify-content: flex-start;
}

.rule-stage,
.graph-shell,
.module-shell,
.batch-shell {
  display: grid;
  gap: 1rem;
  padding: 1rem;
}

.rule-stage {
  grid-template-columns: minmax(250px, 0.9fr) minmax(0, 1.2fr);
}

.rule-card {
  padding: 1rem;
  cursor: pointer;
  transition: border-color 160ms ease, transform 160ms ease;
}

.rule-card:hover,
.rule-card.is-active {
  transform: translateY(-1px);
  border-color: rgba(60, 104, 207, 0.26);
}

.rule-card h4 {
  margin: 0 0 0.35rem;
  font-family: var(--sans);
  font-size: 0.98rem;
}

.rule-card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.94rem;
}

.scrubber-row {
  padding: 0 1rem 1rem;
}

.stage-pill,
.summary-card,
.module-list__item,
.equation-card {
  padding: 0.82rem 0.95rem;
}

.stage-pill {
  min-width: 156px;
}

.stage-pill span,
.summary-card span {
  display: block;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
}

.stage-pill strong,
.summary-card strong {
  display: block;
  margin-top: 0.32rem;
  font-family: var(--sans);
  font-size: 1rem;
}

.scrubber-label {
  display: grid;
  gap: 0.55rem;
  padding: 0 1rem 1rem;
  color: var(--muted);
  font-size: 0.88rem;
}

input[type='range'] {
  width: 100%;
  accent-color: var(--blue);
}

.graph-shell {
  grid-template-columns: minmax(0, 1.5fr) minmax(310px, 0.82fr);
  align-items: start;
}

.graph-surface {
  padding: 0.6rem;
  border-radius: 18px;
  border: 1px solid var(--line);
  background: #fbfbfd;
  overflow: auto hidden;
}

.ledger-table,
.module-list {
  display: grid;
  gap: 0.55rem;
  margin-top: 1rem;
}

.ledger-row {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(90px, 0.8fr) minmax(90px, 0.8fr);
  gap: 0.6rem;
  align-items: center;
  padding: 0.72rem 0.82rem;
  border-radius: 16px;
  background: var(--paper-soft);
  font-family: var(--sans);
  font-size: 0.85rem;
}

.ledger-row strong {
  display: block;
  font-size: 0.93rem;
}

.ledger-row span {
  color: var(--muted);
}

.equation-card {
  background: #f7f8fc;
}

.node-badge {
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 500;
  fill: #fff;
}

.module-shell {
  grid-template-columns: minmax(0, 1.18fr) minmax(280px, 0.85fr);
  align-items: center;
}

.module-list__item strong {
  display: block;
  margin-bottom: 0.2rem;
  font-family: var(--sans);
  font-size: 0.9rem;
}

.batch-shell {
  grid-template-columns: minmax(0, 1.2fr) minmax(320px, 0.82fr);
  align-items: start;
}

.batch-visuals {
  display: grid;
  gap: 1rem;
}

.summary-card {
  flex: 1 1 160px;
}

.batch-panel {
  display: grid;
  gap: 0.95rem;
}

.control-stack {
  display: grid;
  gap: 0.36rem;
  font-family: var(--sans);
  font-size: 0.92rem;
}

.control-stack span,
.batch-narrative,
.card__copy {
  color: var(--muted);
}

.batch-narrative {
  margin: 0;
  padding: 0.9rem 1rem;
  border-radius: 16px;
  background: var(--paper-soft);
  font-size: 0.96rem;
}

.example-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--sans);
  font-size: 0.82rem;
}

.example-table th,
.example-table td {
  padding: 0.66rem 0.45rem;
  text-align: left;
  border-bottom: 1px solid var(--line);
}

.example-table th {
  color: var(--muted);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.takeaway-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-top: 1.4rem;
}

.article-footer {
  margin-top: 2.8rem;
  padding-top: 1.3rem;
  border-top: 1px solid var(--line-strong);
  color: var(--muted);
}

figcaption {
  padding: 0 1rem 1rem;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.85rem;
}

@media (max-width: 1080px) {
  .hero__grid,
  .compare-grid,
  .rule-stage,
  .graph-shell,
  .module-shell,
  .batch-shell {
    grid-template-columns: 1fr;
  }

  .toc ul {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 760px) {
  body {
    font-size: 1.04rem;
  }

  .article {
    padding: 1rem 0.9rem 4rem;
  }

  .hero h1 {
    font-size: clamp(2.7rem, 16vw, 4rem);
  }

  .toc {
    position: static;
  }

  .toc ul,
  .takeaway-grid,
  .rule-grid,
  .compare-grid {
    grid-template-columns: 1fr;
  }

  .hero__actions,
  .figure-toolbar,
  .figure-controls,
  .summary-strip {
    flex-direction: column;
    align-items: stretch;
  }

  .ledger-row {
    grid-template-columns: 1fr;
  }
}