@font-face {
  font-family: "Pagella";
  src: url("../fonts/pagella-regular.otf") format("opentype");
  font-style: normal;
  font-weight: 400;
  font-display: swap;
}

@font-face {
  font-family: "Pagella";
  src: url("../fonts/pagella-bold.otf") format("opentype");
  font-style: normal;
  font-weight: 700;
  font-display: swap;
}

@font-face {
  font-family: "Noto Sans";
  src: url("../fonts/noto-sans-regular.ttf") format("truetype");
  font-style: normal;
  font-weight: 400;
  font-display: swap;
}

@font-face {
  font-family: "Noto Sans";
  src: url("../fonts/noto-sans-bold.ttf") format("truetype");
  font-style: normal;
  font-weight: 700;
  font-display: swap;
}

:root {
  --serif: "Pagella", Georgia, serif;
  --sans: "Noto Sans", Arial, sans-serif;
  --content: min(100% - 3rem, 92rem);
  --text: 46rem;
  --section-space: clamp(5rem, 9vw, 9rem);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  background: var(--paper);
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: clamp(1rem, 0.3vw + 0.96rem, 1.18rem);
  line-height: 1.65;
  text-rendering: optimizeLegibility;
}

body.nav-open {
  overflow: hidden;
}

img,
svg {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.18em;
}

button,
input {
  font: inherit;
}

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 4px;
}

::selection {
  background: var(--amber-wash);
  color: var(--ink);
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1,
h2,
h3 {
  font-family: var(--serif);
  hyphens: auto;
  line-height: 0.98;
  overflow-wrap: anywhere;
  text-wrap: balance;
}

h1 {
  margin-bottom: 1.6rem;
  font-size: clamp(3.2rem, 7.6vw, 7.4rem);
  font-weight: 400;
  letter-spacing: -0.055em;
}

h2 {
  margin-bottom: 1.5rem;
  font-size: clamp(2.4rem, 5vw, 5rem);
  font-weight: 400;
  letter-spacing: -0.045em;
}

h3 {
  margin-bottom: 0.65rem;
  font-size: clamp(1.35rem, 2.2vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.025em;
}

.skip-link {
  position: fixed;
  z-index: 1000;
  top: 0.75rem;
  left: 0.75rem;
  padding: 0.75rem 1rem;
  transform: translateY(-180%);
  background: var(--ink);
  color: var(--on-ink);
  font-family: var(--sans);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: relative;
  z-index: 50;
  display: grid;
  grid-template-columns: auto 1fr;
  align-items: center;
  width: var(--content);
  min-height: 6.35rem;
  margin-inline: auto;
  border-bottom: 1px solid var(--line);
}

.wordmark {
  display: inline-flex;
  flex-direction: column;
  width: max-content;
  text-decoration: none;
}

.wordmark-main {
  font-family: var(--serif);
  font-size: 1.7rem;
  line-height: 0.92;
  letter-spacing: -0.04em;
}

.wordmark-sub {
  margin-top: 0.32rem;
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.67rem;
  font-weight: 700;
  letter-spacing: 0.19em;
  line-height: 1;
  text-transform: uppercase;
}

.site-nav {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: clamp(0.8rem, 2.1vw, 2.3rem);
  font-family: var(--sans);
  font-size: 0.82rem;
  letter-spacing: 0.02em;
}

.site-nav a {
  position: relative;
  padding-block: 0.7rem;
  color: var(--muted);
  text-decoration: none;
}

.site-nav a::after {
  position: absolute;
  right: 0;
  bottom: 0.34rem;
  left: 0;
  height: 1px;
  transform: scaleX(0);
  transform-origin: left;
  background: var(--amber);
  content: "";
  transition: transform 180ms ease;
}

.site-nav a:hover::after,
.site-nav a[aria-current="page"]::after {
  transform: scaleX(1);
}

.site-nav a[aria-current="page"] {
  color: var(--ink);
}

.nav-toggle {
  display: none;
  border: 0;
  background: transparent;
  color: inherit;
  cursor: pointer;
  font-family: var(--sans);
}

.home-hero,
.page-hero,
.book-hero {
  width: var(--content);
  margin-inline: auto;
}

.ruled {
  background-image:
    linear-gradient(90deg, transparent 0, transparent 4.4rem, color-mix(in srgb, var(--amber) 24%, transparent) 4.4rem, color-mix(in srgb, var(--amber) 24%, transparent) calc(4.4rem + 1px), transparent calc(4.4rem + 1px)),
    repeating-linear-gradient(0deg, transparent 0, transparent 2rem, var(--line-faint) calc(2rem + 1px));
}

.home-hero {
  display: grid;
  grid-template-columns: minmax(0, 0.88fr) minmax(31rem, 1.12fr);
  gap: clamp(3rem, 6vw, 7rem);
  align-items: center;
  min-height: calc(100svh - 6.35rem);
  padding: clamp(4rem, 7vw, 7rem) clamp(1.5rem, 4vw, 5rem) clamp(5rem, 9vw, 8rem);
}

.hero-copy h1 {
  max-width: 11ch;
}

.eyebrow,
.plate-number,
.footer-kicker {
  margin-bottom: 1rem;
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  line-height: 1.4;
  text-transform: uppercase;
}

.hero-statement,
.lead,
.path-lead {
  max-width: 43rem;
  color: var(--muted);
  font-size: clamp(1.23rem, 1.3vw, 1.55rem);
  line-height: 1.48;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1.1rem 1.7rem;
  align-items: center;
  margin-top: 2.2rem;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 3.25rem;
  padding: 0.75rem 1.25rem;
  border: 1px solid var(--amber);
  background: var(--amber);
  color: var(--on-accent);
  font-family: var(--sans);
  font-size: 0.84rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-decoration: none;
  transition: background 160ms ease, color 160ms ease, transform 160ms ease;
}

.button:hover {
  transform: translateY(-2px);
  background: transparent;
  color: var(--amber);
}

.button-light {
  border-color: var(--amber-bright);
  background: var(--amber-bright);
  color: var(--on-accent);
}

.button-light:hover {
  color: var(--on-ink);
}

.button-dark {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--paper);
}

.button-dark:hover {
  color: var(--ink);
}

.text-link {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--sans);
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
}

.text-link::after {
  content: "→";
  transition: transform 160ms ease;
}

.text-link:hover::after {
  transform: translateX(0.35rem);
}

.experiment-shell {
  padding: clamp(1.3rem, 2.5vw, 2.1rem);
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--paper-raised) 88%, transparent);
  box-shadow: var(--shadow);
}

.experiment-heading {
  display: flex;
  gap: 1rem;
  align-items: start;
  justify-content: space-between;
}

.experiment-heading h2 {
  margin-bottom: 0;
  font-size: clamp(1.8rem, 3vw, 2.7rem);
}

.experiment-status {
  margin: 0;
  padding: 0.25rem 0.55rem;
  border: 1px solid var(--line);
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.experiment-intro {
  max-width: 49rem;
  margin: 1.25rem 0 0;
  color: var(--muted);
  font-size: 0.96rem;
}

.heat-plot {
  width: 100%;
  margin: 0.8rem 0;
  overflow: visible;
}

.plot-grid path {
  fill: none;
  stroke: var(--line);
  stroke-width: 1;
}

.plot-grid text,
.axis-label {
  fill: var(--muted);
  font-family: var(--sans);
  font-size: 13px;
}

.temperature-area {
  fill: color-mix(in srgb, var(--amber) 20%, transparent);
}

.temperature-line {
  fill: none;
  stroke: var(--amber);
  stroke-width: 4;
  vector-effect: non-scaling-stroke;
}

.mesh-node {
  fill: var(--paper-raised);
  stroke: var(--amber);
  stroke-width: 2;
}

.beam-segment {
  stroke: var(--paper-raised);
  stroke-width: 1;
}

.lab-controls {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.2rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--line);
}

.lab-controls label {
  display: grid;
  gap: 0.65rem;
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
}

.lab-controls label > span {
  display: flex;
  justify-content: space-between;
}

.lab-controls output {
  color: var(--amber);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--amber);
  cursor: pointer;
}

.lab-readout {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  margin: 1.25rem 0 0;
  background: var(--line);
}

.lab-readout div {
  padding: 0.8rem;
  background: var(--paper-raised);
}

.lab-readout dt {
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.66rem;
}

.lab-readout dd {
  margin: 0.18rem 0 0;
  font-family: var(--sans);
  font-size: 1.05rem;
  font-weight: 700;
}

.paper-section,
.ink-section,
.amber-section {
  position: relative;
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  column-gap: clamp(1rem, 2vw, 2rem);
  width: 100%;
  padding: var(--section-space) max(1.5rem, calc((100% - min(100% - 3rem, 92rem)) / 2));
}

.paper-section {
  background: var(--paper);
  color: var(--ink);
}

.ink-section {
  background: var(--contrast-surface);
  color: var(--contrast-ink);
}

.amber-section {
  background: var(--amber-wash);
  color: var(--ink);
}

.section-index {
  grid-column: 1 / span 1;
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
}

.section-heading {
  grid-column: 2 / span 5;
}

.section-copy {
  grid-column: 8 / span 4;
  align-self: center;
}

.section-copy p:last-of-type {
  margin-bottom: 1.5rem;
}

.section-copy.columns {
  grid-column: 7 / span 5;
  column-count: 2;
  column-gap: 2.5rem;
}

.section-copy.columns .text-link,
.section-copy.columns > p:last-of-type {
  column-span: all;
}

.principle-line {
  margin: 2.3rem 0;
  padding: 0;
  border-top: 1px solid var(--line);
  list-style: none;
}

.principle-line li {
  display: grid;
  grid-template-columns: 7.6rem 1fr;
  gap: 1rem;
  padding: 0.85rem 0;
  border-bottom: 1px solid var(--line);
}

.principle-line span {
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
}

.anchor-target {
  scroll-margin-top: 2rem;
}

.learning-path {
  min-height: 52rem;
  align-items: start;
}

.path-heading {
  grid-column: 2 / span 5;
}

.path-heading h2 {
  font-size: clamp(3.5rem, 7vw, 7.2rem);
  /* Lange Einzelwörter wie „Periodensystem" sollen mit Trennstrich umbrechen,
     nicht mitten im Wort abreißen. Das globale `anywhere` greift sonst vor der
     Silbentrennung. Überlauf würde die Browserabnahme melden. */
  overflow-wrap: normal;
}

.path-visual {
  grid-column: 2 / span 8;
  align-self: end;
  margin: 4rem 0 0;
}

.path-visual svg {
  width: 100%;
  border-bottom: 1px solid currentColor;
}

.path-visual figcaption {
  margin-top: 0.8rem;
  color: var(--contrast-muted);
  font-family: var(--sans);
  font-size: 0.72rem;
}

.maxwell-path .path-visual figcaption {
  color: var(--muted);
}

.biofem-visual img {
  width: 100%;
  max-height: 43rem;
  object-fit: contain;
  object-position: left center;
  background: #fff;
}

.path-facts {
  grid-column: 10 / span 3;
  grid-row: 1 / span 2;
  align-self: end;
  padding-left: clamp(1rem, 2vw, 2rem);
  border-left: 1px solid currentColor;
}

.big-number {
  font-family: var(--sans);
  font-size: 0.85rem;
  text-transform: uppercase;
}

.big-number strong {
  display: block;
  color: var(--amber-bright);
  font-family: var(--serif);
  font-size: clamp(5rem, 9vw, 9rem);
  font-weight: 400;
  letter-spacing: -0.07em;
  line-height: 0.8;
}

.maxwell-path .big-number strong {
  color: var(--amber);
}

.sketch-lines,
.wave-grid {
  fill: none;
  stroke: currentColor;
  stroke-width: 1;
  opacity: 0.25;
}

.mesh-nodes circle {
  fill: var(--contrast-surface);
  stroke: var(--contrast-ink);
  stroke-width: 3;
}

.diagram-labels {
  fill: currentColor;
  font-family: var(--sans);
  font-size: 20px;
}

.diagram-labels text:first-child {
  font-size: 24px;
  font-weight: 700;
}

.electric-wave,
.magnetic-wave,
.propagation-arrow {
  fill: none;
  stroke-width: 6;
}

.electric-wave {
  stroke: var(--amber);
}

.magnetic-wave {
  stroke: #527782;
}

.propagation-arrow {
  stroke: var(--ink);
  stroke-width: 2;
}

/* Periodensystem-Lernweg: links das Feldraster, rechts die Dichteverteilung.
   Die Kreise sind bewusst weich abgestuft — im Lehrwerk selbst gilt die Regel,
   dass Schalenkreise keine Bahnen darstellen. */
.element-grid {
  fill: none;
  stroke: currentColor;
  stroke-width: 1;
  opacity: 0.25;
}

.element-highlight {
  fill: var(--amber-wash);
  stroke: var(--amber);
  stroke-width: 2;
}

.orbital-shell circle {
  fill: var(--amber);
  stroke: none;
}

.orbital-curve {
  fill: none;
  stroke: var(--amber);
  stroke-width: 6;
}

.chemie-path .path-visual figcaption {
  color: var(--muted);
}

.chemie-path .big-number strong {
  color: var(--amber);
}

.use-sequence {
  grid-column: 2 / span 10;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1px;
  margin-top: 4rem;
  background: var(--contrast-line);
}

.use-sequence > div {
  min-height: 18rem;
  padding: 1.5rem;
  background: var(--contrast-surface);
}

.use-sequence span {
  color: var(--contrast-accent);
  font-family: var(--sans);
  font-size: 0.7rem;
}

.use-sequence h3 {
  margin-top: 4rem;
}

.use-sequence p {
  color: var(--contrast-muted);
}

.outlook-section {
  min-height: 30rem;
}

.page-hero,
.book-hero {
  position: relative;
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  column-gap: 2rem;
  align-items: center;
  min-height: min(76svh, 50rem);
  padding: clamp(5rem, 10vw, 9rem) clamp(1.5rem, 4vw, 5rem);
}

.page-hero.compact {
  min-height: 30rem;
}

.page-hero .measure {
  grid-column: 2 / span 8;
}

.measure {
  max-width: 70rem;
}

.marginal-note {
  grid-column: 11 / span 2;
  color: var(--amber);
  font-family: var(--sans);
  font-size: clamp(0.9rem, 1.4vw, 1.2rem);
  font-weight: 700;
  letter-spacing: 0.08em;
  line-height: 2.15;
  text-align: center;
  text-transform: uppercase;
}

.wide-heading {
  grid-column: 2 / span 9;
  margin-bottom: 4rem;
}

.principle-list {
  grid-column: 2 / span 10;
  margin: 0;
  padding: 0;
  list-style: none;
}

.principle-list li {
  display: grid;
  grid-template-columns: 5rem minmax(0, 1fr);
  gap: clamp(1.5rem, 4vw, 5rem);
  padding: 2.5rem 0;
  border-top: 1px solid var(--line);
}

.principle-list li:last-child {
  border-bottom: 1px solid var(--line);
}

.principle-list li > div {
  display: grid;
  grid-template-columns: minmax(15rem, 0.8fr) minmax(18rem, 1.2fr);
  gap: clamp(2rem, 5vw, 6rem);
}

.principle-list p {
  max-width: 45rem;
  margin: 0;
  color: var(--muted);
}

.principle-number {
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 700;
}

.choice-section > div:first-of-type {
  grid-column: 2 / span 5;
}

.choice-links {
  grid-column: 8 / span 4;
  display: grid;
}

.choice-links a {
  padding: 1.3rem 0;
  border-top: 1px solid var(--contrast-line);
  color: var(--contrast-muted);
  text-decoration: none;
}

.choice-links a:last-child {
  border-bottom: 1px solid var(--contrast-line);
}

.choice-links span {
  display: block;
  margin-bottom: 0.3rem;
  color: var(--contrast-ink);
  font-family: var(--sans);
  font-weight: 700;
}

.book-title {
  grid-column: 2 / span 7;
}

.book-facts {
  grid-column: 10 / span 3;
  margin: 0;
  border-top: 1px solid var(--line);
}

.book-facts div {
  padding: 1rem 0;
  border-bottom: 1px solid var(--line);
}

.book-facts dt {
  color: var(--amber);
  font-family: var(--sans);
  font-size: 0.67rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.book-facts dd {
  margin: 0.25rem 0 0;
}

.chapter-route .section-heading,
.browser-lab .section-heading {
  grid-column: 2 / span 5;
}

.chapter-bands {
  grid-column: 8 / span 4;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--contrast-line);
  list-style: none;
}

.chapter-bands li {
  padding: 1.15rem 0;
  border-bottom: 1px solid var(--contrast-line);
}

.chapter-bands span {
  display: block;
  color: var(--contrast-accent);
  font-family: var(--sans);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.chapter-bands strong {
  display: block;
  margin-top: 0.25rem;
  font-weight: 400;
}

.lab-sketch,
.wave-lab {
  grid-column: 2 / span 6;
  display: grid;
  align-items: center;
  height: 18rem;
  margin-top: 4rem;
}

.lab-sketch {
  grid-template-columns: repeat(8, 1fr);
}

.lab-sketch span {
  height: clamp(2rem, calc(3rem + var(--index, 0) * 1rem), 12rem);
  border: 1px solid var(--line);
  border-right: 0;
  background: color-mix(in srgb, var(--amber) calc(12% + var(--index, 1) * 8%), var(--paper));
}

.lab-sketch span:last-child {
  border-right: 1px solid var(--line);
}

.lab-sketch span:nth-child(1) { --index: 0; }
.lab-sketch span:nth-child(2) { --index: 1; }
.lab-sketch span:nth-child(3) { --index: 2; }
.lab-sketch span:nth-child(4) { --index: 3; }
.lab-sketch span:nth-child(5) { --index: 4; }
.lab-sketch span:nth-child(6) { --index: 5; }
.lab-sketch span:nth-child(7) { --index: 6; }
.lab-sketch span:nth-child(8) { --index: 7; }

.browser-lab .section-copy {
  grid-column: 9 / span 3;
  grid-row: 1 / span 2;
}

.wave-lab {
  position: relative;
  overflow: hidden;
  border-block: 1px solid var(--line);
}

.wave-lab i {
  position: absolute;
  top: 50%;
  left: 15%;
  width: calc(var(--wave, 1) * 4rem);
  height: calc(var(--wave, 1) * 4rem);
  transform: translate(-50%, -50%);
  border: 2px solid color-mix(in srgb, var(--amber) 70%, transparent);
  border-radius: 50%;
}

.wave-lab i:nth-child(1) { --wave: 1; }
.wave-lab i:nth-child(2) { --wave: 2; }
.wave-lab i:nth-child(3) { --wave: 3; }
.wave-lab i:nth-child(4) { --wave: 4; }
.wave-lab i:nth-child(5) { --wave: 5; }
.wave-lab i:nth-child(6) { --wave: 6; }

.integration-note > div:first-child {
  grid-column: 2 / span 5;
}

.integration-note > div:last-child {
  grid-column: 8 / span 4;
}

.status-line {
  display: flex;
  gap: 0.7rem;
  align-items: center;
  margin: 1.8rem 0;
  font-family: var(--sans);
  font-size: 0.75rem;
  font-weight: 700;
}

.status-line span {
  width: 0.7rem;
  height: 0.7rem;
  border: 2px solid var(--amber);
  border-radius: 50%;
}

.source-flow .section-heading {
  grid-column: 2 / span 5;
}

.source-diagram {
  grid-column: 2 / span 10;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr)) 1.25fr;
  gap: 1px;
  margin-top: 4rem;
  background: var(--contrast-line);
}

.source-diagram > div {
  min-height: 12rem;
  padding: 1.5rem;
  background: var(--contrast-surface);
}

.source-diagram span,
.source-diagram small {
  display: block;
  color: var(--contrast-muted);
  font-family: var(--sans);
  font-size: 0.7rem;
}

.source-diagram strong {
  display: block;
  margin: 2.3rem 0 0.5rem;
  font-size: 1.3rem;
}

.source-diagram .source-output {
  border-left: 0.35rem solid var(--amber-bright);
}

.source-flow .section-copy {
  grid-column: 8 / span 4;
  margin-top: 3rem;
}

.legal-prose {
  grid-column: 3 / span 7;
  max-width: var(--text);
}

.legal-prose h2 {
  margin: 3.6rem 0 1rem;
  font-size: clamp(1.5rem, 2.5vw, 2.2rem);
  letter-spacing: -0.02em;
}

.legal-prose h2:first-child {
  margin-top: 0;
}

.catalog-hero {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  column-gap: 2rem;
  align-items: end;
  width: var(--content);
  min-height: min(72svh, 48rem);
  margin-inline: auto;
  padding: clamp(5rem, 10vw, 9rem) clamp(1.5rem, 4vw, 5rem);
}

.catalog-hero .measure {
  grid-column: 2 / span 8;
}

.catalog-count {
  grid-column: 11 / span 2;
  margin: 0 0 0.8rem;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.75rem;
  line-height: 1.4;
  text-transform: uppercase;
}

.catalog-count strong {
  display: block;
  color: var(--amber);
  font-family: var(--serif);
  font-size: clamp(3.8rem, 7vw, 6.5rem);
  font-weight: 400;
  letter-spacing: -0.07em;
  line-height: 0.8;
}

.catalog-heading {
  grid-column: 2 / span 5;
}

.book-catalog {
  grid-column: 2 / span 10;
  margin: 4rem 0 0;
  padding: 0;
  border-top: 1px solid var(--line);
  list-style: none;
}

.book-catalog li {
  border-bottom: 1px solid var(--line);
}

.book-catalog a {
  display: grid;
  grid-template-columns: 3rem minmax(18rem, 1.5fr) minmax(15rem, 1fr) 2rem;
  gap: clamp(1rem, 3vw, 3.5rem);
  align-items: center;
  min-height: 9rem;
  padding: 1.2rem 0;
  text-decoration: none;
}

.catalog-number,
.catalog-arrow,
.catalog-title small,
.catalog-scope small {
  font-family: var(--sans);
}

.catalog-number {
  color: var(--amber);
  font-size: 0.7rem;
  font-weight: 700;
}

.catalog-title,
.catalog-scope {
  display: grid;
  gap: 0.35rem;
}

.catalog-title strong {
  font-size: clamp(1.35rem, 2.5vw, 2.2rem);
  font-weight: 400;
  line-height: 1.08;
}

.catalog-title small,
.catalog-scope small {
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.45;
}

.catalog-scope strong {
  font-family: var(--sans);
  font-size: 0.78rem;
  text-transform: uppercase;
}

.catalog-arrow {
  color: var(--amber);
  font-size: 1.4rem;
  transition: transform 180ms ease;
}

.book-catalog a:hover .catalog-arrow {
  transform: translate(0.3rem, -0.3rem);
}

.site-footer {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 3rem;
  width: var(--content);
  margin-inline: auto;
  padding: 4rem 0 2rem;
  border-top: 1px solid var(--line);
}

.site-footer p {
  margin-bottom: 0.25rem;
}

.site-footer nav {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem 1.8rem;
  align-items: start;
  font-family: var(--sans);
  font-size: 0.78rem;
}

.footer-note {
  grid-column: 1 / -1;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.68rem;
}

.reveal-ready [data-reveal] {
  opacity: 0;
  transform: translateY(1.5rem);
  transition: opacity 550ms ease, transform 550ms ease;
}

.reveal-ready [data-reveal].is-visible {
  opacity: 1;
  transform: none;
}

@media (max-width: 1120px) {
  .home-hero {
    grid-template-columns: 1fr;
  }

  .hero-copy h1 {
    max-width: 14ch;
  }

  .experiment-shell {
    max-width: 56rem;
  }

  .section-heading,
  .path-heading,
  .chapter-route .section-heading,
  .browser-lab .section-heading,
  .source-flow .section-heading,
  .choice-section > div:first-of-type,
  .integration-note > div:first-child {
    grid-column: 2 / span 6;
  }

  .section-copy,
  .source-flow .section-copy,
  .choice-links,
  .chapter-bands,
  .integration-note > div:last-child {
    grid-column: 9 / span 4;
  }

  .path-visual {
    grid-column: 2 / span 7;
  }

  .path-facts {
    grid-column: 10 / span 3;
  }
}

@media (max-width: 900px) {
  :root {
    --content: min(100% - 2rem, 92rem);
  }

  .site-header {
    min-height: 5.4rem;
  }

  .nav-toggle {
    display: flex;
    gap: 0.7rem;
    align-items: center;
    justify-self: end;
    padding: 0.7rem 0;
  }

  .nav-toggle-mark,
  .nav-toggle-mark::before,
  .nav-toggle-mark::after {
    display: block;
    width: 1.3rem;
    height: 1px;
    background: currentColor;
    content: "";
  }

  .nav-toggle-mark {
    position: relative;
  }

  .nav-toggle-mark::before {
    position: absolute;
    top: -0.35rem;
  }

  .nav-toggle-mark::after {
    position: absolute;
    top: 0.35rem;
  }

  .site-nav {
    position: fixed;
    inset: 5.4rem 0 0;
    display: none;
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
    gap: 0;
    padding: 2rem;
    background: var(--paper);
  }

  .site-nav.is-open {
    display: flex;
  }

  .site-nav a {
    padding: 1.1rem 0;
    border-bottom: 1px solid var(--line);
    font-size: 1rem;
  }

  .home-hero {
    min-height: auto;
    padding-inline: 1.25rem;
  }

  .paper-section,
  .ink-section,
  .amber-section {
    grid-template-columns: repeat(8, minmax(0, 1fr));
  }

  .section-index {
    grid-column: 1;
  }

  .section-heading,
  .path-heading,
  .chapter-route .section-heading,
  .browser-lab .section-heading,
  .source-flow .section-heading,
  .choice-section > div:first-of-type,
  .integration-note > div:first-child {
    grid-column: 2 / span 7;
  }

  .section-copy,
  .section-copy.columns,
  .source-flow .section-copy,
  .choice-links,
  .chapter-bands,
  .integration-note > div:last-child {
    grid-column: 2 / span 7;
    margin-top: 2.5rem;
    column-count: 1;
  }

  .path-visual,
  .lab-sketch,
  .wave-lab {
    grid-column: 2 / span 7;
  }

  .path-facts,
  .browser-lab .section-copy {
    grid-column: 2 / span 7;
    grid-row: auto;
    margin-top: 2.5rem;
  }

  .use-sequence,
  .source-diagram,
  .principle-list,
  .wide-heading {
    grid-column: 2 / span 7;
  }

  .use-sequence {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .source-diagram {
    grid-template-columns: 1fr;
  }

  .principle-list li > div {
    grid-template-columns: 1fr;
    gap: 0.3rem;
  }

  .page-hero,
  .book-hero {
    grid-template-columns: repeat(8, minmax(0, 1fr));
  }

  .page-hero .measure,
  .book-title {
    grid-column: 1 / span 7;
  }

  .marginal-note {
    grid-column: 8;
  }

  .book-facts {
    grid-column: 1 / span 7;
    margin-top: 3rem;
  }

  .legal-prose {
    grid-column: 2 / span 6;
  }

  .catalog-hero {
    grid-template-columns: repeat(8, minmax(0, 1fr));
  }

  .catalog-hero .measure {
    grid-column: 1 / span 6;
  }

  .catalog-count {
    grid-column: 7 / span 2;
  }

  .catalog-heading,
  .book-catalog {
    grid-column: 2 / span 7;
  }

  .book-catalog a {
    grid-template-columns: 2rem minmax(0, 1.4fr) minmax(10rem, 0.8fr) 1.5rem;
    gap: 1.2rem;
  }
}

@media (max-width: 600px) {
  h1 {
    font-size: clamp(2.8rem, 15vw, 4.8rem);
  }

  h2 {
    font-size: clamp(2.2rem, 11vw, 3.6rem);
  }

  .ruled {
    background-image: repeating-linear-gradient(0deg, transparent 0, transparent 2rem, var(--line-faint) calc(2rem + 1px));
  }

  .home-hero {
    padding: 4rem 0 5rem;
  }

  .experiment-shell {
    padding: 1rem;
  }

  .experiment-heading {
    display: block;
  }

  .experiment-status {
    display: inline-block;
    margin-top: 0.8rem;
  }

  .lab-controls,
  .lab-readout {
    grid-template-columns: 1fr;
  }

  .heat-plot {
    margin-inline: -0.5rem;
    max-width: calc(100% + 1rem);
  }

  .paper-section,
  .ink-section,
  .amber-section {
    display: block;
    padding-inline: 1rem;
  }

  .section-index {
    margin-bottom: 1.2rem;
  }

  .path-visual {
    margin-top: 3rem;
  }

  .path-facts {
    padding: 1.5rem 0 0;
    border-top: 1px solid currentColor;
    border-left: 0;
  }

  .use-sequence {
    grid-template-columns: 1fr;
  }

  .use-sequence > div {
    min-height: auto;
  }

  .use-sequence h3 {
    margin-top: 2rem;
  }

  .page-hero,
  .book-hero,
  .catalog-hero {
    display: block;
    min-height: auto;
    padding: 6rem 0;
  }

  .catalog-count {
    margin-top: 3rem;
  }

  .book-catalog a {
    grid-template-columns: 2rem minmax(0, 1fr) 1.5rem;
    min-height: 10rem;
  }

  .catalog-scope {
    grid-column: 2 / span 1;
  }

  .catalog-arrow {
    grid-column: 3;
    grid-row: 1 / span 2;
  }

  .marginal-note {
    display: none;
  }

  .principle-list li {
    grid-template-columns: 2rem 1fr;
    gap: 1rem;
  }

  .principle-list li > div {
    display: block;
  }

  .source-diagram {
    margin-top: 2.5rem;
  }

  .legal-prose {
    max-width: none;
  }

  .site-footer {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .site-footer nav {
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }

  .reveal-ready [data-reveal] {
    opacity: 1;
    transform: none;
  }
}