:root {
  --ink: #17231d;
  --ink-soft: #536158;
  --paper: #f4f0e8;
  --paper-deep: #e8e0d1;
  --panel: rgba(255, 255, 255, 0.72);
  --line: rgba(23, 35, 29, 0.14);
  --teal: #087f73;
  --teal-dark: #075e57;
  --teal-pale: #cce9e1;
  --coral: #e7674f;
  --coral-pale: #f7d6cd;
  --gold: #d89b27;
  --blue: #3f6dd8;
  --shadow: 0 26px 85px rgba(44, 56, 48, 0.13);
  --radius-lg: 30px;
  --radius-md: 20px;
  --content: 1180px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  overflow-x: hidden;
  color: var(--ink);
  background:
    radial-gradient(circle at 7% 3%, rgba(231, 103, 79, 0.10), transparent 28rem),
    radial-gradient(circle at 96% 20%, rgba(8, 127, 115, 0.11), transparent 33rem),
    var(--paper);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.55;
}

button, input { font: inherit; }
a { color: inherit; }
strong { font-weight: 760; }

.skip-link {
  position: fixed;
  z-index: 1000;
  top: 10px;
  left: 10px;
  padding: 10px 14px;
  border-radius: 9px;
  color: white;
  background: var(--ink);
  transform: translateY(-170%);
}

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

.site-header {
  position: sticky;
  z-index: 100;
  top: 0;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 68px;
  padding: 0 4vw;
  border-bottom: 1px solid rgba(23, 35, 29, 0.09);
  background: rgba(244, 240, 232, 0.86);
  backdrop-filter: blur(18px);
}

.brand {
  display: inline-flex;
  gap: 10px;
  align-items: center;
  width: max-content;
  font-size: 0.88rem;
  font-weight: 780;
  letter-spacing: -0.02em;
  text-decoration: none;
}

.brand-mark {
  position: relative;
  width: 24px;
  height: 24px;
  border: 1px solid var(--teal);
  border-radius: 50%;
}

.brand-mark::before,
.brand-mark::after {
  position: absolute;
  top: 11px;
  left: 3px;
  width: 18px;
  height: 1px;
  content: "";
  background: var(--coral);
  transform: rotate(35deg);
}

.brand-mark::after { transform: rotate(-35deg); }

.chapter-nav {
  display: flex;
  gap: 28px;
  color: var(--ink-soft);
  font-size: 0.78rem;
}

.chapter-nav a { text-decoration: none; }
.chapter-nav a:hover, .chapter-nav a:focus-visible { color: var(--teal-dark); }

.header-github-link {
  justify-self: end;
  padding: 8px 13px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--ink-soft);
  background: rgba(255, 255, 255, 0.52);
  font-size: 0.75rem;
  font-weight: 720;
  text-decoration: none;
}

.header-github-link:hover, .header-github-link:focus-visible { border-color: var(--teal); color: var(--teal-dark); }

.hero, .section, footer {
  width: min(var(--content), calc(100% - 40px));
  margin-inline: auto;
}

.hero {
  display: block;
  width: min(1320px, calc(100% - 40px));
  min-height: calc(100vh - 68px);
  padding: 72px 0 88px;
}

.hero-copy { max-width: 1280px; }

.eyebrow, .step-label, .card-kicker {
  margin: 0 0 14px;
  color: var(--teal-dark);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.095em;
  text-transform: uppercase;
}

.eyebrow span { color: var(--coral); }

h1, h2, h3, p { text-wrap: pretty; }

h1, h2 {
  margin: 0;
  font-family: Georgia, "Times New Roman", serif;
  font-weight: 500;
  letter-spacing: -0.046em;
  line-height: 0.99;
}

h1 { max-width: 1200px; font-size: clamp(3.4rem, 6.3vw, 6.15rem); }
h1 em { color: var(--coral); font-weight: inherit; }
h2 { max-width: 900px; font-size: clamp(2.35rem, 4.6vw, 4.25rem); }
h3 { margin: 0; font-size: 1.18rem; letter-spacing: -0.025em; line-height: 1.2; }

.hero-news {
  max-width: 1050px;
  margin-top: 28px;
  padding: 20px 22px;
  border: 1px solid rgba(216, 155, 39, 0.28);
  border-radius: 18px;
  background: rgba(255, 250, 235, 0.64);
}

.hero-news p:not(.card-kicker) { margin: 0; color: var(--ink-soft); font-size: 0.88rem; }

.hero-news-links { display: flex; flex-wrap: wrap; gap: 8px 18px; margin-top: 13px; }
.hero-news-links a { color: var(--teal-dark); font-size: 0.71rem; font-weight: 730; text-underline-offset: 3px; }

.hero-lede { max-width: 1000px; margin: 27px 0 0; color: var(--ink-soft); font-size: clamp(1.02rem, 1.3vw, 1.17rem); }

.hero-actions { display: flex; gap: 24px; align-items: center; margin-top: 32px; }

.button {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  min-height: 46px;
  padding: 0 20px;
  border: 0;
  border-radius: 999px;
  cursor: pointer;
  font-size: 0.86rem;
  font-weight: 760;
  text-decoration: none;
  transition: transform 160ms ease, background 160ms ease, box-shadow 160ms ease;
}

.button:hover, .button:focus-visible { transform: translateY(-2px); }
.button-primary { color: white; background: var(--teal-dark); box-shadow: 0 13px 28px rgba(7, 94, 87, 0.22); }
.button-primary:hover, .button-primary:focus-visible { background: var(--teal); }
.button-secondary { border: 1px solid rgba(8, 127, 115, 0.25); color: var(--teal-dark); background: var(--teal-pale); }
.button-wide { width: 100%; margin-top: 18px; }

.text-link { color: var(--teal-dark); font-size: 0.86rem; font-weight: 740; text-decoration-thickness: 1px; text-underline-offset: 4px; }

.hero-clarifications { max-width: 1050px; margin-top: 38px; padding-top: 22px; border-top: 1px solid var(--line); }
.hero-clarifications > div { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 12px; }
.hero-clarifications article { display: grid; grid-template-columns: auto 1fr; gap: 14px; align-items: start; padding: 19px; border: 1px solid rgba(8,127,115,0.22); border-radius: 16px; background: rgba(255,255,255,0.52); }
.hero-clarifications article > span { display: grid; place-items: center; width: 31px; height: 31px; border-radius: 50%; color: white; background: var(--teal-dark); font-size: 0.66rem; font-weight: 800; }
.hero-clarifications article p { margin: 0; color: var(--ink-soft); font-size: 0.79rem; }
.hero-clarifications article strong { color: var(--ink); }

.section { padding: 112px 0; }
.section + .section { border-top: 1px solid var(--line); }

.section-heading { margin-bottom: 48px; }
.section-heading > p:last-child { max-width: 720px; margin: 24px 0 0; color: var(--ink-soft); font-size: 1.02rem; }

.heading-split {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(300px, 0.75fr);
  gap: clamp(35px, 7vw, 92px);
  align-items: end;
}

.heading-split > p { margin: 0 0 4px; color: var(--ink-soft); font-size: 1rem; }

.glass-panel {
  border: 1px solid rgba(255,255,255,0.76);
  border-radius: var(--radius-lg);
  background: var(--panel);
  box-shadow: var(--shadow);
  backdrop-filter: blur(8px);
}

.tube-lab, .count-lab {
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(300px, 0.65fr);
  gap: 24px;
  align-items: stretch;
}

.tube-stage, .count-stage {
  position: relative;
  min-height: 620px;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 43%, rgba(255,255,255,0.95), rgba(255,255,255,0.42) 55%, rgba(8,127,115,0.09)),
    var(--panel);
}

#packCanvas, #countCanvas { position: absolute; inset: 0; display: block; width: 100%; height: 100%; touch-action: none; }

.visual-topline {
  position: absolute;
  z-index: 3;
  top: 22px;
  right: 24px;
  left: 24px;
  display: flex;
  gap: 9px;
  align-items: center;
  color: var(--ink-soft);
  font-size: 0.69rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  pointer-events: none;
}

.visual-hint { margin-left: auto; }
.live-dot { width: 7px; height: 7px; border-radius: 50%; background: var(--teal); box-shadow: 0 0 0 5px rgba(8,127,115,0.1); }

.stage-caption {
  position: absolute;
  z-index: 4;
  right: 22px;
  bottom: 20px;
  left: 22px;
  padding: 12px 15px;
  border: 1px solid rgba(255,255,255,0.7);
  border-radius: 13px;
  color: var(--ink-soft);
  background: rgba(244,240,232,0.86);
  backdrop-filter: blur(10px);
  font-size: 0.78rem;
  text-align: center;
  pointer-events: none;
}

.axis-key { position: absolute; z-index: 3; top: 55px; left: 24px; display: flex; gap: 5px; pointer-events: none; }
.axis-key span { display: grid; place-items: center; width: 22px; height: 22px; border-radius: 6px; color: white; font: 700 0.66rem Georgia,serif; }
.axis-x { background: var(--coral); } .axis-y { background: var(--teal); } .axis-z { background: var(--blue); }

.tube-controls, .count-controls { display: grid; gap: 16px; align-content: start; }
.control-card, .tube-rule-card, .count-rule-card, .sample-readout {
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.52);
}

.control-title-row { display: flex; justify-content: space-between; gap: 20px; align-items: baseline; }
.control-title-row label { font-size: 0.84rem; font-weight: 740; }
.control-title-row output { color: var(--coral); font-size: 0.77rem; font-weight: 800; }

input[type="range"] { width: 100%; margin: 18px 0 0; accent-color: var(--teal); cursor: pointer; }

.rule-row { display: flex; justify-content: space-between; gap: 20px; padding: 11px 0; border-top: 1px solid var(--line); font-size: 0.81rem; }
.rule-row span { color: var(--ink-soft); }
.rule-row strong { color: var(--teal-dark); }

.sample-readout { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; padding: 16px; }
.sample-readout div { min-width: 0; padding: 10px; border-radius: 13px; background: rgba(255,255,255,0.55); }
.sample-readout span, .sample-readout small { display: block; color: var(--ink-soft); font-size: 0.63rem; line-height: 1.25; }
.sample-readout strong { display: block; margin: 5px 0; color: var(--teal-dark); font-family: Georgia,serif; font-size: 1.5rem; font-weight: 500; }

.union-explanation {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 24px;
  align-items: center;
  margin-top: 28px;
}

.union-explanation article { position: relative; min-height: 174px; padding: 25px 28px 25px 120px; border: 1px solid var(--line); border-radius: var(--radius-md); background: rgba(255,255,255,0.46); }
.union-explanation article p:last-child { margin: 9px 0 0; color: var(--ink-soft); font-size: 0.86rem; }
.union-result { border-color: rgba(8,127,115,0.30) !important; background: rgba(204,233,225,0.4) !important; }
.union-arrow { color: var(--teal); font-size: 1.5rem; }

.union-icon { position: absolute; top: 39px; left: 27px; width: 68px; height: 68px; border: 1px solid var(--line); border-radius: 50%; background: rgba(255,255,255,0.68); }
.union-icon i { position: absolute; top: 32px; left: 10px; width: 48px; height: 4px; border-radius: 999px; background: var(--coral); transform: rotate(-30deg); }
.union-icon i:nth-child(2) { background: var(--teal); transform: rotate(20deg); }
.union-icon i:nth-child(3) { background: var(--gold); transform: rotate(67deg); }
.sum-icon i:nth-child(1) { left: 3px; } .sum-icon i:nth-child(2) { left: 14px; } .sum-icon i:nth-child(3) { left: 24px; }

.plain-note { display: flex; gap: 17px; align-items: flex-start; margin-top: 28px; padding: 21px 24px; border-left: 3px solid var(--gold); border-radius: 0 15px 15px 0; background: rgba(255,250,235,0.58); }
.plain-note p { margin: 0; color: var(--ink-soft); font-size: 0.86rem; }
.note-number { flex: 0 0 auto; display: grid; place-items: center; width: 28px; height: 28px; border-radius: 50%; color: white; background: var(--gold); font-size: 0.72rem; font-weight: 800; }

.continuity-strip {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  gap: 18px;
  align-items: center;
  margin-bottom: 28px;
  padding: 18px;
  border: 1px solid rgba(8,127,115,0.18);
  border-radius: var(--radius-md);
  background: rgba(204,233,225,0.28);
}

.continuity-strip > div { display: grid; grid-template-columns: auto 1fr; column-gap: 12px; align-items: center; }
.continuity-strip strong, .continuity-strip small { display: block; }
.continuity-strip strong { font-size: 0.83rem; }
.continuity-strip small { color: var(--ink-soft); font-size: 0.67rem; }
.continuity-strip > i { color: var(--teal); font-style: normal; }
.continuity-number { grid-row: 1 / 3; display: grid; place-items: center; width: 30px; height: 30px; border-radius: 50%; color: white; background: var(--teal-dark); font-size: 0.72rem; font-weight: 800; }

.count-stage { min-height: 680px; }
.count-legend { position: absolute; z-index: 4; top: 54px; right: 24px; display: flex; gap: 13px; color: var(--ink-soft); font-size: 0.66rem; pointer-events: none; }
.count-legend span { display: inline-flex; gap: 6px; align-items: center; }
.count-legend i { width: 12px; height: 8px; border-radius: 2px; }
.tube-key { background: var(--coral); }
.cube-key { border: 1px solid rgba(8,127,115,0.65); background: rgba(8,127,115,0.24); }

.resolution-buttons, .view-buttons { display: grid; gap: 7px; }
.resolution-buttons { grid-template-columns: repeat(5, 1fr); }
.view-buttons { grid-template-columns: repeat(3, 1fr); }
.resolution-buttons button, .view-buttons button {
  min-width: 0;
  padding: 10px 5px;
  border: 1px solid var(--line);
  border-radius: 12px;
  color: var(--ink-soft);
  background: rgba(255,255,255,0.55);
  cursor: pointer;
  font-size: 0.67rem;
}
.resolution-buttons strong { display: block; margin-top: 2px; color: var(--ink); font-size: 0.72rem; }
.resolution-buttons button.active, .view-buttons button.active { border-color: var(--teal); color: white; background: var(--teal-dark); }
.resolution-buttons button.active strong { color: white; }

.ruler-direction-visual { display: grid; gap: 14px; margin-top: 19px; padding-top: 17px; border-top: 1px solid var(--line); }
.mini-ruler-wrap > span { display: block; color: var(--ink-soft); font-size: 0.67rem; }
.mini-ruler { position: relative; height: 25px; margin-top: 8px; border-bottom: 2px solid var(--ink); }
.mini-ruler i { position: absolute; bottom: -2px; width: 1px; height: 10px; background: var(--ink); transform: translateX(-0.5px); }
.mini-ruler i:first-child, .mini-ruler i:last-child { height: 17px; background: var(--coral); }
.direction-density-wrap { display: grid; grid-template-columns: 92px 1fr; gap: 14px; align-items: center; }
.direction-dot-field { position: relative; width: 92px; aspect-ratio: 1; overflow: hidden; border: 1px solid rgba(8,127,115,0.27); border-radius: 50%; background: radial-gradient(circle at 38% 32%,white,rgba(8,127,115,0.1)); box-shadow: inset -10px -12px 25px rgba(8,127,115,0.08); }
.direction-dot-field::before { position: absolute; z-index: 0; inset: 49% 8%; content: ""; border-top: 1px solid rgba(8,127,115,0.25); border-radius: 50%; transform: rotate(14deg); }
.direction-dot-field i { position: absolute; z-index: 1; width: 3px; height: 3px; border-radius: 50%; background: var(--coral); transform: translate(-50%,-50%); }
.direction-density-wrap p { margin: 0; }
.direction-density-wrap strong, .direction-density-wrap span { display: block; }
.direction-density-wrap strong { color: var(--teal-dark); font-family: Georgia,serif; font-size: 1.15rem; font-weight: 500; }
.direction-density-wrap span { margin-top: 3px; color: var(--ink-soft); font-size: 0.65rem; line-height: 1.3; }

.count-rule-card p:last-child { margin: 14px 0 0; color: var(--ink-soft); font-size: 0.83rem; }
.touch-rule-visual { position: relative; height: 72px; border-radius: 15px; background: rgba(255,255,255,0.54); overflow: hidden; }
.touch-tube { position: absolute; top: 34px; left: 12%; width: 76%; height: 7px; border-radius: 999px; background: linear-gradient(90deg,var(--coral),var(--gold)); transform: rotate(-10deg); }
.touch-cube { position: absolute; top: 17px; left: calc(50% - 19px); width: 38px; height: 38px; border: 2px solid var(--teal); background: rgba(8,127,115,0.20); }
.touch-rule-visual b { position: absolute; top: 8px; right: 13px; display: grid; place-items: center; width: 23px; height: 23px; border-radius: 50%; color: white; background: var(--teal); font-size: 0.72rem; }

.scale-curve-panel { margin: 28px 0 0; padding: 28px; border: 1px solid var(--line); border-radius: var(--radius-lg); background: rgba(255,255,255,0.54); }
.scale-curve-panel figcaption { display: grid; grid-template-columns: minmax(0,1.1fr) minmax(300px,0.7fr); gap: 44px; align-items: end; }
.scale-curve-panel figcaption > p { margin: 0; color: var(--ink-soft); font-size: 0.83rem; }
.curve-legend { display: flex; gap: 20px; justify-content: flex-end; margin: 22px 0 10px; color: var(--ink-soft); font-size: 0.7rem; }
.curve-legend span { display: inline-flex; gap: 7px; align-items: center; }
.curve-legend i { display: inline-block; width: 27px; height: 3px; border-radius: 99px; }
.count-curve-key { background: var(--teal); }
.fraction-curve-key { background: var(--gold); }
.exponent-curve-key { background: var(--blue); }
.curve-scroll { overflow-x: auto; border: 1px solid rgba(8,127,115,0.15); border-radius: 19px; background: rgba(255,255,255,0.68); }
#scaleCurveSvg { display: block; width: 100%; min-width: 760px; height: auto; font-family: Inter,ui-sans-serif,system-ui,sans-serif; }
#scaleCurveSvg .plot-background { fill: rgba(8,127,115,0.025); stroke: rgba(23,35,29,0.08); }
#scaleCurveSvg .grid-line { stroke: rgba(23,35,29,0.10); stroke-width: 1; }
#scaleCurveSvg .axis-label { fill: var(--ink-soft); font-size: 11px; }
#scaleCurveSvg .plot-title { fill: var(--ink); font-size: 13px; font-weight: 760; }
#scaleCurveSvg .count-path { fill: none; stroke: var(--teal); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
#scaleCurveSvg .fraction-path { fill: none; stroke: var(--gold); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
#scaleCurveSvg .exponent-path { fill: none; stroke: var(--blue); stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
#scaleCurveSvg .count-point { fill: white; stroke: var(--teal); stroke-width: 3; }
#scaleCurveSvg .fraction-point { fill: white; stroke: var(--gold); stroke-width: 3; }
#scaleCurveSvg .exponent-point { fill: white; stroke: var(--blue); stroke-width: 3; }
#scaleCurveSvg .point-label { fill: var(--ink); font-size: 10px; font-weight: 720; }
#scaleCurveSvg .exponent-label { fill: var(--blue); }
#scaleCurveSvg .dimension-reference { stroke: var(--blue); stroke-width: 1.5; stroke-dasharray: 7 6; opacity: 0.72; }
#scaleCurveSvg .reference-label { fill: var(--blue); font-size: 10px; font-weight: 720; }
#scaleCurveSvg .selected-guide { stroke: var(--ink); stroke-width: 1; stroke-dasharray: 4 5; opacity: 0.38; }
#scaleCurveSvg .selected-halo { fill: none; stroke: var(--ink); stroke-width: 2; opacity: 0.64; }
.curve-data-strip { display: grid; grid-template-columns: repeat(11,minmax(90px,1fr)); gap: 6px; width: 100%; margin-top: 11px; overflow-x: auto; }
.scale-curve-panel { overflow-x: hidden; }
.curve-data-strip > div { padding: 10px 8px; border: 1px solid var(--line); border-radius: 11px; background: rgba(255,255,255,0.62); text-align: center; }
.curve-data-strip span, .curve-data-strip small { display: block; color: var(--ink-soft); font-size: 0.61rem; }
.curve-data-strip strong { display: block; margin: 3px 0; overflow-wrap: anywhere; color: var(--teal-dark); font-family: Georgia,serif; font-size: 0.95rem; font-weight: 500; }
.curve-data-strip .active { border-color: var(--teal); background: rgba(204,233,225,0.42); }
.curve-data-strip .card-exponent { margin-top: 4px; color: var(--blue); font-weight: 720; }
.curve-caveat { margin: 14px 0 0; color: var(--ink-soft); font-size: 0.71rem; }

.math-inline { white-space: nowrap; font-family: Georgia,serif; color: var(--ink); }

.measurement-bridge { display: grid; grid-template-columns: minmax(0,0.82fr) minmax(0,1.18fr); gap: 24px; margin-top: 28px; }
.fraction-card, .volume-dimension-card { padding: 28px; border: 1px solid var(--line); border-radius: var(--radius-lg); background: rgba(255,255,255,0.48); }
.fraction-card { display: grid; grid-template-columns: minmax(0,0.9fr) minmax(220px,1.1fr); gap: 25px; align-items: center; }
.fraction-card p:not(.card-kicker) { margin: 10px 0 0; color: var(--ink-soft); font-size: 0.8rem; }
.fraction-mosaic { display: grid; grid-template-columns: repeat(10,1fr); gap: 3px; padding: 12px; border: 1px solid var(--line); border-radius: 15px; background: rgba(255,255,255,0.68); }
.fraction-mosaic i { aspect-ratio: 1; border-radius: 2px; background: rgba(23,35,29,0.08); transition: background 220ms ease, transform 220ms ease; }
.fraction-mosaic i.filled { background: var(--teal); transform: scale(1.04); }
.fraction-equation { display: flex; flex-wrap: wrap; gap: 5px; justify-content: center; align-items: baseline; margin-top: 12px; color: var(--ink-soft); font-size: 0.67rem; }
.fraction-equation b { color: var(--coral); }
.fraction-equation strong { color: var(--teal-dark); font-family: Georgia,serif; font-size: 1.15rem; font-weight: 500; }

.volume-dimension-card { display: grid; gap: 17px; }
.measurement-lane { display: grid; grid-template-columns: 112px 1fr; gap: 20px; align-items: center; padding: 18px; border-radius: 18px; background: rgba(255,255,255,0.62); }
.measurement-lane > div:last-child > span, .measurement-lane > div:last-child > strong { display: block; }
.measurement-lane > div:last-child > span { color: var(--ink-soft); font-size: 0.7rem; font-weight: 720; text-transform: uppercase; letter-spacing: 0.04em; }
.measurement-lane > div:last-child > strong { margin-top: 4px; color: var(--teal-dark); font-family: Georgia,serif; font-size: 1.15rem; font-weight: 500; }
.measurement-lane p { margin: 7px 0 0; color: var(--ink-soft); font-size: 0.76rem; }
.measurement-icon { position: relative; width: 84px; height: 64px; margin-inline: auto; border: 2px solid var(--teal); border-radius: 8px; background: linear-gradient(90deg,var(--teal) 0 var(--fraction-fill,27%),rgba(8,127,115,0.08) var(--fraction-fill,27%)); box-shadow: 8px -8px 0 -2px rgba(8,127,115,0.09),8px -8px 0 0 var(--teal); }
.measurement-icon::after { position: absolute; right: 7px; bottom: 7px; content: "one scale"; color: var(--ink-soft); font-size: 0.51rem; }
.scale-film { display: flex; gap: 5px; align-items: center; justify-content: center; }
.scale-film i { display: grid; place-items: center; width: 30px; aspect-ratio: 1; border: 1px solid var(--teal); color: var(--teal-dark); background: rgba(8,127,115,0.10); font-style: normal; }
.scale-film i:nth-of-type(2) { width: 42px; background-image: linear-gradient(rgba(8,127,115,0.2) 1px,transparent 1px),linear-gradient(90deg,rgba(8,127,115,0.2) 1px,transparent 1px); background-size: 7px 7px; }
.scale-film i:nth-of-type(3) { width: 52px; background-image: linear-gradient(rgba(8,127,115,0.18) 1px,transparent 1px),linear-gradient(90deg,rgba(8,127,115,0.18) 1px,transparent 1px); background-size: 5px 5px; }
.scale-film b { padding: 2px; color: var(--ink); background: rgba(244,240,232,0.88); font-size: 0.52rem; }
.scale-film span { color: var(--coral); font-size: 0.72rem; }

.theorem-card { margin-top: 112px; padding: clamp(32px,5vw,58px); border-radius: 36px; color: white; background: linear-gradient(135deg,#15231d,#064f49 78%,#087f73); box-shadow: 0 34px 100px rgba(7,70,63,0.28); }
.theorem-kicker { display: flex; justify-content: space-between; align-items: center; padding-bottom: 18px; border-bottom: 1px solid rgba(255,255,255,0.16); color: rgba(255,255,255,0.72); font-size: 0.69rem; text-transform: uppercase; letter-spacing: 0.08em; }
.theorem-kicker b { padding: 6px 10px; border-radius: 999px; color: var(--ink); background: var(--teal-pale); font-size: 0.64rem; }
.theorem-layout { display: grid; grid-template-columns: 1.1fr 0.9fr; gap: clamp(35px,6vw,80px); margin-top: 40px; }
.theorem-card .step-label { color: var(--teal-pale); }
.theorem-card h2 { color: white; }
.theorem-copy p { margin: 0 0 18px; color: rgba(255,255,255,0.75); }
.theorem-copy strong { color: white; }
.theorem-copy .theorem-takeaway { margin-bottom: 19px; color: white; font-family: Georgia,serif; font-size: clamp(1.45rem,2.2vw,2rem); font-weight: 500; letter-spacing: -0.03em; line-height: 1.08; }
.theorem-results { display: grid; grid-template-columns: repeat(3,1fr); gap: 10px; margin-top: 42px; }
.theorem-results > div { padding: 19px; border: 1px solid rgba(255,255,255,0.14); border-radius: 16px; background: rgba(255,255,255,0.06); }
.theorem-results span, .theorem-results small { display: block; color: rgba(255,255,255,0.65); font-size: 0.68rem; }
.theorem-results strong { display: block; margin: 6px 0; color: white; font-family: Georgia,serif; font-size: 1.55rem; font-weight: 500; }

footer { display: flex; justify-content: space-between; gap: 40px; align-items: start; padding: 38px 0 50px; border-top: 1px solid var(--line); color: var(--ink-soft); font-size: 0.74rem; }
footer p { max-width: 800px; margin: 0 0 7px; }
footer a { flex: 0 0 auto; color: var(--teal-dark); font-weight: 730; text-underline-offset: 3px; }

.noscript-message { position: fixed; z-index: 999; right: 20px; bottom: 20px; left: 20px; padding: 16px; border-radius: 12px; color: white; background: var(--ink); text-align: center; }

@media (max-width: 980px) {
  .site-header { grid-template-columns: 1fr auto; }
  .chapter-nav { display: none; }
  .hero { min-height: 0; }
  .heading-split { grid-template-columns: 1fr; gap: 24px; }
  .tube-lab, .count-lab { grid-template-columns: 1fr; }
  .tube-controls, .count-controls { grid-template-columns: repeat(2,1fr); }
  .sample-readout, .count-rule-card { grid-column: 1 / -1; }
  .measurement-bridge { grid-template-columns: 1fr; }
  .theorem-layout { grid-template-columns: 1fr; }
}

@media (max-width: 760px) {
  .hero, .section, footer { width: min(100% - 28px, var(--content)); }
  .hero { padding: 58px 0 70px; }
  h1 { font-size: clamp(3rem,15vw,4.4rem); }
  h2 { font-size: clamp(2.25rem,11vw,3.4rem); }
  .section { padding: 82px 0; }
  .hero-actions { align-items: flex-start; flex-direction: column; gap: 16px; }
  .hero-clarifications > div { grid-template-columns: 1fr; }
  .hero-news-links { flex-direction: column; }
  .tube-stage, .count-stage { min-height: 500px; border-radius: 22px; }
  .tube-controls, .count-controls { grid-template-columns: 1fr; }
  .sample-readout, .count-rule-card { grid-column: auto; }
  .union-explanation { grid-template-columns: 1fr; }
  .union-arrow { transform: rotate(90deg); justify-self: center; }
  .continuity-strip { grid-template-columns: 1fr; }
  .continuity-strip > i { transform: rotate(90deg); justify-self: center; }
  .scale-curve-panel { padding: 20px; }
  .scale-curve-panel figcaption { grid-template-columns: 1fr; gap: 14px; }
  .curve-legend { flex-wrap: wrap; justify-content: flex-start; }
  .curve-data-strip { grid-template-columns: repeat(22,90px); }
  .fraction-card { grid-template-columns: 1fr; }
  .fraction-gauge-wrap { width: min(100%,330px); margin-inline: auto; }
  .measurement-lane { grid-template-columns: 100px 1fr; padding: 15px; }
  .theorem-results { grid-template-columns: 1fr; }
  footer { flex-direction: column; }
}

@media (max-width: 480px) {
  .site-header { min-height: 60px; padding: 0 14px; }
  .brand { font-size: 0.78rem; }
  .header-github-link { padding: 7px 10px; font-size: 0.68rem; }
  .hero { padding-top: 46px; }
  .hero-clarifications article { padding: 16px; }
  .tube-stage, .count-stage { min-height: 440px; }
  .visual-topline { top: 16px; right: 16px; left: 16px; }
  .visual-hint { display: none; }
  .stage-caption { right: 14px; bottom: 14px; left: 14px; }
  .axis-key { top: 48px; left: 16px; }
  .resolution-buttons { grid-template-columns: repeat(5,1fr); }
  .resolution-buttons button { padding-inline: 3px; }
  .direction-density-wrap { grid-template-columns: 82px 1fr; }
  .direction-dot-field { width: 82px; }
  .fraction-card, .volume-dimension-card { padding: 20px; }
  .measurement-lane { grid-template-columns: 1fr; text-align: center; }
  .measurement-icon { margin-bottom: 5px; }
  .theorem-card { margin-top: 82px; border-radius: 25px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; scroll-behavior: auto !important; }
}