:root {
  --bg: #0b1020;
  --bg2: #10182d;
  --panel: #151f3b;
  --panel-soft: #1a2748;
  --text: #f4f7ff;
  --muted: #a9b7d3;
  --line: rgba(175, 196, 235, .18);
  --accent: #78aaff;
  --accent-2: #62dfaa;
  --warm: #ff8c7d;
  --shadow: 0 20px 50px rgba(0, 0, 0, .22);
  color-scheme: dark;
}

:root[data-theme="light"] {
  --bg: #f1f5ff;
  --bg2: #e8efff;
  --panel: #ffffff;
  --panel-soft: #edf3ff;
  --text: #15223f;
  --muted: #5b6a86;
  --line: rgba(31, 59, 111, .16);
  --accent: #356fe0;
  --accent-2: #148d60;
  --warm: #d55348;
  --shadow: 0 18px 44px rgba(32, 57, 104, .12);
  color-scheme: light;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.55;
}

button, input, textarea { font: inherit; }
button { cursor: pointer; }
button:focus-visible,
a:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}
[hidden] { display: none !important; }

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  height: 66px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 max(18px, calc((100vw - 1180px) / 2));
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(16px);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  font-weight: 850;
  letter-spacing: -.03em;
  text-decoration: none;
}

.brand-mark {
  position: relative;
  display: block;
  width: 27px;
  height: 27px;
  border: 2px solid var(--accent);
  border-radius: 50%;
}

.brand-mark::after {
  position: absolute;
  inset: 7px;
  border-radius: 50%;
  background: var(--accent);
  content: "";
}

.brand-mark i {
  position: absolute;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--accent);
}
.brand-mark i:nth-child(1) { top: -5px; left: 9px; }
.brand-mark i:nth-child(2) { top: 9px; right: -5px; }
.brand-mark i:nth-child(3) { bottom: -5px; left: 9px; }
.brand-mark i:nth-child(4) { top: 9px; left: -5px; }

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

.icon-btn,
.secondary-btn {
  min-height: 42px;
  padding: 7px 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: transparent;
  color: var(--text);
  font-size: .82rem;
  font-weight: 750;
}

.icon-btn:hover,
.secondary-btn:hover { background: var(--panel-soft); }

.hero {
  position: relative;
  min-height: 430px;
  overflow: hidden;
  padding: 95px max(20px, calc((100vw - 1060px) / 2)) 72px;
  background:
    radial-gradient(circle at 82% 30%, rgba(95, 116, 255, .25), transparent 24rem),
    radial-gradient(circle at 71% 80%, rgba(63, 220, 166, .13), transparent 25rem),
    var(--bg2);
}

.hero::before,
.hero::after {
  position: absolute;
  top: 70px;
  right: 9%;
  width: 270px;
  height: 270px;
  border: 1px solid rgba(139, 170, 255, .2);
  border-radius: 50%;
  content: "";
}

.hero::after {
  top: 30px;
  right: 5%;
  width: 350px;
  height: 350px;
  border-style: dashed;
}

.hero > * { position: relative; z-index: 1; }

.eyebrow,
.mini-kicker,
.tag,
.card-number {
  color: var(--accent);
  font-size: .72rem;
  font-weight: 800;
  letter-spacing: .13em;
  text-transform: uppercase;
}

.hero h1 {
  max-width: 680px;
  margin: 5px 0 10px;
  font-size: clamp(2.75rem, 7vw, 5.7rem);
  line-height: .95;
  letter-spacing: -.075em;
}

.hero h1 em {
  color: var(--accent-2);
  font-style: normal;
}

.lede {
  max-width: 700px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(1.05rem, 2.4vw, 1.25rem);
}

.hero-facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 190px));
  gap: 20px;
  margin: 37px 0 31px;
}

.hero-facts div {
  padding-left: 12px;
  border-left: 2px solid var(--accent);
}

.hero-facts strong {
  display: block;
  font-size: .95rem;
}

.hero-facts span {
  display: block;
  margin-top: 3px;
  color: var(--muted);
  font-size: .8rem;
  line-height: 1.35;
}

.primary-link,
.action-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  gap: 12px;
  padding: 11px 18px;
  border: 0;
  border-radius: 10px;
  background: var(--accent-2);
  color: #081528;
  box-shadow: 0 7px 20px rgba(44, 211, 151, .18);
  font-weight: 850;
  text-decoration: none;
}

.primary-link:hover,
.action-btn:hover {
  transform: translateY(-1px);
  filter: brightness(1.06);
}

.section-nav {
  display: flex;
  max-width: 1120px;
  gap: 6px;
  overflow-x: auto;
  margin: 0 auto;
  padding: 13px 20px;
  border-bottom: 1px solid var(--line);
}

.section-nav a {
  padding: 8px 11px;
  color: var(--muted);
  font-size: .85rem;
  font-weight: 700;
  text-decoration: none;
  white-space: nowrap;
}

.section-nav a:hover {
  border-radius: 8px;
  background: var(--panel);
  color: var(--text);
}

.content-section {
  max-width: 1120px;
  margin: auto;
  padding: 76px 20px;
  scroll-margin-top: 65px;
}

.content-section.alternate {
  max-width: none;
  padding-right: max(20px, calc((100vw - 1080px) / 2));
  padding-left: max(20px, calc((100vw - 1080px) / 2));
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--panel) 48%, transparent);
}

.section-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 44px;
  margin-bottom: 34px;
}

.section-heading h2 {
  margin: 6px 0 0;
  font-size: clamp(2rem, 4.3vw, 3.2rem);
  line-height: 1;
  letter-spacing: -.06em;
}

.section-heading > p {
  max-width: 455px;
  margin: 0;
  color: var(--muted);
}

.anatomy-layout {
  display: grid;
  grid-template-columns: 1.15fr .85fr;
  gap: 26px;
  align-items: stretch;
}

.virus-stage,
.info-card,
.mini-card,
.scale-tool,
.cycle-demo,
.simulation-panel,
.sim-settings,
.chart-card,
.example-card,
.analogy-card,
.quiz-card,
.notes-card {
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.virus-stage {
  display: flex;
  min-height: 380px;
  flex-direction: column;
  justify-content: center;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 40%, color-mix(in srgb, var(--accent) 18%, transparent), transparent 34%),
    var(--panel);
}

.virus-model {
  position: relative;
  width: min(300px, 78vw);
  aspect-ratio: 1;
  margin: 20px auto 4px;
}

.envelope-shape {
  position: absolute;
  inset: 16%;
  border-radius: 50%;
  background: radial-gradient(circle at 35% 30%, #d2e5ff, #759de8 55%, #486bc1);
  box-shadow: inset -18px -18px 30px rgba(20, 41, 100, .38), 0 0 0 11px rgba(127, 160, 240, .24);
}

.capsid-shape {
  position: absolute;
  z-index: 2;
  inset: 28%;
  border-radius: 46% 54% 51% 49%;
  background: #d8f7d9;
  box-shadow: inset -12px -10px 15px rgba(39, 120, 74, .28);
}

.genome-shape {
  position: absolute;
  z-index: 3;
  inset: 39%;
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  transform: rotate(-17deg);
}

.genome-shape b {
  display: block;
  height: 9px;
  border-radius: 10px;
  background: #ff806d;
}

.genome-shape b:nth-child(even) {
  transform: translateX(7px);
  background: #ffbc71;
}

.spike {
  position: absolute;
  z-index: 5;
  width: 15px;
  height: 43px;
  border-radius: 12px;
  background: #62dfaa;
  box-shadow: 0 0 0 4px rgba(98, 223, 170, .22);
  transform-origin: 50% 100%;
}

.s1 { top: 2%; left: 46%; }
.s2 { top: 13%; right: 10%; transform: rotate(48deg); }
.s3 { top: 47%; right: 1%; transform: rotate(89deg); }
.s4 { right: 13%; bottom: 9%; transform: rotate(137deg); }
.s5 { bottom: 1%; left: 44%; transform: rotate(180deg); }
.s6 { top: 47%; left: 5%; transform: rotate(-88deg); }

.part {
  position: absolute;
  z-index: 7;
  left: var(--x);
  top: var(--y);
  width: 32px;
  height: 32px;
  border: 2px solid white;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 5px rgba(120, 170, 255, .2);
  transform: translate(-50%, -50%);
}

.part::after {
  position: absolute;
  top: 14px;
  width: 70px;
  height: 1px;
  background: white;
  opacity: .8;
  content: "";
  transform-origin: left;
}

.part-envelope::after { transform: rotate(-54deg); }
.part-capsid::after { transform: rotate(158deg); }
.part-genome::after { transform: rotate(24deg); }
.part-spike::after { transform: rotate(-25deg); }

.part.active {
  background: var(--warm);
  transform: translate(-50%, -50%) scale(1.15);
}

.diagram-caption {
  margin: 7px 15px 18px;
  color: var(--muted);
  font-size: .78rem;
  text-align: center;
}

.info-card {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 32px;
}

.info-card h3,
.mini-card h3,
.scale-tool h3,
.cycle-explain h3,
.chart-card h3,
.example-card h3,
.analogy-card h3,
.quiz-card h3,
.notes-card h3 {
  margin: 4px 0 10px;
  font-size: 1.42rem;
  line-height: 1.1;
  letter-spacing: -.035em;
}

.info-card p,
.mini-card p,
.scale-tool p,
.cycle-explain p,
.example-card p,
.analogy-card > p,
.notes-card p {
  color: var(--muted);
}

.real-example {
  margin-top: 20px;
  padding: 13px;
  border-left: 3px solid var(--accent);
  border-radius: 10px;
  background: color-mix(in srgb, var(--accent) 11%, transparent);
  font-size: .88rem;
}

.comparison-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 18px;
}

.mini-card { padding: 22px; }
.mini-card h3 { margin-top: 5px; font-size: 1.12rem; }
.mini-card p { margin-bottom: 0; font-size: .89rem; }

.scale-tool {
  display: grid;
  grid-template-columns: .75fr 1.25fr;
  gap: 30px;
  margin-top: 22px;
  padding: 27px;
}

.scale-controls label,
.sim-settings label {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 4px;
  color: var(--muted);
  font-size: .84rem;
  font-weight: 700;
}

output {
  color: var(--accent-2);
  font-weight: 850;
}

input[type="range"] {
  width: 100%;
  min-height: 35px;
  accent-color: var(--accent-2);
}

.scale-ruler {
  display: flex;
  align-items: end;
  justify-content: space-around;
  min-height: 94px;
  gap: 14px;
  padding: 0 4px 12px;
  border-bottom: 2px solid var(--line);
}

.object {
  position: relative;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--accent);
  transition: transform .3s ease;
}

.object span {
  position: absolute;
  top: calc(100% + 8px);
  left: 50%;
  min-width: 82px;
  color: var(--muted);
  font-size: .67rem;
  line-height: 1.15;
  text-align: center;
  transform: translateX(-50%);
}

.human-cell { width: 59px; height: 59px; background: #6b96ea; }
.bacterium { width: 25px; height: 25px; border-radius: 45%; background: var(--accent-2); }
.virus-dot { width: 12px; height: 12px; background: var(--warm); }
.protein { width: 6px; height: 6px; background: #cf9fff; }

.scale-ruler[data-zoom="0"] .human-cell { transform: scale(1.3); }
.scale-ruler[data-zoom="2"] .virus-dot { transform: scale(2); }
.scale-ruler[data-zoom="3"] .protein { transform: scale(4); }

.small-note {
  margin: 12px 0 0;
  color: var(--muted);
  font-size: .77rem;
}

.cycle-wrap {
  display: grid;
  grid-template-columns: 170px 1fr;
  gap: 18px;
}

.cycle-controls {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.cycle-step {
  min-height: 54px;
  padding: 8px;
  border: 1px solid var(--line);
  border-radius: 11px;
  background: transparent;
  color: var(--muted);
  font-weight: 800;
  text-align: left;
}

.cycle-step b {
  display: inline-grid;
  width: 29px;
  height: 29px;
  place-items: center;
  margin-right: 7px;
  border-radius: 50%;
  background: var(--panel);
  color: var(--accent);
}

.cycle-step.active {
  border-color: transparent;
  background: var(--accent);
  color: #07162c;
}

.cycle-step.active b {
  background: #eaf2ff;
  color: #1d55ba;
}

.cycle-demo {
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  min-height: 335px;
  gap: 26px;
  padding: 23px;
  overflow: hidden;
}

.cell-scene {
  position: relative;
  width: min(280px, 100%);
  aspect-ratio: 1;
  margin: auto;
  overflow: hidden;
  border-radius: 46% 54% 52% 48%;
  background: #d7e8f6;
  box-shadow: inset -20px -25px 0 rgba(60, 119, 172, .2), 0 0 0 10px rgba(122, 185, 227, .2);
}

.cell-membrane {
  position: absolute;
  inset: 7px;
  border: 5px solid #73b6db;
  border-radius: inherit;
}

.cell-nucleus {
  position: absolute;
  top: 33%;
  left: 37%;
  display: grid;
  width: 37%;
  aspect-ratio: 1;
  place-items: center;
  border-radius: 50%;
  background: #9c92d9;
  color: #fff;
  font-size: .61rem;
  text-align: center;
}

.cell-ribosome {
  position: absolute;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #e2a660;
}

.r1 { top: 30%; left: 20%; }
.r2 { right: 21%; bottom: 28%; }
.r3 { bottom: 18%; left: 29%; }

.demo-virus {
  position: absolute;
  top: 42%;
  left: -15%;
  width: 38px;
  height: 38px;
  border: 7px solid #ffb17d;
  border-radius: 50%;
  background: #ff816f;
  transition: .5s ease;
}

.demo-virus i {
  position: absolute;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: #63dca7;
}

.demo-virus i:nth-child(1) { top: -11px; left: 8px; }
.demo-virus i:nth-child(2) { top: 10px; right: -11px; }
.demo-virus i:nth-child(3) { bottom: -10px; left: 13px; }

.copy-particles::before,
.copy-particles::after {
  position: absolute;
  display: none;
  width: 21px;
  height: 21px;
  border: 4px solid #ffb17d;
  border-radius: 50%;
  background: #ff816f;
  content: "";
}

.cell-scene[data-step="1"] .demo-virus { left: 5%; }
.cell-scene[data-step="2"] .demo-virus { top: 48%; left: 43%; transform: scale(.55); }
.cell-scene[data-step="2"] .copy-particles::before { top: 58%; left: 22%; display: block; }
.cell-scene[data-step="3"] .demo-virus { top: 23%; left: 58%; transform: scale(.7); }
.cell-scene[data-step="3"] .copy-particles::before { top: 60%; left: 20%; display: block; }
.cell-scene[data-step="3"] .copy-particles::after { right: 20%; bottom: 21%; display: block; }
.cell-scene[data-step="4"] { overflow: visible; }
.cell-scene[data-step="4"] .demo-virus { top: 30%; left: 97%; }
.cell-scene[data-step="4"] .copy-particles::before { top: 57%; left: 108%; display: block; }
.cell-scene[data-step="4"] .copy-particles::after { top: -19%; left: 74%; display: block; }

.callout {
  margin-top: 20px;
  padding: 18px 20px;
  border: 1px solid color-mix(in srgb, var(--accent-2) 30%, transparent);
  border-radius: 12px;
  background: color-mix(in srgb, var(--accent-2) 9%, transparent);
  color: var(--muted);
}

.callout strong { color: var(--accent-2); }

.sim-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(280px, .55fr);
  gap: 18px;
}

.simulation-panel {
  padding: 12px;
  overflow: hidden;
}

.simulation-panel canvas {
  display: block;
  width: 100%;
  height: 370px;
  border-radius: 11px;
}

.sim-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  padding: 10px 6px 2px;
  color: var(--muted);
  font-size: .8rem;
}

.legend-dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  margin-right: 5px;
  border-radius: 50%;
}

.susceptible { background: #9aacc8; }
.infected { background: var(--warm); }
.recovered { background: var(--accent-2); }

.sim-settings { padding: 23px; }

.stat-row {
  display: flex;
  justify-content: space-between;
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
  color: var(--muted);
}

.stat-row strong { color: var(--text); }
.sim-settings label { margin-top: 21px; }

.button-row {
  display: flex;
  gap: 9px;
  margin-top: 20px;
}

.button-row .action-btn { flex: 1; }
.button-row .secondary-btn { flex: .65; }

.chart-card {
  margin-top: 18px;
  padding: 23px;
}

.chart-card h3 { margin-bottom: 13px; }

.chart-card canvas {
  display: block;
  width: 100%;
  height: 210px;
  border-radius: 10px;
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}

.filter {
  min-height: 42px;
  padding: 7px 15px;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: transparent;
  color: var(--muted);
  font-weight: 750;
}

.filter.active {
  border-color: var(--accent);
  background: var(--accent);
  color: #09162c;
}

.example-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
}

.example-card {
  display: flex;
  min-height: 236px;
  flex-direction: column;
  padding: 21px;
}

.example-card h3 { font-size: 1.15rem; }

.example-card p {
  margin: 3px 0 17px;
  font-size: .88rem;
}

.example-card footer {
  margin-top: auto;
  padding-top: 11px;
  border-top: 1px solid var(--line);
  color: var(--accent-2);
  font-size: .75rem;
}

.tag {
  display: inline-block;
  width: max-content;
  padding: 4px 8px;
  border-radius: 4px;
  font-size: .62rem;
}

.tag.human { background: rgba(116,169,255,.16); }
.tag.animal { color: #f3b466; background: rgba(243,180,102,.14); }
.tag.plant { color: var(--accent-2); background: rgba(98,223,170,.13); }
.tag.bacteria { color: #dca3ff; background: rgba(220,163,255,.13); }

.compare-table {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 15px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.table-row {
  display: grid;
  grid-template-columns: .7fr 1fr 1fr;
  border-bottom: 1px solid var(--line);
}

.table-row:last-child { border-bottom: 0; }

.table-row > div {
  padding: 16px;
  border-right: 1px solid var(--line);
  color: var(--muted);
  font-size: .91rem;
}

.table-row > div:last-child { border-right: 0; }

.table-row > div:first-child {
  color: var(--text);
  font-weight: 760;
}

.table-head { background: var(--panel-soft); }

.table-head > div {
  color: var(--accent) !important;
  font-size: .7rem;
  letter-spacing: .08em;
  text-transform: uppercase;
}

.analogy-card {
  margin-top: 20px;
  padding: 28px;
}

.analogy-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.analogy-item {
  padding: 15px;
  border: 1px solid var(--line);
  border-radius: 12px;
}

.analogy-item p {
  margin: 0 0 12px;
  font-size: .9rem;
  font-weight: 700;
}

.sort-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.sort-buttons button {
  min-height: 34px;
  padding: 4px 9px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: transparent;
  color: var(--muted);
  font-size: .76rem;
  text-transform: capitalize;
}

.sort-buttons button.correct {
  border-color: var(--accent-2);
  background: rgba(98, 223, 170, .18);
  color: var(--accent-2);
}

.sort-buttons button.wrong {
  border-color: var(--warm);
  background: rgba(255, 140, 125, .18);
  color: var(--warm);
}

.feedback {
  min-height: 24px;
  margin: 16px 0 0;
  font-weight: 700;
}

.feedback.good { color: var(--accent-2); }
.feedback.try-again { color: var(--warm); }

.quiz-card {
  max-width: 780px;
  margin: auto;
  padding: 31px;
}

.quiz-progress {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 15px;
  color: var(--muted);
  font-size: .82rem;
  font-weight: 750;
}

.quiz-progress > div {
  width: 40%;
  height: 7px;
  overflow: hidden;
  border-radius: 10px;
  background: var(--panel-soft);
}

.quiz-progress i {
  display: block;
  width: 0;
  height: 100%;
  background: var(--accent-2);
  transition: .3s;
}

.quiz-card h3 {
  margin: 26px 0 19px;
  font-size: clamp(1.35rem, 3vw, 1.75rem);
}

.answers {
  display: grid;
  gap: 10px;
}

.answer-btn {
  display: flex;
  width: 100%;
  min-height: 54px;
  align-items: center;
  gap: 13px;
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: transparent;
  color: var(--text);
  font-weight: 650;
  text-align: left;
}

.answer-btn:hover:not(:disabled) { background: var(--panel-soft); }

.answer-btn span {
  display: grid;
  width: 28px;
  height: 28px;
  flex: 0 0 auto;
  place-items: center;
  border-radius: 7px;
  background: var(--panel-soft);
  color: var(--accent);
  font-size: .78rem;
}

.answer-btn.correct {
  border-color: var(--accent-2);
  background: rgba(98,223,170,.10);
}

.answer-btn.wrong {
  border-color: var(--warm);
  background: rgba(255,140,125,.10);
}

.quiz-explanation {
  margin: 18px 0;
  padding: 14px;
  border-radius: 10px;
  background: var(--panel-soft);
  color: var(--muted);
}

.notes-card {
  max-width: 780px;
  margin: 20px auto 0;
  padding: 27px;
}

.notes-card textarea {
  width: 100%;
  min-height: 135px;
  margin-top: 15px;
  padding: 13px;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg);
  color: var(--text);
}

.notes-footer {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin-top: 8px;
  color: var(--muted);
  font-size: .75rem;
}

footer {
  display: flex;
  max-width: 1120px;
  flex-wrap: wrap;
  gap: 12px 22px;
  margin: auto;
  padding: 33px 20px 46px;
  color: var(--muted);
  font-size: .8rem;
}

footer strong { color: var(--text); }

@media (max-width: 820px) {
  .hero { padding-top: 72px; }
  .hero::before,
  .hero::after { right: -110px; opacity: .35; }

  .hero-facts {
    grid-template-columns: 1fr;
    max-width: 420px;
    gap: 12px;
  }

  .section-heading { display: block; }
  .section-heading > p { margin-top: 18px; }

  .anatomy-layout,
  .scale-tool,
  .sim-layout,
  .cycle-demo {
    grid-template-columns: 1fr;
  }

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

  .cycle-wrap { grid-template-columns: 1fr; }

  .cycle-controls {
    flex-direction: row;
    overflow-x: auto;
  }

  .cycle-step {
    min-width: 125px;
    white-space: nowrap;
  }

  .example-grid { grid-template-columns: 1fr 1fr; }
  .analogy-list { grid-template-columns: 1fr; }
  .cell-scene { width: min(250px, 70vw); }
}

@media (max-width: 510px) {
  .topbar { padding: 0 14px; }
  .icon-btn { padding: 6px 8px; font-size: .73rem; }

  .hero {
    min-height: 410px;
    padding-right: 20px;
    padding-left: 20px;
  }

  .content-section {
    padding-top: 56px;
    padding-bottom: 56px;
  }

  .virus-stage { min-height: 330px; }
  .info-card { padding: 24px; }
  .simulation-panel canvas { height: 290px; }
  .chart-card { padding: 15px; }
  .chart-card canvas { height: 185px; }
  .example-grid { grid-template-columns: 1fr; }

  .table-row { grid-template-columns: 1fr; }
  .table-row > div {
    padding: 11px 14px;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }
  .table-row > div:last-child { border-bottom: 0; }
  .table-head { display: none; }
  .table-row > div:first-child { background: var(--panel-soft); }

  .quiz-card,
  .notes-card { padding: 21px; }
}