:root {
  --ode-ink: #17332d;
  --ode-muted: #58716a;
  --ode-paper: #fbfaf5;
  --ode-panel: #f2f7f3;
  --ode-line: #c9d9d2;
  --ode-green: #087f5b;
  --ode-green-dark: #056246;
  --ode-coral: #df6843;
  --ode-gold: #d99b2b;
  --ode-blue: #277da1;
  --ode-error: #a33b34;
  --ode-shadow: 0 12px 34px rgba(23, 51, 45, 0.1);
}

.ayu,
.navy,
.coal {
  --ode-ink: #e6f1ed;
  --ode-muted: #a9bdb6;
  --ode-paper: #14201d;
  --ode-panel: #1b2b27;
  --ode-line: #3b5049;
  --ode-green: #42d3a2;
  --ode-green-dark: #75e6bf;
  --ode-coral: #ff9878;
  --ode-gold: #f1bd55;
  --ode-blue: #65badc;
  --ode-error: #ff8d85;
  --ode-shadow: 0 12px 34px rgba(0, 0, 0, 0.24);
}

html {
  scroll-behavior: smooth;
}

body {
  color: var(--ode-ink);
}

.content main {
  max-width: 880px;
}

main h1 {
  color: var(--ode-ink);
  font-size: clamp(2.25rem, 5vw, 4.2rem);
  letter-spacing: -0.045em;
  line-height: 0.98;
  margin-bottom: 1.6rem;
}

main h2 {
  border-top: 1px solid var(--ode-line);
  color: var(--ode-ink);
  font-size: clamp(1.55rem, 3vw, 2.2rem);
  letter-spacing: -0.025em;
  margin-top: 3.8rem;
  padding-top: 1.25rem;
}

main h3 {
  color: var(--ode-green-dark);
  font-size: 1.22rem;
  margin-top: 2.3rem;
}

main p,
main li {
  line-height: 1.72;
}

main a {
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

.eyebrow {
  color: var(--ode-green-dark);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  margin: 0 0 0.75rem;
  text-transform: uppercase;
}

.hero-grid {
  align-items: center;
  display: grid;
  gap: 2rem;
  grid-template-columns: minmax(0, 1.1fr) minmax(280px, 0.9fr);
  margin: 0 0 3rem;
}

.hero-copy {
  color: var(--ode-muted);
  font-size: 1.18rem;
  line-height: 1.65;
  margin: 0;
}

.hero-actions {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-top: 1.4rem;
}

.primary-action,
.secondary-action {
  border-radius: 0.4rem;
  display: inline-flex;
  font: inherit;
  font-weight: 750;
  justify-content: center;
  min-height: 2.65rem;
  padding: 0.7rem 1rem;
}

.primary-action {
  background: var(--ode-green);
  color: white !important;
  text-decoration: none;
}

.primary-action:hover {
  background: var(--ode-green-dark);
}

.text-action {
  color: var(--ode-green-dark) !important;
  font-weight: 700;
}

.secondary-action {
  background: transparent;
  border: 1px solid var(--ode-line);
  color: var(--ode-ink);
  cursor: pointer;
}

.hero-orbit {
  background:
    radial-gradient(circle at 76% 16%, color-mix(in srgb, var(--ode-coral) 18%, transparent), transparent 24%),
    radial-gradient(circle at 18% 80%, color-mix(in srgb, var(--ode-green) 18%, transparent), transparent 27%),
    var(--ode-panel);
  border: 1px solid var(--ode-line);
  border-radius: 1.2rem 0.3rem 1.2rem 0.3rem;
  box-shadow: var(--ode-shadow);
  padding: 0.55rem;
}

.hero-orbit svg {
  display: block;
  width: 100%;
}

.hero-field path {
  fill: none;
  opacity: 0.75;
  stroke: var(--ode-muted);
  stroke-linecap: round;
  stroke-width: 2.2;
}

.hero-solution {
  fill: none;
  stroke: url(#hero-line);
  stroke-linecap: round;
  stroke-width: 6;
}

.hero-point {
  fill: var(--ode-coral);
  stroke: var(--ode-paper);
  stroke-width: 3;
}

.hero-orbit text {
  fill: var(--ode-ink);
  font-size: 13px;
  font-weight: 700;
}

.question-grid {
  display: grid;
  gap: 0.85rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 1.4rem 0 2.25rem;
}

.question-card {
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  border-radius: 0.5rem;
  padding: 1.05rem 1.15rem;
}

.question-card > span {
  align-items: center;
  background: var(--ode-green);
  border-radius: 50%;
  color: white;
  display: inline-flex;
  font-size: 0.78rem;
  font-weight: 800;
  height: 1.65rem;
  justify-content: center;
  margin-right: 0.45rem;
  width: 1.65rem;
}

.question-card p {
  color: var(--ode-muted);
  margin: 0.5rem 0 0 2.15rem;
}

.representation-loop {
  align-items: center;
  display: grid;
  gap: 0.45rem;
  grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr auto;
  margin: 1.6rem 0;
}

.representation-loop div {
  align-items: center;
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  border-radius: 0.35rem;
  display: flex;
  flex-direction: column;
  font-size: 0.86rem;
  font-weight: 700;
  gap: 0.25rem;
  min-height: 5rem;
  justify-content: center;
  padding: 0.55rem;
  text-align: center;
}

.representation-loop span {
  color: var(--ode-coral);
  font-size: 1.15rem;
}

.representation-loop b {
  color: var(--ode-green);
  font-size: 1.4rem;
}

.callout {
  background: var(--ode-panel);
  border-left: 5px solid var(--ode-green);
  margin: 1.5rem 0;
  padding: 1rem 1.2rem;
}

.callout.warning {
  border-left-color: var(--ode-coral);
}

.callout.insight {
  border-left-color: var(--ode-gold);
}

.callout-title {
  color: var(--ode-green-dark);
  font-size: 0.8rem;
  font-weight: 850;
  letter-spacing: 0.09em;
  margin: 0 0 0.35rem;
  text-transform: uppercase;
}

.callout p:last-child {
  margin-bottom: 0;
}

.progress-panel {
  align-items: center;
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  margin: 1.5rem 0;
  padding: 1rem 1.1rem;
}

.progress-panel p {
  color: var(--ode-muted);
  margin: 0.15rem 0 0;
}

.checkpoint {
  align-items: flex-start;
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  cursor: pointer;
  display: flex;
  font-weight: 700;
  gap: 0.65rem;
  margin: 2rem 0;
  padding: 0.85rem 1rem;
}

.checkpoint input {
  accent-color: var(--ode-green);
  height: 1.15rem;
  margin-top: 0.2rem;
  width: 1.15rem;
}

.quick-check {
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  margin: 1.25rem 0;
  padding: 1rem 1.1rem;
}

.quiz-prompt {
  margin-top: 0;
}

.choice-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.choice-row button,
.method-picker button {
  background: var(--ode-paper);
  border: 1px solid var(--ode-line);
  border-radius: 0.35rem;
  color: var(--ode-ink);
  cursor: pointer;
  font: inherit;
  min-height: 2.5rem;
  padding: 0.55rem 0.75rem;
  text-align: left;
}

.choice-row button:hover,
.choice-row button:focus-visible,
.method-picker button:hover,
.method-picker button:focus-visible {
  border-color: var(--ode-green);
  outline: 2px solid color-mix(in srgb, var(--ode-green) 25%, transparent);
  outline-offset: 1px;
}

.choice-row button.is-correct {
  background: color-mix(in srgb, var(--ode-green) 14%, var(--ode-paper));
  border-color: var(--ode-green);
}

.choice-row button.is-wrong {
  background: color-mix(in srgb, var(--ode-error) 10%, var(--ode-paper));
  border-color: var(--ode-error);
}

.quiz-feedback {
  color: var(--ode-muted);
  font-weight: 700;
  margin-bottom: 0;
  min-height: 1.3em;
}

.quiz-feedback.correct {
  color: var(--ode-green-dark);
}

.quiz-feedback.wrong {
  color: var(--ode-error);
}

.ode-lab {
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  box-shadow: var(--ode-shadow);
  margin: 1.75rem 0 2.3rem;
  padding: 1rem;
}

.lab-heading {
  align-items: baseline;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}

.lab-heading strong {
  font-size: 1.08rem;
}

.lab-heading span {
  color: var(--ode-muted);
  font-size: 0.88rem;
}

.lab-controls {
  align-items: end;
  display: grid;
  gap: 0.7rem;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  margin-bottom: 0.8rem;
}

.lab-controls label {
  color: var(--ode-muted);
  display: grid;
  font-size: 0.76rem;
  font-weight: 800;
  gap: 0.25rem;
  letter-spacing: 0.035em;
  text-transform: uppercase;
}

.lab-controls input,
.lab-controls select {
  accent-color: var(--ode-green);
  background: var(--ode-paper);
  border: 1px solid var(--ode-line);
  border-radius: 0.3rem;
  color: var(--ode-ink);
  font: inherit;
  min-height: 2.35rem;
  padding: 0.35rem 0.45rem;
  text-transform: none;
}

.lab-controls input[type="range"] {
  border: 0;
  padding-inline: 0;
}

.lab-controls output {
  color: var(--ode-ink);
  font-weight: 800;
}

.ode-lab canvas {
  background: var(--ode-paper);
  border: 1px solid var(--ode-line);
  display: block;
  height: auto;
  max-height: 500px;
  touch-action: none;
  width: 100%;
}

.lab-readout {
  color: var(--ode-muted);
  font-size: 0.9rem;
  margin: 0.65rem 0 0;
  min-height: 1.35em;
}

.legend-row {
  display: flex;
  flex-wrap: wrap;
  font-size: 0.82rem;
  gap: 0.45rem 1rem;
  margin-top: 0.55rem;
}

.legend-row span::before {
  background: var(--legend-color, var(--ode-green));
  border-radius: 50%;
  content: "";
  display: inline-block;
  height: 0.6rem;
  margin-right: 0.35rem;
  width: 0.6rem;
}

.worked-example {
  border: 1px solid var(--ode-line);
  margin: 1.4rem 0;
}

.worked-example > header {
  align-items: center;
  background: var(--ode-panel);
  display: flex;
  gap: 0.75rem;
  justify-content: space-between;
  padding: 0.7rem 1rem;
}

.worked-example > header strong {
  color: var(--ode-green-dark);
}

.worked-example > header span {
  color: var(--ode-muted);
  font-size: 0.82rem;
}

.worked-example > div {
  padding: 0.25rem 1rem 0.9rem;
}

.solution-steps {
  counter-reset: solution-step;
  list-style: none;
  padding-left: 0;
}

.solution-steps li {
  counter-increment: solution-step;
  display: grid;
  gap: 0.55rem;
  grid-template-columns: 1.9rem 1fr;
  margin: 0.9rem 0;
}

.solution-steps li::before {
  align-items: center;
  background: var(--ode-green);
  border-radius: 50%;
  color: white;
  content: counter(solution-step);
  display: flex;
  font-size: 0.78rem;
  font-weight: 800;
  height: 1.7rem;
  justify-content: center;
  margin-top: 0.25rem;
  width: 1.7rem;
}

.fade-grid {
  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 1.4rem 0;
}

.fade-card {
  border: 1px solid var(--ode-line);
  min-width: 0;
  padding: 0.85rem;
}

.fade-card strong {
  color: var(--ode-green-dark);
  display: block;
  margin-bottom: 0.4rem;
}

.fade-card p:last-child {
  margin-bottom: 0;
}

.fade-card.is-you {
  border-color: var(--ode-coral);
}

details.hint,
details.answer {
  border: 1px solid var(--ode-line);
  margin: 0.8rem 0;
}

details.hint summary,
details.answer summary {
  color: var(--ode-green-dark);
  cursor: pointer;
  font-weight: 750;
  padding: 0.65rem 0.85rem;
}

details.hint > :not(summary),
details.answer > :not(summary) {
  margin-left: 0.85rem;
  margin-right: 0.85rem;
}

.fingerprint {
  align-items: stretch;
  display: grid;
  gap: 0.65rem;
  grid-template-columns: minmax(150px, 0.8fr) minmax(220px, 1.2fr) minmax(150px, 0.8fr);
  margin: 1rem 0;
}

.fingerprint > div {
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 0.8rem;
  text-align: center;
}

.fingerprint .fingerprint-form {
  border-color: var(--ode-green);
  font-size: 1.08rem;
  font-weight: 750;
}

.concept-figure {
  background: var(--ode-panel);
  border: 1px solid var(--ode-line);
  margin: 1.4rem 0;
  padding: 0.85rem;
}

.concept-figure svg {
  display: block;
  height: auto;
  margin: 0 auto;
  max-width: 100%;
}

.concept-figure figcaption {
  color: var(--ode-muted);
  font-size: 0.86rem;
  margin-top: 0.6rem;
  text-align: center;
}

.concept-figure svg text {
  fill: var(--ode-ink);
  font-family: sans-serif;
}

.concept-figure svg .axis,
.concept-figure svg .guide {
  fill: none;
  stroke: var(--ode-muted);
}

.concept-figure svg .accent {
  fill: none;
  stroke: var(--ode-green);
}

.concept-figure svg .accent-two {
  fill: none;
  stroke: var(--ode-coral);
}

.method-map {
  display: grid;
  gap: 0.65rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 1.2rem 0;
}

.method-map > div {
  background: var(--ode-panel);
  border-top: 4px solid var(--ode-green);
  padding: 0.85rem 1rem;
}

.method-map code {
  display: block;
  margin: 0.45rem 0;
  white-space: normal;
}

.method-map p {
  color: var(--ode-muted);
  margin-bottom: 0;
}

.error-clinic {
  background: color-mix(in srgb, var(--ode-coral) 7%, var(--ode-paper));
  border: 1px solid color-mix(in srgb, var(--ode-coral) 42%, var(--ode-line));
  margin: 1.2rem 0;
  padding: 0.85rem 1rem;
}

.error-clinic > strong {
  color: var(--ode-error);
}

.practice-set {
  counter-reset: practice-item;
  list-style: none;
  padding-left: 0;
}

.practice-set > li {
  border-top: 1px solid var(--ode-line);
  counter-increment: practice-item;
  display: grid;
  gap: 0.65rem;
  grid-template-columns: 2rem 1fr;
  padding: 1rem 0;
}

.practice-set > li::before {
  color: var(--ode-coral);
  content: counter(practice-item, decimal-leading-zero);
  font-weight: 850;
}

.difficulty {
  color: var(--ode-muted);
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.next-step {
  border-top: 1px solid var(--ode-line);
  margin-top: 3rem;
  padding-top: 1rem;
}

.solution-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 1.2rem 0;
}

.solution-nav a {
  border: 1px solid var(--ode-line);
  padding: 0.35rem 0.6rem;
  text-decoration: none;
}

.source-note {
  color: var(--ode-muted);
  font-size: 0.9rem;
}

@media (max-width: 760px) {
  .hero-grid,
  .question-grid,
  .fade-grid,
  .method-map {
    grid-template-columns: 1fr;
  }

  .representation-loop {
    grid-template-columns: 1fr;
  }

  .representation-loop b {
    transform: rotate(90deg);
  }

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

  .hero-orbit {
    order: -1;
  }

  .progress-panel {
    align-items: stretch;
    flex-direction: column;
  }
}

@media (max-width: 480px) {
  main h1 {
    font-size: 2.5rem;
  }

  .choice-row,
  .choice-row button {
    width: 100%;
  }

  .ode-lab {
    margin-left: -0.6rem;
    margin-right: -0.6rem;
    padding: 0.65rem;
  }
}

@media print {
  .hero-actions,
  .progress-panel,
  .checkpoint,
  .choice-row,
  .lab-controls {
    display: none !important;
  }

  .ode-lab,
  .worked-example,
  .question-card {
    box-shadow: none;
    break-inside: avoid;
  }
}