:root {
  --ink: #171717;
  --muted: #5c6470;
  --line: #d8dce2;
  --paper: #fffdf8;
  --panel: #f5f7f9;
  --accent: #0f766e;
  --accent-2: #7c2d12;
  --ok: #166534;
  --bad: #991b1b;
  --code: #1f2937;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: ui-serif, Georgia, "Times New Roman", serif;
  line-height: 1.55;
}

main {
  width: min(920px, calc(100% - 32px));
  margin: 0 auto;
  padding: 48px 0 72px;
}

header {
  border-bottom: 1px solid var(--line);
  margin-bottom: 28px;
  padding-bottom: 18px;
}

.kicker {
  color: var(--accent);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  line-height: 1.12;
}

h1 {
  font-size: clamp(2rem, 4vw, 3.2rem);
  margin: 0.35rem 0 0.7rem;
}

h2 {
  border-top: 1px solid var(--line);
  font-size: 1.45rem;
  margin-top: 2rem;
  padding-top: 1.25rem;
}

h3 {
  font-size: 1.08rem;
  margin-top: 1.35rem;
}

p,
li {
  font-size: 1.04rem;
}

a {
  color: var(--accent);
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.18em;
}

.lede {
  color: var(--muted);
  font-size: 1.18rem;
  max-width: 760px;
}

.grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.box {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
}

.box h3 {
  margin-top: 0;
}

.formula {
  background: #ffffff;
  border-left: 4px solid var(--accent);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  overflow-x: auto;
  padding: 14px 16px;
  white-space: pre;
}

.small {
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.9rem;
}

.quiz {
  display: grid;
  gap: 14px;
}

.quiz-card {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
}

.quiz-options {
  display: grid;
  gap: 8px;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}

button {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 6px;
  color: var(--ink);
  cursor: pointer;
  font: 600 0.95rem ui-sans-serif, system-ui, sans-serif;
  padding: 10px 12px;
  text-align: left;
}

button:hover {
  border-color: var(--accent);
}

button.correct {
  border-color: var(--ok);
  color: var(--ok);
}

button.incorrect {
  border-color: var(--bad);
  color: var(--bad);
}

.feedback {
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  min-height: 1.4em;
}

.callout {
  border: 1px solid var(--line);
  border-radius: 8px;
  margin: 20px 0;
  padding: 16px;
}

.lab {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 8px;
  display: grid;
  gap: 16px;
  margin: 20px 0;
  padding: 16px;
}

.lab-controls {
  display: grid;
  gap: 14px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.lab label {
  display: grid;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.95rem;
  gap: 6px;
}

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

.metric-row {
  display: grid;
  gap: 10px;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
}

.metric {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
}

.metric strong {
  display: block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.metric span {
  display: block;
  font-size: 1.45rem;
  margin-top: 4px;
}

.chart-wrap {
  background: #ffffff;
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.chart-wrap canvas {
  display: block;
  height: 280px;
  width: 100%;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 16px;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.9rem;
}

.legend span::before {
  border-radius: 999px;
  content: "";
  display: inline-block;
  height: 0.75em;
  margin-right: 6px;
  vertical-align: -0.06em;
  width: 0.75em;
}

.legend .objective::before {
  background: var(--accent);
}

.legend .wall::before {
  background: var(--accent-2);
}

.legend .solution::before {
  background: var(--ink);
}

footer {
  border-top: 1px solid var(--line);
  color: var(--muted);
  margin-top: 36px;
  padding-top: 18px;
}

@media print {
  body {
    background: #ffffff;
  }

  main {
    width: 100%;
    padding: 0;
  }

  button {
    display: none;
  }
}