:root {
  color-scheme: light;
  --ink: #182026;
  --muted: #5d6971;
  --paper: #f7f8f6;
  --surface: #ffffff;
  --line: #cfd6d3;
  --teal: #0b6b61;
  --teal-soft: #e4f1ed;
  --coral: #a6422b;
  --coral-soft: #f8e9e4;
  --gold: #7a5a0b;
  --gold-soft: #f4edd8;
  --blue: #245b78;
  --blue-soft: #e5eef3;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 17px;
  line-height: 1.68;
  letter-spacing: 0;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
}

main {
  width: min(100% - 32px, 980px);
  margin: 0 auto;
  padding: 52px 0 80px;
}

header { margin-bottom: 40px; }

.kicker {
  margin: 0 0 10px;
  color: var(--teal);
  font-size: 0.78rem;
  font-weight: 750;
  text-transform: uppercase;
}

h1, h2, h3 {
  line-height: 1.2;
  letter-spacing: 0;
}

h1 {
  max-width: 780px;
  margin: 0;
  font-family: Georgia, "Times New Roman", serif;
  font-size: 4.2rem;
  font-weight: 500;
}

h1.compact-title { font-size: 3.55rem; }

h2 {
  margin: 52px 0 16px;
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.85rem;
  font-weight: 500;
}

h3 { margin: 0 0 8px; font-size: 1rem; }

p { max-width: 760px; }

.lede {
  max-width: 720px;
  margin-top: 22px;
  color: var(--muted);
  font-size: 1.12rem;
}

a { color: var(--teal); text-underline-offset: 3px; }

code {
  padding: 0.12em 0.35em;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--surface);
  font-size: 0.88em;
}

.callout {
  margin: 28px 0;
  padding: 20px 24px;
  border-left: 4px solid var(--coral);
  background: var(--coral-soft);
}

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

.architecture {
  display: grid;
  gap: 12px;
  margin: 28px 0;
}

.flow-row {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 10px;
  align-items: stretch;
}

.node, .layer, .quiz {
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--surface);
}

.node {
  min-height: 104px;
  padding: 14px;
}

.node b { display: block; margin-bottom: 4px; }
.node small { color: var(--muted); line-height: 1.45; }
.node.model { border-top: 4px solid var(--teal); }
.node.action { border-top: 4px solid var(--coral); }
.node.state { border-top: 4px solid var(--blue); }
.node.control { border-top: 4px solid var(--gold); }

.loop-label {
  margin: 0;
  padding: 8px 12px;
  border-radius: 4px;
  background: var(--ink);
  color: white;
  text-align: center;
  font-size: 0.82rem;
}

.layer-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.layer { padding: 18px; }
.layer p { margin: 0; color: var(--muted); font-size: 0.9rem; }
.layer[data-tone="teal"] { border-left: 4px solid var(--teal); }
.layer[data-tone="coral"] { border-left: 4px solid var(--coral); }
.layer[data-tone="blue"] { border-left: 4px solid var(--blue); }
.layer[data-tone="gold"] { border-left: 4px solid var(--gold); }

.compare {
  width: 100%;
  table-layout: fixed;
  border-collapse: collapse;
  background: var(--surface);
  font-size: 0.92rem;
}

.compare th, .compare td {
  padding: 13px 15px;
  border: 1px solid var(--line);
  overflow-wrap: anywhere;
  text-align: left;
  vertical-align: top;
}

.compare th { background: var(--blue-soft); }

.quiz { margin-top: 24px; padding: 22px; }
.quiz p { margin-top: 0; }
.answers { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
.answers button {
  min-height: 46px;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font: inherit;
}
.answers button:hover { border-color: var(--teal); background: var(--teal-soft); }
.answers button.correct { border-color: var(--teal); background: var(--teal-soft); }
.answers button.wrong { border-color: var(--coral); background: var(--coral-soft); }
.feedback { min-height: 1.7em; margin: 12px 0 0; font-weight: 650; }

.reading {
  margin-top: 48px;
  padding: 22px;
  border: 1px solid var(--line);
  background: var(--gold-soft);
}

.nav { display: flex; gap: 18px; flex-wrap: wrap; margin-top: 36px; }

@media (max-width: 760px) {
  main { padding-top: 32px; }
  h1 { font-size: 2.6rem; }
  h1.compact-title { font-size: 2.35rem; }
  .flow-row, .layer-grid { grid-template-columns: 1fr; }
  .answers { grid-template-columns: 1fr; }
  .node { min-height: auto; }
  .compare { font-size: 0.8rem; }
  .compare th, .compare td { padding: 9px; }
}

@media print {
  body { background: white; }
  main { width: 100%; padding: 0; }
  .quiz { break-inside: avoid; }
  a { color: var(--ink); }
}