:root {
  --bg: #fdfdfd;
  --fg: #1a1a2e;
  --accent: #e05d38;
  --code-bg: #f4f4f8;
  --border: #e2e2e8;
  --muted: #6b7280;
  --success: #16a34a;
  --error: #dc2626;
  --max-width: 42rem;
  --font-body: "Georgia", serif;
  --font-mono: "JetBrains Mono", "Fira Code", monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--font-body);
  font-size: 1.05rem;
  line-height: 1.75;
  color: var(--fg);
  background: var(--bg);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
}

h1 { font-size: 1.8rem; margin-bottom: 0.5rem; line-height: 1.2; }
h2 { font-size: 1.35rem; margin-top: 2rem; margin-bottom: 0.75rem; }
h3 { font-size: 1.1rem; margin-top: 1.5rem; margin-bottom: 0.5rem; }

p { margin-bottom: 1rem; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--code-bg);
  padding: 0.15em 0.35em;
  border-radius: 3px;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1rem 1.25rem;
  overflow-x: auto;
  margin-bottom: 1.25rem;
  font-size: 0.88rem;
  line-height: 1.6;
}

pre code { background: none; padding: 0; }

.lesson-meta {
  color: var(--muted);
  font-size: 0.85rem;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.callout {
  background: #fff7ed;
  border-left: 4px solid var(--accent);
  padding: 0.75rem 1rem;
  margin: 1.25rem 0;
  border-radius: 0 6px 6px 0;
}

.callout-info {
  background: #eff6ff;
  border-left-color: #3b82f6;
}

.quiz-block {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.25rem;
  margin: 1.5rem 0;
}

.quiz-block .question { font-weight: 600; margin-bottom: 0.75rem; }

.quiz-block .options label {
  display: block;
  padding: 0.4rem 0.6rem;
  margin-bottom: 0.3rem;
  border-radius: 4px;
  cursor: pointer;
  transition: background 0.15s;
}

.quiz-block .options label:hover { background: var(--code-bg); }

.quiz-block .feedback {
  margin-top: 0.75rem;
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
  display: none;
  font-size: 0.9rem;
}

.quiz-block .feedback.correct {
  display: block;
  background: #f0fdf4;
  color: var(--success);
}

.quiz-block .feedback.incorrect {
  display: block;
  background: #fef2f2;
  color: var(--error);
}

nav.lesson-nav {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  font-size: 0.9rem;
}

@media print {
  body { max-width: 100%; padding: 1rem; }
  .quiz-block { break-inside: avoid; }
  nav.lesson-nav { display: none; }
}