/* Site nav */
.site-nav {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
  flex-wrap: wrap;
  padding-bottom: 0.75rem;
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--rule);
}
.site-nav .brand { font-weight: 600; }
.site-nav .brand a { color: var(--ink); text-decoration: none; }
.site-nav .links a { margin-left: 0.9rem; text-decoration: none; font-size: 0.92rem; }

/* Breadcrumb */
.breadcrumb {
  font-size: 0.9rem;
  color: var(--muted);
  margin: 0 0 1rem;
}
.breadcrumb a { text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { color: var(--ink); }

/* Shared lesson stylesheet — System Design (medior → senior) */

:root {
  --ink: #1a1a1a;
  --muted: #6b6b6b;
  --accent: #b0413e;
  --accent-soft: #f5e9e8;
  --rule: #e0e0e0;
  --paper: #ffffff;
  --code-bg: #f6f6f4;
}

* { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  line-height: 1.65;
  color: var(--ink);
  max-width: 740px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
  background: var(--paper);
}

h1 {
  font-size: 1.75rem;
  line-height: 1.2;
  letter-spacing: -0.01em;
  margin: 0 0 0.25rem;
}

h2 {
  font-size: 1.25rem;
  margin: 2.25rem 0 0.5rem;
  letter-spacing: -0.01em;
}

h3 {
  font-size: 1.05rem;
  margin: 1.5rem 0 0.4rem;
}

p { margin: 0.6rem 0; }

ul, ol { margin: 0.6rem 0; padding-left: 1.4rem; }
li { margin: 0.3rem 0; }

a { color: var(--accent); }

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
  background: var(--code-bg);
  padding: 0.1em 0.35em;
  border-radius: 3px;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-radius: 6px;
  padding: 0.9rem 1rem;
  overflow-x: auto;
  font-size: 0.9rem;
  line-height: 1.5;
}
pre code { background: none; padding: 0; }

blockquote {
  margin: 1rem 0;
  padding: 0.25rem 0 0.25rem 1rem;
  border-left: 3px solid var(--accent);
  color: var(--muted);
}

.meta {
  color: var(--muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}

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

.callout p { margin: 0.25rem 0; }

.diagram {
  margin: 1.5rem 0;
  overflow-x: auto;
}

table {
  border-collapse: collapse;
  width: 100%;
  margin: 1rem 0;
  font-size: 0.92rem;
}
th, td {
  text-align: left;
  padding: 0.5rem 0.7rem;
  border-bottom: 1px solid var(--rule);
}
th { font-weight: 600; border-bottom: 2px solid var(--ink); }

/* Quiz */
.quiz-question { margin: 1.5rem 0; }
.quiz-options { display: flex; flex-direction: column; gap: 0.5rem; }
.quiz-option {
  text-align: left;
  font: inherit;
  color: var(--ink);
  background: #fff;
  border: 1px solid var(--rule);
  border-radius: 6px;
  padding: 0.6rem 0.9rem;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}
.quiz-option:hover { border-color: var(--accent); }
.quiz-option.correct {
  border-color: #2e7d32;
  background: #e8f5e9;
}
.quiz-option.wrong {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.quiz-option:disabled { cursor: default; }
.quiz-feedback { margin-top: 0.5rem; font-size: 0.92rem; }
.quiz-feedback.ok { color: #2e7d32; }
.quiz-feedback.bad { color: var(--accent); }

.footer {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-size: 0.9rem;
}

@media print {
  body { max-width: none; padding: 0; }
  .quiz-option { border: none; padding: 0.2rem 0; cursor: default; }
}