/* Shared Lesson Stylesheet — All Courses
   Dark mode via prefers-color-scheme + manual toggle via [data-theme] attribute.
   Per-repo accent: override --color-accent and --color-accent-light in a theme <style>. */

:root {
  --font-body: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Helvetica Neue', Helvetica, Arial, sans-serif;
  --font-heading: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Helvetica Neue', Helvetica, Arial, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Consolas', 'Menlo', monospace;

  --color-text: #1d1d1f;
  --color-muted: #6e6e73;
  --color-accent: #0071e3;
  --color-accent-hover: #0077ed;
  --color-accent-light: #e8f0fe;
  --color-bg: #fff;
  --color-code-bg: #f5f5f7;
  --color-border: #d2d2d7;
  --color-callout-bg: #f5f5f7;
  --color-card-bg: #fbfbfd;
  --color-success: #34c759;
  --color-warning: #ff9f0a;
  --color-danger: #ff3b30;

  --max-width: 740px;
  --line-height: 1.58;
  --radius: 12px;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.04), 0 4px 12px rgba(0,0,0,0.06);
}

/* ─── Dark Mode (system) ─── */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-text: #f5f5f7;
    --color-muted: #a1a1a6;
    --color-accent: #64d2ff;
    --color-accent-hover: #5ac8f5;
    --color-accent-light: rgba(100, 210, 255, 0.1);
    --color-bg: #000000;
    --color-code-bg: #1c1c1e;
    --color-border: rgba(255, 255, 255, 0.08);
    --color-callout-bg: #1c1c1e;
    --color-card-bg: rgba(28, 28, 30, 0.72);
    --color-success: #30d158;
    --color-warning: #ffd60a;
    --color-danger: #ff453a;
    --shadow-card: 0 1px 3px rgba(0,0,0,0.3), 0 4px 12px rgba(0,0,0,0.4);
  }
}

/* ─── Dark Mode (manual toggle) ─── */
[data-theme="dark"] {
  --color-text: #f5f5f7;
  --color-muted: #a1a1a6;
  --color-accent: #64d2ff;
  --color-accent-hover: #5ac8f5;
  --color-accent-light: rgba(100, 210, 255, 0.1);
  --color-bg: #000000;
  --color-code-bg: #1c1c1e;
  --color-border: rgba(255, 255, 255, 0.08);
  --color-callout-bg: #1c1c1e;
  --color-card-bg: rgba(28, 28, 30, 0.72);
  --color-success: #30d158;
  --color-warning: #ffd60a;
  --color-danger: #ff453a;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.3), 0 4px 12px rgba(0,0,0,0.4);
}

/* ─── Base Reset ─── */
* { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: var(--line-height);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 3rem 2rem 5rem;
}

/* ─── Typography ─── */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin-top: 2.5rem;
  margin-bottom: 0.75rem;
}

h1 {
  font-size: 2.4rem;
  margin-top: 0;
  margin-bottom: 0.5rem;
  letter-spacing: -0.03em;
}

h2 { font-size: 1.6rem; margin-top: 3rem; }
h3 { font-size: 1.2rem; }
h4 { font-size: 1rem; font-weight: 600; }

p {
  margin-bottom: 1.2rem;
  color: var(--color-text);
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.2s;
}
a:hover { color: var(--color-accent-hover); text-decoration: underline; }

strong { font-weight: 600; }

/* ─── Lists ─── */
ul, ol {
  margin-bottom: 1.2rem;
  padding-left: 1.5rem;
}
li {
  margin-bottom: 0.5rem;
  line-height: 1.5;
}

/* ─── Code ─── */
code {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  background: var(--color-code-bg);
  padding: 0.2rem 0.45rem;
  border-radius: 6px;
  color: var(--color-text);
}

pre {
  position: relative;
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  overflow-x: auto;
  margin-bottom: 1.75rem;
  line-height: 1.55;
}

pre code {
  background: none;
  padding: 0;
  font-size: 0.8rem;
  border-radius: 0;
  color: var(--color-text);
}

/* ─── Callouts ─── */
.callout {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.75rem;
  box-shadow: var(--shadow-card);
}

.callout-title {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 0.5rem;
  color: var(--color-accent);
}

.callout.tip { border-color: var(--color-success); }
.callout.tip .callout-title { color: var(--color-success); }

.callout.warning { border-color: var(--color-warning); }
.callout.warning .callout-title { color: var(--color-warning); }

.callout.danger { border-color: var(--color-danger); }
.callout.danger .callout-title { color: var(--color-danger); }

/* ─── Comparison Blocks ─── */
.comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1.75rem;
}

.comparison-side {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem;
}

.comparison-side h4 {
  margin-top: 0;
  margin-bottom: 0.75rem;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.comparison-side.git h4 { color: #f05133; }
.comparison-side.jj h4 { color: var(--color-accent); }
.comparison-side.traditional h4 { color: var(--color-muted); }
.comparison-side.workers h4 { color: var(--color-accent); }

/* ─── Diagrams / ASCII Art ─── */
.diagram {
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.75rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  line-height: 1.4;
  white-space: pre;
  color: var(--color-text);
}

/* ─── Tables ─── */
table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  margin-bottom: 1.75rem;
  font-size: 0.9rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}

th, td {
  padding: 0.65rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}

th {
  font-family: var(--font-heading);
  font-weight: 600;
  background: var(--color-code-bg);
  font-size: 0.82rem;
  color: var(--color-muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

tr:last-child td { border-bottom: none; }

.table-wrap {
  overflow-x: auto;
  margin-bottom: 1.75rem;
}

/* ─── Quiz ─── */
.quiz {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.75rem;
  box-shadow: var(--shadow-card);
}

.quiz-question {
  font-weight: 600;
  margin-bottom: 1rem;
  font-size: 0.95rem;
}

.quiz-options {
  list-style: none;
  padding: 0;
}

.quiz-options li {
  padding: 0.7rem 1rem;
  margin-bottom: 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
  font-size: 0.9rem;
}

.quiz-options li:hover {
  background: var(--color-accent-light);
  border-color: var(--color-accent);
  transform: translateY(-1px);
  box-shadow: 0 2px 8px rgba(0,113,227,0.1);
}

.quiz-options li.correct {
  background: #e8f8ed;
  border-color: var(--color-success);
}

.quiz-options li.incorrect {
  background: #ffeaea;
  border-color: var(--color-danger);
}

.quiz-feedback {
  margin-top: 0.75rem;
  padding: 0.85rem 1rem;
  border-radius: 8px;
  display: none;
  font-size: 0.88rem;
  line-height: 1.5;
}

.quiz-feedback.show { display: block; }
.quiz-feedback.correct { background: #e8f8ed; color: #1a7f37; }
.quiz-feedback.incorrect { background: #ffeaea; color: #c33; }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .quiz-options li.correct { background: rgba(48, 209, 88, 0.15); }
  :root:not([data-theme="light"]) .quiz-options li.incorrect { background: rgba(255, 69, 58, 0.15); }
  :root:not([data-theme="light"]) .quiz-feedback.correct { background: rgba(48, 209, 88, 0.15); color: #30d158; }
  :root:not([data-theme="light"]) .quiz-feedback.incorrect { background: rgba(255, 69, 58, 0.15); color: #ff453a; }
}

[data-theme="dark"] .quiz-options li.correct { background: rgba(48, 209, 88, 0.15); }
[data-theme="dark"] .quiz-options li.incorrect { background: rgba(255, 69, 58, 0.15); }
[data-theme="dark"] .quiz-feedback.correct { background: rgba(48, 209, 88, 0.15); color: #30d158; }
[data-theme="dark"] .quiz-feedback.incorrect { background: rgba(255, 69, 58, 0.15); color: #ff453a; }

/* ─── Lesson Metadata ─── */
.lesson-meta {
  font-family: var(--font-heading);
  font-size: 0.85rem;
  color: var(--color-muted);
  margin-bottom: 2.5rem;
  letter-spacing: 0.01em;
}

/* ─── Top Navigation ─── */
.lesson-top-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
  font-size: 0.88rem;
}

.lesson-back-top {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-weight: 400;
  text-decoration: none;
  color: var(--color-accent);
  transition: color 0.2s;
  margin-right: 1rem;
  padding-right: 1rem;
  border-right: 1px solid var(--color-border);
}

.lesson-back-top:hover {
  color: var(--color-accent-hover);
  text-decoration: none;
}

.lesson-back-top svg { transition: transform 0.2s; }
.lesson-back-top:hover svg { transform: translateX(-2px); }

.lesson-home-top {
  display: flex;
  align-items: center;
  text-decoration: none;
  color: var(--color-accent);
  opacity: 0.6;
  transition: opacity 0.2s, color 0.2s;
}

.lesson-home-top:hover {
  opacity: 1;
  color: var(--color-accent-hover);
  text-decoration: none;
}

.lesson-next-top {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.88rem;
  font-weight: 400;
  text-decoration: none;
  color: var(--color-accent);
  transition: color 0.2s;
  margin-left: 1rem;
  padding-left: 1rem;
  border-left: 1px solid var(--color-border);
}

.lesson-next-top:hover {
  color: var(--color-accent-hover);
  text-decoration: none;
}

.lesson-next-top svg { transition: transform 0.2s; }
.lesson-next-top:hover svg { transform: translateX(2px); }

/* ─── Bottom Navigation ─── */
.lesson-nav {
  margin-top: 4rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-heading);
  font-size: 0.88rem;
}

.lesson-nav a {
  color: var(--color-accent);
  font-weight: 500;
}

.lesson-nav-disabled {
  opacity: 0.4;
  pointer-events: none;
}

/* ─── Source Recommendation ─── */
.primary-source {
  background: var(--color-card-bg);
  border: 1px solid var(--color-accent);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.75rem;
  box-shadow: 0 2px 8px rgba(0,113,227,0.08);
}

.primary-source-label {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-accent);
  margin-bottom: 0.4rem;
}

/* ─── Ask Teacher ─── */
.ask-teacher {
  background: var(--color-accent-light);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-top: 2.5rem;
  font-size: 0.9rem;
}

/* ─── Copy Button (code blocks) ─── */
.copy-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  padding: 0.3rem 0.6rem;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.2s, background 0.2s;
  color: var(--color-muted);
}

pre:hover .copy-btn { opacity: 1; }
.copy-btn:hover { background: var(--color-code-bg); }
.copy-btn.copied { color: var(--color-success); }

/* ─── Tags ─── */
.tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
  background: var(--color-accent-light);
  color: var(--color-accent);
}

/* ─── Print ─── */
@media print {
  body { max-width: 100%; padding: 1rem; font-size: 10pt; }
  a { color: var(--color-text); }
  .quiz-options li { cursor: default; }
  .ask-teacher, .callout, .quiz { border: 1px solid #ccc; box-shadow: none; }
  pre { border: 1px solid #ccc; }
  .lesson-top-nav, .lesson-nav { display: none; }
}

/* ─── Responsive ─── */
@media (max-width: 600px) {
  html { font-size: 16px; }
  body { padding: 2rem 1.25rem 3rem; }
  h1 { font-size: 1.8rem; }
  h2 { font-size: 1.3rem; }
  .comparison { grid-template-columns: 1fr; }
  .diagram { font-size: 0.68rem; }
  .lesson-nav { font-size: 0.82rem; }
}