/* ── Claude Code Advanced Teaching — Shared Stylesheet ── */
/* Inspired by Tufte CSS — clean, readable, print-friendly   */

:root {
  --text: #1a1a2e;
  --bg: #faf9f6;
  --accent: #4361ee;
  --accent-light: #eef0ff;
  --code-bg: #f0f0f5;
  --border: #d0d0dd;
  --muted: #666680;
  --success: #2ec4b6;
  --warning: #ff9f1c;
  --sans: 'Inter', -apple-system, 'Segoe UI', system-ui, sans-serif;
  --mono: 'JetBrains Mono', 'Cascadia Code', 'Fira Code', monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --text: #e0e0f0;
    --bg: #16162a;
    --accent: #6c8cff;
    --accent-light: #1e1e3a;
    --code-bg: #1e1e32;
    --border: #2a2a48;
    --muted: #8888aa;
  }
}

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

body {
  font-family: var(--sans);
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  max-width: 720px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
  font-size: 16px;
}

/* Course navigation lives outside the reading column, so it never changes
   the article's width or horizontal position when it is collapsed. */
.course-nav {
  --nav-width: 17rem;
  position: fixed;
  z-index: 10;
  top: 1.5rem;
  left: max(1rem, calc(50% - 43rem));
  width: var(--nav-width);
  max-height: calc(100vh - 3rem);
  overflow: hidden auto;
  padding: 1rem 1rem 1.25rem;
  color: var(--text);
  background: color-mix(in srgb, var(--bg) 96%, var(--accent-light));
  border: 1px solid var(--border);
  border-radius: 0.65rem;
  box-shadow: 0 0.5rem 1.5rem rgb(20 20 46 / 8%);
  transition: width 180ms ease, padding 180ms ease;
}

.course-nav__label {
  display: block;
  margin-bottom: 0.7rem;
  padding-right: 2.1rem;
  color: var(--muted);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.course-nav__list { list-style: none; margin: 0; }
.course-nav__list li { margin: 0; }
.course-nav__list a {
  display: block;
  padding: 0.38rem 0.45rem;
  border-radius: 0.3rem;
  color: var(--muted);
  font-size: 0.82rem;
  line-height: 1.35;
}
.course-nav__list a:hover, .course-nav__list a:focus-visible {
  color: var(--accent);
  background: var(--accent-light);
  text-decoration: none;
}
.course-nav__list a[aria-current="page"] {
  color: var(--accent);
  background: var(--accent-light);
  font-weight: 700;
}

.course-nav__toggle {
  position: absolute;
  z-index: 1;
  top: 0.45rem;
  right: 0.45rem;
  width: 1.8rem;
  height: 1.8rem;
  padding: 0;
  color: var(--accent);
  background: var(--accent-light);
  border: 1px solid var(--border);
  border-radius: 0.4rem;
  cursor: pointer;
  font-size: 1rem;
  line-height: 1;
  box-shadow: none;
}
.course-nav__toggle:hover,
.course-nav__toggle:focus-visible {
  color: white;
  background: var(--accent);
  border-color: var(--accent);
}

body.nav-collapsed .course-nav {
  width: 3rem;
  height: 3rem;
  padding: 0.5rem;
  overflow: hidden;
}
body.nav-collapsed .course-nav__toggle {
  top: 50%;
  right: 50%;
  transform: translate(50%, -50%);
}
body.nav-collapsed .course-nav__label,
body.nav-collapsed .course-nav__list { display: none; }
body.nav-collapsed .course-nav__toggle::before { content: '›'; }
body:not(.nav-collapsed) .course-nav__toggle::before { content: '‹'; }

@media (max-width: 70rem) {
  .course-nav { left: 0.75rem; top: 0.75rem; }
}

@media (max-width: 48rem) {
  .course-nav { transform: translateX(calc(-100% - 0.75rem)); }
  body.nav-collapsed .course-nav { transform: translateX(0); }
  body.nav-collapsed .course-nav__label,
  body.nav-collapsed .course-nav__list { display: block; }
  body.nav-collapsed .course-nav { width: var(--nav-width); height: auto; padding-inline: 1rem; overflow: hidden auto; }
  body.nav-collapsed .course-nav__toggle { top: 0.45rem; right: 0.45rem; transform: none; }
  body.nav-collapsed .course-nav__toggle::before { content: '‹'; }
  body:not(.nav-collapsed) .course-nav__toggle::before { content: '›'; }
}

/* ── Typography ── */

h1 {
  font-size: 2rem;
  font-weight: 700;
  margin: 2.5rem 0 0.5rem;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h2 {
  font-size: 1.35rem;
  font-weight: 600;
  margin: 2rem 0 0.75rem;
  padding-bottom: 0.25rem;
  border-bottom: 2px solid var(--accent);
  line-height: 1.3;
}

h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 1.5rem 0 0.5rem;
  line-height: 1.4;
}

p { margin: 0.75rem 0; }

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

ul, ol { margin: 0.5rem 0 0.75rem 1.5rem; }
li { margin: 0.3rem 0; }

strong { font-weight: 600; }

/* ── Lesson Header ── */

.lesson-header {
  margin-bottom: 1.5rem;
}

.lesson-number {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  font-weight: 600;
}

.lesson-title {
  font-size: 2rem;
  font-weight: 700;
  margin: 0.15rem 0 0.5rem;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.lesson-subtitle {
  font-size: 1rem;
  color: var(--muted);
  margin: 0;
}

/* ── Infobox ── */

.info-box {
  background: var(--accent-light);
  border-left: 4px solid var(--accent);
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  border-radius: 0 6px 6px 0;
  font-size: 0.92rem;
}

.info-box strong:first-child {
  display: block;
  margin-bottom: 0.25rem;
  color: var(--accent);
}

/* ── Code ── */

code {
  font-family: var(--mono);
  font-size: 0.85em;
  background: var(--code-bg);
  padding: 0.15em 0.4em;
  border-radius: 4px;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  margin: 1rem 0;
  font-size: 0.8rem;
  line-height: 1.5;
}

pre code {
  background: none;
  padding: 0;
  font-size: inherit;
}

/* ── Blockquote (for tips / notes) ── */

blockquote {
  border-left: 3px solid var(--border);
  padding-left: 1rem;
  margin: 1.25rem 0;
  color: var(--muted);
  font-style: italic;
}

/* ── Call to action (exercise) ── */

.exercise {
  background: var(--accent-light);
  border: 2px solid var(--accent);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  margin: 2rem 0;
}

.exercise h3 {
  margin: 0 0 0.5rem;
  color: var(--accent);
  font-weight: 700;
  border: none;
  padding: 0;
}

.exercise p { margin: 0.5rem 0; }

/* ── Step List ── */

.steps {
  counter-reset: step;
  list-style: none;
  margin: 1rem 0;
  padding: 0;
}

.steps li {
  counter-increment: step;
  padding: 0.75rem 0 0.75rem 2.5rem;
  position: relative;
  margin: 0;
}

.steps li::before {
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0.75rem;
  width: 1.6rem;
  height: 1.6rem;
  background: var(--accent);
  color: white;
  font-size: 0.75rem;
  font-weight: 700;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ── Success / Tip banners ── */

.banner {
  padding: 0.75rem 1rem;
  border-radius: 6px;
  margin: 1rem 0;
  font-size: 0.9rem;
}
.banner-success { background: #d4f5f0; color: #0d5e56; border-left: 4px solid var(--success); }
.banner-warning { background: #fff3e0; color: #7a4a00; border-left: 4px solid var(--warning); }
@media (prefers-color-scheme: dark) {
  .banner-success { background: #0d2f2a; color: #8de8dc; }
  .banner-warning { background: #2d1f00; color: #ffc970; }
}

/* ─── Retrieval practice ─── */

/* ── Table ── */

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
  font-size: 0.9rem;
}

th, td {
  border: 1px solid var(--border);
  padding: 0.5rem 0.75rem;
  text-align: left;
}

th {
  background: var(--code-bg);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ── Print ── */

@media print {
  body { font-size: 11pt; max-width: 100%; padding: 0.5in; }
  pre { break-inside: avoid; }
}