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

body {
  font-family: system-ui, -apple-system, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: #1a1a1a;
  background: #f8f8f8;
}

a { color: #1a6fa0; text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Shared container ── */
.container { max-width: 960px; margin: 0 auto; padding: 0 24px; }

/* ── Lesson nav (injected by nav.js) ── */
#lesson-nav {
  position: sticky;
  top: 0;
  background: #fff;
  border-bottom: 1px solid #e0e0e0;
  z-index: 100;
  padding: 10px 24px;
}
.nav-inner {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  font-size: 14px;
}
.nav-back { color: #999; display: flex; align-items: center; }
.nav-back:hover { color: #555; }
.nav-steps { display: flex; gap: 24px; }
.nav-prev, .nav-next { color: #1a6fa0; white-space: nowrap; }

/* ── Group badges ── */
.badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: 12px;
  margin-bottom: 12px;
}
.badge.foundation { background: #deedf7; color: #1a6fa0; }
.badge.craft       { background: #dff0d8; color: #3a7a10; }
.badge.project     { background: #fde8d0; color: #b05010; }

/* ── Index page ── */
.site-header {
  background: #fff;
  border-bottom: 1px solid #e0e0e0;
  padding: 32px 24px 24px;
  text-align: center;
}
.site-header h1 { font-size: 28px; font-weight: 800; }
.site-header p  { color: #666; margin-top: 6px; }

.index-main { max-width: 960px; margin: 0 auto; padding: 32px 24px 64px; }

.group-section { margin-bottom: 40px; }
.group-section h2 {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 2px;
  text-transform: uppercase;
  margin-bottom: 14px;
  padding-bottom: 6px;
  border-bottom: 2px solid currentColor;
}
.group-section.foundation h2 { color: #1a6fa0; border-color: #90c4e0; }
.group-section.craft h2      { color: #3a7a10; border-color: #8dc45a; }
.group-section.project h2    { color: #b05010; border-color: #e0a060; }

.module-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 12px;
}
.module-card {
  background: #fff;
  border: 1px solid #e4e4e4;
  border-radius: 8px;
  padding: 16px;
  display: block;
  color: inherit;
  position: relative;
  transition: box-shadow 0.15s, border-color 0.15s;
}
.module-card:hover { box-shadow: 0 2px 8px rgba(0,0,0,0.1); text-decoration: none; }
.foundation .module-card:hover { border-color: #90c4e0; }
.craft .module-card:hover      { border-color: #8dc45a; }
.project .module-card:hover    { border-color: #e0a060; }

.card-num { font-size: 12px; color: #aaa; margin-bottom: 4px; }
.card-title { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.card-desc  { font-size: 13px; color: #666; }
.card-time  { font-size: 11px; color: #bbb; position: absolute; top: 12px; right: 12px; }

/* ── Lesson page ── */
.lesson-header-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}
.lesson-time { font-size: 12px; color: #aaa; }
.lesson-page {
  max-width: 760px;
  margin: 0 auto;
  padding: 40px 24px 80px;
}
.lesson-page h1 { font-size: 28px; font-weight: 800; margin-bottom: 4px; }
.lesson-page .subtitle { color: #666; margin-bottom: 24px; }

.lesson-page section { margin-bottom: 36px; }
.lesson-page h2 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
  padding-bottom: 6px;
  border-bottom: 1px solid #eee;
}
.lesson-page h3 { font-size: 15px; font-weight: 600; margin: 16px 0 8px; }
.lesson-page p  { margin-bottom: 12px; }
.lesson-page ul, .lesson-page ol { padding-left: 20px; margin-bottom: 12px; }
.lesson-page li { margin-bottom: 4px; }

/* ── Callouts ── */
.callout {
  border-radius: 6px;
  padding: 14px 16px;
  margin-bottom: 24px;
  font-size: 14px;
}
.callout.analogy  { background: #fff8e6; border-left: 4px solid #f0b020; }
.callout.tip      { background: #e8f4fb; border-left: 4px solid #1a6fa0; }
.callout.warning  { background: #fdecea; border-left: 4px solid #d32f2f; }
.callout strong   { display: block; margin-bottom: 4px; }

/* ── Code blocks ── */
pre {
  background: #1e1e1e;
  color: #d4d4d4;
  border-radius: 6px;
  padding: 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.5;
  margin-bottom: 16px;
}
code {
  font-family: 'SF Mono', 'Fira Code', Consolas, monospace;
  font-size: 0.9em;
}
pre code { font-size: inherit; background: none; padding: 0; }
p code, li code {
  background: #f0f0f0;
  padding: 1px 5px;
  border-radius: 3px;
  font-size: 0.88em;
}

.code-label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: #888;
  margin-bottom: 4px;
}

.split-code {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}
@media (max-width: 600px) { .split-code { grid-template-columns: 1fr; } }

/* ── Takeaways ── */
.takeaways {
  background: #f0f8e8;
  border: 1px solid #8dc45a;
  border-radius: 8px;
  padding: 20px 24px;
  margin-top: 40px;
}
.takeaways h3 { font-size: 14px; font-weight: 700; text-transform: uppercase; letter-spacing: 1px; color: #3a7a10; margin-bottom: 10px; }
.takeaways ul { padding-left: 18px; }
.takeaways li { margin-bottom: 6px; font-size: 14px; }

/* ── Tables ── */
.lesson-page table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 16px;
  font-size: 14px;
}
.lesson-page th,
.lesson-page td {
  padding: 8px 12px;
  text-align: left;
  border: 1px solid #ddd;
}
.lesson-page thead th {
  background: #f0f0f0;
  font-weight: 700;
}
.lesson-page tbody tr:nth-child(even) { background: #fafafa; }

/* ── File tree ── */
.file-tree {
  background: #1e1e1e;
  color: #d4d4d4;
  border-radius: 6px;
  padding: 16px;
  font-family: 'SF Mono', Consolas, monospace;
  font-size: 13px;
  line-height: 1.7;
  margin-bottom: 16px;
  white-space: pre;
  overflow-x: auto;
}
.file-tree .dir   { color: #9cdcfe; }
.file-tree .ann   { color: #6a9955; font-style: italic; }

/* ── Nav height variable ── */
:root { --nav-h: 42px; }

/* ── Sidebar layout ── */
.page-layout {
  display: flex;
  align-items: flex-start;   /* required: lets sidebar use position:sticky */
  min-height: calc(100vh - var(--nav-h));
}

.page-layout > main.lesson-page {
  flex: 1 1 auto;
  min-width: 0;   /* prevents wide <pre> blocks from blowing out the flex child */
}

#lesson-sidebar {
  width: 220px;
  flex-shrink: 0;
  position: sticky;
  top: var(--nav-h);
  height: calc(100vh - var(--nav-h));
  overflow-y: auto;
  background: #fff;
  border-right: 1px solid #e0e0e0;
  padding: 16px 0;
}

/* Sidebar groups */
.sidebar-group { margin-bottom: 20px; }

.sidebar-group__label {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  padding: 0 0 6px;
  margin: 0 16px 6px;
}
.sidebar-group--foundation .sidebar-group__label { color: #1a6fa0; border-bottom: 2px solid #90c4e0; }
.sidebar-group--craft      .sidebar-group__label { color: #3a7a10; border-bottom: 2px solid #8dc45a; }
.sidebar-group--project    .sidebar-group__label { color: #b05010; border-bottom: 2px solid #e0a060; }

/* Sidebar lesson links */
.sidebar-lesson {
  display: block;
  padding: 5px 16px;
  font-size: 13px;
  color: #444;
  text-decoration: none;
  line-height: 1.4;
  border-left: 3px solid transparent;
  transition: background 0.1s, color 0.1s;
}
.sidebar-lesson:hover { background: #f0f4f8; color: #1a1a1a; text-decoration: none; }

/* Active lesson */
.sidebar-lesson.active { font-weight: 700; color: #1a1a1a; }
.sidebar-group--foundation .sidebar-lesson.active { border-left-color: #1a6fa0; background: #eef5fb; }
.sidebar-group--craft      .sidebar-lesson.active { border-left-color: #3a7a10; background: #eef5ee; }
.sidebar-group--project    .sidebar-lesson.active { border-left-color: #b05010; background: #fdf0e8; }

/* Align nav text with content column start */
#lesson-nav .nav-inner { max-width: none; padding-left: 236px; }

/* Hamburger button (hidden on desktop) */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 24px;
  height: 18px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
  flex-shrink: 0;
}
.hamburger span { display: block; height: 2px; background: #444; border-radius: 1px; }

/* Mobile overlay */
#sidebar-overlay { display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.4); z-index: 99; }
#sidebar-overlay.active { display: block; }

/* ── Responsive: mobile (<900px) ── */
@media (max-width: 899px) {
  .hamburger { display: flex; }

  #lesson-nav .nav-inner { padding-left: 0; }
  .nav-back { margin-left: 8px; margin-right: auto; }

  #lesson-sidebar {
    position: fixed;
    top: var(--nav-h);
    left: 0;
    height: calc(100vh - var(--nav-h));
    z-index: 200;
    transform: translateX(-220px);
    transition: transform 0.25s ease;
    box-shadow: 2px 0 8px rgba(0,0,0,0.15);
  }

  #lesson-sidebar.open { transform: translateX(0); }
}