/* ==========================================================================
   codelabs.kambale.dev — design system
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. Custom properties (light theme defaults)
   -------------------------------------------------------------------------- */
:root {
  /* backgrounds */
  --bg:          hsl(0 0% 98%);
  --bg-card:     hsl(0 0% 100%);
  --bg-sidebar:  hsl(222 18% 97%);
  --bg-code:     hsl(220 14% 95%);
  --bg-header:   hsl(0 0% 100%);

  /* text */
  --text:        hsl(222 12% 14%);
  --text-muted:  hsl(222 8%  46%);
  --text-subtle: hsl(222 8%  62%);

  /* accent */
  --accent:        hsl(215 90% 48%);
  --accent-hover:  hsl(215 90% 40%);
  --accent-light:  hsl(215 90% 94%);
  --accent-rgb:    25, 118, 210;

  /* borders & surfaces */
  --border:    hsl(222 14% 88%);
  --surface:   hsl(222 16% 94%);
  --shadow-sm: 0 1px 3px hsl(222 14% 10% / 0.06), 0 1px 2px hsl(222 14% 10% / 0.04);
  --shadow-md: 0 4px 12px hsl(222 14% 10% / 0.08), 0 2px 4px hsl(222 14% 10% / 0.05);
  --shadow-lg: 0 12px 32px hsl(222 14% 10% / 0.10), 0 4px 8px hsl(222 14% 10% / 0.06);

  /* status */
  --success: hsl(142 68% 38%);
  --warning: hsl(38  90% 48%);
  --danger:  hsl(354 78% 48%);

  /* category accent hues */
  --cat-ml:    hsl(250 80% 55%);
  --cat-dl:    hsl(215 90% 48%);
  --cat-nlp:   hsl(170 72% 38%);
  --cat-cv:    hsl(28  95% 50%);
  --cat-data:  hsl(340 78% 48%);
  --cat-cloud: hsl(195 85% 42%);
  --cat-mlops: hsl(222 8%  50%);
  --cat-default: hsl(222 8% 55%);

  /* layout */
  --sidebar-w:    260px;
  --header-h:     60px;
  --content-max:  860px;
  --radius-sm:    6px;
  --radius-md:    10px;
  --radius-lg:    16px;

  /* type */
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'Roboto Mono', 'Fira Code', 'Courier New', monospace;

  /* syntax highlighting (light) */
  --hl-comment:     hsl(220 12% 50%);
  --hl-keyword:     hsl(295 72% 38%);
  --hl-function:    hsl(215 88% 44%);
  --hl-class:       hsl(38 90% 38%);
  --hl-string:      hsl(142 66% 30%);
  --hl-number:      hsl(28 95% 42%);
  --hl-boolean:     hsl(28 95% 42%);
  --hl-operator:    hsl(222 14% 36%);
  --hl-punctuation: hsl(222 12% 46%);
  --hl-variable:    hsl(350 78% 44%);
  --hl-property:    hsl(215 85% 44%);
  --hl-tag:         hsl(350 78% 44%);
  --hl-attr-name:   hsl(28 95% 42%);
  --hl-attr-value:  hsl(142 66% 30%);
  --hl-builtin:     hsl(190 90% 32%);
  --hl-constant:    hsl(28 95% 42%);

  /* transitions */
  --ease-std:  cubic-bezier(0.4, 0, 0.2, 1);
  --ease-out:  cubic-bezier(0, 0, 0.2, 1);
  --dur-fast:  120ms;
  --dur-std:   200ms;
  --dur-slow:  350ms;
}

/* dark theme */
[data-theme="dark"] {
  --bg:          hsl(222 16% 8%);
  --bg-card:     hsl(222 16% 11%);
  --bg-sidebar:  hsl(222 16% 9%);
  --bg-code:     hsl(222 16% 14%);
  --bg-header:   hsl(222 16% 10%);

  --text:        hsl(220 16% 90%);
  --text-muted:  hsl(220 10% 58%);
  --text-subtle: hsl(220 8%  44%);

  --accent:        hsl(213 90% 65%);
  --accent-hover:  hsl(213 90% 58%);
  --accent-light:  hsl(213 90% 16%);

  --border:    hsl(222 14% 20%);
  --surface:   hsl(222 14% 16%);
  --shadow-sm: 0 1px 3px hsl(0 0% 0% / 0.25);
  --shadow-md: 0 4px 12px hsl(0 0% 0% / 0.35);
  --shadow-lg: 0 12px 32px hsl(0 0% 0% / 0.45);

  /* syntax highlighting (dark) */
  --hl-comment:     hsl(220 12% 56%);
  --hl-keyword:     hsl(295 85% 76%);
  --hl-function:    hsl(213 92% 72%);
  --hl-class:       hsl(38 92% 70%);
  --hl-string:      hsl(142 68% 62%);
  --hl-number:      hsl(30 95% 68%);
  --hl-boolean:     hsl(30 95% 68%);
  --hl-operator:    hsl(220 16% 82%);
  --hl-punctuation: hsl(220 14% 65%);
  --hl-variable:    hsl(354 88% 74%);
  --hl-property:    hsl(195 88% 70%);
  --hl-tag:         hsl(354 88% 74%);
  --hl-attr-name:   hsl(38 92% 70%);
  --hl-attr-value:  hsl(142 68% 62%);
  --hl-builtin:     hsl(180 80% 62%);
  --hl-constant:    hsl(30 95% 68%);
}

/* --------------------------------------------------------------------------
   2. Reset & base
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  transition: background var(--dur-std) var(--ease-std),
              color var(--dur-std) var(--ease-std);
  min-height: 100dvh;
}

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

img, svg { display: block; max-width: 100%; }

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

input, select, textarea {
  font-family: inherit;
  font-size: inherit;
}

ul, ol { list-style: none; }

h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  color: var(--text);
}

code, pre {
  font-family: var(--font-mono);
}

/* --------------------------------------------------------------------------
   3. Typography scale
   -------------------------------------------------------------------------- */
.text-xs   { font-size: 0.75rem; }
.text-sm   { font-size: 0.8125rem; }
.text-base { font-size: 1rem; }
.text-lg   { font-size: 1.125rem; }
.text-xl   { font-size: 1.25rem; }
.text-2xl  { font-size: 1.5rem; }
.text-3xl  { font-size: 1.875rem; }
.text-muted  { color: var(--text-muted); }
.text-subtle { color: var(--text-subtle); }
.font-medium { font-weight: 500; }
.font-semi   { font-weight: 600; }
.font-bold   { font-weight: 700; }

/* --------------------------------------------------------------------------
   4. Layout utilities
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 24px;
}

.flex        { display: flex; }
.flex-center { display: flex; align-items: center; }
.flex-between{ display: flex; align-items: center; justify-content: space-between; }
.flex-col    { display: flex; flex-direction: column; }
.gap-4  { gap: 4px; }
.gap-8  { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.gap-24 { gap: 24px; }

/* --------------------------------------------------------------------------
   5. Header (shared)
   -------------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: background var(--dur-std) var(--ease-std),
              border-color var(--dur-std) var(--ease-std);
}

.site-header .container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

/* logo */
.site-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}

/* --------------------------------------------------------------------------
   Offline Status Banner & Fallback
   -------------------------------------------------------------------------- */
.offline-banner {
  background: hsl(38 90% 48% / 0.15);
  border-bottom: 1px solid var(--warning);
  color: var(--text);
  padding: 8px 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 0.8125rem;
  font-weight: 500;
  position: sticky;
  top: 0;
  z-index: 150;
  animation: slideDown 250ms var(--ease-out);
}

.offline-banner svg {
  color: var(--warning);
  flex-shrink: 0;
}

.offline-banner[hidden] {
  display: none !important;
}

@keyframes slideDown {
  from { transform: translateY(-100%); opacity: 0; }
  to   { transform: translateY(0); opacity: 1; }
}

.offline-fallback {
  text-align: center;
  padding: 64px 24px;
  max-width: 520px;
  margin: 0 auto;
}

.offline-fallback__icon {
  width: 56px;
  height: 56px;
  color: var(--warning);
  margin: 0 auto 20px;
  display: block;
}

.offline-fallback__title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}

.offline-fallback__desc {
  color: var(--text-muted);
  font-size: 0.9375rem;
  line-height: 1.6;
  margin-bottom: 28px;
}

.offline-fallback__btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  height: 42px;
  padding: 0 20px;
  border-radius: var(--radius-md);
  background: var(--accent);
  color: hsl(0 0% 100%);
  font-size: 0.875rem;
  font-weight: 500;
  text-decoration: none;
  transition: background var(--dur-fast) var(--ease-std);
}

.offline-fallback__btn:hover {
  background: var(--accent-hover);
  color: hsl(0 0% 100%);
  text-decoration: none;
}

.site-logo__icon {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  flex-shrink: 0;
}

.site-logo__name {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.01em;
}

.site-logo__name span {
  color: var(--accent);
}

/* header search */
.header-search {
  flex: 1;
  max-width: 480px;
  position: relative;
}

.header-search__input {
  width: 100%;
  height: 36px;
  padding: 0 32px 0 38px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--surface);
  color: var(--text);
  font-size: 0.875rem;
  outline: none;
  transition: border-color var(--dur-fast) var(--ease-std),
              box-shadow var(--dur-fast) var(--ease-std),
              background var(--dur-std) var(--ease-std);
}

.header-search__input:focus {
  border-color: var(--accent);
  background: var(--bg-card);
  box-shadow: 0 0 0 3px hsl(215 90% 48% / 0.12);
}

.header-search__icon {
  position: absolute;
  left: 11px;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  color: var(--text-subtle);
  pointer-events: none;
}

.header-search__clear {
  position: absolute;
  right: 8px;
  top: 50%;
  transform: translateY(-50%);
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: none;
  background: var(--border);
  color: var(--text-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  padding: 0;
  transition: background var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std),
              transform var(--dur-fast) var(--ease-std);
}

.header-search__clear:hover {
  background: var(--border-focus);
  color: var(--text);
}

.header-search__clear[hidden] {
  display: none !important;
}

/* theme toggle */
.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid transparent;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
  flex-shrink: 0;
}

.theme-toggle:hover {
  background: var(--surface);
  border-color: var(--border);
  color: var(--text);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
  transition: transform var(--dur-std) var(--ease-out),
              opacity var(--dur-fast) var(--ease-std);
}

.theme-toggle .icon-sun  { display: none; }
.theme-toggle .icon-moon { display: block; }

[data-theme="dark"] .theme-toggle .icon-sun  { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

/* --------------------------------------------------------------------------
   6. Index page: filter bar
   -------------------------------------------------------------------------- */
.filter-bar {
  padding: 16px 0;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
  transition: border-color var(--dur-std) var(--ease-std);
  position: sticky;
  top: var(--header-h);
  z-index: 90;
}

.filter-bar .container {
  display: flex;
  align-items: center;
  gap: 12px;
  overflow-x: auto;
  scrollbar-width: none;
}

.filter-bar .container::-webkit-scrollbar { display: none; }

/* category tabs */
.cat-tabs {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.cat-tab {
  height: 32px;
  padding: 0 14px;
  border-radius: 20px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid var(--border);
  white-space: nowrap;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.cat-tab:hover {
  background: var(--surface);
  border-color: var(--border);
  color: var(--text);
}

.cat-tab.active {
  background: var(--accent);
  border-color: var(--accent);
  color: hsl(0 0% 100%);
}

/* filter selects */
.filter-select {
  height: 32px;
  padding: 0 28px 0 10px;
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  color: var(--text-muted);
  background: var(--bg-card);
  border: 1px solid var(--border);
  outline: none;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23888' stroke-width='2'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 8px center;
  cursor: pointer;
  transition: border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
  white-space: nowrap;
  flex-shrink: 0;
}

.filter-select:focus {
  border-color: var(--accent);
  color: var(--text);
}

.filter-divider {
  width: 1px;
  height: 20px;
  background: var(--border);
  flex-shrink: 0;
}

/* results meta */
.results-meta {
  padding: 20px 0 0;
}

.results-count {
  font-size: 0.8125rem;
  color: var(--text-muted);
}

/* --------------------------------------------------------------------------
   7. Codelab card grid
   -------------------------------------------------------------------------- */
.codelab-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  padding: 20px 0 40px;
}

@media (max-width: 1024px) {
  .codelab-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 600px) {
  .codelab-grid { grid-template-columns: 1fr; gap: 14px; }
}

/* card */
.codelab-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  position: relative;
  overflow: hidden;
  transition: transform var(--dur-std) var(--ease-out),
              box-shadow var(--dur-std) var(--ease-out),
              border-color var(--dur-std) var(--ease-std);
  animation: fadeIn var(--dur-slow) var(--ease-out) both;
}

.codelab-card::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 3px;
  border-radius: 3px 0 0 3px;
  background: var(--card-accent, var(--cat-default));
}

.codelab-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: hsl(215 90% 48% / 0.25);
}

.codelab-card__header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px;
}

.codelab-card__category {
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--card-accent, var(--cat-default));
}

.codelab-card__duration {
  font-size: 0.75rem;
  color: var(--text-subtle);
  white-space: nowrap;
  flex-shrink: 0;
}

.codelab-card__title {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.codelab-card__summary {
  font-size: 0.8125rem;
  color: var(--text-muted);
  line-height: 1.55;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  flex: 1;
}

.codelab-card__footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: auto;
  padding-top: 4px;
}

.codelab-card__meta {
  font-size: 0.75rem;
  color: var(--text-subtle);
  line-height: 1.4;
}

.codelab-card__level {
  font-size: 0.6875rem;
  font-weight: 500;
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--surface);
  color: var(--text-muted);
}

.codelab-card__start {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  height: 32px;
  padding: 0 14px;
  border-radius: var(--radius-sm);
  background: var(--accent);
  color: hsl(0 0% 100%);
  font-size: 0.8125rem;
  font-weight: 500;
  text-decoration: none;
  transition: background var(--dur-fast) var(--ease-std),
              transform var(--dur-fast) var(--ease-out);
  flex-shrink: 0;
}

.codelab-card__start:hover {
  background: var(--accent-hover);
  text-decoration: none;
  transform: translateY(-1px);
}

/* category colour mapping */
.cat--ml    { --card-accent: var(--cat-ml);    }
.cat--dl    { --card-accent: var(--cat-dl);    }
.cat--nlp   { --card-accent: var(--cat-nlp);   }
.cat--cv    { --card-accent: var(--cat-cv);    }
.cat--data  { --card-accent: var(--cat-data);  }
.cat--cloud { --card-accent: var(--cat-cloud); }
.cat--mlops { --card-accent: var(--cat-mlops); }

/* --------------------------------------------------------------------------
   8. Pagination
   -------------------------------------------------------------------------- */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 0 48px;
}

.page-btn {
  min-width: 36px;
  height: 36px;
  padding: 0 6px;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid var(--border);
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.page-btn:hover {
  background: var(--surface);
  border-color: var(--border);
  color: var(--text);
}

.page-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: hsl(0 0% 100%);
}

.page-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

/* --------------------------------------------------------------------------
   9. Empty state
   -------------------------------------------------------------------------- */
.empty-state {
  text-align: center;
  padding: 80px 24px;
  grid-column: 1 / -1;
}

.empty-state__icon {
  width: 56px;
  height: 56px;
  margin: 0 auto 16px;
  color: var(--border);
}

.empty-state__title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.empty-state__body {
  font-size: 0.875rem;
  color: var(--text-subtle);
}

/* --------------------------------------------------------------------------
   10. Lab reader — progress bar
   -------------------------------------------------------------------------- */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--border);
  z-index: 200;
}

.progress-bar__fill {
  height: 100%;
  background: var(--accent);
  border-radius: 0 2px 2px 0;
  transition: width var(--dur-slow) var(--ease-std);
  width: 0%;
}

/* --------------------------------------------------------------------------
   11. Lab reader — header
   -------------------------------------------------------------------------- */
.lab-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
  transition: background var(--dur-std) var(--ease-std),
              border-color var(--dur-std) var(--ease-std);
}

.lab-header .container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.lab-header__back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-std);
  flex-shrink: 0;
}

.lab-header__back:hover {
  color: var(--accent);
  text-decoration: none;
}

.lab-header__back svg {
  width: 16px;
  height: 16px;
}

.lab-header__title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  text-align: center;
  flex: 1;
}

.lab-header__controls {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

/* --------------------------------------------------------------------------
   12. Lab reader — layout
   -------------------------------------------------------------------------- */
.lab-layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  min-height: calc(100dvh - var(--header-h));
}

/* step sidebar */
.lab-sidebar {
  position: sticky;
  top: var(--header-h);
  height: calc(100dvh - var(--header-h));
  overflow-y: auto;
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  padding: 20px 0;
  transition: background var(--dur-std) var(--ease-std),
              border-color var(--dur-std) var(--ease-std);
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.lab-sidebar::-webkit-scrollbar { width: 4px; }
.lab-sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 2px; }

.sidebar-meta {
  padding: 0 16px 16px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 8px;
}

.sidebar-meta__row {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 8px;
}

.sidebar-meta__label {
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--text-subtle);
  margin-bottom: 4px;
}

.sidebar-meta__duration {
  font-size: 0.8125rem;
  color: var(--text-muted);
}

.sidebar-meta__remaining-wrap {
  text-align: right;
}

.sidebar-meta__remaining {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--accent);
  background: hsl(215 90% 48% / 0.08);
  padding: 2px 7px;
  border-radius: var(--radius-sm);
  white-space: nowrap;
}

.sidebar-footer {
  padding: 16px;
  margin-top: 16px;
  border-top: 1px solid var(--border);
}

.btn-restart-sidebar {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  width: 100%;
  height: 32px;
  padding: 0 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 500;
  cursor: pointer;
  justify-content: center;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.btn-restart-sidebar:hover {
  background: var(--surface);
  border-color: var(--border-focus);
  color: var(--text);
}

.btn-restart-sidebar svg {
  color: var(--text-subtle);
  transition: transform var(--dur-fast) var(--ease-std);
}

.btn-restart-sidebar:hover svg {
  transform: rotate(-45deg);
  color: var(--accent);
}

/* step list */
.step-list {
  padding: 0;
}

.step-item {
  position: relative;
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 9px 16px;
  cursor: pointer;
  border: none;
  background: transparent;
  text-align: left;
  width: 100%;
  text-decoration: none;
  color: inherit;
  transition: background var(--dur-fast) var(--ease-std);
}

.step-item::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 3px;
  border-radius: 0 3px 3px 0;
  background: transparent;
  transition: background var(--dur-fast) var(--ease-std);
}

.step-item:hover {
  background: hsl(215 90% 48% / 0.05);
  text-decoration: none;
}

.step-item.active {
  background: var(--accent-light);
}

.step-item.active::before {
  background: var(--accent);
}

.step-item__num {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--surface);
  border: 1.5px solid var(--border);
  font-size: 0.6875rem;
  font-weight: 600;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-top: 1px;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.step-item.active .step-item__num {
  background: var(--accent);
  border-color: var(--accent);
  color: hsl(0 0% 100%);
}

.step-item.done .step-item__num {
  background: var(--success);
  border-color: var(--success);
  color: hsl(0 0% 100%);
}

.step-item__label {
  font-size: 0.8125rem;
  line-height: 1.4;
  color: var(--text-muted);
  transition: color var(--dur-fast) var(--ease-std);
}

.step-item.active .step-item__label { color: var(--accent); font-weight: 500; }
.step-item.done  .step-item__label { color: var(--text-muted); }

.step-item__duration {
  font-size: 0.6875rem;
  color: var(--text-subtle);
  margin-left: auto;
  flex-shrink: 0;
  padding-top: 3px;
}

/* --------------------------------------------------------------------------
   13. Lab reader — content area
   -------------------------------------------------------------------------- */
.lab-content {
  min-width: 0;
  padding: 48px 40px 80px;
  max-width: calc(var(--content-max) + 80px);
}

.step-header {
  margin-bottom: 32px;
}

.step-number {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--accent);
  margin-bottom: 8px;
}

.step-title {
  font-size: 1.625rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
  line-height: 1.25;
}

/* step body prose */
.step-body {
  color: var(--text);
  font-size: 1rem;
  line-height: 1.7;
}

.step-body h2 {
  font-size: 1.125rem;
  font-weight: 600;
  margin: 32px 0 12px;
  color: var(--text);
}

.step-body h2:first-child { margin-top: 0; }

.step-body h3 {
  font-size: 1rem;
  font-weight: 600;
  margin: 24px 0 8px;
}

.step-body p {
  margin-bottom: 16px;
}

.step-body p:last-child { margin-bottom: 0; }

.step-body ul,
.step-body ol {
  margin-bottom: 16px;
  padding-left: 20px;
}

.step-body ul { list-style: disc; }
.step-body ol { list-style: decimal; }

.step-body li {
  margin-bottom: 6px;
}

.step-body a {
  color: var(--accent);
}

.step-body strong { font-weight: 600; }

.step-body img {
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  margin: 20px 0;
  max-width: 100%;
}

/* aside boxes */
.step-body aside {
  padding: 14px 16px;
  border-radius: var(--radius-md);
  border-left: 3px solid;
  margin: 20px 0;
  font-size: 0.9375rem;
}

.step-body aside.note    { background: hsl(215 90% 48% / 0.07); border-color: var(--accent); }
.step-body aside.warning { background: hsl(38 90% 48% / 0.08); border-color: var(--warning); }
.step-body aside.special { background: hsl(142 68% 38% / 0.07); border-color: var(--success); }

/* code blocks */
.step-body pre,
.code-block {
  position: relative;
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px 18px;
  margin: 20px 0;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.65;
  tab-size: 2;
  -webkit-overflow-scrolling: touch;
}

.step-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--bg-code);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
  color: var(--text);
}

.step-body pre code {
  background: none;
  padding: 0;
  border: none;
  font-size: inherit;
  font-family: inherit;
  color: var(--text);
  white-space: pre;
  word-spacing: normal;
  word-break: normal;
  word-wrap: normal;
}

/* Syntax Highlighting Tokens */
.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
  color: var(--hl-comment);
  font-style: italic;
}

.token.punctuation {
  color: var(--hl-punctuation);
}

.token.namespace {
  opacity: 0.75;
}

.token.property,
.token.constant,
.token.symbol,
.token.deleted {
  color: var(--hl-property);
}

.token.boolean,
.token.number {
  color: var(--hl-number);
}

.token.tag {
  color: var(--hl-tag);
}

.token.attr-name {
  color: var(--hl-attr-name);
}

.token.attr-value,
.token.string,
.token.char,
.token.inserted {
  color: var(--hl-string);
}

.token.operator,
.token.entity,
.token.url {
  color: var(--hl-operator);
}

.token.atrule,
.token.keyword {
  color: var(--hl-keyword);
  font-weight: 500;
}

.token.function {
  color: var(--hl-function);
}

.token.class-name {
  color: var(--hl-class);
  font-weight: 500;
}

.token.regex,
.token.important,
.token.variable {
  color: var(--hl-variable);
}

.token.builtin {
  color: var(--hl-builtin);
}

.token.important,
.token.bold {
  font-weight: 600;
}

.token.italic {
  font-style: italic;
}

.token.entity {
  cursor: help;
}

.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  z-index: 2;
  cursor: pointer;
  transition: opacity var(--dur-fast) var(--ease-std),
              background var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std);
}

pre:hover .copy-btn,
.code-block:hover .copy-btn,
.copy-btn:focus,
.copy-btn.copied {
  opacity: 1;
}

.copy-btn:hover {
  background: var(--accent);
  border-color: var(--accent);
  color: hsl(0 0% 100%);
}

.copy-btn.copied {
  background: var(--success);
  border-color: var(--success);
  color: hsl(0 0% 100%);
  opacity: 1;
}

.copy-btn svg {
  width: 13px;
  height: 13px;
}

/* step navigation */
.step-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  gap: 12px;
}

.step-nav__btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  height: 40px;
  padding: 0 18px;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  border: 1px solid var(--border);
  color: var(--text);
  background: var(--bg-card);
  text-decoration: none;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              transform var(--dur-fast) var(--ease-out),
              color var(--dur-fast) var(--ease-std);
}

.step-nav__btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-1px);
  text-decoration: none;
}

.step-nav__btn--primary {
  background: var(--accent);
  border-color: var(--accent);
  color: hsl(0 0% 100%);
}

.step-nav__btn--primary:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: hsl(0 0% 100%);
}

.step-nav__btn svg { width: 16px; height: 16px; }

.step-nav__btn:disabled,
.step-nav__btn[disabled] {
  opacity: 0.35;
  cursor: not-allowed;
  transform: none;
}

.step-nav__center {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  font-size: 0.8125rem;
  color: var(--text-subtle);
}

.step-nav__counter {
  font-weight: 500;
  color: var(--text-muted);
}

.step-nav__kbd-hint {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.6875rem;
  color: var(--text-subtle);
  opacity: 0.85;
}

.kbd-hint {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 18px;
  height: 18px;
  padding: 0 4px;
  font-family: inherit;
  font-size: 0.6875rem;
  font-weight: 600;
  line-height: 1;
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: 0 1px 0 var(--border);
}

.kbd-hint--primary {
  color: hsl(0 0% 100% / 0.9);
  background: hsl(0 0% 100% / 0.18);
  border-color: hsl(0 0% 100% / 0.3);
  box-shadow: 0 1px 0 hsl(0 0% 100% / 0.2);
}

/* Completion screen actions */
.finished-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
}

.btn-restart-finish {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  height: 44px;
  padding: 0 20px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-size: 0.9375rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              transform var(--dur-fast) var(--ease-std);
}

.btn-restart-finish:hover {
  background: var(--bg-card);
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-1px);
}

/* --------------------------------------------------------------------------
   14. Mobile: sidebar drawer
   -------------------------------------------------------------------------- */
@media (max-width: 768px) {
  .lab-layout {
    grid-template-columns: 1fr;
  }

  .lab-sidebar {
    position: fixed;
    top: var(--header-h);
    left: 0;
    bottom: 0;
    width: min(var(--sidebar-w), 86vw);
    z-index: 80;
    transform: translateX(-100%);
    transition: transform var(--dur-std) var(--ease-out);
    box-shadow: var(--shadow-lg);
  }

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

  .sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    top: var(--header-h);
    background: hsl(222 16% 8% / 0.5);
    z-index: 79;
    backdrop-filter: blur(2px);
  }

  .sidebar-overlay.open { display: block; }

  .lab-content {
    padding: 32px 20px 60px;
  }

  .lab-header__title { display: none; }

  .step-title { font-size: 1.375rem; }

  .header-search { display: none; }
}

@media (min-width: 769px) {
  .sidebar-toggle,
  .sidebar-overlay { display: none; }
}

/* sidebar toggle btn (mobile) */
.sidebar-toggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  height: 32px;
  padding: 0 12px;
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-muted);
  border: 1px solid var(--border);
  background: transparent;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.sidebar-toggle:hover {
  background: var(--surface);
  border-color: var(--border);
  color: var(--text);
}

.sidebar-toggle svg { width: 15px; height: 15px; }

/* --------------------------------------------------------------------------
   15. Footer
   -------------------------------------------------------------------------- */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 32px 0;
  margin-top: auto;
  background: var(--bg);
  transition: border-color var(--dur-std) var(--ease-std);
}

.site-footer .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.site-footer__copy {
  font-size: 0.8125rem;
  color: var(--text-subtle);
}

.site-footer__links {
  display: flex;
  gap: 20px;
}

.site-footer__links a {
  font-size: 0.8125rem;
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-std);
}

.site-footer__links a:hover {
  color: var(--accent);
}

/* --------------------------------------------------------------------------
   16. Skeleton loading
   -------------------------------------------------------------------------- */
.skeleton {
  background: var(--surface);
  border-radius: var(--radius-sm);
  animation: shimmer 1.6s ease-in-out infinite;
  background-image: linear-gradient(
    90deg,
    var(--surface) 0%,
    var(--border) 50%,
    var(--surface) 100%
  );
  background-size: 200% 100%;
}

@keyframes shimmer {
  0%   { background-position: -200% 0; }
  100% { background-position:  200% 0; }
}

.skeleton-card {
  border-radius: var(--radius-lg);
  height: 220px;
  background: var(--bg-card);
  border: 1px solid var(--border);
}

/* --------------------------------------------------------------------------
   17. Animations
   -------------------------------------------------------------------------- */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes slideInLeft {
  from { opacity: 0; transform: translateX(-12px); }
  to   { opacity: 1; transform: translateX(0); }
}

.animate-fade  { animation: fadeIn var(--dur-slow) var(--ease-out) both; }
.animate-slide { animation: slideInLeft var(--dur-slow) var(--ease-out) both; }

/* stagger cards */
.codelab-card:nth-child(1)  { animation-delay:  0ms; }
.codelab-card:nth-child(2)  { animation-delay: 40ms; }
.codelab-card:nth-child(3)  { animation-delay: 80ms; }
.codelab-card:nth-child(4)  { animation-delay:120ms; }
.codelab-card:nth-child(5)  { animation-delay:160ms; }
.codelab-card:nth-child(6)  { animation-delay:200ms; }
.codelab-card:nth-child(7)  { animation-delay:240ms; }
.codelab-card:nth-child(8)  { animation-delay:280ms; }
.codelab-card:nth-child(9)  { animation-delay:320ms; }
.codelab-card:nth-child(10) { animation-delay:360ms; }
.codelab-card:nth-child(11) { animation-delay:400ms; }
.codelab-card:nth-child(12) { animation-delay:440ms; }

/* --------------------------------------------------------------------------
   18. Utility
   -------------------------------------------------------------------------- */
.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}

.hidden { display: none !important; }

/* --------------------------------------------------------------------------
   19. Print button & Print Export Container
   -------------------------------------------------------------------------- */
.print-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  height: 32px;
  padding: 0 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-muted);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--dur-fast) var(--ease-std),
              border-color var(--dur-fast) var(--ease-std),
              color var(--dur-fast) var(--ease-std);
}

.print-btn:hover {
  background: var(--surface);
  border-color: var(--border-focus);
  color: var(--text);
}

.print-btn svg {
  color: var(--text-subtle);
  transition: color var(--dur-fast) var(--ease-std);
}

.print-btn:hover svg {
  color: var(--accent);
}

.print-full-view {
  padding: 40px 48px;
  max-width: var(--content-w);
  margin: 0 auto;
  width: 100%;
}

.print-full-view[hidden] {
  display: none !important;
}

.print-cover {
  margin-bottom: 40px;
  padding-bottom: 24px;
  border-bottom: 2px solid var(--border);
}

.print-cover__title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 8px;
  line-height: 1.25;
}

.print-cover__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.print-cover__summary {
  font-size: 1rem;
  color: var(--text);
  line-height: 1.6;
}

.print-step {
  margin-bottom: 48px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--border);
}

.print-step:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.print-step__num {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.print-step__title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 16px;
}

.print-step__content {
  font-size: 1rem;
  line-height: 1.7;
  color: var(--text);
}

/* --------------------------------------------------------------------------
   20. Print Stylesheet
   -------------------------------------------------------------------------- */
@media print {
  /* Hide all interactive UI and navigation chrome */
  .site-header,
  .lab-header,
  .lab-sidebar,
  .sidebar-overlay,
  .sidebar-toggle,
  .theme-toggle,
  .print-btn,
  .progress-bar,
  .step-nav,
  .copy-btn,
  .finished-actions,
  .sidebar-footer,
  .header-search,
  .site-footer,
  [data-theme-toggle] {
    display: none !important;
  }

  /* Reset layout to full page */
  html, body {
    background: #fff !important;
    color: #000 !important;
    font-size: 11pt !important;
    line-height: 1.5 !important;
  }

  .lab-layout {
    display: block !important;
    grid-template-columns: 1fr !important;
    min-height: auto !important;
    width: 100% !important;
  }

  .lab-content,
  .print-full-view {
    display: block !important;
    max-width: 100% !important;
    width: 100% !important;
    padding: 0 !important;
    margin: 0 !important;
    box-shadow: none !important;
    background: transparent !important;
  }

  /* Typography & contrast */
  h1, h2, h3, h4, h5, h6 {
    color: #000 !important;
    page-break-after: avoid;
    break-after: avoid;
  }

  p, li, td, th {
    color: #111 !important;
  }

  a {
    color: #000 !important;
    text-decoration: underline !important;
  }

  /* Prevent page breaks inside code blocks and callouts */
  pre,
  code,
  .code-block,
  table,
  aside.note,
  aside.warning,
  aside.special,
  figure,
  img {
    page-break-inside: avoid !important;
    break-inside: avoid !important;
  }

  pre {
    background: #f8f9fa !important;
    color: #111 !important;
    border: 1px solid #ddd !important;
    border-radius: 4px !important;
    padding: 10px 14px !important;
    white-space: pre-wrap !important;
    word-break: break-word !important;
    font-size: 9.5pt !important;
  }

  code {
    background: #f3f4f6 !important;
    color: #111 !important;
    border: 1px solid #e5e7eb !important;
    font-size: 9.5pt !important;
  }

  aside {
    background: #f9fafb !important;
    border: 1px solid #d1d5db !important;
    border-left: 4px solid #4b5563 !important;
    color: #111 !important;
    padding: 10px 14px !important;
    margin: 14px 0 !important;
  }

  /* Page breaks between tutorial steps when full-export printing */
  .print-step {
    page-break-after: always;
    break-after: page;
    margin-bottom: 24pt;
    padding-bottom: 18pt;
    border-bottom: 1px solid #eee;
  }

  .print-step:last-child {
    page-break-after: auto;
    break-after: auto;
    border-bottom: none;
  }

  .print-cover {
    page-break-after: always;
    break-after: page;
    border-bottom: 2px solid #000 !important;
    padding-bottom: 20pt !important;
    margin-bottom: 24pt !important;
  }

  .print-cover__title {
    font-size: 24pt !important;
    color: #000 !important;
  }
}