:root {
  /* Google Design / Material 3 Tokens */
  --color-blue: #0b57d0;
  --color-blue-hover: #0842a0;
  --color-blue-surface: #e8f0fe;
  --color-blue-text: #042b70;

  --color-green: #146c2e;
  --color-green-surface: #e6f4ea;
  --color-green-text: #0d381e;

  --color-amber: #b06000;
  --color-amber-surface: #fef7e0;
  --color-amber-text: #4e2c00;

  --color-purple: #7627bb;
  --color-purple-surface: #f3e8fd;
  --color-purple-text: #3c096c;

  --bg-page: #ffffff;
  --bg-surface: #f8fafd;
  --bg-card: #ffffff;
  --bg-container: #f1f3f4;
  --bg-container-high: #e8eaed;
  
  --text-main: #202124;
  --text-muted: #5f6368;
  --text-dim: #80868b;
  
  --border: #dadce0;
  --border-subtle: #f1f3f4;
  --border-outline: #bdc1c6;

  --font-google: 'Google Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'Space Mono', monospace;

  --radius-xs: 4px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-pill: 9999px;

  --shadow-card: 0 1px 3px 0 rgba(60, 64, 67, 0.08), 0 1px 2px -1px rgba(60, 64, 67, 0.04);
  --shadow-hover: 0 4px 14px 1px rgba(60, 64, 67, 0.12);

  /* Default theme cascade values (Blue) */
  --accent: var(--color-blue);
  --accent-surface: var(--color-blue-surface);
  --accent-text: var(--color-blue-text);
}

[data-theme="dark"] {
  --color-blue: #a8c7fa;
  --color-blue-hover: #c2e7ff;
  --color-blue-surface: #0842a0;
  --color-blue-text: #d3e3fd;

  --color-green: #81c995;
  --color-green-surface: #0d381e;
  --color-green-text: #c4eed0;

  --color-amber: #fdd663;
  --color-amber-surface: #4e2c00;
  --color-amber-text: #feefc3;

  --color-purple: #d7aefb;
  --color-purple-surface: #3c096c;
  --color-purple-text: #f3e8fd;

  --bg-page: #121316;
  --bg-surface: #1a1b1f;
  --bg-card: #1e1f24;
  --bg-container: #282a30;
  --bg-container-high: #33363e;

  --text-main: #e8eaed;
  --text-muted: #9aa0a6;
  --text-dim: #80868b;

  --border: #3c4043;
  --border-subtle: #25272c;
  --border-outline: #5f6368;

  --shadow-card: 0 1px 3px 0 rgba(0, 0, 0, 0.3);
  --shadow-hover: 0 4px 16px 2px rgba(0, 0, 0, 0.45);
}

/* Color theme cascades */
body.theme-blue   { --accent: var(--color-blue);   --accent-surface: var(--color-blue-surface);   --accent-text: var(--color-blue-text); }
body.theme-purple { --accent: var(--color-purple); --accent-surface: var(--color-purple-surface); --accent-text: var(--color-purple-text); }
body.theme-amber  { --accent: var(--color-amber);  --accent-surface: var(--color-amber-surface);  --accent-text: var(--color-amber-text); }
body.theme-green  { --accent: var(--color-green);  --accent-surface: var(--color-green-surface);  --accent-text: var(--color-green-text); }

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-google);
  background-color: var(--bg-page);
  color: var(--text-main);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  transition: background-color 0.2s ease, color 0.2s ease;
}

/* Header */
header.site-header {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--bg-page);
  border-bottom: 1px solid var(--border);
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 32px;
  transition: background-color 0.2s ease, border-color 0.2s ease;
}

.brand-group {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: inherit;
}

.brand-mark {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
  display: block;
}

.brand-title {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.5px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.brand-title span.sub {
  color: var(--text-dim);
  font-weight: 400;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.theme-toggle-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border);
  background: var(--bg-surface);
  color: var(--text-main);
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.theme-toggle-btn:hover {
  background: var(--bg-container);
  border-color: var(--border-outline);
}

.theme-toggle-btn svg {
  width: 16px;
  height: 16px;
  fill: currentColor;
}

/* Page Container */
.page-container {
  max-width: 900px;
  margin: 0 auto;
  padding: 56px 24px 100px;
}

/* Breadcrumb */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--text-dim);
  margin-bottom: 28px;
}

.breadcrumb a {
  color: var(--accent);
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

/* Hero Section */
.hero {
  margin-bottom: 48px;
}

.hero-tag {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--accent);
  margin-bottom: 12px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.hero-title {
  font-size: 36px;
  font-weight: 500;
  line-height: 1.25;
  letter-spacing: -0.6px;
  color: var(--text-main);
  margin-bottom: 14px;
}

.hero-subtitle {
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-muted);
  max-width: 760px;
}

.hero-index {
  padding: 16px 0 0;
}

.verification-note {
  font-size: 14px;
  color: var(--text-muted);
}

.start-here {
  padding: 20px 24px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
}

.start-here .section-title {
  color: var(--accent);
  margin-bottom: 8px;
}

.starter-steps {
  padding-left: 20px;
  font-size: 14px;
  color: var(--text-main);
}

.starter-steps li + li {
  margin-top: 8px;
}

.starter-steps li::marker {
  color: var(--accent);
  font-family: var(--font-mono);
}

.verification-note {
  margin-bottom: 12px;
}

/* Stage Cards on Index */
.stages-list {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.stage-card {
  display: flex;
  flex-direction: column;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 30px 32px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.stage-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-card);
  transform: translateY(-2px);
}

.stage-card.theme-blue   { --accent: var(--color-blue);   --accent-surface: var(--color-blue-surface);   --accent-text: var(--color-blue-text); }
.stage-card.theme-purple { --accent: var(--color-purple); --accent-surface: var(--color-purple-surface); --accent-text: var(--color-purple-text); }
.stage-card.theme-amber  { --accent: var(--color-amber);  --accent-surface: var(--color-amber-surface);  --accent-text: var(--color-amber-text); }
.stage-card.theme-green  { --accent: var(--color-green);  --accent-surface: var(--color-green-surface);  --accent-text: var(--color-green-text); }

.card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.stage-pill {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 700;
  color: var(--accent-text);
  background: var(--accent-surface);
  padding: 3px 9px;
  border-radius: var(--radius-xs);
}

.stage-category {
  font-size: 11px;
  font-family: var(--font-mono);
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.card-name {
  font-size: 21px;
  font-weight: 500;
  color: var(--text-main);
  margin-bottom: 10px;
  letter-spacing: -0.2px;
}

.card-desc {
  font-size: 14.5px;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 18px;
}

.card-skills-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}

.skill-pill {
  font-size: 12px;
  background: var(--accent-surface);
  color: var(--accent-text);
  padding: 4px 10px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--accent);
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  border-top: 1px solid var(--border-subtle);
}

.card-goal-preview {
  font-size: 13px;
  color: var(--text-dim);
}

.card-link-text {
  font-size: 13px;
  font-weight: 500;
  color: var(--accent);
}

/* Detail Page Layout */
.detail-section {
  margin-bottom: 44px;
}

.section-title {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-dim);
  margin-bottom: 16px;
}

.bullet-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.bullet-item {
  position: relative;
  padding-left: 24px;
  font-size: 15px;
  line-height: 1.6;
  color: var(--text-main);
}

.bullet-item::before {
  position: absolute;
  left: 0;
  top: 3px;
  content: '•';
  color: var(--accent);
  font-weight: bold;
  font-size: 18px;
  line-height: 1.2;
}

.bullet-item strong {
  font-weight: 500;
  color: var(--text-main);
}

.skills-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

/* Milestones */
.milestones-clean {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.milestone-entry {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 18px 22px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: border-color 0.15s ease;
}

.milestone-entry:hover {
  border-color: var(--border-outline);
}

.ms-index-badge {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 700;
  color: var(--accent-text);
  background: var(--accent-surface);
  padding: 3px 8px;
  border-radius: var(--radius-xs);
  flex-shrink: 0;
  margin-top: 2px;
}

.ms-body {
  flex: 1;
  min-width: 0;
}

.ms-headline {
  font-size: 15px;
  font-weight: 500;
  color: var(--text-main);
  margin-bottom: 4px;
}

.ms-description {
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.55;
}

.code-inline {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: var(--bg-container);
  color: var(--text-main);
  padding: 1px 6px;
  border-radius: var(--radius-xs);
  overflow-wrap: anywhere;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
}

.code-block {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px 18px;
  overflow-x: auto;
  line-height: 1.5;
  color: var(--text-main);
  white-space: pre;
}

.code-block code {
  font: inherit;
}

.test-criteria-clean {
  background: var(--color-green-surface);
  color: var(--color-green-text);
  border-left: 4px solid var(--color-green);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 16px 20px;
  font-size: 14px;
  line-height: 1.6;
}

.detail-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 56px;
  padding-top: 24px;
  border-top: 1px solid var(--border-subtle);
}

.nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  text-decoration: none;
  font-size: 13.5px;
  font-weight: 500;
  color: var(--accent);
  padding: 8px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  transition: all 0.15s ease;
}

.nav-btn:hover {
  background: var(--bg-container);
  border-color: var(--border-outline);
}

/* Footer */
footer.site-footer {
  margin-top: 56px;
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--text-dim);
  font-family: var(--font-mono);
}

@media (max-width: 600px) {
  header.site-header { padding: 0 20px; }
  .page-container { padding: 32px 20px 64px; }
  .hero-title { font-size: 30px; }
  .hero-index { padding: 0; }
  .stage-card { padding: 24px 20px; }
  .card-top, .card-footer, .detail-nav, footer.site-footer {
    flex-wrap: wrap;
    gap: 12px;
  }
  .milestone-entry { padding: 16px; gap: 12px; }
}