:root {
  --bg: #0a0a0a;
  --fg: #d4d4d4;
  --fg-bright: #f5f5f5;
  --muted: #8a8a8a;
  --accent: #e5e5e5;
  --accent-dim: #a3a3a3;
  --surface: #141414;
  --border: #262626;
  --border-bright: #404040;
  --max-w: 52rem;
  --serif: "Playfair Display", Georgia, serif;
  --sans: "Source Sans 3", "Noto Sans SC", sans-serif;
  --mono: "JetBrains Mono", "SF Mono", monospace;
  --ease: cubic-bezier(0.16, 1, 0.3, 1);
  --timeline-col: 8.5rem;
  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #fafaf9;
    --fg: #292524;
    --fg-bright: #0c0a09;
    --muted: #78716c;
    --accent: #0c0a09;
    --accent-dim: #78716c;
    --surface: #f5f5f4;
    --border: #e7e5e4;
    --border-bright: #d6d3d1;
  }
}

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

html { scroll-behavior: smooth; }

::selection {
  background: var(--accent-dim);
  color: var(--fg-bright);
}

body {
  font-family: var(--sans);
  font-size: 16px;
  font-weight: 400;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.7;
  padding: 3rem 1.5rem;
  max-width: var(--max-w);
  margin: 0 auto;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 {
  font-family: var(--serif);
  color: var(--fg-bright);
  font-weight: 400;
  letter-spacing: -0.01em;
}

h1 {
  font-size: 2.4rem;
  line-height: 1.15;
  margin-top: 0;
  margin-bottom: var(--space-sm);
}

h2 {
  font-size: 1.6rem;
  line-height: 1.25;
  margin-top: var(--space-lg);
  margin-bottom: var(--space-sm);
  scroll-margin-top: var(--space-lg);
}

h3 {
  font-size: 1.1rem;
  line-height: 1.4;
  margin-top: var(--space-lg);
  margin-bottom: var(--space-xs);
  scroll-margin-top: var(--space-lg);
}

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

a:hover {
  color: var(--fg-bright);
}

.page-content a {
  text-decoration: underline;
  text-decoration-color: var(--border-bright);
  text-underline-offset: 0.15em;
}

.page-content a:hover {
  text-decoration-color: var(--accent);
}

p { margin-bottom: var(--space-md); }

strong { color: var(--fg-bright); font-weight: 500; }

code {
  font-family: var(--mono);
  font-size: 0.9em;
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 0.15em 0.4em;
  border-radius: 3px;
}

pre {
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 1.25rem;
  border-radius: 4px;
  overflow-x: auto;
  margin-bottom: 1.5em;
  line-height: 1.6;
}

pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.85em;
}

ul, ol {
  padding-left: 1.5em;
  margin-bottom: var(--space-md);
}

li {
  margin-bottom: 0.4em;
}

li::marker {
  color: var(--muted);
}

/* --- Site Header --- */

.site-header {
  margin-bottom: 4rem;
  padding-bottom: 2rem;
  border-bottom: 2px solid var(--border-bright);
}

.header-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

.site-header h1 {
  font-size: 3rem;
  letter-spacing: -0.03em;
  margin-bottom: 0.25rem;
}

.tagline {
  font-size: 0.85rem;
  color: var(--muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

/* --- Language Toggle --- */

.lang-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.3em;
  padding: 0.3em 0.7em;
  border: 1px solid var(--border);
  border-radius: 3px;
  font-family: var(--mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--muted);
  transition: all 0.2s var(--ease);
}

.lang-toggle:hover {
  color: var(--fg-bright);
  border-color: var(--accent);
  background: var(--surface);
}

/* --- Page Header --- */

.breadcrumbs {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  margin-bottom: 1.5rem;
  letter-spacing: 0.02em;
}

.breadcrumbs a {
  color: var(--muted);
}

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

.breadcrumbs .sep {
  margin: 0 0.4em;
  opacity: 0.5;
}

.page-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-md);
  border-bottom: 1px solid var(--border-bright);
}

.last-updated {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  letter-spacing: 0.02em;
}

.last-updated:empty { display: none; }

.heading-anchor {
  opacity: 0;
  position: absolute;
  left: -1.2em;
  color: var(--muted);
  text-decoration: none;
  font-weight: 400;
  transition: opacity 0.15s var(--ease);
}

.page-content h2,
.page-content h3 { position: relative; }

h2:hover .heading-anchor,
h3:hover .heading-anchor,
.heading-anchor:focus-visible { opacity: 1; }

.heading-anchor:hover { color: var(--accent); }

.page-content { max-width: 42rem; }

.page-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}

.page-footer a {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}

.page-footer a:hover {
  color: var(--accent);
}

/* --- Header Actions --- */

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.contribute-link {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}

.contribute-link:hover {
  color: var(--accent);
}

/* --- Sections (Index) --- */

.quickstart {
  margin-bottom: 3.5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

.quickstart h2 {
  text-transform: uppercase;
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  color: var(--accent);
  border-top: none;
  padding-top: 0;
  margin-top: 0;
  margin-bottom: 0.75rem;
}

.quickstart-desc {
  color: var(--fg);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.quickstart-hint {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 0.75rem;
  margin-bottom: 0;
}

.prompt-block {
  position: relative;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 4px;
  overflow: hidden;
}

.prompt-block pre {
  margin: 0;
  border: none;
  border-radius: 0;
  padding: 1.25rem;
  padding-right: 4rem;
  max-height: 12rem;
  overflow-y: auto;
  white-space: pre-wrap;
  word-break: break-word;
}

.prompt-block code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.8rem;
  line-height: 1.6;
  color: var(--fg);
}

.copy-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  background: var(--bg);
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.25rem 0.6rem;
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.05em;
  cursor: pointer;
  transition: all 0.15s var(--ease);
  z-index: 1;
}

.copy-btn:hover {
  color: var(--fg-bright);
  border-color: var(--accent);
}

.copy-btn.copied {
  color: var(--accent);
  border-color: var(--accent);
}

.section {
  margin-bottom: 2.5rem;
}

.section h2 {
  text-transform: uppercase;
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  color: var(--muted);
  border-top: none;
  padding-top: 0;
  margin-top: 0;
  margin-bottom: 1rem;
}

.section ul {
  list-style: none;
  padding-left: 0;
}

.section li {
  margin-bottom: 0;
}

.section li a {
  display: block;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--border);
  color: var(--fg);
  font-family: var(--serif);
  font-size: 1.15rem;
  transition: all 0.15s var(--ease);
}

.section li a:hover {
  color: var(--accent);
  padding-left: 0.5rem;
}

/* --- Timeline --- */

.timeline {
  margin-bottom: 3.5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

.timeline h2 {
  text-transform: uppercase;
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  color: var(--accent);
  border-top: none;
  padding-top: 0;
  margin-top: 0;
  margin-bottom: 1.5rem;
}

.timeline-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: var(--border-bright) transparent;
  padding: 0 1rem 0.5rem;
}

.timeline-track {
  display: grid;
  grid-template-rows: 1fr auto auto auto 1fr;
  grid-auto-columns: var(--timeline-col);
  width: max-content;
  position: relative;
}

.timeline-track::before {
  content: '';
  position: absolute;
  top: 50%;
  left: calc(var(--timeline-col) / 2);
  right: calc(var(--timeline-col) / 2);
  height: 2px;
  background: var(--border-bright);
  transform: translateY(-50%);
  z-index: 0;
}

.timeline-node {
  display: contents;
}

.timeline-card {
  display: flex;
  flex-direction: column;
  text-align: center;
  padding: 0.4rem 0.25rem;
  position: relative;
}

.timeline-node.above .timeline-card {
  grid-row: 1;
  justify-content: flex-end;
}

.timeline-node.below .timeline-card {
  grid-row: 5;
  justify-content: flex-start;
}

.timeline-dot {
  grid-row: 3;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg);
  justify-self: center;
  align-self: center;
  position: relative;
  z-index: 2;
}


.timeline-stem {
  width: 2px;
  background: var(--border-bright);
  justify-self: center;
  min-height: 1.5rem;
}

.timeline-node.above .timeline-stem {
  grid-row: 2;
}

.timeline-node.below .timeline-stem {
  grid-row: 4;
}

.timeline-year {
  display: block;
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--accent);
  letter-spacing: 0.08em;
  margin-bottom: 0.2rem;
}

.timeline-card h3 {
  font-family: var(--serif);
  font-size: 0.9rem;
  text-transform: none;
  letter-spacing: normal;
  color: var(--fg-bright);
  margin: 0 0 0.2rem;
  line-height: 1.3;
}

.timeline-credit a {
  color: var(--muted);
  text-decoration: underline;
  text-decoration-color: var(--border);
  text-underline-offset: 0.15em;
  transition: color 0.15s var(--ease), text-decoration-color 0.15s var(--ease);
}

.timeline-credit a:hover {
  color: var(--fg-bright);
  text-decoration-color: var(--fg-bright);
}

.timeline-credit {
  display: block;
  font-family: var(--mono);
  font-size: 0.6rem;
  color: var(--muted);
  letter-spacing: 0.02em;
}

.timeline-info {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 14px;
  height: 14px;
  margin-left: 0.3em;
  border-radius: 50%;
  border: 1px solid var(--border-bright);
  font-size: 0.5rem;
  font-style: italic;
  color: var(--muted);
  cursor: help;
  position: relative;
  vertical-align: middle;
  transition: border-color 0.2s var(--ease), color 0.2s var(--ease);
}

.timeline-info:hover,
.timeline-info:focus-visible {
  border-color: var(--accent);
  color: var(--accent);
}

.timeline-tip {
  visibility: hidden;
  opacity: 0;
  position: absolute;
  left: 50%;
  transform: translateX(-50%) translateY(4px);
  width: 200px;
  padding: 0.5rem 0.6rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 4px;
  font-size: 0.7rem;
  font-style: normal;
  color: var(--fg);
  line-height: 1.45;
  text-align: left;
  z-index: 10;
  pointer-events: none;
  transition: opacity 0.2s var(--ease), transform 0.2s var(--ease), visibility 0.2s;
}

.timeline-tip::before {
  content: '';
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  border: 5px solid transparent;
}

.timeline-node.above .timeline-tip {
  top: calc(100% + 6px);
}

.timeline-node.above .timeline-tip::before {
  bottom: 100%;
  border-bottom-color: var(--border);
}

.timeline-node.below .timeline-tip {
  bottom: calc(100% + 6px);
  transform: translateX(-50%) translateY(-4px);
}

.timeline-node.below .timeline-tip::before {
  top: 100%;
  border-top-color: var(--border);
}

.edge-start .timeline-tip {
  left: -0.5rem;
  transform: translateX(0) translateY(4px);
}

.edge-start .timeline-tip::before {
  left: 1rem;
  transform: none;
}

.edge-end .timeline-tip {
  left: auto;
  right: -0.5rem;
  transform: translateX(0) translateY(4px);
}

.edge-end .timeline-tip::before {
  left: auto;
  right: 1rem;
  transform: none;
}

.timeline-node.below .edge-start .timeline-tip {
  transform: translateX(0) translateY(-4px);
}

.timeline-node.below .edge-end .timeline-tip {
  transform: translateX(0) translateY(-4px);
}

.timeline-info:hover .timeline-tip,
.timeline-info:focus-visible .timeline-tip {
  visibility: visible;
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

.edge-start .timeline-info:hover .timeline-tip,
.edge-start .timeline-info:focus-visible .timeline-tip {
  transform: translateX(0) translateY(0);
}

.edge-end .timeline-info:hover .timeline-tip,
.edge-end .timeline-info:focus-visible .timeline-tip {
  transform: translateX(0) translateY(0);
}

/* --- Footer --- */

.site-footer {
  margin-top: 5rem;
  padding-top: 1.5rem;
  font-size: 0.75rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}

.site-footer a {
  text-decoration: underline;
  text-decoration-color: var(--border-bright);
  text-underline-offset: 0.15em;
}

.footer-rule {
  width: 100%;
  height: 1px;
  background: var(--border-bright);
  margin-bottom: 1rem;
}

/* --- Responsive --- */

@media (max-width: 640px) {
  body { padding: 2rem 1rem; }
  .site-header h1 { font-size: 2.2rem; }
  h1 { font-size: 1.8rem; }
  .page-header { flex-direction: column; gap: 1rem; }

  .timeline-scroll {
    overflow-x: visible;
  }

  .timeline-track {
    display: flex;
    flex-direction: column;
    padding-left: 1.5rem;
    position: relative;
    width: auto;
    min-width: 0;
  }

  .timeline-track::before {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    left: 1.5rem;
    width: 2px;
    background: var(--border-bright);
  }

  .timeline-node {
    display: block;
    position: relative;
    padding: 1rem 0 1rem 1.5rem;
  }

  .timeline-dot {
    position: absolute;
    left: -5px;
    top: 1.25rem;
  }

  .timeline-dot::before { display: none; }

  .timeline-stem { display: none; }

  .timeline-card {
    text-align: left;
    padding: 0;
  }

  .timeline-tip {
    visibility: visible;
    opacity: 1;
    position: static;
    transform: none;
    width: auto;
    padding: 0;
    background: none;
    border: none;
    border-radius: 0;
    margin-top: 0.25rem;
    color: var(--muted);
    pointer-events: auto;
    display: block;
  }

  .timeline-tip::before { display: none; }

  .timeline-info {
    display: none;
  }
}