:root {
  color-scheme: dark;
  --page: #121212;
  --surface: #1a1a19;
  --raised: #212120;
  --ink: #f4f4f2;
  --ink-2: #c3c2b7;
  --muted: #8f8d86;
  --grid: #2c2c2a;
  --axis: #43433f;
  --line: rgba(255, 255, 255, 0.1);
  --accent: #7aa7ff;
  --accent-hover: #9dbfff;
  --on-accent: #0e1a33;
  --s1: #3987e5;
  --s2: #d95926;
  --s3: #199e70;
  --s4: #c98500;
  --s5: #d55181;
  --s6: #8a6cf0;
  --good: #0ca30c;
  --good-ink: #3fc13f;
  --warn-ink: #e0a526;
  --critical: #e25555;
  --good-bg: rgba(12, 163, 12, 0.14);
  --warn-bg: rgba(201, 133, 0, 0.16);
  --bad-bg: rgba(226, 85, 85, 0.16);
  --new-bg: rgba(122, 167, 255, 0.14);
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --radius: 10px;
}

* { box-sizing: border-box; }
html { scroll-padding-top: 4rem; }
body {
  margin: 0;
  background: var(--page);
  color: var(--ink);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  -webkit-text-size-adjust: 100%;
}
a { color: var(--accent); }
a:hover { color: var(--accent-hover); }
h1, h2, h3 { line-height: 1.2; margin: 0; }
p { margin: 0 0 0.85em; }
code { font-family: var(--mono); font-size: 0.88em; background: var(--raised); padding: 0.05em 0.3em; border-radius: 4px; }
[hidden] { display: none !important; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: color-mix(in srgb, var(--page) 88%, transparent);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: 76rem;
  margin: 0 auto;
  padding: 0 1rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  height: 3.25rem;
}
.brand {
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.brand:hover { color: var(--ink); }
.brand svg { color: var(--accent); }
.topnav {
  display: flex;
  gap: 0.25rem;
  overflow-x: auto;
  scrollbar-width: none;
  margin-left: auto;
}
.topnav::-webkit-scrollbar { display: none; }
.topnav a {
  color: var(--ink-2);
  text-decoration: none;
  font-size: 0.9rem;
  padding: 0.35rem 0.7rem;
  border-radius: 6px;
  white-space: nowrap;
}
.topnav a:hover { color: var(--ink); background: var(--raised); }
.topnav a.active { color: var(--ink); background: var(--raised); box-shadow: inset 0 0 0 1px var(--line); }
.topnav .n { color: var(--muted); margin-right: 0.3rem; font-variant-numeric: tabular-nums; }

main { max-width: 76rem; margin: 0 auto; padding: 1.5rem 1rem 3rem; }

/* ---------- home ---------- */
.hero { padding: 2.5rem 0 2rem; max-width: 46rem; }
.hero h1 { font-size: clamp(1.9rem, 4.5vw, 2.8rem); letter-spacing: -0.02em; margin-bottom: 1rem; }
.hero p { font-size: 1.1rem; color: var(--ink-2); }
.cards {
  list-style: none;
  padding: 0;
  margin: 0 0 2rem;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(17rem, 1fr));
  gap: 1rem;
}
.card {
  position: relative;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  transition: border-color 0.15s;
}
.card:hover, .card:focus-within { border-color: var(--accent); }
.card h2 { font-size: 1.15rem; margin-bottom: 0.5rem; }
.card h2 a { color: var(--ink); text-decoration: none; }
.card h2 a::after { content: ""; position: absolute; inset: 0; border-radius: var(--radius); }
.card p { color: var(--ink-2); font-size: 0.95rem; flex: 1; }
.card .tech { font-size: 0.85rem; color: var(--muted); margin: 0; flex: none; }
.kicker {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 0.5rem;
}
.card .kicker { flex: none; margin-bottom: 0.4rem; }
.disclaimer {
  border-left: 3px solid var(--axis);
  padding: 0.25rem 0 0.25rem 1rem;
  color: var(--ink-2);
  font-size: 0.92rem;
  max-width: 46rem;
}

/* ---------- chapter ---------- */
.chapter-head { max-width: 50rem; padding: 1rem 0 1.25rem; border-bottom: 1px solid var(--line); margin-bottom: 1.5rem; }
.chapter-head h1 { font-size: clamp(1.6rem, 3.6vw, 2.2rem); letter-spacing: -0.015em; margin-bottom: 0.6rem; }
.chapter-head .lede { color: var(--ink-2); font-size: 1.05rem; margin: 0; }

.step-grid {
  display: grid;
  grid-template-columns: minmax(0, 20rem) minmax(0, 1fr);
  gap: 1.75rem;
  align-items: start;
}
.step-grid + .step-grid { margin-top: 2.5rem; padding-top: 2rem; border-top: 1px solid var(--line); }
.prose h2 { font-size: 1.35rem; margin-bottom: 0.8rem; color: var(--ink); }
.prose { color: var(--ink-2); font-size: 0.97rem; }
.prose strong { color: var(--ink); }
.prose ul { padding-left: 1.1rem; margin: 0 0 0.85em; }
.prose li { margin-bottom: 0.35em; }
.try {
  background: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 8px;
  padding: 0.75rem 0.9rem;
  margin: 1rem 0;
  color: var(--ink);
}
.try b:first-child { display: block; font-size: 0.78rem; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); margin-bottom: 0.25rem; }
.stage { display: flex; flex-direction: column; gap: 1rem; min-width: 0; }
.panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.9rem 1rem 1rem;
  min-width: 0;
}
.panel-title { font-size: 0.92rem; font-weight: 600; color: var(--ink); margin: 0 0 0.2rem; }
.panel-sub { font-size: 0.82rem; color: var(--muted); margin: 0 0 0.6rem; }
.row { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.row.r3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.chapter-foot {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
}

/* ---------- controls ---------- */
.controls { display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center; }
.controls + .controls { margin-top: 0.6rem; }
.btn {
  appearance: none;
  font: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.45rem 0.9rem;
  border-radius: 7px;
  border: 1px solid var(--line);
  background: var(--raised);
  color: var(--ink);
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  white-space: nowrap;
  min-height: 2.25rem;
}
.btn:hover { border-color: var(--axis); color: var(--ink); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.btn.primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); color: var(--on-accent); }
.btn.ghost { background: transparent; }
.btn.danger { border-color: rgba(226, 85, 85, 0.5); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; padding: 2px; background: var(--page); flex-wrap: wrap; }
.seg button {
  appearance: none;
  font: inherit;
  font-size: 0.85rem;
  border: 0;
  background: transparent;
  color: var(--ink-2);
  padding: 0.35rem 0.7rem;
  border-radius: 6px;
  cursor: pointer;
  min-height: 2rem;
}
.seg button[aria-pressed="true"] { background: var(--raised); color: var(--ink); box-shadow: 0 0 0 1px var(--line); font-weight: 600; }
.ctl { display: grid; grid-template-columns: 1fr auto; gap: 0.1rem 0.75rem; align-items: baseline; font-size: 0.88rem; color: var(--ink-2); }
.ctl input[type="range"] { grid-column: 1 / -1; width: 100%; accent-color: var(--accent); margin: 0.2rem 0 0; }
.ctl output { font-variant-numeric: tabular-nums; color: var(--ink); font-weight: 600; }
.ctls { display: grid; grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr)); gap: 0.8rem 1.25rem; }
.check { display: inline-flex; align-items: center; gap: 0.45rem; font-size: 0.88rem; color: var(--ink-2); cursor: pointer; }
.check input { accent-color: var(--accent); width: 1rem; height: 1rem; }
.checks { display: grid; grid-template-columns: repeat(auto-fill, minmax(14rem, 1fr)); gap: 0.4rem 1rem; }
select {
  font: inherit;
  font-size: 0.88rem;
  background: var(--page);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 0.4rem 0.5rem;
  min-height: 2.25rem;
  max-width: 100%;
}
.lbl { font-size: 0.82rem; color: var(--muted); }

/* ---------- readouts ---------- */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(7.5rem, 1fr)); gap: 0.6rem; }
.stat { background: var(--page); border-radius: 8px; padding: 0.5rem 0.7rem; min-width: 0; }
.stage > .stats .stat { background: var(--surface); border: 1px solid var(--line); }
.stat-label { display: block; font-size: 0.76rem; color: var(--muted); }
.stat-value { display: block; font-size: 1.25rem; font-weight: 600; color: var(--ink); font-variant-numeric: tabular-nums; }
.stat-note { display: block; font-size: 0.75rem; color: var(--muted); }
.code {
  font-family: var(--mono);
  font-size: 0.8rem;
  background: var(--page);
  border-radius: 8px;
  padding: 0.6rem 0.75rem;
  color: var(--ink-2);
  line-height: 1.55;
  overflow-x: auto;
  white-space: pre;
  margin: 0;
}
.code .kw { color: var(--accent); }
.callout { font-size: 0.88rem; color: var(--ink-2); margin: 0.6rem 0 0; }
.msg { font-size: 0.88rem; border-radius: 8px; padding: 0.55rem 0.75rem; margin: 0; background: var(--page); color: var(--ink-2); }
.msg.good { background: var(--good-bg); color: var(--ink); }
.msg.bad { background: var(--bad-bg); color: var(--ink); }
.msg.warn { background: var(--warn-bg); color: var(--ink); }
.good-text { color: var(--good-ink); font-weight: 600; }
.bad-text { color: var(--critical); font-weight: 600; }
.warn-text { color: var(--warn-ink); font-weight: 600; }

.legend { display: flex; flex-wrap: wrap; gap: 0.35rem 1rem; font-size: 0.82rem; color: var(--ink-2); margin: 0 0 0.5rem; }
.legend span { display: inline-flex; align-items: center; gap: 0.4rem; }
.sw { width: 10px; height: 10px; border-radius: 2px; display: inline-block; flex: none; }

/* ---------- tables ---------- */
.tbl-wrap { overflow-x: auto; -webkit-overflow-scrolling: touch; }
table.data { width: 100%; border-collapse: collapse; font-size: 0.84rem; font-variant-numeric: tabular-nums; }
table.data th, table.data td { text-align: left; padding: 0.3rem 0.5rem; border-bottom: 1px solid var(--line); white-space: nowrap; }
table.data th { font-weight: 600; color: var(--muted); font-size: 0.76rem; }
table.data td.num, table.data th.num { text-align: right; }
table.data tr.good td { background: var(--good-bg); }
table.data tr.bad td { background: var(--bad-bg); }
table.data tr.warn td { background: var(--warn-bg); }
table.data tr.new td { background: var(--new-bg); }
table.data tr.dim td { color: var(--muted); }
table.data tr.strike td { color: var(--muted); text-decoration: line-through; }
table.data td.bad-cell { color: var(--critical); font-weight: 600; }
table.data td.empty { color: var(--muted); font-style: italic; text-align: center; }
.tag { display: inline-block; font-size: 0.72rem; font-weight: 600; padding: 0.05rem 0.4rem; border-radius: 4px; background: var(--raised); color: var(--ink-2); margin-right: 0.2rem; }
.tag.bad { background: var(--bad-bg); color: #ff9a9a; }
.tag.good { background: var(--good-bg); color: var(--good-ink); }
.tag.warn { background: var(--warn-bg); color: var(--warn-ink); }

/* ---------- ch1 pipeline lanes ---------- */
.lanes { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0.75rem; }
.lane { background: var(--page); border: 1px solid var(--line); border-radius: 8px; padding: 0.6rem; min-width: 0; }
.lane.active { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent); }
.lane h3 { font-size: 0.85rem; margin: 0 0 0.15rem; }
.lane .panel-sub { margin-bottom: 0.4rem; }
.flow { display: flex; flex-wrap: wrap; gap: 0.35rem; align-items: center; margin-bottom: 0.8rem; font-size: 0.85rem; }
.flow .st { padding: 0.25rem 0.6rem; border-radius: 999px; border: 1px solid var(--line); color: var(--muted); }
.flow .st.done { color: var(--ink); border-color: var(--axis); }
.flow .st.now { color: var(--on-accent); background: var(--accent); border-color: var(--accent); font-weight: 600; }
.flow .arr { color: var(--muted); }

/* ---------- ch2 timeline canvas ---------- */
.timeline { width: 100%; display: block; background: var(--page); border-radius: 8px; }

/* ---------- ch5 schema diagram ---------- */
.schema svg { width: 100%; height: auto; display: block; }
.schema .tbox rect { fill: var(--page); stroke: var(--axis); stroke-width: 1.2; }
.schema .tbox text { fill: var(--ink-2); font: 12px system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
.schema .tbox text.tn { fill: var(--ink); font-weight: 600; font-size: 13px; }
.schema .tbox.fact rect { stroke-dasharray: 0; }
.schema .tbox.hit rect { stroke: var(--accent); stroke-width: 2.4; fill: color-mix(in srgb, var(--accent) 12%, var(--page)); }
.schema .edge { stroke: var(--axis); stroke-width: 1.5; fill: none; }
.schema .edge.hit { stroke: var(--accent); stroke-width: 3; }

/* ---------- ch7 storage blocks ---------- */
.files { display: flex; flex-wrap: wrap; gap: 0.6rem; }
.file { background: var(--page); border: 1px solid var(--line); border-radius: 6px; padding: 0.35rem 0.4rem 0.45rem; }
.file.skipped { opacity: 0.35; border-style: dashed; }
.file .fname { font-family: var(--mono); font-size: 0.7rem; color: var(--muted); margin-bottom: 0.25rem; white-space: nowrap; }
.cells { display: grid; gap: 2px; }
.cell { width: 11px; height: 11px; border-radius: 2px; opacity: 0.22; }
.cell.read { opacity: 1; box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.35); }

/* ---------- ch9 DAG ---------- */
.dag svg { width: 100%; height: auto; display: block; }
.dag .node { cursor: pointer; }
.dag .node rect { fill: var(--page); stroke: var(--axis); stroke-width: 1.4; }
.dag .node text { fill: var(--ink); font: 12px var(--mono); pointer-events: none; }
.dag .node text.st { fill: var(--muted); font: 10.5px system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
.dag .node.running rect { stroke: var(--accent); stroke-width: 2.4; }
.dag .node.success rect { stroke: var(--good); fill: var(--good-bg); }
.dag .node.failed rect { stroke: var(--critical); fill: var(--bad-bg); stroke-width: 2.2; }
.dag .node.upstream_failed rect { stroke: var(--warn-ink); fill: var(--warn-bg); stroke-dasharray: 4 3; }
.dag .node.up_for_retry rect { stroke: var(--warn-ink); stroke-width: 2.2; }
.dag .node.queued rect { stroke: var(--ink-2); stroke-dasharray: 2 2; }
.dag .node .flag { fill: var(--critical); }
.dag .edge { stroke: var(--axis); stroke-width: 1.4; fill: none; marker-end: url(#dag-arrow); }
.grid-runs { display: grid; gap: 3px; font-size: 0.75rem; align-items: center; }
.grid-runs .gl { font-family: var(--mono); color: var(--ink-2); white-space: nowrap; padding-right: 0.4rem; overflow: hidden; text-overflow: ellipsis; }
.grid-runs .gh { color: var(--muted); text-align: center; font-size: 0.68rem; white-space: nowrap; }
.grid-runs .gc { height: 16px; border-radius: 3px; background: var(--grid); }
.gc.success { background: var(--good); }
.gc.failed { background: var(--critical); }
.gc.upstream_failed { background: var(--warn-ink); }
.gc.running, .gc.queued, .gc.up_for_retry { background: var(--accent); }

/* ---------- wrap-up ---------- */
.checklist { list-style: none; padding: 0; margin: 0 0 2rem; display: grid; grid-template-columns: repeat(auto-fill, minmax(18rem, 1fr)); gap: 1rem; }
.checklist li { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 1rem 1.1rem; color: var(--ink-2); font-size: 0.95rem; }
.checklist h3 { font-size: 1rem; color: var(--ink); margin-bottom: 0.4rem; }
.checklist p:last-child { margin: 0; }
.section-h { font-size: 1.3rem; margin: 0 0 1rem; }

footer.site {
  max-width: 76rem;
  margin: 0 auto;
  padding: 1.25rem 1rem 2.5rem;
  border-top: 1px solid var(--line);
  text-align: center;
  font-size: 0.85rem;
  color: var(--muted);
}

@media (max-width: 980px) {
  .step-grid { grid-template-columns: minmax(0, 1fr); gap: 1.25rem; }
  .prose { max-width: 42rem; }
}
@media (max-width: 640px) {
  main { padding-top: 1rem; }
  .row, .row.r3, .lanes { grid-template-columns: minmax(0, 1fr); }
  .brand span { display: none; }
  .panel { padding: 0.75rem; }
  .hero { padding-top: 1.25rem; }
}
@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}
@media (min-width: 981px) and (max-width: 1150px) {
  .lanes { grid-template-columns: minmax(0, 1fr); }
}