:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --ink: #1a2027;
  --ink-soft: #51606f;
  --ink-faint: #8a97a6;
  --border: #e3e8ee;
  --accent: #3b5bdb;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 4px 16px rgba(16, 24, 40, 0.06);
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

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

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }

/* ---- Top bar ---- */
.topbar {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
}
.topbar .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}
.brand { font-weight: 700; font-size: 15px; letter-spacing: -0.01em; color: var(--ink); }
.brand .dot { color: var(--accent); }
.brand small { display: block; font-weight: 500; font-size: 11px; color: var(--ink-faint); letter-spacing: 0; }
.topnav { display: flex; gap: 18px; font-size: 13px; font-weight: 500; }
.topnav a { color: var(--ink-soft); }

/* ---- Hero / intro ---- */
.hero { padding: 44px 0 8px; }
.hero h1 { font-size: 30px; line-height: 1.2; margin: 0 0 10px; letter-spacing: -0.02em; }
.hero p.lede { font-size: 16px; color: var(--ink-soft); margin: 0; max-width: 760px; }

.questions {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
  margin: 26px 0 8px;
}
.qcard {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  box-shadow: var(--shadow);
}
.qcard .qnum { font-size: 12px; font-weight: 700; color: var(--accent); }
.qcard p { margin: 4px 0 0; font-size: 14px; color: var(--ink-soft); }

/* ---- Section headings ---- */
.section { padding: 36px 0; }
.section h2 { font-size: 20px; margin: 0 0 6px; letter-spacing: -0.01em; }
.section .sub { color: var(--ink-faint); font-size: 13px; margin: 0 0 18px; }

.spine {
  font-family: var(--mono);
  font-size: 13px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  color: var(--ink-soft);
  overflow-x: auto;
}
.spine b { color: var(--ink); }

/* ---- Mermaid container ---- */
.diagram {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  overflow-x: auto;
}
.diagram .mermaid { display: flex; justify-content: center; min-height: 40px; }
.diagram-caption { font-size: 12px; color: var(--ink-faint); margin-top: 10px; text-align: center; }

/* ---- Legend ---- */
.legend { display: flex; flex-wrap: wrap; gap: 10px 18px; margin: 16px 0 0; }
.legend .item { display: flex; align-items: center; gap: 7px; font-size: 12.5px; color: var(--ink-soft); }
.legend .swatch { width: 14px; height: 14px; border-radius: 4px; border: 1px solid rgba(0,0,0,0.08); }

/* ---- Stage card grid ---- */
.grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}
.stage-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: var(--shadow);
  color: inherit;
  transition: transform 0.12s ease, box-shadow 0.12s ease;
}
.stage-card:hover {
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: 0 6px 22px rgba(16, 24, 40, 0.1);
}
.stage-card .badge {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--ink-faint);
}
.stage-card h3 { margin: 4px 0 6px; font-size: 17px; letter-spacing: -0.01em; }
.stage-card .purpose { font-size: 13.5px; color: var(--ink-soft); margin: 0 0 14px; }
.stage-card .flow { display: flex; flex-direction: column; gap: 6px; font-size: 12.5px; }
.stage-card .flow .row { display: flex; gap: 8px; }
.stage-card .flow .k {
  flex: 0 0 64px;
  font-weight: 700;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--ink-faint);
  padding-top: 1px;
}
.stage-card .flow .v { color: var(--ink-soft); }

/* ---- Stage page header ---- */
.stage-head { padding: 36px 0 8px; }
.stage-head .crumb { font-size: 12px; color: var(--ink-faint); margin-bottom: 10px; }
.stage-head .badge {
  display: inline-block;
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em;
  color: #fff; padding: 3px 9px; border-radius: 999px;
}
.stage-head h1 { font-size: 28px; margin: 12px 0 8px; letter-spacing: -0.02em; }
.stage-head p.purpose { font-size: 16px; color: var(--ink-soft); margin: 0; max-width: 760px; }

/* ---- IO panel ---- */
.io {
  display: grid;
  grid-template-columns: 1fr 1.2fr 1fr;
  gap: 16px;
  margin: 28px 0;
}
.io .col {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  box-shadow: var(--shadow);
}
.io .col h4 {
  margin: 0 0 12px;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  display: flex; align-items: center; gap: 8px;
}
.io .col.inputs h4 { color: #1565c0; }
.io .col.process h4 { color: #6a1b9a; }
.io .col.outputs h4 { color: #2e7d32; }
.io .col h4 .ico { font-size: 14px; }
.io ul { margin: 0; padding-left: 18px; }
.io li { font-size: 13.5px; color: var(--ink-soft); margin-bottom: 7px; }
.io .col.outputs li { color: var(--ink); }

.io-arrow { display: none; }

/* ---- Why callout ---- */
.why {
  background: #fffdf3;
  border: 1px solid #f4e7b8;
  border-left: 4px solid #e6b800;
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 28px 0;
}
.why h4 { margin: 0 0 6px; font-size: 13px; text-transform: uppercase; letter-spacing: 0.05em; color: #8a6d00; }
.why p { margin: 0; font-size: 14.5px; color: #5c4f1f; }

/* ---- Prev/next nav ---- */
.pager {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  margin: 40px 0 56px;
}
.pager a {
  flex: 1;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  box-shadow: var(--shadow);
  color: inherit;
}
.pager a:hover { text-decoration: none; border-color: var(--accent); }
.pager a.next { text-align: right; }
.pager a.disabled { visibility: hidden; }
.pager .dir { font-size: 11px; text-transform: uppercase; letter-spacing: 0.05em; color: var(--ink-faint); }
.pager .lbl { font-size: 15px; font-weight: 600; margin-top: 2px; }

/* ---- Playbook catalog ---- */
.pb-group { margin: 0 0 34px; }
.pb-group-head { display: flex; align-items: baseline; gap: 12px; margin: 0 0 14px; flex-wrap: wrap; }
.pb-group-head h3 { margin: 0; font-size: 17px; letter-spacing: -0.01em; }
.pb-gnum { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: #fff; background: var(--accent); padding: 3px 9px; border-radius: 999px; }
.pb-gnote { font-size: 12.5px; color: var(--ink-faint); }

.pb-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: var(--shadow);
  margin-bottom: 14px;
}
.pb-card-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.pb-arch { font-family: var(--mono); font-size: 12.5px; color: var(--accent); background: #eef2ff; padding: 2px 8px; border-radius: 6px; }
.pb-mode { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.03em; padding: 2px 8px; border-radius: 999px; }
.mode-concrete_fix { background: #e8f5e9; color: #2e7d32; }
.mode-ab_test { background: #ede7f6; color: #5e35b1; }
.mode-investigation { background: #fff3e0; color: #ef6c00; }
.mode-monitor_only, .mode-suppress { background: #eceff1; color: #546e7a; }
.pb-flag { font-size: 11px; font-weight: 600; color: #8a6d00; background: #fff8e1; border: 1px solid #f4e7b8; padding: 2px 8px; border-radius: 999px; }
.pb-card h4 { margin: 12px 0 4px; font-size: 16px; letter-spacing: -0.01em; }
.pb-desc { margin: 0 0 14px; font-size: 13.5px; color: var(--ink-soft); }

.pb-rows { display: flex; flex-direction: column; gap: 0; border-top: 1px solid var(--border); }
.pb-row { display: grid; grid-template-columns: 180px 1fr; gap: 14px; padding: 10px 0; border-bottom: 1px solid var(--border); }
.pb-row:last-child { border-bottom: none; }
.pb-k { font-size: 12px; font-weight: 700; color: var(--ink); text-transform: uppercase; letter-spacing: 0.03em; }
.pb-k .pb-sub { display: block; font-weight: 500; text-transform: none; letter-spacing: 0; color: var(--ink-faint); font-size: 11px; margin-top: 2px; }
.pb-v { display: flex; flex-wrap: wrap; gap: 6px; align-items: flex-start; }

.chip { font-family: var(--mono); font-size: 11.5px; padding: 2px 7px; border-radius: 6px; border: 1px solid transparent; }
.chip.req { background: #e3f2fd; color: #1565c0; border-color: #bbdefb; }
.chip.any { background: #e0f7fa; color: #00838f; border-color: #b2ebf2; }
.chip.strong { background: #e8f5e9; color: #2e7d32; border-color: #c8e6c9; }
.chip.excl { background: #ffebee; color: #c62828; border-color: #ffcdd2; }
.chip.soft { background: #fff8e1; color: #8a6d00; border-color: #f4e7b8; }
.chip.tpl { background: #f3e5f5; color: #6a1b9a; border-color: #e1bee7; }
.pb-v .none { color: var(--ink-faint); }
ul.pb-mech { margin: 0; padding-left: 18px; }
ul.pb-mech li { font-size: 13px; color: var(--ink-soft); margin-bottom: 4px; }

.pb-legend { display: flex; flex-wrap: wrap; gap: 8px 14px; margin: 0 0 8px; font-size: 12px; color: var(--ink-soft); }
.pb-legend .chip { cursor: default; }

/* ================= Advisor edition ================= */
.topnav a.edition, .topnav a.engineering {
  background: var(--accent); color: #fff; padding: 5px 11px; border-radius: 999px; font-size: 12px;
}
.topnav a.edition:hover, .topnav a.engineering:hover { text-decoration: none; opacity: 0.9; }

.adv-hero { padding: 44px 0 8px; }
.adv-hero h1 { font-size: 30px; margin: 0 0 12px; letter-spacing: -0.02em; }
.adv-hero p.lede { font-size: 17px; color: var(--ink-soft); margin: 0; max-width: 780px; line-height: 1.6; }
.adv-callout {
  background: #eef2ff; border: 1px solid #d7defb; border-radius: var(--radius);
  padding: 14px 18px; margin: 22px 0 0; font-size: 14.5px; color: #2a3a8c;
}
.adv-callout b { color: #1f2a6b; }

/* Steps */
.steps { display: flex; flex-direction: column; gap: 16px; }
.step { display: flex; gap: 18px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px 22px; box-shadow: var(--shadow); }
.step-num { flex: 0 0 38px; height: 38px; border-radius: 50%; color: #fff; font-weight: 700; font-size: 17px; display: flex; align-items: center; justify-content: center; }
.step-body { flex: 1; min-width: 0; }
.step-body h3 { margin: 4px 0 8px; font-size: 19px; letter-spacing: -0.01em; }
.step-plain { margin: 0 0 16px; font-size: 15px; color: var(--ink-soft); line-height: 1.6; }
.duo { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.duo-col { background: var(--bg); border: 1px solid var(--border); border-radius: 10px; padding: 12px 16px; }
.duo-col h4 { margin: 0 0 8px; font-size: 12px; text-transform: uppercase; letter-spacing: 0.04em; }
.duo-col.watches h4 { color: #1565c0; }
.duo-col.produces h4 { color: #2e7d32; }
.duo-col ul { margin: 0; padding-left: 18px; }
.duo-col li { font-size: 13.5px; color: var(--ink-soft); margin-bottom: 6px; }
.duo-col .muted { margin: 0; font-size: 13px; color: var(--ink-faint); font-style: italic; }
.step-metrics { margin-top: 14px; background: #f4f7fb; border: 1px solid #dde6f2; border-radius: 10px; padding: 12px 16px; }
.step-metrics h4 { margin: 0 0 8px; font-size: 11.5px; text-transform: uppercase; letter-spacing: 0.05em; color: #3b5572; }
.step-metrics ul { margin: 0; padding-left: 18px; }
.step-metrics li { font-size: 13px; color: #38465a; margin-bottom: 6px; line-height: 1.5; }
.step-metrics li:last-child { margin-bottom: 0; }
.step-note { margin-top: 14px; background: #fffdf3; border-left: 3px solid #e6b800; border-radius: 8px; padding: 10px 14px; font-size: 13.5px; color: #5c4f1f; }
.step-link { display: inline-block; margin-top: 14px; font-weight: 600; font-size: 14px; }

/* Confidence ladder */
.ladder { display: flex; flex-direction: column; gap: 8px; }
.ladder-row { display: grid; grid-template-columns: 200px 1fr; gap: 14px; align-items: baseline; border: 1px solid var(--border); border-left-width: 5px; border-radius: 10px; padding: 14px 16px; background: var(--surface); }
.ladder-label { font-weight: 700; font-size: 14.5px; }
.ladder-plain { font-size: 13.5px; color: var(--ink-soft); }
.ladder-tech { font-size: 12.5px; color: var(--ink-faint); margin-top: 4px; }
.c-confirmed { border-left-color: #2e7d32; }
.c-strong { border-left-color: #689F38; }
.c-plausible { border-left-color: #FB8C00; }
.c-needs { border-left-color: #90a4ae; }

/* Notify */
.notify { display: flex; flex-direction: column; gap: 8px; }
.notify-row { display: grid; grid-template-columns: 150px 1fr 200px; gap: 14px; align-items: center; border: 1px solid var(--border); border-radius: 10px; padding: 12px 16px; background: var(--surface); }
.notify-band { font-weight: 700; font-size: 14px; }
.notify-plain { font-size: 13.5px; color: var(--ink-soft); }
.notify-action { font-size: 13px; font-weight: 600; text-align: right; }
.n-full .notify-action { color: #c62828; }
.n-inapp .notify-action { color: #ef6c00; }
.n-none .notify-action { color: var(--ink-faint); }

/* Problem library */
.prob-group { margin: 0 0 32px; }
.prob-group-head { display: flex; align-items: baseline; gap: 12px; margin: 0 0 14px; flex-wrap: wrap; border-bottom: 2px solid var(--border); padding-bottom: 8px; }
.prob-group-head h3 { margin: 0; font-size: 18px; }
.prob-gnote { font-size: 13px; color: var(--ink-faint); }
.prob-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px 20px; box-shadow: var(--shadow); margin-bottom: 12px; }
.prob-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.prob-head h4 { margin: 0; font-size: 16px; }
.prob-mode { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.03em; padding: 3px 9px; border-radius: 999px; white-space: nowrap; }
.prob-desc { margin: 8px 0 10px; font-size: 14px; color: var(--ink-soft); line-height: 1.55; }
.prob-trigger { margin: 0 0 14px; font-size: 12.5px; color: #38465a; background: #f4f7fb; border: 1px solid #dde6f2; border-radius: 8px; padding: 8px 12px; line-height: 1.5; }
.prob-trigger .pt-k { font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; font-size: 11px; color: #3b5572; margin-right: 6px; }
.prob-duo { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.prob-duo h5 { margin: 0 0 6px; font-size: 12px; text-transform: uppercase; letter-spacing: 0.04em; color: var(--ink-faint); }
.prob-duo ul { margin: 0; padding-left: 18px; }
.prob-duo li { font-size: 13.5px; color: var(--ink-soft); margin-bottom: 5px; }

footer.site {
  border-top: 1px solid var(--border);
  padding: 24px 0;
  font-size: 12.5px;
  color: var(--ink-faint);
}
footer.site code { font-family: var(--mono); }

@media (max-width: 820px) {
  .questions { grid-template-columns: 1fr; }
  .grid { grid-template-columns: 1fr; }
  .io { grid-template-columns: 1fr; }
  .pb-row { grid-template-columns: 1fr; gap: 6px; }
  .duo, .prob-duo { grid-template-columns: 1fr; }
  .ladder-row { grid-template-columns: 1fr; gap: 4px; }
  .notify-row { grid-template-columns: 1fr; gap: 4px; }
  .notify-action { text-align: left; }
  .step { flex-direction: column; gap: 12px; }
}