/* ————————————————————————————————————————————————
   Engine docs — same tokens and motion language as the landing page
   (docs/30-Design-System.md v2.0). Source of truth: apps/web/docs.css,
   copied into apps/web/docs/ by build-docs.mjs.
   ———————————————————————————————————————————————— */

:root {
  --accent: #2f6feb;
  --accent-wash: #eef3fe;
  --good: #1a7f52;
  --warn: #b4690e;
  --bg: #f7f8fa;
  --surface: #ffffff;
  --surface-2: #f1f2f4;
  --text: #1a1d21;
  --muted: #616a75;
  --faint: #8b95a1;
  --border: #e4e7eb;
  --border-strong: #d3d8de;

  --serif: "Instrument Serif", Georgia, "Times New Roman", serif;
  --sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;

  --ease-out: cubic-bezier(0.23, 1, 0.32, 1);
  --ease-out-quint: cubic-bezier(0.22, 1, 0.36, 1);
  --ease-in-out: cubic-bezier(0.77, 0, 0.175, 1);

  --z-bg: 0; --z-content: 10; --z-nav: 20;
}

:root[data-theme="dark"] {
  --accent: #4d84ff;
  --accent-wash: #16223c;
  --good: #3fb27f;
  --warn: #d99a3c;
  --bg: #0d0f12;
  --surface: #16181d;
  --surface-2: #1d2026;
  --text: #e7e9ec;
  --muted: #9aa2ad;
  --faint: #6b7480;
  --border: #262a31;
  --border-strong: #333842;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100svh;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
  transition: background 320ms var(--ease-out), color 320ms var(--ease-out);
}

a { color: inherit; }

:focus-visible {
  outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px;
}

.progress {
  position: fixed; top: 0; left: 0; right: 0; height: 2px;
  transform-origin: 0 50%; transform: scaleX(0);
  background: var(--accent); z-index: var(--z-nav); opacity: 0.9;
}
@supports (animation-timeline: scroll()) {
  .progress { animation: grow linear both; animation-timeline: scroll(root block); }
  @keyframes grow { to { transform: scaleX(1); } }
}

.shell {
  position: relative; z-index: var(--z-content);
  min-height: 100svh;
  display: flex; flex-direction: column;
  max-width: 1120px; margin: 0 auto;
  padding: clamp(20px, 4vw, 36px);
}

/* ———————— top bar ———————— */
.doc-top {
  display: flex; align-items: center; gap: 16px;
  flex-wrap: wrap;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}
.wordmark {
  font-family: var(--serif); font-size: 26px; letter-spacing: 0.01em;
  line-height: 1; display: inline-flex; align-items: baseline; gap: 8px;
  text-decoration: none;
}
.wordmark .dot {
  width: 7px; height: 7px; border-radius: 50%; background: var(--accent);
  transform: translateY(-2px);
  animation: pulse 3.4s var(--ease-out) infinite;
}
@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 0 color-mix(in oklab, var(--accent) 55%, transparent); }
  50% { box-shadow: 0 0 0 6px color-mix(in oklab, var(--accent) 0%, transparent); }
}

.doc-nav {
  display: flex; align-items: center; gap: 4px;
  margin-left: auto; flex-wrap: wrap;
}
.doc-nav-link {
  font-size: 13.5px; color: var(--muted); text-decoration: none;
  padding: 6px 11px; border-radius: 8px;
  transition: color 160ms var(--ease-out), background 160ms var(--ease-out);
}
.doc-nav-link:hover { color: var(--text); background: var(--surface-2); }
.doc-nav-link.on { color: var(--accent); background: var(--accent-wash); }

.toggle {
  appearance: none; cursor: pointer; flex: none;
  width: 34px; height: 34px; border-radius: 9px;
  border: 1px solid var(--border); background: var(--surface);
  color: var(--muted); display: grid; place-items: center;
  transition: transform 160ms var(--ease-out), border-color 160ms var(--ease-out), color 160ms var(--ease-out);
}
.toggle:hover { color: var(--text); border-color: var(--border-strong); }
.toggle:active { transform: scale(0.94); }
.toggle svg { width: 17px; height: 17px; }
.toggle .moon { display: none; }
:root[data-theme="dark"] .toggle .sun { display: none; }
:root[data-theme="dark"] .toggle .moon { display: block; }

/* ———————— page ———————— */
.doc-main {
  flex: 1;
  padding: clamp(32px, 6vh, 64px) 0 clamp(40px, 8vh, 80px);
  animation: soft-in 620ms var(--ease-out) both;
}
@keyframes soft-in { from { opacity: 0; transform: translateY(8px); } }

.kicker {
  font-family: var(--mono); font-size: 12px; letter-spacing: 0.04em;
  color: var(--accent); margin: 0 0 18px;
  display: inline-flex; align-items: center; gap: 9px;
}
.kicker::before {
  content: ""; width: 22px; height: 1px; background: var(--accent);
  display: inline-block;
}

.doc-h1 {
  font-family: var(--serif); font-weight: 400;
  font-size: clamp(2.2rem, 5.5vw, 3.4rem);
  line-height: 1.02; letter-spacing: -0.02em;
  margin: 0 0 18px; text-wrap: balance;
}
.doc-lede {
  font-size: clamp(1rem, 1.4vw, 1.13rem); color: var(--muted);
  line-height: 1.62; max-width: 62ch; margin: 0;
}
.doc-note { font-size: 13.5px; color: var(--faint); }

.back {
  display: block; width: fit-content; margin-bottom: 22px;
  font-family: var(--mono); font-size: 12px; color: var(--muted);
  text-decoration: none;
  transition: color 160ms var(--ease-out);
}
.back:hover { color: var(--accent); }

.rule { border: 0; border-top: 1px solid var(--border); margin: 36px 0; }

/* ———————— long-form prose ———————— */
.prose { max-width: 74ch; }
.prose h2 {
  font-family: var(--serif); font-weight: 400;
  font-size: clamp(1.5rem, 2.8vw, 2rem); line-height: 1.16;
  letter-spacing: -0.015em;
  margin: 52px 0 14px; text-wrap: balance;
  scroll-margin-top: 24px;
}
.prose h3 {
  font-size: 15px; font-weight: 600; letter-spacing: 0.01em;
  color: var(--muted);
  margin: 30px 0 10px;
  text-transform: uppercase; letter-spacing: 0.06em; font-size: 12px;
  font-family: var(--mono);
}
.prose p { margin: 0 0 16px; color: var(--muted); line-height: 1.68; }
.prose li { margin: 0 0 10px; color: var(--muted); line-height: 1.65; }
.prose ul, .prose ol { padding-left: 22px; margin: 0 0 18px; }
.prose b, .prose strong { color: var(--text); font-weight: 600; }
.prose a { color: var(--accent); text-decoration-color: color-mix(in oklab, var(--accent) 35%, transparent); text-underline-offset: 2px; }
.prose hr { border: 0; border-top: 1px solid var(--border); margin: 44px 0; }

.prose code {
  font-family: var(--mono); font-size: 0.875em;
  background: var(--surface-2); color: var(--text);
  padding: 2px 6px; border-radius: 5px;
  border: 1px solid var(--border);
}
.prose pre {
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 12px; padding: 16px 18px;
  overflow-x: auto; margin: 0 0 20px;
}
.prose pre code { background: none; border: 0; padding: 0; font-size: 13px; }
/* A changelog heading often names the package it touched — keep the code
   token subordinate to the serif display type rather than matching it. */
.prose h2 code { font-size: 0.52em; padding: 3px 7px; vertical-align: 0.22em; }
.prose h3 code { font-size: 0.94em; }

.prose blockquote {
  margin: 0 0 20px; padding: 2px 0 2px 18px;
  border-left: 2px solid var(--accent);
  color: var(--muted); font-style: italic;
}

.prose table {
  width: 100%; border-collapse: collapse; margin: 0 0 22px;
  font-size: 14px; display: block; overflow-x: auto;
}
.prose th, .prose td {
  text-align: left; padding: 10px 14px;
  border-bottom: 1px solid var(--border); color: var(--muted);
  vertical-align: top;
}
.prose th {
  color: var(--text); font-weight: 600; font-size: 12px;
  font-family: var(--mono); letter-spacing: 0.03em;
  text-transform: uppercase; white-space: nowrap;
}

/* Each changelog day becomes its own quiet slab. */
.prose > h2 { padding-top: 8px; }

/* ———————— cards ———————— */
.card-grid {
  display: grid; gap: 16px;
  grid-template-columns: repeat(auto-fit, minmax(248px, 1fr));
  margin-top: 44px;
}
.card {
  display: flex; flex-direction: column; gap: 8px;
  border: 1px solid var(--border); border-radius: 14px;
  background: color-mix(in oklab, var(--surface) 82%, transparent);
  padding: 22px; text-decoration: none;
  transition: transform 220ms var(--ease-out-quint), border-color 220ms var(--ease-out);
}
.card:hover { transform: translateY(-3px); border-color: var(--border-strong); }
.card h3 { margin: 0; font-size: 16px; font-weight: 600; letter-spacing: -0.005em; }
.card p { margin: 0; font-size: 14px; color: var(--muted); line-height: 1.6; }
.card-meta {
  margin-top: auto; padding-top: 10px;
  font-family: var(--mono); font-size: 11.5px; color: var(--faint);
  letter-spacing: 0.02em;
}

/* ———————— features ———————— */
.pillar { margin-top: clamp(44px, 7vh, 72px); }
.pillar-h {
  font-family: var(--serif); font-weight: 400;
  font-size: clamp(1.5rem, 3vw, 2rem); line-height: 1.1;
  letter-spacing: -0.015em; margin: 0 0 8px;
}
.pillar-blurb { margin: 0 0 22px; color: var(--muted); font-size: 15px; max-width: 62ch; }

.feature-grid {
  display: grid; gap: 14px;
  grid-template-columns: repeat(auto-fit, minmax(268px, 1fr));
}
.feature-card {
  display: flex; flex-direction: column; gap: 8px;
  border: 1px solid var(--border); border-radius: 14px;
  background: color-mix(in oklab, var(--surface) 82%, transparent);
  padding: 20px; text-decoration: none;
  transition: transform 220ms var(--ease-out-quint), border-color 220ms var(--ease-out);
}
.feature-card:hover { transform: translateY(-3px); border-color: var(--border-strong); }
.feature-card-top {
  display: flex; align-items: baseline; justify-content: space-between; gap: 12px;
}
.feature-card h3 { margin: 0; font-size: 15.5px; font-weight: 600; letter-spacing: -0.005em; }
.feature-card p { margin: 0; font-size: 13.5px; color: var(--muted); line-height: 1.58; }

.pill-row { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin-bottom: 6px; }
.pill, .badge {
  font-family: var(--mono); font-size: 11px; letter-spacing: 0.03em;
  padding: 4px 9px; border-radius: 999px;
  border: 1px solid var(--border); color: var(--muted);
  background: color-mix(in oklab, var(--surface) 60%, transparent);
  white-space: nowrap;
}
.badge { flex: none; }
.badge-available {
  color: var(--good);
  border-color: color-mix(in oklab, var(--good) 34%, transparent);
  background: color-mix(in oklab, var(--good) 9%, transparent);
}
.badge-early {
  color: var(--warn);
  border-color: color-mix(in oklab, var(--warn) 34%, transparent);
  background: color-mix(in oklab, var(--warn) 9%, transparent);
}
/* "Coming soon" stays neutral — it is not a warning. */

.principles { margin-top: clamp(48px, 8vh, 80px); }

/* ———————— architecture diagram ———————— */
.arch { margin-top: clamp(40px, 6vh, 60px); }
.arch-flow { list-style: none; margin: 0; padding: 0; }

.arch-stage {
  padding: 26px 0 30px;
  transition: opacity 640ms var(--ease-out), transform 640ms var(--ease-out);
}
html.js-arch .arch-stage:not(.in-view) { opacity: 0; transform: translateY(16px); }

.arch-stage-head { display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap; margin-bottom: 20px; }
.arch-stage-index {
  font-family: var(--mono); font-size: 11px; color: var(--faint);
  border: 1px solid var(--border); border-radius: 999px; padding: 3px 9px;
  flex: none;
}
.arch-stage-title {
  font-family: var(--serif); font-weight: 400;
  font-size: clamp(1.3rem, 2.8vw, 1.7rem); letter-spacing: -0.01em;
  margin: 0;
}
.arch-stage-blurb { margin: 6px 0 0; color: var(--muted); font-size: 14px; max-width: 58ch; flex-basis: 100%; }

.arch-nodes { list-style: none; margin: 0; padding: 0; display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(232px, 1fr)); }
.arch-nodes--single { grid-template-columns: minmax(0, 340px); justify-content: center; }

.arch-node-btn {
  all: unset; box-sizing: border-box; cursor: pointer;
  display: flex; flex-direction: column; gap: 8px; width: 100%;
  border: 1px solid var(--border); border-radius: 14px;
  background: color-mix(in oklab, var(--surface) 82%, transparent);
  padding: 16px 18px;
  transition: transform 220ms var(--ease-out-quint), border-color 220ms var(--ease-out);
}
.arch-node-btn:hover { transform: translateY(-2px); border-color: var(--border-strong); }
.arch-node-btn:active { transform: scale(0.99); }
.arch-node-top { display: flex; align-items: baseline; justify-content: space-between; gap: 10px; }
.arch-node-name { font-weight: 600; font-size: 14.5px; letter-spacing: -0.005em; }
.arch-node-teaser { margin: 0; font-size: 13px; color: var(--muted); line-height: 1.55; }
.arch-node-foot { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-top: 2px; }
.arch-node-cta { font-family: var(--mono); font-size: 11px; color: var(--faint); }

.arch-node-icon { flex: none; width: 15px; height: 15px; position: relative; }
.arch-node-icon::before, .arch-node-icon::after {
  content: ""; position: absolute; background: var(--muted); border-radius: 1px;
  transition: transform 220ms var(--ease-out), opacity 220ms var(--ease-out);
}
.arch-node-icon::before { top: 7px; left: 0; width: 15px; height: 1.5px; }
.arch-node-icon::after { top: 0; left: 7px; width: 1.5px; height: 15px; }
.arch-node-btn[aria-expanded="true"] .arch-node-icon::after { opacity: 0; transform: rotate(90deg); }

.arch-detail {
  display: grid; grid-template-rows: 1fr; overflow: hidden;
  transition: grid-template-rows 260ms var(--ease-out);
}
html.js-arch .arch-detail { grid-template-rows: 0fr; }
html.js-arch .arch-detail.is-open { grid-template-rows: 1fr; }
.arch-detail-inner { min-height: 0; padding: 12px 2px 4px; }
.arch-detail-inner p { margin: 0 0 10px; font-size: 13.5px; color: var(--muted); line-height: 1.62; }
.arch-detail-link { font-family: var(--mono); font-size: 12px; color: var(--accent); text-decoration: none; }
.arch-detail-link:hover { text-decoration: underline; }

/* decorative range indicator under the score node — "a range, not a point" */
.arch-range { position: relative; height: 6px; width: 100%; max-width: 220px; margin-top: 4px; }
.arch-range-track { position: absolute; inset: 0; border-radius: 999px; background: var(--surface-2); }
.arch-range-band {
  position: absolute; top: 0; bottom: 0; left: 37%; width: 24%; border-radius: 999px;
  background: color-mix(in oklab, var(--accent) 40%, transparent);
}
.arch-range-marker { position: absolute; top: -3px; left: 47%; width: 2px; height: 12px; background: var(--accent); border-radius: 1px; }
html.js-arch .in-view .arch-range-band { animation: arch-range-breathe 3.6s var(--ease-in-out) infinite; }
@keyframes arch-range-breathe {
  0%, 100% { left: 35%; width: 22%; }
  50% { left: 41%; width: 27%; }
}

/* connectors between stages — a collector line, not literal wiring */
.arch-connector { display: flex; flex-direction: column; align-items: center; height: 58px; position: relative; }
.arch-connector-bar {
  width: min(70%, 520px); height: 1px; background: var(--border-strong);
  transform: scaleX(0); transition: transform 700ms var(--ease-out);
}
.arch-connector.in-view .arch-connector-bar { transform: scaleX(1); }
.arch-connector-stem {
  width: 1px; flex: 1; background: var(--border-strong);
  transform-origin: top; transform: scaleY(0); transition: transform 700ms var(--ease-out) 150ms;
}
.arch-connector.in-view .arch-connector-stem { transform: scaleY(1); }
.arch-connector-arrow {
  width: 6px; height: 6px; margin-top: -4px;
  border-right: 1.5px solid var(--border-strong); border-bottom: 1.5px solid var(--border-strong);
  transform: rotate(45deg); opacity: 0; transition: opacity 300ms var(--ease-out) 780ms;
}
.arch-connector.in-view .arch-connector-arrow { opacity: 1; }
.arch-connector-dot {
  position: absolute; top: 0; left: calc(50% - 2px); width: 4px; height: 4px;
  border-radius: 50%; background: var(--accent); opacity: 0;
}
html.js-arch .arch-connector.in-view .arch-connector-dot { animation: arch-flow 2.6s var(--ease-in-out) infinite; }
.arch-connector-dot--b { animation-delay: 1.3s !important; }
@keyframes arch-flow {
  0% { opacity: 0; top: 4px; }
  12% { opacity: 1; }
  85% { opacity: 1; }
  100% { opacity: 0; top: 100%; }
}

/* the fix chain — a sequence, not a grid */
.arch-chain { display: flex; align-items: stretch; flex-wrap: wrap; gap: 14px 8px; }
.arch-chain-step {
  flex: 1 1 150px; min-width: 140px;
  border: 1px solid var(--border); border-radius: 14px;
  background: color-mix(in oklab, var(--surface) 82%, transparent);
  padding: 16px 16px 18px;
}
.arch-chain-step h3 { margin: 8px 0 6px; font-size: 14.5px; font-weight: 600; letter-spacing: -0.005em; }
.arch-chain-step p { margin: 0; font-size: 13px; color: var(--muted); line-height: 1.55; }
.arch-chain-num {
  display: inline-grid; place-items: center; width: 22px; height: 22px;
  border-radius: 50%; font-family: var(--mono); font-size: 11px;
  color: var(--accent); background: var(--accent-wash);
}
.arch-chain-step--good .arch-chain-num { color: var(--good); background: color-mix(in oklab, var(--good) 14%, transparent); }
.arch-chain-step--warn .arch-chain-num { color: var(--warn); background: color-mix(in oklab, var(--warn) 14%, transparent); }
.arch-chain-arrow {
  align-self: center; flex: none; color: var(--faint); font-family: var(--mono);
  font-size: 14px; padding: 0 2px;
}
.arch-chain-branch { flex: 1 1 150px; min-width: 140px; display: flex; flex-direction: column; gap: 10px; }
.arch-chain-branch .arch-chain-step { flex: none; }

.arch-dest-note { margin: 0 0 16px; color: var(--muted); font-size: 14px; }
.arch-dest-row { display: flex; flex-wrap: wrap; gap: 10px; }
.arch-dest-row .pill { font-size: 12.5px; padding: 7px 14px; color: var(--text); }

footer {
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; flex-wrap: wrap;
  padding-top: 26px; border-top: 1px solid var(--border);
  font-family: var(--mono); font-size: 11.5px; color: var(--faint);
  letter-spacing: 0.02em;
}
footer .sep { color: var(--border-strong); }

@media (max-width: 640px) {
  .doc-nav { order: 3; margin-left: 0; width: 100%; }
  .doc-nav-link { padding: 6px 9px; font-size: 13px; }
  .toggle { margin-left: auto; }
  .arch-chain { flex-direction: column; }
  .arch-chain-arrow { align-self: center; transform: rotate(90deg); }
  .arch-chain-branch { flex-direction: row; flex-wrap: wrap; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 120ms !important;
  }
  .doc-main { opacity: 1 !important; transform: none !important; }
  .arch-stage, .arch-connector-bar, .arch-connector-stem, .arch-connector-arrow {
    opacity: 1 !important; transform: none !important;
  }
  .arch-connector-dot { display: none !important; }
}