:root {
  --bg: #f4f1ea;
  --paper: #fffdf8;
  --ink: #1c1917;
  --muted: #78716c;
  --line: #d6d3d1;
  --accent: #0f766e;
  --accent-soft: #ccfbf1;
  --navy: #1e3a5f;
  --code-bg: #1c1917;
  --code-ink: #f5f5f4;
  --mono: "JetBrains Mono", "Cascadia Code", "SF Mono", Consolas, monospace;
  --sans: "Segoe UI", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--sans);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  font-size: 15px;
}

.shell {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  min-height: 100vh;
}

.toc {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
  padding: 28px 20px;
  background: var(--navy);
  color: #e2e8f0;
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 28px;
  padding-bottom: 18px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.12);
}

.logo {
  width: 42px;
  height: 42px;
  border-radius: 10px;
  display: grid;
  place-items: center;
  background: var(--accent);
  color: white;
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 700;
}

.toc .muted { color: #94a3b8; font-size: 12px; }
.toc nav { display: flex; flex-direction: column; gap: 4px; }
.toc a {
  color: #cbd5e1;
  text-decoration: none;
  padding: 8px 10px;
  border-radius: 6px;
  font-size: 13px;
}
.toc a:hover, .toc a.active {
  background: rgba(255, 255, 255, 0.08);
  color: white;
}
.toc-foot { margin-top: 28px; font-size: 11px; }

.content {
  max-width: 920px;
  padding: 48px 56px 80px;
}

.hero {
  margin-bottom: 48px;
  padding-bottom: 28px;
  border-bottom: 1px solid var(--line);
}
.eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 12px;
}
.hero h1 {
  font-family: var(--mono);
  font-size: clamp(28px, 4vw, 40px);
  line-height: 1.2;
  margin: 0 0 16px;
  font-weight: 650;
}
.lede { font-size: 17px; color: #44403c; max-width: 52em; }
.meta-row { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 20px; }
.pill {
  font-family: var(--mono);
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid #99f6e4;
}

section { margin: 48px 0; scroll-margin-top: 24px; }
h2 {
  font-family: var(--mono);
  font-size: 22px;
  margin: 0 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--ink);
}
h3 { font-size: 16px; margin: 24px 0 10px; color: var(--navy); }

p { margin: 0 0 12px; }
ul, ol { margin: 0 0 14px; padding-left: 1.3em; }
li { margin: 6px 0; }
code {
  font-family: var(--mono);
  font-size: 0.9em;
  background: #e7e5e4;
  padding: 1px 5px;
  border-radius: 4px;
}
pre {
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 16px 18px;
  border-radius: 10px;
  overflow: auto;
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.55;
}
pre code { background: none; padding: 0; color: inherit; }
pre.flow { background: var(--paper); color: var(--ink); border: 1px solid var(--line); }

.callout {
  background: var(--paper);
  border-left: 4px solid var(--accent);
  padding: 14px 16px;
  border-radius: 0 8px 8px 0;
  margin: 16px 0;
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 14px;
  margin: 16px 0;
}
.card {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px 18px;
}
.card h3 { margin-top: 0; }

.table-wrap { overflow-x: auto; margin: 12px 0 18px; }
table {
  width: 100%;
  border-collapse: collapse;
  background: var(--paper);
  font-size: 14px;
}
th, td {
  border: 1px solid var(--line);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
th {
  background: #e7e5e4;
  font-family: var(--mono);
  font-size: 12px;
}

.diagram {
  margin: 20px 0;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px;
}
.diagram svg { width: 100%; height: auto; display: block; }

ul.check { list-style: none; padding-left: 0; }
ul.check li {
  padding-left: 1.5em;
  position: relative;
}
ul.check li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 700;
}

.milestones li { margin: 10px 0; }
.muted { color: var(--muted); }
.foot { margin-top: 64px; padding-top: 20px; border-top: 1px solid var(--line); }

@media (max-width: 900px) {
  .shell { grid-template-columns: 1fr; }
  .toc { position: relative; height: auto; }
  .content { padding: 28px 20px 48px; }
}