:root {
  --bg: #f6f6f2;
  --card: #ffffff;
  --ink: #111111;
  --muted: #6a6a6a;
  --soft: #d6d6d6;
  --hr: #e2e2dc;
  --accent: #0066cc;
  --accent-bg: #e8f1fb;
  --warn: #b35900;
  --warn-bg: #fff4d9;
  --ok: #1b6e2b;
  --ok-bg: #e6f5ea;
  --err: #a3210f;
  --err-bg: #fbe9e6;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.55 var(--sans);
}

/* Top bar */
.topbar {
  display: flex; justify-content: space-between; align-items: center;
  padding: 0.75rem 1.25rem;
  background: var(--card);
  border-bottom: 1px solid var(--soft);
  font-family: var(--mono);
}
.topbar .brand { font-size: 1.15rem; color: var(--ink); text-decoration: none; letter-spacing: 0.04em; }
.topbar .repo-link { color: var(--accent); text-decoration: none; font-size: 0.9rem; }
.topbar .repo-link:hover { text-decoration: underline; }

/* Layout grid */
.layout { display: grid; grid-template-columns: 220px minmax(0, 760px); gap: 1.5rem; padding: 1.5rem 1.25rem; max-width: 1100px; margin: 0 auto; }

/* Sidebar. Hierarchical numbering (1, 2, 3, 3.1, 3.2 ...) via nested CSS counters:
   every <ol> resets `sec`, every <li> increments it, and counters(sec, ".") prints
   the full chain so sub-pages read as 3.1, 3.2, and so on. */
.sidebar { position: sticky; top: 1.5rem; align-self: start; }
.sidebar ol { margin: 0; padding-left: 1.4rem; list-style: none; counter-reset: sec; }
.sidebar ol ol { margin: 0.3rem 0; }
.sidebar li { margin: 0.4rem 0; counter-increment: sec; }
.sidebar li::before { content: counters(sec, ".") " "; color: var(--muted); font-variant-numeric: tabular-nums; }
.sidebar a { color: var(--ink); text-decoration: none; }
.sidebar a:hover { color: var(--accent); text-decoration: underline; }
.sidebar a.active { color: var(--accent); font-weight: 600; }
.sidebar .group { color: var(--ink); font-weight: 600; }

/* Main content */
.content h1 { font-family: var(--mono); font-size: 1.5rem; margin: 0 0 0.5rem 0; }
.content h2 { font-family: var(--mono); font-size: 1.15rem; margin: 1.8rem 0 0.6rem 0; }
.content h3 { font-family: var(--sans); font-size: 1.0rem; margin: 1.4rem 0 0.4rem 0; }
.content p { margin: 0.6rem 0; }
.content a { color: var(--accent); }
.content a.src {
  font-family: var(--mono);
  font-size: 0.92em;
  background: var(--accent-bg);
  padding: 0.1em 0.35em;
  border-radius: 3px;
  text-decoration: none;
}
.content a.src:hover { text-decoration: underline; }

/* Cards */
.card { background: var(--card); border: 1px solid var(--soft); border-radius: 4px; padding: 1rem 1.25rem; margin: 1rem 0; }
.card.warn { background: var(--warn-bg); border-color: var(--warn); }
.card.ok   { background: var(--ok-bg);   border-color: var(--ok); }
.card.err  { background: var(--err-bg);  border-color: var(--err); }

/* Tables */
.content table { width: 100%; border-collapse: collapse; margin: 1rem 0; font-size: 0.95rem; }
.content th, .content td { border-bottom: 1px solid var(--hr); padding: 0.4rem 0.5rem; text-align: left; vertical-align: top; }
.content th { font-family: var(--mono); font-weight: 600; }

/* Code blocks */
.content pre { background: #fafaf6; border: 1px solid var(--hr); border-radius: 3px; padding: 0.75rem 1rem; overflow-x: auto; font-family: var(--mono); font-size: 0.9rem; }
.content code { font-family: var(--mono); font-size: 0.92em; background: #fafaf6; padding: 0.05em 0.3em; border-radius: 2px; }
.content pre code { background: none; padding: 0; }

/* SVG illustrations */
.content figure { margin: 1.5rem 0; text-align: center; }
.content figure svg, .content figure img { max-width: 100%; height: auto; }
.content figcaption { color: var(--muted); font-size: 0.85rem; margin-top: 0.4rem; }

/* Screenshots (CLI/TUI/website walkthroughs) get a frame so the capture edge is clear. */
.content figure img.shot { border: 1px solid var(--soft); border-radius: 5px; box-shadow: 0 1px 3px rgba(0,0,0,0.08); }

/* "Try it live" demo banner + embedded app frame. */
.demo-banner { background: var(--warn-bg); border: 2px solid var(--warn); border-radius: 6px; padding: 1rem 1.25rem; margin: 1rem 0 1.5rem; }
.demo-banner h2 { color: var(--warn); margin: 0 0 0.4rem; font-family: var(--mono); font-size: 1.15rem; }
.demo-banner p { margin: 0.4rem 0; }
.demo-frame { width: 100%; height: 780px; border: 1px solid var(--soft); border-radius: 6px; background: #fff; }

/* Numbered walkthrough steps. */
.content .step { margin: 1.6rem 0; }
.content .step > h3 { margin-top: 0; }
.content .step-num { font-family: var(--mono); color: var(--accent); font-weight: 600; margin-right: 0.4rem; }

/* Page navigation (prev/next) */
.page-nav { display: flex; justify-content: space-between; margin: 3rem 0 1rem; padding-top: 1rem; border-top: 1px solid var(--hr); }
.page-nav a { color: var(--accent); text-decoration: none; }
.page-nav a:hover { text-decoration: underline; }
.page-nav .prev::before { content: ""; }
.page-nav .next::after { content: ""; }

/* "Coming soon" inline marker (used where a chapter forward-references a page that lives in a later sub-project) */
.coming-soon { color: var(--muted); font-style: italic; }
.coming-soon::before { content: "[coming soon] "; font-style: normal; }

/* Hamburger (mobile) */
.hamburger { display: none; background: none; border: 1px solid var(--soft); border-radius: 3px; padding: 0.3rem 0.6rem; cursor: pointer; font: 1rem var(--mono); }

/* Responsive */
@media (max-width: 768px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { position: static; }
  .sidebar.collapsed { display: none; }
  .hamburger { display: inline-block; }
}

/* Mermaid. The raw flowchart source stays hidden; the static SVG fallback shows
   instead. mermaid-lazy.js swaps the two only after Mermaid loads and renders. */
pre.mermaid { background: transparent; border: none; padding: 0; text-align: center; display: none; }
img.mermaid-fallback { display: block; margin: 0 auto; max-width: 100%; }