:root {
  /* Layout idea: a reading column with a track sidebar; each track owns one accent (hybrid = Azure teal, security = signal red). */
  --bg: #f5f6f4;
  --surface: #ffffff;
  --ink: #1a2128;
  --muted: #5a6670;
  --line: #dde2e5;
  --code-bg: #eef1f2;
  --hybrid: #0a6c86;
  --hybrid-soft: #e0eff4;
  --security: #a8322a;
  --security-soft: #f7e6e3;
  --accent: #0a6c86;
  --accent-soft: #e0eff4;
  --font-display: "Newsreader", Georgia, "Times New Roman", serif;
  --font-body: "IBM Plex Sans", "Segoe UI", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", Consolas, "Courier New", monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #11161a; --surface: #182027; --ink: #e5eaee; --muted: #9eabb5; --line: #2b3741; --code-bg: #1f2a33;
    --hybrid: #5ec4e0; --hybrid-soft: #143340; --security: #f0897d; --security-soft: #3a1d1a;
    --accent: #5ec4e0; --accent-soft: #143340;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #11161a; --surface: #182027; --ink: #e5eaee; --muted: #9eabb5; --line: #2b3741; --code-bg: #1f2a33;
  --hybrid: #5ec4e0; --hybrid-soft: #143340; --security: #f0897d; --security-soft: #3a1d1a;
  --accent: #5ec4e0; --accent-soft: #143340;
  color-scheme: dark;
}
body.track-security { --accent: var(--security); --accent-soft: var(--security-soft); }
body.track-hybrid { --accent: var(--hybrid); --accent-soft: var(--hybrid-soft); }

* { box-sizing: border-box; }
html, body { margin: 0; }
body { background: var(--bg); color: var(--ink); font: 16px/1.65 var(--font-body); }
a { color: var(--accent); text-underline-offset: 2px; }
a:focus-visible, button:focus-visible, input:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
img { max-width: 100%; height: auto; }

.skip { position: absolute; left: -999px; top: 8px; background: var(--surface); padding: 6px 10px; z-index: 10; }
.skip:focus { left: 8px; }

/* Top bar */
.top { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 12px;
  padding: 14px 24px; border-bottom: 1px solid var(--line); background: var(--surface); position: sticky; top: 0; z-index: 5; }
.brand { display: flex; align-items: center; gap: 10px; font: 600 1.05rem var(--font-body); color: var(--ink); text-decoration: none; }
.brand-mark { width: 18px; height: 18px; border-radius: 4px; background: linear-gradient(135deg, var(--hybrid) 50%, var(--security) 50%); }
.tracks { display: flex; gap: 6px; }
.tracks a { padding: 6px 12px; border-radius: 6px; color: var(--muted); text-decoration: none; font-weight: 500; }
.tracks a:hover { color: var(--ink); background: var(--bg); }
.tracks a[aria-current="true"] { color: var(--accent); background: var(--accent-soft); }

/* Layout */
.layout { max-width: 1180px; margin: 0 auto; padding: 32px 24px 48px; display: grid; gap: 40px; }
.layout.with-side { grid-template-columns: 260px minmax(0, 1fr); align-items: start; }
.layout.plain { max-width: 1040px; }
@media (max-width: 900px) {
  .layout.with-side { grid-template-columns: 1fr; gap: 24px; }
  .side { position: static !important; max-height: none !important; }
}

/* Sidebar */
.side { position: sticky; top: 76px; max-height: calc(100vh - 96px); overflow-y: auto; font-size: 0.92rem;
  border-right: 1px solid var(--line); padding-right: 16px; }
@media (max-width: 900px) { .side { border-right: 0; border-bottom: 1px solid var(--line); padding: 0 0 16px; } }
.side-title { margin: 0 0 8px; font: 500 0.75rem var(--font-mono); text-transform: uppercase; letter-spacing: 0.08em; color: var(--accent); }
.side ol { list-style: none; margin: 0; padding: 0; display: grid; gap: 2px; }
.side ol ol { padding-left: 12px; margin: 2px 0 6px; border-left: 2px solid var(--line); }
.side a { display: block; padding: 4px 8px; border-radius: 5px; color: var(--muted); text-decoration: none; line-height: 1.35; }
.side a:hover { color: var(--ink); background: var(--surface); }
.side a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); font-weight: 500; }
.side .group > a { color: var(--ink); font-weight: 500; }

/* Prose */
.prose { min-width: 0; max-width: 780px; }
.layout.plain .prose { max-width: none; }
.prose h1, .prose h2, .prose h3 { font-family: var(--font-display); font-weight: 600; line-height: 1.2; text-wrap: balance; }
.prose h1 { font-size: 2.3rem; margin: 0 0 16px; }
.prose h2 { font-size: 1.55rem; margin: 40px 0 12px; padding-top: 16px; border-top: 1px solid var(--line); }
.prose h3 { font-size: 1.2rem; margin: 28px 0 8px; }
.prose p, .prose li { max-width: 70ch; }
.prose ol, .prose ul { padding-left: 1.4em; }
.prose li + li { margin-top: 4px; }
.prose code { font-family: var(--font-mono); font-size: 0.88em; background: var(--code-bg); padding: 1px 5px; border-radius: 4px; }
.prose pre { background: var(--code-bg); border: 1px solid var(--line); border-radius: 8px; padding: 14px 16px; overflow-x: auto; line-height: 1.5; }
.prose pre code { background: none; padding: 0; font-size: 0.86rem; }
.prose pre.mermaid { background: var(--surface); text-align: center; }
.prose blockquote { margin: 18px 0; padding: 12px 16px; background: var(--accent-soft); border-left: 4px solid var(--accent); border-radius: 6px; }
.prose blockquote p { margin: 6px 0; }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 32px 0; }
.table-wrap { overflow-x: auto; margin: 16px 0; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); }
.prose table { width: 100%; border-collapse: collapse; font-size: 0.93rem; }
.prose th, .prose td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
.prose tr:last-child td { border-bottom: 0; }
.prose th { font-weight: 600; background: var(--bg); }
.pager { display: flex; flex-wrap: wrap; gap: 6px 16px; font-size: 0.92rem; margin: 0 0 20px; color: var(--muted); }
.pager a { text-decoration: none; padding: 4px 10px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); }
.pager a:hover { border-color: var(--accent); }
li.task { list-style: none; margin-left: -1.4em; }
li.task input { margin-right: 8px; accent-color: var(--accent); }

/* Home */
.eyebrow { margin: 0 0 8px; font: 500 0.78rem var(--font-mono); text-transform: uppercase; letter-spacing: 0.07em; color: var(--muted); }
.hero { padding: 16px 0 8px; }
.hero h1 { font-size: 3rem; max-width: 18ch; margin-bottom: 14px; }
.lede { font-size: 1.15rem; color: var(--muted); max-width: 62ch; }
.tracks-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 20px; margin: 32px 0; }
.track-card { background: var(--surface); border: 1px solid var(--line); border-top: 4px solid var(--c); border-radius: 10px; padding: 24px; display: flex; flex-direction: column; gap: 4px; }
.track-card.hybrid { --c: var(--hybrid); --cs: var(--hybrid-soft); }
.track-card.security { --c: var(--security); --cs: var(--security-soft); }
.track-card .eyebrow { color: var(--c); }
.track-card h2 { margin: 0 0 8px; border: 0; padding: 0; font-size: 1.6rem; }
.track-card h2 a { color: var(--ink); text-decoration: none; }
.track-card h2 a:hover { color: var(--c); }
.track-card .mini { font-size: 0.92rem; margin: 10px 0 16px; padding-left: 1.3em; color: var(--muted); }
.track-card .mini a { color: var(--ink); }
.track-card .count { color: var(--muted); font-size: 0.85em; }
.track-card p:last-child { margin-top: auto; }
.button { display: inline-block; background: var(--c, var(--accent)); color: var(--surface); text-decoration: none; font-weight: 500;
  padding: 9px 16px; border-radius: 6px; }
.button:hover { filter: brightness(1.08); }
.how-steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 14px; list-style: none; padding: 0; counter-reset: s; }
.how-steps li { background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 14px; margin: 0; max-width: none; counter-increment: s; }
.how-steps li::before { content: counter(s, decimal-leading-zero); display: block; font: 500 0.8rem var(--font-mono); color: var(--muted); margin-bottom: 4px; }
.needs { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; }
.needs div { background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 16px; }
.needs h3 { margin-top: 0; }

/* Footer */
.foot { border-top: 1px solid var(--line); padding: 20px 24px 32px; color: var(--muted); font-size: 0.9rem; text-align: center; }
.foot p { margin: 4px auto; max-width: 80ch; }
.foot .small { font-size: 0.82rem; }

@media (max-width: 600px) {
  .hero h1 { font-size: 2.1rem; }
  .prose h1 { font-size: 1.8rem; }
  .top { padding: 12px 16px; }
  .layout { padding: 20px 16px 40px; }
}
@media (prefers-reduced-motion: reduce) { * { scroll-behavior: auto !important; transition: none !important; } }