:root {
  --brand: #1f3df5;          /* AI ASTRA blue */
  --brand-ink: #1830b8;
  --ink: #10141b;
  --muted: #5b6573;
  --bg: #ffffff;
  --soft: #f5f7fb;
  --line: #e6e9f0;
  --maxw: 820px;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI",
    "Noto Sans Thai", "Sarabun", Roboto, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.75;
  font-size: 16px;
}

/* top navigation (matches aiastra.co) */
.nav {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 16px;
  padding: 14px 22px;
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--line);
}
.brand {
  font-weight: 800; letter-spacing: .04em; font-size: 18px;
  text-decoration: none; color: var(--ink);
}
.brand .ai { color: var(--brand); }
.nav .spacer { flex: 1; }
.langbar { display: inline-flex; align-items: center; gap: 2px; }
.langbar button {
  font: inherit; font-weight: 700; font-size: 14px; cursor: pointer;
  border: 0; background: none; color: var(--muted);
  padding: 4px 8px; border-radius: 6px;
}
.langbar .sep { color: var(--line); }
.langbar button[aria-pressed="true"] { color: var(--brand); }

/* page head */
.pagehead {
  max-width: var(--maxw); margin: 0 auto; padding: 48px 22px 8px;
}
.pagehead h1 { font-size: 34px; line-height: 1.2; margin: 0 0 8px; letter-spacing: -.01em; }
.pagehead .lead { color: var(--muted); margin: 0; font-size: 16px; }
.pagehead::after {
  content: ""; display: block; width: 56px; height: 4px; margin-top: 18px;
  background: var(--brand); border-radius: 4px;
}

main { max-width: var(--maxw); margin: 0 auto; padding: 8px 22px 72px; }
.updated { color: var(--muted); font-size: 14px; margin: 18px 0 26px; }
h2 {
  font-size: 20px; margin: 34px 0 8px; letter-spacing: -.01em;
  scroll-margin-top: 70px;
}
h3 { font-size: 16px; margin: 20px 0 6px; }
p, li { color: var(--ink); }
ul { padding-left: 22px; }
.muted { color: var(--muted); }
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

.toc {
  display: flex; flex-wrap: wrap; gap: 10px; margin: 26px 0;
}
.toc a {
  background: var(--soft); border: 1px solid var(--line); border-radius: 8px;
  padding: 9px 16px; font-size: 14px; font-weight: 600; color: var(--ink);
}
.toc a:hover { border-color: var(--brand); text-decoration: none; }

/* footer (multi-column, matches corporate site) */
footer {
  border-top: 1px solid var(--line); background: var(--soft);
  margin-top: 40px;
}
.fwrap { max-width: var(--maxw); margin: 0 auto; padding: 36px 22px 16px; }
.fcols {
  display: flex; flex-wrap: wrap; gap: 28px; justify-content: space-between;
}
.fcols .brand { font-size: 17px; }
.fcols .col a { display: block; color: var(--muted); font-size: 14px; padding: 3px 0; }
.fcols .col a:hover { color: var(--brand); }
.copy { color: var(--muted); font-size: 13px; padding: 18px 22px 28px;
  max-width: var(--maxw); margin: 0 auto; }

[lang-block] { display: none; }
[lang-block].active { display: block; }

@media (max-width: 600px) {
  .pagehead h1 { font-size: 27px; }
  .pagehead { padding-top: 34px; }
}