:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --fg: #0f1419;
  --muted: #536471;
  --line: #eff3f4;
  --accent: #1d9bf0;
  --accent-ink: #ffffff;
  --card: #f7f9f9;
  --code-bg: #f7f9f9;
  --radius: 16px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, Ubuntu, Cantarell, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Code", Consolas, monospace;
  --maxw: 820px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15202b;
    --fg: #e7e9ea;
    --muted: #8b98a5;
    --line: #2f3b43;
    --card: #1c2733;
    --code-bg: #1c2733;
  }
}

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--fg);
  background: var(--bg);
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px 80px; }

.topbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px 24px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--fg);
  text-decoration: none;
  font-weight: 700;
  font-size: 1rem;
}

.brand img { width: 36px; height: 36px; }

.topnav { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 18px; }

.topnav a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
  font-size: .95rem;
}

.topnav a:hover { color: var(--accent); }

.topnav .topnav-cta {
  color: var(--accent-ink);
  background: var(--accent);
  padding: 8px 16px;
  border-radius: 999px;
}

.topnav .topnav-cta:hover { color: var(--accent-ink); filter: brightness(1.08); }

header.hero { text-align: center; padding: 56px 0 8px; }

.logo { width: 96px; height: 96px; display: block; margin: 0 auto 20px; }

h1 { font-size: clamp(1.8rem, 5vw, 2.6rem); line-height: 1.2; margin: 0 0 12px; }

.lead {
  font-size: clamp(1rem, 2.5vw, 1.15rem);
  color: var(--muted);
  margin: 0 auto;
  max-width: 560px;
}

.cta { margin: 28px 0 8px; }

.btn {
  display: inline-block;
  background: var(--accent);
  color: var(--accent-ink);
  text-decoration: none;
  font-weight: 700;
  padding: 12px 26px;
  border-radius: 999px;
}

.btn:hover { filter: brightness(1.08); }

.btn:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }

.note { color: var(--muted); font-size: .9rem; }

nav.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 16px;
  justify-content: center;
  padding: 28px 0 8px;
}

nav.toc a { color: var(--accent); text-decoration: none; font-weight: 600; font-size: .95rem; }

nav.toc a:hover { text-decoration: underline; }

section { margin-top: 56px; }

h2 { font-size: 1.4rem; margin: 0 0 10px; }

h3 { font-size: 1.05rem; margin: 22px 0 6px; }

p, li { font-size: 1rem; }

ul, ol { padding-left: 1.3em; }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin: 14px 0;
}

.card h3:first-child { margin-top: 0; }

.table { overflow-x: auto; }

table { border-collapse: collapse; width: 100%; margin: 14px 0; }

th, td { border: 1px solid var(--line); padding: 10px 12px; text-align: left; font-size: .95rem; }

th { background: var(--card); }

code, .mono {
  font-family: var(--mono);
  font-size: .88em;
  background: var(--code-bg);
  padding: .12em .4em;
  border-radius: 6px;
  word-break: break-all;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px;
  overflow-x: auto;
  font-size: .85rem;
}

pre code { background: none; padding: 0; }

a { color: var(--accent); }

footer {
  margin-top: 72px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: .9rem;
  text-align: center;
}

footer p { margin: 6px 0; }

@media (max-width: 540px) {
  .topbar { justify-content: center; text-align: center; }
  header.hero { padding-top: 36px; }
}