:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --text: #1c2530;
  --muted: #5c6b7a;
  --border: #e4e8ee;
  --accent: #1fa971;
  --accent-strong: #17845a;
  --accent-soft: #e7f6ef;
  --shadow: 0 1px 2px rgba(20, 40, 60, 0.04), 0 8px 24px rgba(20, 40, 60, 0.06);
  --radius: 16px;
  --maxw: 760px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0e1319;
    --surface: #161d26;
    --text: #e7edf3;
    --muted: #9aa9b8;
    --border: #26313d;
    --accent: #35c88c;
    --accent-strong: #4dd89e;
    --accent-soft: #16302440;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent-strong); text-decoration: none; }
a:hover { text-decoration: underline; }

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

/* Header / nav */
.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--surface);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav {
  max-width: 1040px;
  margin: 0 auto;
  padding: 14px 20px;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
}
.brand:hover { text-decoration: none; }
.brand .logo {
  width: 30px; height: 30px;
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  flex: none;
}
.nav-links {
  margin-left: auto;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.nav-links a {
  color: var(--muted);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 0.95rem;
  font-weight: 500;
}
.nav-links a:hover { background: var(--accent-soft); color: var(--accent-strong); text-decoration: none; }
.nav-links a.active { background: var(--accent-soft); color: var(--accent-strong); }

/* Hero */
.hero {
  text-align: center;
  padding: 72px 20px 48px;
}
.hero h1 { font-size: clamp(2rem, 5vw, 3rem); line-height: 1.15; margin: 0 0 16px; letter-spacing: -0.02em; }
.hero p.lead { font-size: 1.2rem; color: var(--muted); max-width: 640px; margin: 0 auto 28px; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--accent);
  color: #fff;
  padding: 12px 22px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 1rem;
  border: none;
  transition: background 0.15s ease;
}
.btn:hover { background: var(--accent-strong); text-decoration: none; color: #fff; }
.btn.secondary { background: transparent; color: var(--accent-strong); border: 1.5px solid var(--border); }
.btn.secondary:hover { background: var(--accent-soft); }

.btn-row { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }

/* Content pages */
main.page { padding: 48px 0 72px; }
main.page h1 { font-size: clamp(1.8rem, 4vw, 2.4rem); margin: 0 0 8px; letter-spacing: -0.02em; }
main.page .updated { color: var(--muted); font-size: 0.95rem; margin: 0 0 32px; }
main.page h2 { font-size: 1.3rem; margin: 40px 0 12px; letter-spacing: -0.01em; }
main.page h3 { font-size: 1.1rem; margin: 24px 0 8px; }
main.page p, main.page li { color: var(--text); }
main.page ul { padding-left: 22px; }
main.page li { margin: 6px 0; }
main.page .muted { color: var(--muted); }

/* Cards / feature grid */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
  margin: 40px 0;
}
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
}
.card .icon { font-size: 1.6rem; margin-bottom: 8px; }
.card h3 { margin: 0 0 6px; font-size: 1.05rem; }
.card p { margin: 0; color: var(--muted); font-size: 0.98rem; }

/* Callout box */
.callout {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 22px 24px;
  margin: 28px 0;
  box-shadow: var(--shadow);
}
.callout h3 { margin: 0 0 6px; }
.callout p:last-child { margin-bottom: 0; }

.note {
  font-size: 0.9rem;
  color: var(--muted);
  background: var(--accent-soft);
  border-radius: 10px;
  padding: 12px 16px;
  margin: 24px 0;
}

/* Definition table */
.dl {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 20px 0;
}
.dl .row {
  display: grid;
  grid-template-columns: 200px 1fr;
  border-top: 1px solid var(--border);
}
.dl .row:first-child { border-top: none; }
.dl .k { background: var(--surface); font-weight: 600; padding: 12px 16px; }
.dl .v { padding: 12px 16px; }
@media (max-width: 560px) {
  .dl .row { grid-template-columns: 1fr; }
  .dl .k { border-bottom: 1px solid var(--border); }
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  padding: 32px 20px;
  color: var(--muted);
  font-size: 0.9rem;
}
.site-footer .inner {
  max-width: 1040px;
  margin: 0 auto;
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
}
.site-footer a { color: var(--muted); }
.site-footer .foot-links { display: flex; gap: 16px; flex-wrap: wrap; }