:root {
  --bg: #f6f8fa;
  --panel: #ffffff;
  --panel-border: #e2e8f0;
  --text: #0f172a;
  --text-muted: #475569;
  --accent: #0d9488;
  --accent-dark: #0f766e;
  --danger: #b91c1c;
  --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
  background-color: var(--bg);
  color: var(--text);
  font-family: var(--font-main);
  line-height: 1.7;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}
header {
  background: var(--panel);
  border-bottom: 1px solid var(--panel-border);
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav-wrap {
  max-width: 900px;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: var(--text);
  font-weight: 800;
  font-size: 1.05rem;
}
.brand-mark {
  background: var(--accent);
  color: #fff;
  border-radius: 10px;
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  font-weight: 900;
  font-size: 0.95rem;
}
nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  margin-left: 1.1rem;
}
nav a:hover, nav a.active { color: var(--accent); }
main {
  flex: 1;
  width: 100%;
  max-width: 900px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
}
h1 { font-size: 1.8rem; line-height: 1.3; margin-bottom: 0.75rem; }
h2 { font-size: 1.2rem; margin-bottom: 0.5rem; }
p { margin-bottom: 1rem; }
.lead { color: var(--text-muted); font-size: 1.05rem; }
.card {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  padding: 1.5rem;
  margin-bottom: 1.25rem;
}
.card ul { margin: 0.5rem 0 0 1.2rem; }
.card li { margin-bottom: 0.4rem; }
a { color: var(--accent-dark); }
.small { font-size: 0.85rem; color: var(--text-muted); }
.warn {
  border-left: 5px solid var(--danger);
  background: #fef2f2;
  border: 1px solid #fecaca;
  border-radius: 10px;
  padding: 1rem 1.25rem;
  margin: 1.25rem 0;
}
.meta { font-size: 0.82rem; color: var(--text-muted); }
footer {
  border-top: 1px solid var(--panel-border);
  background: var(--panel);
  padding: 1.5rem;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}
footer a { color: var(--accent-dark); margin: 0 0.4rem; }
code {
  background: #eef2f7;
  padding: 0.15rem 0.4rem;
  border-radius: 6px;
  font-size: 0.85em;
}