:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --accent: #0b72b9;
  --muted: #6b7280;
  --radius: 10px;
  --maxw: 900px;
  font-family: Inter, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  color: #0f172a;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  background: linear-gradient(180deg, #eef4fb, var(--bg));
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 32px 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.container {
  width: 100%;
  max-width: var(--maxw);
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: 0 8px 30px rgba(15, 23, 42, 0.08);
  padding: 28px;
  box-sizing: border-box;
}

header {
  display: flex;
  gap: 16px;
  align-items: center;
  margin-bottom: 18px;
}

.logo {
  width: 56px;
  height: 56px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent), #2aa4ff);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-weight: 700;
  font-size: 20px;
  box-shadow: 0 6px 16px rgba(11, 114, 185, 0.18);
}

h1 {
  margin: 0;
  font-size: 20px;
}

p.lead {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 14px;
}

nav.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 18px 0 18px;
  border-radius: 8px;
  padding: 8px;
  background: #fbfdff;
  border: 1px solid #eef6ff;
}

nav.toc a {
  color: var(--accent);
  text-decoration: none;
  padding: 6px 10px;
  border-radius: 6px;
  font-size: 13px;
  background: transparent;
  border: 1px dashed transparent;
}

nav.toc a:hover {
  background: #eef7ff;
  border-color: #e0f0ff;
}

section {
  margin-top: 14px;
  line-height: 1.6;
  color: #0f172a;
}

h2 {
  font-size: 16px;
  margin: 18px 0 8px;
}

h3 {
  font-size: 14px;
  margin: 12px 0 6px;
}

ul {
  margin: 8px 0 12px 20px;
}

.muted {
  color: var(--muted);
  font-size: 13px;
}

.small {
  font-size: 13px;
  color: var(--muted);
}

footer {
  margin-top: 22px;
  border-top: 1px solid #f0f3f8;
  padding-top: 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.btn {
  background: var(--accent);
  color: white;
  padding: 8px 12px;
  border-radius: 8px;
  border: 0;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 6px 16px rgba(11, 114, 185, 0.12);
}

.btn.ghost {
  background: transparent;
  color: var(--accent);
  box-shadow: none;
  border: 1px solid #e8f4ff;
}

pre {
  background: #0b1220;
  color: #e6f0ff;
  padding: 12px;
  border-radius: 8px;
  overflow: auto;
  font-size: 13px;
}

@media (max-width: 640px) {
  .container {
    padding: 18px;
  }
  
  header {
    gap: 12px;
  }
  
  .logo {
    width: 48px;
    height: 48px;
  }
  
  footer {
    flex-direction: column;
    gap: 12px;
    align-items: flex-start;
  }
  
  nav.toc {
    flex-direction: column;
  }
}