/* Base */
:root {
  --bg: #f4f6f8;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #e5e7eb;
  --soft: #f7f9fc;
  --primary: #004080;
  --title-color: #3730a3; /* Requested color */
}

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

body {
  font-family: Arial, sans-serif;
  background-color: var(--bg);
  color: var(--text);
  margin: 0;
  padding: 24px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Layout */
.container {
  max-width: 820px;
  margin: 3rem auto;
  background: var(--card);
  padding: 2rem;
  border-radius: 10px;
  border: 1px solid var(--border);
  box-shadow: 0 2px 10px rgba(0,0,0,0.06);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  color: var(--title-color);
  margin-top: 1.5em;
  margin-bottom: 0.5em;
  font-weight: 700;
  line-height: 1.2;
}

h1 {
  font-size: 2rem;
  text-align: center;
  margin-bottom: 0.5rem;
}

h2 {
  font-size: 1.5rem;
  margin-top: 2rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

h3 {
  font-size: 1.25rem;
  color: var(--title-color);
}

p, ul, ol {
  margin-bottom: 1rem;
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

ul {
  padding-left: 1.5rem;
}

li {
  margin-bottom: 0.5rem;
}

/* Header */
header {
  text-align: center;
  margin-bottom: 2rem;
}

.subtitle {
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
  margin-bottom: 2rem;
  display: block;
}

/* Table of Contents */
#toc {
  background-color: var(--soft);
  padding: 1.5rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  margin-bottom: 2rem;
}

#toc h2 {
  margin-top: 0;
  border-bottom: none;
  font-size: 1.25rem;
}

#toc ul {
  list-style-type: none;
  padding-left: 0;
  margin: 0;
}

#toc li {
  margin-bottom: 0.5rem;
}

#toc a {
  color: var(--primary);
  font-weight: 500;
}

/* Utilities */
.text-muted {
  color: var(--muted);
}

.text-center {
  text-align: center;
}

/* Logo */
.logo {
  max-width: 120px;
  margin-bottom: 1rem;
}