/* Modern Reset & Typography */
:root {
  --primary: #111827;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --bg-light: #f9fafb;
  --card-bg: #ffffff;
  --text-main: #374151;
  --text-dark: #111827;
  --border-color: #e5e7eb;
  --radius: 12px;
  --shadow: 0 4px 20px -2px rgba(0, 0, 0, 0.05);
  --shadow-hover: 0 10px 25px -5px rgba(0, 0, 0, 0.1);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--text-main);
  background-color: var(--bg-light);
  line-height: 1.7;
  font-size: 1.125rem;
  -webkit-font-smoothing: antialiased;
}

/* Layout Container */
.container {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Navigation Header */
header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border-color);
  padding: 20px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-wrapper {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--text-dark);
  text-decoration: none;
  letter-spacing: -0.02em;
}

nav a {
  color: var(--text-main);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
}

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

/* Content & Typography */
.content {
  padding: 60px 24px;
  background: var(--card-bg);
  margin-top: 40px;
  margin-bottom: 40px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

h1 {
  font-size: 2.5rem;
  color: var(--text-dark);
  line-height: 1.2;
  margin-bottom: 16px;
  letter-spacing: -0.03em;
}

.lead {
  font-size: 1.25rem;
  color: #4b5563;
  margin-bottom: 32px;
  font-weight: 400;
}

h2 {
  font-size: 1.75rem;
  color: var(--text-dark);
  margin: 40px 0 16px;
  letter-spacing: -0.02em;
}

h3 {
  font-size: 1.25rem;
  color: var(--text-dark);
  margin-bottom: 8px;
}

p {
  margin-bottom: 20px;
}

ul, ol {
  margin-bottom: 24px;
  padding-left: 24px;
}

li {
  margin-bottom: 8px;
}

code {
  background: #f3f4f6;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.9em;
  color: #1f2937;
}

/* TOC Cards Grid (Index Page) */
.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
  margin-top: 24px;
}

.toc-card {
  display: block;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  padding: 24px;
  border-radius: var(--radius);
  text-decoration: none;
  transition: all 0.2s ease-in-out;
  box-shadow: var(--shadow);
}

.toc-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
  border-color: var(--accent);
}

.toc-card h3 {
  color: var(--accent);
  font-size: 1.1rem;
}

.toc-card p {
  color: var(--text-main);
  font-size: 0.95rem;
  margin-bottom: 0;
  line-height: 1.5;
}

/* Coaching Banner */
.coaching-banner {
  background: #1e293b;
  color: #ffffff;
  padding: 48px 24px;
  border-radius: var(--radius);
  margin: 40px auto;
  max-width: 860px;
  text-align: center;
}

.coaching-banner h3 {
  color: #ffffff;
  font-size: 1.5rem;
  margin-bottom: 12px;
}

.coaching-banner p {
  color: #94a3b8;
  margin-bottom: 24px;
}

.btn-coaching {
  display: inline-block;
  background: var(--accent);
  color: #ffffff;
  padding: 14px 28px;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 600;
  font-size: 1rem;
  transition: background 0.2s;
}

.btn-coaching:hover {
  background: var(--accent-hover);
}

/* Footer */
footer {
  text-align: center;
  padding: 40px 0;
  color: #9ca3af;
  font-size: 0.9rem;
}