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

html {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  line-height: 1.6;
  color: #333;
}

body {
  background: #f9f9f9;
}

header {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 40px 20px;
  text-align: center;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

header h1 {
  margin-bottom: 20px;
  font-size: 2.5em;
}

nav {
  display: flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

nav a {
  color: white;
  text-decoration: none;
  padding: 10px 20px;
  border-radius: 4px;
  transition: background 0.3s;
}

nav a:hover {
  background: rgba(255,255,255,0.2);
}

main {
  max-width: 900px;
  margin: 40px auto;
  padding: 0 20px;
}

section {
  background: white;
  padding: 30px;
  margin-bottom: 30px;
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}

h2 {
  margin-bottom: 15px;
  color: #667eea;
}

p {
  margin-bottom: 10px;
}

button {
  background: #667eea;
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: 4px;
  cursor: pointer;
  font-size: 1em;
  transition: background 0.3s;
}

button:hover {
  background: #764ba2;
}

details {
  margin-top: 20px;
  padding: 15px;
  background: #f5f5f5;
  border-radius: 4px;
}

summary {
  cursor: pointer;
  font-weight: bold;
  color: #667eea;
}

pre {
  background: #2d2d2d;
  color: #f8f8f2;
  padding: 15px;
  border-radius: 4px;
  overflow-x: auto;
  margin-top: 10px;
  font-size: 0.9em;
}

footer {
  background: #333;
  color: white;
  text-align: center;
  padding: 20px;
  margin-top: 60px;
}

@media (max-width: 768px) {
  header h1 {
    font-size: 1.8em;
  }

  nav {
    flex-direction: column;
    gap: 10px;
  }

  nav a {
    display: block;
  }

  section {
    padding: 20px;
  }
}