/* Light mode (default) */
body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: #f4f4f4;
  color: #111;
  transition: background 0.3s, color 0.3s;
}

.container {
  max-width: 600px;
  margin: 100px auto;
  text-align: center;
  padding: 40px;
  background: white;
  border-radius: 12px;
  box-shadow: 0 0 20px rgba(0,0,0,0.1);
  transition: background 0.3s;
}

button {
  margin-top: 20px;
  padding: 12px 20px;
  font-size: 16px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: #222;
  color: white;
}

/* Dark mode */
body.dark {
  background: #121212;
  color: #f1f1f1;
}

body.dark .container {
  background: #1e1e1e;
  box-shadow: 0 0 20px rgba(255,255,255,0.05);
}

body.dark button {
  background: white;
  color: black;
}