body {
  font-family: Arial, sans-serif;
  transition: background-color 0.3s, color 0.3s;
}
.card {
  box-shadow: 0 0 10px rgba(0,0,0,0.2);
}
.dark-mode {
  background-color: #121212;
  color: #ffffff;
}
.dark-mode .card {
  background-color: #1e1e1e;
  color: #ffffff;
}