body {
  font-family: sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.container {
  text-align: center;
}

#card {
  border: 1px solid #ccc;
  padding: 2rem;
  border-radius: 8px;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.hidden {
  display: none;
}

button {
  margin: 0.5rem;
  padding: 0.5rem 1rem;
  font-size: 1rem;
}