body {
  font-family: Arial, sans-serif;
  background: #f9fafb;
  padding: 2rem;
}
#calculator {
  background: white;
  padding: 2rem;
  max-width: 500px;
  margin: 0 auto;
  border: 1px solid #ddd;
  border-radius: 8px;
}
label {
  display: block;
  margin-bottom: 1rem;
}
input {
  width: 100%;
  padding: 0.5rem;
  margin-top: 0.25rem;
}
button {
  margin-top: 1rem;
  padding: 0.75rem 1rem;
  background: #007bff;
  border: none;
  color: white;
  border-radius: 4px;
  cursor: pointer;
}
button:hover {
  background: #0056b3;
}
#result {
  margin-top: 2rem;
  font-size: 1.1rem;
}