body {
  font-family: Arial, sans-serif;
  background-color: #f3f3f3;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.calculator {
  background-color: white;
  padding: 30px;
  border-radius: 10px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
  text-align: center;
}

input, select, button {
  margin: 10px 0;
  padding: 10px;
  width: 100%;
  font-size: 16px;
}