.calculator {
  background: #fff;
  padding: 2rem;
  border-radius: 20px;
  box-shadow: 0 8px 25px rgba(0,0,0,0.15);
  max-width: 600px;
  margin: 2rem auto;
}
.calculator h2 {
  text-align: center;
  color: #0073e6;
}
.calculator label {
  display: block;
  margin-top: 1rem;
  font-weight: 600;
}
.calculator input,
.calculator select,
.calculator button {
  width: 100%;
  padding: 0.75rem;
  margin-top: 0.4rem;
  border: 1px solid #ccd;
  border-radius: 10px;
  font-size: 1rem;
}
.calculator button {
  background: #0073e6;
  color: #fff;
  font-weight: bold;
  margin-top: 1.5rem;
  cursor: pointer;
}
.calculator button:disabled {
  background: #ccc;
  cursor: not-allowed;
}
.result {
  margin-top: 2rem;
  padding: 1rem;
  border-left: 6px solid #0073e6;
  background: #f0f9ff;
  border-radius: 12px;
}