.calculator {
  max-width: 500px;
  margin: 0 auto;
  padding: 20px;
  border: 2px solid #ccc;
}

.input-group {
  margin-bottom: 10px;
}

.input-group label {
  display: block;
  margin-bottom: 5px;
}

.input-group input {
  width: 100%;
  padding: 10px;
  border: 1px solid #ccc;
  border-radius: 4px;
}

#calculate-btn {
  display: block;
  margin: 20px auto;
  padding: 10px 20px;
  background-color: #007bff;
  color: #fff;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}

#result {
  display: none;
  margin-top: 20px;
}

.output-group {
  margin-bottom: 10px;
}

.output-group label {
  display: inline-block;
  width: 150px;
}

.output-group span {
  font-weight: bold;
}

#error-message {
  color: red;
  font-weight: bold;
  margin-top: 10px;
}

#download-btn {
  display: block;
  margin-top: 20px;
  padding: 10px 20px;
  background-color: #28a745;
  color: #fff;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}