body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  text-align: center;
  background: #f8f9fa;
  color: #333;
}

header {
  background: #0077b6;
  color: white;
  padding: 2rem;
}

h1 {
  margin: 0;
}

.calculator {
  margin: 2rem auto;
  padding: 1rem;
  max-width: 400px;
  background: white;
  border-radius: 10px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

input {
  width: 80%;
  padding: 0.5rem;
  margin: 0.5rem 0;
  font-size: 1rem;
}

button {
  padding: 0.5rem 1rem;
  font-size: 1rem;
  background: #0077b6;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

button:hover {
  background: #023e8a;
}

#result {
  margin-top: 1rem;
  font-weight: bold;
  font-size: 1.2rem;
}

.methodology {
  max-width: 600px;
  margin: 2rem auto;
  padding: 1rem;
  text-align: left;
}