body {
  font-family: sans-serif;
  padding: 20px;
  max-width: 400px;
}
label, select, input {
  display: block;
  margin-top: 10px;
  width: 100%;
}
input[type="number"] {
  padding: 5px;
  font-size: 1em;
}
button {
  margin-top: 15px;
  padding: 10px;
  width: 100%;
  font-size: 1em;
}
.result {
  margin-top: 20px;
  font-weight: bold;
}
.assumptions {
  margin-top: 15px;
  font-size: 0.9em;
  color: #555;
  background: #f9f9f9;
  padding: 10px;
  border-radius: 5px;
  white-space: pre-wrap;
}