body { font-family: Arial, sans-serif; margin: 0; }
header {
  background: #333; color: yellow;
  text-align: center; padding: 20px;
  font-size: x-large; cursor: pointer;
}
header:hover { color: red; font-size: xx-large; }

nav {
  display: flex; justify-content: center;
  background: #444;
}
nav a {
  color: white; padding: 14px 20px;
  text-decoration: none; transition: 0.3s;
}
nav a:hover {
  background: #ddd; color: black; font-weight: bold;
}
main { padding: 20px; text-align: center; }
footer {
  background: #333; color: white;
  text-align: center; padding: 10px;
  position: fixed; width: 100%; bottom: 0;
}
input, select, button {
  margin: 5px; padding: 5px 10px;
}
.result {
  margin-top: 20px; font-size: 20px; font-weight: bold;
}