body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
  background: #f5f5f5;
  text-align: center;
}

header {
  background: #4CAF50;
  color: white;
  padding: 1em;
}

main {
  margin: 2em;
}

button {
  padding: 10px 20px;
  font-size: 16px;
  background: #4CAF50;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

button:hover {
  background: #45a049;
}

footer {
  background: #333;
  color: white;
  padding: 1em;
  position: fixed;
  bottom: 0;
  width: 100%;
}