html, body {
  height: 100%;
  color: white;
  font-family: sans-serif;
}

body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

button {
  margin: 10px;
  padding: 10px 20px;
  border-radius: 5px;
  border: none;
}

button:active {
  background: #ddd;
}