a.button {
  text-align: center;
  margin: 0 auto;
  width: 50%;
  display: block;
  padding: 10px;
  border: 0;
  color: #fff;
  background: #2DA3D6;
  cursor: pointer;
  border-radius: 5px;
}
  a.button:hover {
    text-decoration: none;
  }

.text-center { text-align: center; }


h1 { color: blue; }

@media (max-width: 600px) {
  h1 { color: red; }
}