.btn {
  padding: 1em;
  display: inline-block;
  border-radius: 22px;
  background: white;
  color: black;
  text-decoration: none;
  cursor: pointer;
  text-align: center;
  transition: background-color 0.8s;
}
.btn:hover {
  background-color: gray;
}
footer {
  background: gray;
  position: absolute;
  width: 100%;
  bottom: 0;
}