body {
  flex-direction: row;
  height: 100vh;
  display: flex;
}

button {
  width: 100%;
  height: 100%;
  font-size: 1.5rem;
  cursor: pointer;
}

a {
  flex: 1;
  text-decoration: none;
}

button:hover {
  background-color: grey;
}

@media (max-width: 768px) {
  body {
    flex-direction: column;
  }
}