button {
  background: black;
  color: lime;
  border: 2px solid lime;
  padding: 10px;
  font-family: monospace;
  cursor: pointer;
}

button:hover {
  background: lime;
  color: black;
  text-shadow: 0 0 5px lime;
}

button:active {
  transform: translateY(2px);
  box-shadow: inset 0 0 5px black;
}