body {
  margin: 0;
  background: black;
  color: red;
  font-family: monospace;
  height: 100vh;
}

.overlay {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
  text-shadow: 0 0 10px red;
}

button {
  background: black;
  border: 1px solid red;
  color: red;
  padding: 10px 20px;
  margin: 10px;
  cursor: pointer;
}