body, html {
  margin: 0;
  padding: 0;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #1e1e2f;
  color: #fff;
  font-family: Arial, sans-serif;
}

.screen {
  text-align: center;
}

.hidden {
  display: none;
}

input {
  padding: 10px;
  margin: 10px;
  font-size: 16px;
}

button {
  padding: 10px 20px;
  margin: 10px;
  font-size: 16px;
  background-color: #4a90e2;
  color: #fff;
  border: none;
  cursor: pointer;
  border-radius: 5px;
}

button:hover {
  background-color: #357ab7;
}