* {
  margin: 0;
  padding: 0;
  text-align: center;
  background-color: black;
  color: snow;
}

.num-positive {
  color: green;
}

.num-negative {
  color: tomato;
}

button {
  margin: 1rem 0.5rem;
  padding: 0.375rem;
  border-radius: 5px;
}