body {
  font-family: sans-serif;
  background-color: palegreen;
  color: brown;
  text-align: center;
}

.cell {
  background-color: yellow;
  border: 1px solid black;
  min-width: 7rem;
  min-height: 7rem;
  display: inline-block;
  text-align: center;
  vertical-align: middle;
  line-height: 7rem;
  font-size: 4rem;
}

.row {
  padding: 0.1rem;
}

.blue {
  color: blue;
}

.purple {
  color: purple;
}

.button {
  font-size: 1.1rem;
  color: purple;
  background-color: yellow;
  border: 1px solid black;
}