body {
  font-family: Arial, Helvetica, sans-serif;
}

td {
  height: 150px;
  width: 150px;
  border: 5px solid black;
  text-align: center;
  font-size: 90px;
}

#mark_black {
  height: 120px;
  width: 120px;
  font-size: 90px;
}

#mark_white {
  height: 120px;
  width: 120px;
  font-size: 90px;
}