.game-container {
  margin: auto;
  
  width: 450px;
  height: 450px;  
}

.square {
  width: 140px;
  height: 140px;
  border: 2px solid black;
  /* display: inline-block; */
  float: left;
  font-size: 100px;
  text-align: center;
  line-height: 140px;
}

.btn-xo {
  text-align: center;
  width: 75px;
  margin: auto;
}

.div-center {
  width: 160px;
  margin: auto;
 
}