.body {
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  align-items: centers;
  height: 100vh;
}

#gameboard {
  width: 300px;
  height: 300px;
  background-color: black;
  display: flex;
  flex-wrap: wrap;
  border: solid 1px black;
}

.square {
  width: 100px;
  height: 100px;
  background-color: white;
  border: solid 2px black;
  box-sizing: border-box;
  display: flex;
  justify-content: center;
  align-items: center;
}

.circle {
  height: 90%;
  height: 90%;
  border-radius: 50%;
  border: 15px solid blue;
  box-sizing: border-box;
}

.cross {
  height: 90px;
  width: 90px;
  position: relative;
  transform: rotate(45deg);
}

.cross:before,
.cross:after {
    content: "";
    position: absolute;
    background-color: red;

}

.cross:before{
    left: 50%;
    width: 30%;
    height: 100%;
    margin-left: -15%;
}
.cross:after{
    top: 50%;
    width: 100%;
    height: 30%;
    margin-top: -15%;
}