.ticktacktoe {
    padding: 10px;
    margin: 0px;
    width: 200px;
    background-color: antiquewhite;
    text-align: center;
}

.cell {
    width: 50px;
    height: 50px;
    background-color: lightgray;
    margin:5px;
    display: inline-block;
}

.sel-a {
    background-color: lightgreen;
}
.win-a {
    background-color: darkgreen;
}

.sel-b {
    background-color: orange;
}
.win-b {
    background-color: red;
}