table {
    margin: 2em auto;
    --vertex-size: 15px;
    --edge-size: 50px;
}

#board td:nth-child(odd) {
    width: var(--vertex-size);
}

#board td:nth-child(even) {
    width: var(--edge-size);
}

#board tr:nth-child(odd) {
    height: var(--vertex-size);
}

#board tr:nth-child(even) {
    height: var(--edge-size);
}

#results th,
#results td {
    text-align: center;
}

.VERTEX,
.CLOSED_BORDER {
    background-color: black;
}

.OPEN_BORDER,
.EMPTY {
    background-color: white;
}

.PLAYER1,
.OPEN_BORDER:hover {
    background-color: red;
}

.PLAYER2 {
    background-color: blue;
}