#container {
    width: 100%;
    text-align: center;
}

table {
    border-collapse: collapse;
    margin-right: auto;
    margin-left: auto;
}

.mainField {
    width: 30vmin;
    height: 30vmin;
    border: 2px solid black;
}

.smallField {
    width: 6.5vmin;
    height: 6.5vmin;
    text-align: center;
}

.border-left-right {
    border-left: 2px solid black;
    border-right: 2px solid black;
}

.border-top-bottom {
    border-top: 2px solid black;
    border-bottom: 2px solid black;
}