#mine-wrapper,
#mine-wrapper * {
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}

#mine-wrapper .grid {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    width: 642px;
    border: 1px solid red;
}

#mine-wrapper .grid .field {
    background: #fff;
    width: 40px;
    height: 40px;
    border: 1px solid red;
}

#mine-wrapper .grid .field.active {
    background: blue;
    color: #FFFFFF;
}

#mine-wrapper .grid .field.active.mine {
    background: red;
    color: #FFFFFF;
}