#tablero {
    display: inline-block;
    border:5px solid;
}
.fila {
    background-color: black;
    display: table;
}
.recuadro {
    width:50px;
    height:50px;
    float:left;
}
.fila:nth-child(odd) .recuadro:nth-child(even),
.fila:nth-child(even) .recuadro:nth-child(odd) {
    background-color: white;
}

body, .card-body {
    background-color: black;
    font-family: Arial, Helvetica, sans-serif;
    color: white;
}

.container {
    display: flex;  
    align-items: center;      
    justify-content: center;    
    min-height: 100vh;
}