html, body{
    height: 90%;
    background: -webkit-linear-gradient(left, black, white);
}
.full-height{
    height: 100%;
}
.cajaPrincipal{
    margin: 1rem;
    padding: 1rem;
    text-align: center;
    display: flex;
    align-items: center;
    justify-content: center;
}