/* Extra small devices (portrait phones, less than 576px) */
@media (max-width: 575px) {
    .principal{
      padding-top: 50%;
    }
    .card{margin-bottom: .6em;}
}

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) and (max-width: 767px) {
    .principal{
      padding-top: 10%;
    }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) and (max-width: 991px) {
    .principal{
      padding-top: 20%;
    }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) and (max-width: 1199px) {
    .principal{
      padding-top: 20%;
    }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
    .principal{
      padding-top: 20%;
    }
    
    .logo{
    background-image: url(../images/logo.svg);
    display: block;
    z-index: 1;
    background-size: 100% 100%;
    height: 55px;
    width: 100px;
    margin-bottom: 1em;

    background-size:100% 100%;
    -o-background-size: 100% 100%;
    -webkit-background-size: 100% 100%;
    background-size:cover;
}
}

.gray{
    margin-top: 1em;
    color: #aaa;
}