.header {
    position: relative;
    text-align: center;
}

    .header img {
        width: 700px;
    }

#logo-web {
    display: inline;
}

#logo-rwd {
    display: none;
}

.centered {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    min-height: 100vh;
}

.cardcenter {
    margin: 0 10px 10px 10px;
    width: 30em;
}

.captcha {
    padding: .65em 0 0 0;
}

.announcement-box {
    margin: .3em .6em .1em 1em;
    width: 30em;
}

    .announcement-box .item {
        min-width: 14.2em;
        margin: 0 .5em .7em .3em;
        text-align: left;
        white-space: normal;
    }

@media (max-width:640px) {
    .header img {
        width: 25rem;
    }

    .announcement-box {
        width: 20rem;
    }

    #logo-web {
        display: none;
    }

    #logo-rwd {
        display: inline;
    }

    body {
        overflow: scroll;
        white-space: nowrap;
    }

    .cardcenter {
        width: 20rem;
    }

    .captcha {
        padding: .6em 0 0 0;
        margin-left: -.5em;
    }
}