body {
    width: 100vw;
    height: 100vh;
    display: table-cell;
    vertical-align: middle;
    background-color: #f5f8fa;
}

#message-frame {
    width: 630px;
    margin: auto;
    background: #FFF;
    border: 1px solid #DDDADA;
    padding: 70px;
}

.btn {
    margin-right: 10px;
}

@media (max-width: 640px) {
    body {
        display: block;
    }

    #message-frame {
        width: 100%;
        height: 100%;
        padding: 20px;
    }

    .btn {
        width: 100%;
        margin-bottom: 20px;
    }
}
