:root {
    --bgUrl: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8Xw8AAoMBgDTD2qgAAAAASUVORK5CYII=);
    --bgSmUrl: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8Xw8AAoMBgDTD2qgAAAAASUVORK5CYII=);
}

html {
    background-image: var(--bgUrl);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center center;
    background-attachment: fixed;
}

@media only screen and (max-width: 767px) {
    html { background-image: var(--bgSmUrl); }
    .content { 
        text-align: left; 
        margin: 0; 
        min-height: 60px;
    }
    .content-container { 
        padding: 5px; 
        display: block; 
        margin: 0; 
        width: 100%;
    }
    #header-content > h1 {
        font-size: 38px;
    }
    #content-title {
        margin: 0 0 4px 0;
    }
    #content-message > h1 {
        position: relative; 
        top: 0;
    }
    .form {
        flex-direction: column;
        align-items: stretch;
    }
    #content-form > form > input[type=text] {
        flex: 2;
        margin: 0;
    }
    #content-form > form > input[type=submit] {
        margin: 0 6px 0 0;
    }
}