twitter-embed-while-loading-style.css

figure.wp-block-embed-twitter blockquote.twitter-tweet {
    font: normal normal 16px/1.4 Helvetica,Roboto,"Segoe UI",Calibri,sans-serif;
    max-width: 100%;
    width: 550px;
    margin: auto;
    padding: 73px 20px 40px 20px;
    border-radius: 4px;
    visibility: hidden;
}

figure.wp-block-embed-twitter blockquote.twitter-tweet p {
    visibility: visible;
}