Make twitter photo alt-text visible on hover, have an indicator visible normally.

twitter_alt-text_visible_on_hover.css

div[data-testid="tweetPhoto"]:not([aria-label="Image"]) {
    margin: 0 !important;
}
div[data-testid="tweetPhoto"]:not([aria-label="Image"]):hover::after {
    content: attr(aria-label);
    width: 95%;
    background: rgba(0,0,0,.75);
    color: #fff;
    padding: 10px;
    font-family: sans-serif;
    font-size: 10px;
}
div[data-testid="tweetPhoto"]:not([aria-label="Image"]):after {
    width: 20px;
    content: 'Alt';
    text-align: center;
    background: rgba(0,0,0,.75);
    color: DodgerBlue;
    font-size: 12px;
}

/* Swaps state, so alt-text is visible except on hover.
div[data-testid="tweetPhoto"]:not([aria-label="Image"]):after {
    content: attr(aria-label);
    background: rgba(0,0,0,.75);
    color: #fff;
    padding: 10px;
    font-family: sans-serif;
}
div[data-testid="tweetPhoto"]:not([aria-label="Image"]):hover::after {
    content: '';
    background: rgba(0,0,0,0);
}
*/