.block-close, .block-close:hover{
    width: 30px;
    height: 30px;
    cursor: pointer;
    position: absolute;
    top: -16px;
    right: -16px;
    border: 3px solid #eaeaea;
    border-radius: 50%;
    padding: 0 6px;
    background-color: #222222;
    color: #eaeaea;
    box-shadow: -1px 2px 4px #222222;
}

a.close, a.close:hover {
    font-size: 21px;
    font-weight: 600;
    line-height: 1;
    color: #eaeaea;
    text-shadow: none;
    margin-top: 0;
    opacity: 1;
    display: inline-block;
    font-family: sans-serif !important;
}

body[os="MacOS"][browser="Firefox"] a.close {
    margin-top: 1px;
}

body[os="Windows"] a.close {
    margin-top: 2px;
}