open-ww3-project-ww3-tw/public/static/html/black-block.html

<style>
#black_block
{
    background-color: rgba(0, 0, 0, 0.68);
    position: fixed;
    width: 1150px;
    height: 100%;
    margin: auto;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
}
</style>