dev-preview.css

.video-js button.vjs-splash-play {
    position: absolute;
    right: 50%;
    top: 50%;
    transform: translate(50%, -50%);
    box-sizing: border-box;
    display:block;
    width:80px;
    height:80px;
    border: 6px solid #fff;
    border-radius: 50%;
}

.video-js button.vjs-splash-play:after {
    content: '';
    border-top: 20px solid transparent;
    border-bottom: 20px solid transparent;
    border-left: 30px solid white;
    height: 0px;
    display: block;
    position: absolute;
    right: 45%;
    top: 50%;
    transform: translate(50%, -50%);
}

.video-js#videojs-splash-play-player .vjs-big-play-button {
    display: none;
}