everything is explained in the documentation. The video scripts have a lot of problems in mobile and tablet devices. In this cases, the template changes the video by an image. The class ‘.poster-image’ is added to the body. If you don’t want this feature, you have to use the files video2.js (in index_video.html), video_youtube2.js (in index_video2.html) or video_vimeo2.js (in index_video3.html).
If you want to change the class ‘.poster-image’, you have to edit the file style.css: