Automatically dim the page and highlight the video player when you click on the play button. This page is only for developer of Turn Off the Lights to test the browser extension features. Such as the "automatically dim the page when you click on the play button" etc.
The extension can detect all the play status. If one of the video is still playing, the page stay dark. This thinking is done in the opensource "injected.js" script file in the Turn Off the Lights Browser extension.