Hides the page content — except videos, games and other media — with a simple black overlay. No fancy extras, just darkness!
Also available for Firefox: https://addons.mozilla.org/firefox/addon/page-dark/
Page Dark covers the webpage with a black screen when you click the toolbar button or trigger the hotkey. Everything except media like videos or games, frames and Flash objects will be hidden by it. This allows you to watch online videos, play Flash games, etc in a much more enjoyable way.
Please check the linked homepage for more complete information. Issues can be filed on the linked support site.