You can read past comments related to "Unclaimed World" but you cannot post new, because we have locked it for now to save time on moderation. Instead we encourage you to go to our Steam forum http://steamcommunity.com/app/284100/discussions/
There are Options. Start a game, click the Menu Button at the top-left of the screen. You get a window saying "Options" where you can tick the fullscreen option on and off.