It's no secret that you can use Facebook Messenger for a whole lot more than just chatting with pals, but there's still a surprise or two in store. Social networkers have discovered that Messenger has a hidden chess game (quietly available for a least a month before now) that you invoke by typing "@fbchess play" when you're in a conversation. Just don't expect an intuitive interface -- you have to use text commands for everything, so you'd better brush up on your standard chess notation. If you can live with that, though, it's a free and easy way to improve your strategic thinking when you're not busy sending stickers.