Default [Q] An app that can turn screen off (not device lock) with a shortcut hardware button

I know this has been asked too many times, but what I want is (I think) simple, just an app to turn JUST the screen off with a shortcut hardware key (vol up or down or anything), so for example when I click that button while I am recording a video, it continues recording it, or when I am playing a game it continues where I left it because locking the device is not good with some of the games I play. BTW I don't mind if the app needs root. Thanks in advance.