Software to horizonally flip (not rotate) OSX's monitor output? For display reasons we've got a setup where a user watches videos on a MacBook via a mirror.  Of course, this works okay for videos normally, but the user would like to be able to do more than watch videos, including play some games and read comics and the like.

Since the user views the display though a mirror (there are disability issues around this - I'm aware it's a relatively odd question) obviously the text is backwards. Is it possible to horizonally flip OS X's output? Either to the main screen or a external monitor? At the moment it looks like two mirrors is going to be the only solution and that's going to be tricky to arrange.

To be clear - I'm trying to flip horizontally, not rotate by 180 degrees. So the Apple menu is in the top right and the spotlight Notification Center are top left. 

Please indicate/edit and OS version requirements in your answer.
I realize how old this is, but the answer is VLC player. I have an El Capitan Macbook 13". Open VLC, then Window - Video Effects - Geometry - Transform. From there you can rotate 90/180/270, flip horizontally or vertically, magnify, clone etc. Perfect if you have a p/w locked no remote garage sale projector like mine.