Every game can already do this.
In fact, every Windows application can already do this. Let me broaden that search a little bit: GOOGLE LINK
It looks like in Windows there is a single flag for each window in the heirarchy that says whether to draw the border. Just turning that flag off is all you need. A utility that can do so is linked in the first video in the result above, and also here.
I haven\'t done a search for Mac OS, but I imagine it\'s not much more complicated.
In short, nobody nowhere never should have to implement this manually. It is, both conceptually and geometrically, outside of the scope of the application. In this case, I\'d rather that effort be put into improving the game itself.