I just posted this on Facebook: https://www.facebook.com/chessboardify/?fref=nf https://www.facebook.com/chessboardify/?fref=nf There is a lot of math involved

I just posted this on Facebook: https://www.facebook.com/chessboardify/?fref=nf https://www.facebook.com/chessboardify/?fref=nf There is a lot of math involved in this game and you can quite quickly note some less obvious rules like this one. Maybe there are some very nontrivial, but interesting things out there. I'm not good enough in combinatorics to tell... :D