[%c_effect c5;square;c5;type;Interesting;persistent;true] This is an interesting variation of the Bogo-Indian Defense, a favorite of the legendary GM Viktor Korchnoi. I played this move many times during my career, but I must admit that my results were not as good as Korchnoi's and Nakamura's, which is not so surprising, to be honest.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... f8b4  4. c1d2 