[%c_effect c4;square;c4;type;Interesting;persistent;true] An interesting idea and only the third most popular move, although it's the trendy choice at the moment.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. e2e3  4... c7c5  5. f1d3  5... b8c6  6. g1e2  6... d7d5  7. c4d5  7... e6d5  8. e1g1  8... e8g8  9. a2a3 