[%c_effect d5;square;d5;type;GreatFind;persistent;true] It's necessary to capture the bishop to have compensation for the pawn by exploiting the weak light-squares on Black's queenside.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... b7b6  4. g2g3  4... c8a6  5. b2b3  5... f8b4  6. c1d2  6... b4e7  7. b1c3  7... d7d5  8. f1g2  8... e8g8  9. e1g1  9... d5c4 [%c_effect c4;square;c4;type;Inaccuracy;persistent;true] A risky move, especially considering that Black didn't need to unbalance the game. 10. b3c4 This move, surprisingly, is a novelty. 10... a6c4  11. f3e5  11... c4d5 