This might look surprising but Vidit is immediately aiming the  hook on h6.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. g2g3  4... f8b4  5. c1d2  5... b4e7  6. f1g2  6... e8g8  7. e1g1  7... c7c6  8. d1c2  8... b8d7  9. b2b3  9... b7b6  10. d2c3  10... c8b7  11. b1d2  11... d8c7  12. f1d1  12... c6c5  13. a1c1  13... d5c4  14. d2c4  14... b6b5 Another energetic novelty by  the rising star! 15. c3a5  15... c7b8  16. c4e5  16... d7e5  17. d4e5  17... f6d5  18. a5d2 Vidit is well aware that the bishop might get locked  out of the game. 18... h7h6 Firouzja anticipates a possible jump of a minor piece on  the g5 square and prevents it.