comment: Both 15...Be7 and 15...Bc7 are good for Black.
context: 1. f2f4 The most natural and also the best move, opening the diagonal for the bishop and attacking the a7-pawn. No wonder it was played in all four games of the round. 1... a8b6  2. a1b3  2... f7f5  3. e2e4 Judging by the other games, this is a kind of \"theoretical line\" from this starting position. The computer doesn't approve of this move. 3... f5e4  4. e1e4  4... g8d5 A logical move, improving the position of the bishop and leaving room for the queen. However, the bishop can be attacked by the knight after Ne3. 5. e4e1  5... h8g8  6. g1f2  6... f8g6  7. f4f5  7... g6f4  8. f1e3  8... e7e5 A difficult decision, allowing White to capture the valuable bishop. An option is to move it to f7 or c6. 9. e3d5  9... f4d5  10. g2g4 Opening the diagonal for the queen and securing the pawn on f5. 10... c7c6  11. b1a1 A subtle move, preparing a4-a5. 11... d5f4 The knight stabilizes itself in a comfortable square, making way for the queen.. 12. a2a4  12... a7a5 It's necessary to stop a4-a5. 13. b3c5 White has a few tempting moves: 13... b6d5  14. c5e4 The knight is ready to go to d6. There are three ways to cover this square, and all are reasonable. 14... g8f8  15. g4g5 A very risky move, destabilizing the pawns on the kingside.