Normally White continues like this after playing b2-b4, but in this position it leads to problems.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1c4  3... f8c5  4. c2c3  4... g8f6  5. d2d3  5... d7d6  6. c1g5  6... h7h6  7. g5h4  7... d8e7 A rare move that certainly caught Nepomniachtchi by surprise, since in just two moves his position becomes much inferior. The plans with a quick g7-g5 are more common. 8. b2b4 The beginning of a wrong plan. 8... c5b6 