1. d2d4  1... d7d5  2. c2c4  2... e7e6  3. g1f3  3... d5c4  4. e2e4  4... b7b5  5. a2a4  5... c7c6  6. b1c3 A rare move, but the game will quickly transpose to a well-known position. 6... f8b4 Now we're back to a position with more than a thousand games played. It makes sense for Black to try to exploit White's move order with the move 6...b4. Considering the time spent, it's likely Tan didn't expect this opening and was improvising from this moment on. 7. c1d2  7... d8b6 Another rare move, this time leading to truly unexplored positions already on move eight, something we also saw in the first game of the match. 8. f1e2  8... g8e7 A new move. It makes sense to develop the knight here, to escape from the move e4-e5. 9. d1c2 By protecting the knight, White prepares the thematic break on b3. 9... c8b7  10. b2b3 [%c_effect b3;square;b3;type;GreatFind;persistent;true] 10... c4b3  11. c2b3  11... a7a5 [%c_effect a5;square;a5;type;GreatFind;persistent;true] It's necessary to return the pawn. Exchanging the dark-squared bishop would be positional suicide. 12. a4b5  12... c6b5 