Now Black has a problem with his kingside as he cannot castle  easily.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. a2a3 The world champion often chooses this line against the Nimzo-Indian in blitz and rapid. 4... b4c3  5. b2c3  5... c7c5  6. e2e3  6... b8c6  7. f1d3  7... d7d6  8. g1e2  8... e6e5 In return Giri builds the Hubner-Portisch  wall. 9. e2g3 A pawn sacrifice that Black sensibly rejects. 9... h7h5  10. h2h4 A novelty. Carlsen understands these positions in the  smallest detail and is often getting this same pawn structure as Black  when facing the Rossolimo Sicilian. 10... d8e7  11. d4d5  11... c6b8 