Donchenko castles under a pawn attack but hopes to open the  center and make it to the enemy king first.
1. d2d4  1... d7d5  2. c2c4  2... c7c6  3. g1f3  3... g8f6  4. e2e3  4... c8f5  5. b1c3  5... e7e6  6. f3h4  6... f5e4  7. f2f3  7... e4g6  8. c1d2  8... f8e7  9. h4g6  9... h7g6 Caruana chose a very solid line that he tested last  year at the (ongoing) Candidates. 10. d1c2  10... b8d7 