A sharp move and a  novelty. White wants to immediately profit from his space advantage.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. f2f3 "A sharp line that is also very risky for White. I have never played this before." (Caruana) 4... d7d5  5. a2a3  5... b4e7  6. e2e4  6... d5e4  7. f3e4  7... c7c5  8. d4d5  8... e6d5  9. e4d5  9... e8g8  10. f1e2  10... f8e8  11. g1f3  11... c8g4 "An extremely decent plan for Black." (Caruana) 12. e1g1  12... b8d7 