1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... g8f6 There are many ways to face the Berlin Defense, probably the most reliable variation for Black, along with the Petroff. It's possible to choose a long-term strategic game with 4.d3 to fight in the endgame like how Kasparov got so much headache in his match with Kramnik or look for a computer line in which your opponent needs to remember many moves to make a draw. Firouzja chooses the last option. 4. e1g1  4... f6e4  5. f1e1  5... e4d6  6. f3e5  6... f8e7  7. b5f1  7... c6e5  8. e1e5  8... e8g8  9. d2d4  9... e7f6 