1. e2e4  1... e7e5  2. g1f3  2... g8f6  3. d2d4  3... f6e4  4. d4e5  4... d7d5  5. b1d2  5... d8d7 A very fresh line, invented by Caruana back in 2018. What adds educational value to the story is the fact that the American found the idea after honestly analyzing his own epic win against Grischuk at the Berlin Candidates. 6. f1d3 The most natural development.