context: 1. c2c4  1... g8f6  2. b1c3  2... e7e5  3. g1f3  3... b8c6  4. g2g3  4... f8b4  5. f1g2  5... e8g8  6. c3d5  6... e5e4 This is considered the best reply according to theory, although other moves are possible. 7. f3h4  7... d7d6  8. e1g1  8... g7g5 Black bravely goes after the knight. There is a price to pay: the king is weakened. 9. d2d4  9... h7h6 This position has already been played in more than 80 games, and now comes something new from Caruana's opening lab that borders on the unbelievable. 10. g3g4 What can I say about this play $2 It seems absurd, but it's a fantastic and interesting idea, at the very least useful for a rapid game. The white knight is lost against other moves as well, but White usually try more conventional lines in the search for compensation. 10... f8e8 Keymer immediately makes a mistake, and his position becomes losing. We could say that Caruana's new move is a \"semi-bluff,\" because Black is doing well with accurate play, but not well enough to have a winning position. The bet is: will my opponent find all the best moves even with little time $2 And if that happens, Black's advantage is small, nothing too dramatic. On the other hand, there is the risk that Black will make a mistake and be immediately lost, as happened in the game. Finding this type of move in the analysis and having the courage to use it show the dual quality of Caruana's opening preparation. 11. h4f5 The white knight escapes, and the weaknesses around the black king make the position practically indefensible. 11... f6g4  12. f2f3  12... e4f3 