A desperate attempt to push the c-pawn and finish development, but it's too late now.
1. f2f3 A strange first move, since it looks passive and the pawn takes away a square from the knight. Advancing the f-pawn two squares seems to be better—this was played by Gukesh in his game against Nakamura. In all other games 1.e4 was tried. 1... f7f5 Black takes the chance to gain some space and create a pawn formation that allows for freer development. 2. d2d4  2... d7d6  3. e1d3  3... e8f6  4. h1g3  4... h8g6 Only four moves have been played and White's position is already difficult, something that can only happen at this level in a freestyle game. Carlsen has problems finishing his development: If e2-e4 is played, then he loses castling rights after the pawn exchange and a check on g4 (although he will allow this later). I thought of 5.Qf2 to castle on the kingside, but then the plan of a6 or a5 followed by Ba7 is unpleasant. Another plan is to develop the bishop to a2 (Carlsen's attempt) or c2 (with 5.c3). 5. a2a4  5... a7a5  6. e2e4 A very risky move. 6... f5e4  7. f3e4  7... b8a7  8. h2h3 Preventing any Ng4 tactics when the bishop goes to e3. 8... e7e5 This simplifies the game, but it helps White to equalize. 9. c1e3  9... e5d4  10. e3d4  10... a7d4  11. g1d4  11... c8e6  12. d1f1  12... f6d7 Controlling the e5-square. White needs to be careful now not to put himself at a positional disadvantage. 13. g3f5 There are simpler moves. 13... g6e5  14. d3f4 This puts White under a lot of pressure. 14... e6c4  15. f1f2  15... g7g6  16. f5e3  16... g6g5  17. f4d5  17... f8f2  18. g1f2  18... c4d5  19. e4d5  19... d7c5 An excellent move, improving the knight while preventing White from moving the c-pawn. 20. a1a3 An ugly move, but what to do $2 20... g8g6 Again preventing the c-pawn from moving.