Hi,

GM Huschenbeth and GM Gustafsson released a White repertoire called "Keymer Repertoire" based on 1.Nf3 d5 2.e3. The repertoire can be bought under the following link:
https://modernchess.de/keymer-system/

In the introduction video GM Gustafson talks about some lines of the course. After 1.Nf3 Nf6 2.c4 c5 he recommends 3.b3, but I wonder what is his idea/main game/line after 3...d5.

Does anybody has this course and give some direction what is his idea after 1.Nf3 Nf6 2.c4 c5 3.b3 d5?

Thanks!