The beginning of a flawed plan. More solid seems 4...b5 5.h5 Bxd4! 6.Rxd4 Qb6 , followed by ...Qe6.
More prophylaxis. At this moment a draw was agreed, but let's see what would have happened if White carried on with his plan.
Thanks to his clever second move Black manages to regroup his knight to e5 with an excellent game.
By avoiding a check on f4 in advance White maintains maximum flexibility in his central attack.