Puzzle - find the 4-move sequence.

Dinkydoe
Dinkydoe
Sep 19, 2008, 7:04 AM |
4

Here is a nice non-realistic puzzle. This is a position after black and white played 4 moves. The question is, what moves did black and white play. There is only one possible solution. ( The position can also be reached in 3 moves but both players have to play 4 moves).

It's not an easy one, but for the ones willing to solve, i can give tips.