Chess960: two move ideas no. 5

Here black has decided not to spend the time calculating the effects of symmetrical play after 1.f4 ...f5 and is not particularly inspired by 1.f4 ... Nb6. So instead of other possible replies to 1.f4 such as 1...b6 or 1...c5!?/Bb6 or 1...f6, black comes up with a nice harmonious gambit idea instead:

SP357 white to play: trace back the moves and try to see black's ideas

Enjoy 960

Hint: Bb6, Nc7, d5/d6, f5/f6 not in any particular order