Much much later... continued

So looking at this with hindsight and HIARC's suggestion, the obvious move is 8....c4,  Why obvious? Well, puts pressure on the bishop, puts a protected pawn on c4 which has to be good (why? stops an easy advance by white into that square).  In fact it means the bishop has to move in a way which I assume he would have preferred not to. Still the bishop has a reasonably clear digaonal left - maybe comes later that I can turn him into a bad bishop!

Anyway what I did as opposed to this was 8. ...e5.  Now if white leaves me alone and doesn't move the knight or bishop then 9. ...e4 looks pretty good.  But white of course takes the pawn 9 dxe5.  But this in turn is not the best move apparently: it initiates a swap off:knight takes pawn, knight takes knight, bishop takes knight so we end up even.  I have a bishop sitting in the middle of the board which doesn't seem all that good. At this stage though I have to ask who if anyone is controlling the central squares(d4 d5 e4 e5). It seems pretty even to me.  So the question I am left with and don't have an answer to is why HIARCS suggests white would have done better with 9. dxe5.  So more next time as I think about this in advance of my lesson.