probably My most famous lost

This is a miniature that I thought was really good even though I lost i give my opponent credit for playing so aggressive.

For one I think 10.d4 is more of a aggressive move for white.

Usually it takes several mistakes to loose this quickly but sometimes one really bad one is enough and I think that might be the case here. I don't see much wrong in your position after 12... Bg7. White could try to use the dark squares on the kingside with 13. Bg5 but I doubt it comes to nothing after 13... h6 or even simply 13... 0-0.

The fianchetto with 9... g6 appears to be playable but maybe faster development with Nf6 and Be7 would be simpler.

Was 12...Bg7 13.Nxc5/Nd4 is this outpost for the knight compensation for the lost c-pawn ?

at 9... i thought of f5.

13. Nxc5? would be a mistake that costs a piece. I'll leave it to you to find the refutation.

Holy crap that was fast. I dunno if you even made mistakes to warrant that. I think the only thing is you weren't trying to castle straight away like most people do. (Although neither were they). Dunno

 I see 13.Nxc5?/Qa5+ wins it

Correct.